Supermassive Black Holes with High Accretion Rates in Active Galactic Nuclei. XIII. Ultraviolet Time Lag of Hβ Emission in Mrk 142

Accretion onto supermassive black holes through an accretion disk of ionized gas powers active galactic nuclei (AGNs) at the centers of massive galaxies. AGNs accreting at typical rates (a few percent of the Eddington limit) have a geometrically thin but optically thick disk—the "thin-disk" model (Shakura & Sunyaev 1973). However, theoretical models predict a notably different structure for the AGN with high accretion rates significantly above the Eddington limit—super-Eddington AGN (e.g., Abramowicz et al. 1988). The occurrence of such AGNs is likely higher during the peak era of supermassive black hole growth during cosmic noon (redshifts, z = 1–3; Brandt & Alexander 2010; Shen et al. 2020). Understanding the structure of the accretion system in high-Eddington AGNs remains an open issue in accretion physics.

Although models exist for slim-disk systems, observational tests of the structure of the accretion flow in super-Eddington AGN are rare. At high accretion rates, radiation pressure is expected to dominate, causing the inner disk to inflate vertically—now called a "slim" (rather than thin) disk—with a scale height, H ≤ R, where R is the disk radius (e.g., Abramowicz et al. 1988). Photons are trapped in the fast-flowing matter, eventually falling into the black hole. Given that not all photons escape, the disks in super-Eddington AGNs are underluminous relative to the accretion rates as compared to thin disks (Jaroszyński et al. 1980). Begelman (2002) proposed an alternative scenario where the "photon-bubble instability" principle can cause the disks in super-Eddington AGNs to become inhomogeneous at scales much smaller than the disk scale height.

Reverberation mapping (RM; Blandford & McKee 1982; Peterson 1993) provides a way to observationally study the slim-disk model and broad-line region (BLR) in super-Eddington AGNs. RM takes advantage of the observed continuum variability of AGNs on many timescales (from several days to weeks and years; e.g., Peterson et al. 1982). The accretion-disk emission illuminates the BLR on larger scales, and sets the ionization structure and thus the location of the gas generating the broad emission lines (e.g., Hβ). An increase in continuum emission from the accretion disk results in an increase in broad emission-line flux after a time lag set by the sum total of the light travel time between the continuum-emitting region and the BLR (Peterson 2014), and the recombination timescale, where the latter is much smaller than the former for typical BLR densities (and therefore ignored in the time-lag calculations). RM converts this time lag into a spatial distance, the size of the BLR. Thus, applying RM to high-accretion-rate AGNs gives an observational method to test the structure of the accretion flow and BLR in these systems, and place super-Eddington AGNs on the radius–luminosity (R–L) relationship for AGNs (Kaspi et al. 2005; Bentz et al. 2013).

The Narrow-Line Seyfert 1 (NLS1) class of AGNs are considered to have high accretion rates, and typically display narrow broad emission lines (e.g., the Hβ line has an FWHM ≲ 2000 km s⁻¹) in comparison to other broad-line objects (and broader than the narrow lines seen in type 2 objects), strong Fe ii emission lines, and weak [O iii] lines (e.g., Osterbrock & Pogge 1987; Boroson & Green 1992; Boller et al. 1996; Véron-Cetty et al. 2001) in their spectra. The Super-Eddington Accreting Massive Black Holes (SEAMBH) campaign has been performing photometric and spectroscopic monitoring over the past 9 yr of high accretion-rate AGNs that display spectral characteristics of NLS1s (e.g., Du et al. 2014, 2015, 2016a, 2016b, 2018; Wang et al. 2014a; Hu et al. 2015; Li et al. 2018, 2021). Du et al. (2016b) showed that the BLRs in super-Eddington AGNs are smaller than those with sub-Eddington accretion rates. In the context of the slim-disk model, the smaller BLR sizes can be explained as a consequence of the increased scale height of the inner accretion disk that shields the BLR from the central ionizing flux (Wang et al. 2014b). Hβ, a marker of the hydrogen ionization front in the BLR, can thus exist at smaller radii than in thin accretion-disk systems. Fonseca Alvarez et al. (2020) offered an alternative explanation. In their correlation analysis of the physical and spectral properties of the Sloan Digital Sky Survey (SDSS) RM AGNs, Fonseca Alvarez et al. (2020) found that the R–L offset (defined as the ratio of the measured Hβ time lag to the expected time lag from the best-fit R–L such as that given by Bentz et al. 2013) is positively correlated to the [O iii] λ5008 to Hβ luminosity ratio, which is often used as a proxy for the number of ionizing photons (e.g., Baldwin et al. 1981). The smaller BLR sizes are therefore likely a result of the changes in the shape of the ultraviolet (UV)/optical spectral energy distribution (SED) of AGNs (Fonseca Alvarez et al. 2020).

As the most promising SEAMBH object—a bright target with an extremely super-Eddington accretion rate ($\dot{M}/{\dot{M}}_{\mathrm{Edd}}=250;$ Li et al. 2018) and a well-measured Hβ lag—Markarian 142 (Mrk 142 or PG 1022+519, R.A. = 10^h25^m3120, decl. = +51°40'3487, z = 0.045) is the target of our study to probe the structure of its BLR. In the 2012 SEAMBH campaign, Mrk 142 was highly variable with a fractional variability amplitude of F_var = 8.1% at 5100 Å over a period of 6 months. Its variable nature makes it amenable to RM studies of both accretion-disk structure (from X-ray/UV/optical continuum time-lag studies) and the BLR structure (from continuum-emission line time lags). Accretion-disk RM applies the same principle as BLR RM to the inner and outer regions of the accretion disk to determine its size and temperature profile (Cackett et al. 2007). The more energetic X-ray/UV radiation from the inner disk illuminates the disk at larger radii where the optical photons are generated. Therefore, the lower-energy emission will respond with a positive time lag to changes in the high-energy radiation giving rise to correlated continuum light curves. Mrk 142 has a total Hβ time lag (τ) with respect to the 5100 Å continuum emission of ${7.9}_{-1.1}^{+1.2}$ days (Du et al. 2015) and a black hole mass of $\mathrm{log}({M}_{\bullet }/{M}_{\odot })$ = ${6.23}_{-0.45}^{+0.26}$ (Li et al. 2018).

In this paper, we present Mrk 142 time-lag measurements from two ground-based, optical spectroscopic RM campaigns of Mrk 142 concurrent with the photometric monitoring of the target with the Neil Gehrels Swift Observatory (Swift) in a UV band; and the Las Cumbres Observatory (LCO), Dan Zowada Memorial Observatory (Zowada), and Liverpool Telescope (Liverpool; Steele et al. 2004) in an optical band. With our joint campaign, we performed, for the first time, simultaneous measurements of the inner accretion disk and BLR size in a super-Eddington AGN. This paper is organized as follows. In Section 2, we provide details of the observations, and in Section 3, we explain the process of data reduction. In Section 4, we describe our spectral modeling followed by light-curve analysis in Section 5. In Section 6, we outline and discuss our results in the context of previous studies. Section 7 provides closing remarks. Throughout this work, we use the standard cosmology with H₀ = 67 km s⁻¹ Mpc⁻¹, Ω_Λ = 0.68, and Ω_M = 0.32 (Planck Collaboration et al. 2014).

We obtained concurrent observations of Mrk 142 with multiple telescopes to perform RM analysis of the accretion disk and BLR simultaneously. Figure 1 shows the continuum light curves of Mrk 142, highlighting the simultaneous coverage with different telescopes.

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2.1. Gemini North Telescope

We obtained new observations of Mrk 142 long-slit spectra taken with the Gemini Multi-Object Spectrograph (GMOS; Hook et al. 2004) on the 8.1 m Gemini North Telescope (Gemini) on Maunakea, Hawai'i with 33 epochs from 2019 February 6 through June 1. These spectral observations are concurrent with the Mrk 142 photometric data from the Swift telescope comprising 180 epochs of 1 ks exposures at X-ray, UV, and optical wavelengths from 2019 January 1 through April 30 (P.I.: E. Cackett) as well as with the photometric g-band data from LCO (P.I.: R. Edelson), Zowada (P.I.: E.Cackett), and Liverpool (P.I.: M. Goad); the photometric data are presented in Cackett et al. (2020). The Swift observations had a twice-daily cadence until March 19, and the cadence was decreased to daily from March 20 onward. We required observations from Gemini in early 2019 with considerable overlap with the Swift campaign to allow, for the first time, simultaneous measurements of the UV-emitting accretion disk and the BLR of a super-Eddington AGN. The cadence of the Gemini observations was set to 1 day. We obtained data for only two, sparsely separated epochs in February during the beginning of the observing period due to weather interruptions. However, observations were more frequent in March and May, and the daily cadence was achieved in the first week of April.

The spectra were taken with the GMOS-North Hamamatsu detector and a single grating, B600 with two different slits, 075 (narrow slit) and 500 (wide slit), in the two-target acquisition mode, where Mrk 142 and a comparison star were observed in the same slit. The GMOS-North Hamamatsu detector comprises three ∼2048 × 4176 pixel chips (full detector size of 6278 × 4176 pixels, mosaicked) arranged in a row with pixel size of 00807 with two chip gaps 488 wide. The choice of the grating was made to obtain the broad emission line of interest, Hβ λ4861, in the spectra. The narrow 075 slit was selected to obtain a spectral resolution of ∼1125 (narrow-slit data) required to study the velocity structure of Hβ. Accuracy in spectrophotometric calibration is a key for RM studies, and therefore, we used the wide slit at a resolution of ∼170 (wide-slit data) to correct for slit losses due to the narrow slit. To satisfy this calibration requirement, Mrk 142 and a comparison star for flux calibration (hereafter, calibration star) were placed simultaneously in the same slit. We achieved this for all observations by fixing the position angle of the slits at 15520 east of north such that Mrk 142 appeared at the center of the slit. The selected G-type calibration star (R.A. = 10^h25^m3637, decl. = +51°38'5218, r-band magnitude = 15.9 from the SDSS catalog) has a well-calibrated spectrum and was used for previous LJT campaigns. Flatfield images were taken for every object (science target and calibration star) with the Gemini Facility Calibration Unit (GCAL) in the sequence FLAT–OBJECT–OBJECT–FLAT with both slits. The on-target exposures were 90 s long. We also took daytime arc-lamp spectra with the CuAr lamp, again, for both slits. Binning of 1 in the spectral (X) direction and 2 in the spatial (Y) direction (1 × 2) was used for all data except for the wide-slit arc-lamp spectra, which used the binning of 1 × 1. A summary of the GMOS-North science observations is provided in Table 1. The object spectra from all epochs except the narrow-slit spectra from epoch 30 were assigned a Pass ("P") flag.

Table 1. Summary of Mrk 142 GMOS Observations from 2019 February to June

Epoch	UT a Date	MJD b Start Time		Airmass
	(YYYY-MM-DD)	075 Slit	500 Slit	075 Slit	500 Slit
1	2019-02-06	58520.412	58520.418	1.275	1.258
		58520.414	58520.420	1.270	1.254
2	2019-02-26	58540.415	58540.421	1.181	1.178
		58540.417	58540.423	1.180	1.177
3	2019-03-03	58545.433	58545.439	1.178	1.181
		58545.435	58545.441	1.178	1.182
4	2019-03-09	58551.430	58551.437	1.187	1.193
		58551.432	58551.438	1.188	1.194
5	2019-03-12	58554.550	58554.557	1.679	1.734
		58554.552	58554.558	1.693	1.750
6	2019-03-15	58557.427	58557.433	1.200	1.209
		58557.428	58557.442	1.202	1.225
7	2019-03-16	58558.355	58558.362	1.189	1.184
		58558.357	58558.363	1.188	1.183
8	2019-03-23	58565.281	58565.287	1.299	1.280
		58565.283	58565.289	1.293	1.276
9	2019-03-26	58568.254	58568.260	1.365	1.341
		58568.256	58568.262	1.359	1.335
10	2019-03-27	58569.410	58569.416	1.225	1.237
		58569.411	58569.418	1.228	1.241
11	2019-03-29	58571.233 c	58571.239	1.424	1.394
		58571.235 d	58571.241	1.416	1.387
12	2019-03-31	58573.233	58573.239	1.398	1.370
		58573.235	58573.241	1.390	1.364
13	2019-04-03	58576.457	58576.463	1.451	1.486
		58576.459	58576.465	1.460	1.496
14	2019-04-04	58577.234	58577.240	1.350	1.327
		58577.235	58577.241	1.343	1.321
15	2019-04-05	58578.241	58578.248	1.312	1.292
		58578.243	58578.249	1.306	1.287
16	2019-04-06	58579.236	58579.242	1.322	1.302
		58579.237	58579.243	1.317	1.297
17	2019-04-07	58580.461	58580.467	1.543	1.585
		58580.463	58580.469	1.554	1.597
18	2019-04-08	58581.331	58581.337	1.177	1.179
		58581.333	58581.339	1.177	1.180
19	2019-04-09	58582.432	58582.438	1.408	1.439
		58582.434	58582.440	1.416	1.447
20	2019-04-25	58598.274	58598.280	1.175	1.176
		58598.276	58598.282	1.175	1.176
21	2019-04-27	58600.391	58600.397 c	1.447	1.481
		58600.392	58600.398	1.456	1.491
22	2019-05-01	58604.338	58604.344 c	1.282	1.300
		58604.340	58604.346	1.286	1.305
23	2019-05-02	58605.327	58605.333	1.259	1.275
		58605.329	58605.335	1.263	1.280
24	2019-05-07	58610.317	58610.323	1.267	1.285
		58610.318	58610.324	1.272	1.289
25	2019-05-08	58611.361	58611.367	1.450	1.485
		58611.363 c	58611.369 c	1.459	1.494
26	2019-05-09	58612.246	58612.253	1.177	1.179
		58612.248	58612.254	1.177	1.180
27	2019-05-12	58615.269	58615.275	1.201	1.209
		58615.270	58615.276	1.203	1.212
28	2019-05-13	58616.320 e	58616.326	1.329	1.353
		58616.322	58616.328	1.335	1.359
29	2019-05-24	58627.266	58627.272	1.256	1.272
		58627.267	58627.273	1.260	1.276
30	2019-05-25	58628.242 f	58628.248	1.213	1.223
		58628.243 f	58628.249	1.216	1.227
31	2019-05-26	58629.251	58629.257	1.235	1.249
		58629.253	58629.259	1.239	1.252
32	2019-05-28	58631.251	58631.257	1.246	1.261
		58631.252	58631.258	1.250	1.265
33	2019-06-01	58635.255	58635.262	1.287	1.307
		58635.257	58635.263	1.292	1.312

Notes. Observations were done with the GMOS-North Hamamatsu detector in the two-target acquisition mode (Mrk 142 and a comparison star in the same slit) positioning the slit at 15520 east of north, with the B600 grating (covering the broad Hβ emission line at ∼4862 Å) and two slits, 075 (narrow slit) and 500 (wide slit). Two exposures were taken with every grating/slit combination, each 90 s long. A data quality flag (DQF) of "P" (passable) or "U" (usable) was assigned to all data at the time of observing. Unless stated otherwise, all science spectra were assigned a DQF of "P." SpectroPhotometric CALibration Flag (SPCALF) indicates whether the science spectra were calibrated ("1") or not calibrated ("0") during spectral reduction (see Section 3.1.4 for more details). SpectroPhotometric CALibration Grade (SPCALG) indicates the grade assigned to the spectrophotometric calibration based on the epoch and exposure of the calibration star spectrum used for calibrating the science spectra (see Section 3.1.4 for more details). All science spectra were assigned an SPCALF of 1 and an SPCALG of "A" unless indicated otherwise.

^a UT: universal Time dates. ^b MJD: Modified Julian Date recorded at the start of the observations for individual exposures. ^c Science spectrum assigned SPCALF (see Note below) = 0. ^d Science spectrum calibrated with the narrow-slit standard star spectrum from exposure 1 and hence assigned SPCALG (see Note below) = B. ^e Science spectrum likely had a calibration issue and hence was not used for further analysis (see Appendix for details). ^f Science spectrum assigned DQF (see Note below) = U.

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2.2. Lijiang Telescope

3.1. Gemini Spectral Reduction

3.2. LJT Spectral Reduction

3.3. Comparison between Gemini and LJT Spectra

Gemini spectra from 33 epochs and LJT spectra from 69 epochs provided 102 epochs of Mrk 142 spectral observations overlapping with the Swift and LCO+Zowada+Liverpool photometric campaigns. A mean spectrum allows us to visualize spectral features with a high signal-to-noise ratio (S/N) from the combined observations, while an rms spectrum signifies the variability in the spectral features. Figure 2 displays the mean and rms of the Gemini (top) and LJT (bottom) spectra. The higher-resolution Gemini mean spectrum shows sharper emission-line profiles (Hβ, [O iii], and He i) as compared to the LJT mean. At lower resolution, LJT spectra are affected by instrumental broadening, which results in the narrow emission lines, e.g., [O iii], appearing broader than in the Gemini mean. The instrumental broadening effect also blurs the Fe ii emission (shaded in faint blue) and the coronal lines (high-ionization forbidden transitions shaded in brown) in the LJT mean spectrum. In contrast to the Gemini mean, the Fe ii features at ∼4925 Å and ∼5030 Å in the LJT mean appear blended with the Hβ wings on the longer-wavelength (red) side and [O iii] λ5008, respectively. The rms of the Gemini spectra shows a noisy region blueward of 4750 Å, likely dominated by calibration noise. It is worth noting, however, that the finer wavelength sampling of the Gemini spectra (owing to the narrow-slit observations) makes that region appear even noisier. On the other hand, the region toward the blue end of the LJT rms spectrum shows clear evidence of variability in the He ii λ4687 line although it is heavily contaminated with Fe ii in the surrounding region. Variability in Hβ is revealed by both the Gemini and the LJT rms spectra. Although no variability in He i is evident from the Gemini rms, the LJT rms shows a weak signature of variability in broad He i. A very low, broad wave appears from ∼5250 to ∼5450 Å and from ∼5650 to ∼5950 Å in the LJT rms spectrum, likely resulting from calibration. The GMOS chip-gap region in the Gemini spectrum extends from ∼5350 to ∼5410 Å, which also appears as a low bump in the rms spectrum.

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To measure the Hβ and He i emission lines in the calibrated spectra, we first corrected any discrepancies in the calibrations of the Gemini and LJT spectra, independently with PrepSpec, and then modeled their spectral features with Sherpa. For PrepSpec modeling of Gemini spectra, we used the spectral region from ∼4430 to ∼6300 Å. For LJT spectra, we kept the spectral region from ∼3390 to ∼6300 Å.

4.1.  PrepSpec Modeling

We independently modeled the 64 narrow-slit Gemini spectra and the 69 LJT spectra with PrepSpec ¹⁴ (developer: K. Horne) to correct for any relative deviations in the calibrated wavelength and flux scales. PrepSpec models spectra by fitting the continuum and emission lines with a composite model through an iterative process. We included the following model components for fitting the Mrk 142 spectra: (1) [A]verage spectrum (specified by "A")—mean of the input spectra; (2) [C]ontinuum—variations in the continuum emission from the accretion disk modeled as a polynomial defined by $\mathrm{log}\lambda$ with time-dependent coefficients; (3) [W]avelength jitter—inter-spectra shifts in the wavelength scales; (4) [F]lux jitter—time-dependent photometric corrections to minimize the scatter of narrow emission-line fluxes relative to their median; and (4) [B]road-line variations—variability in the broad emission-line features. Modeling emission lines in PrepSpec takes into account the velocity window half-widths of the broad as well as the narrow lines, whose initial values were set to 3000 km s⁻¹ and 500 km s⁻¹, respectively. We set the broad Hβ λ4861 and He i λ5877 as variable lines for Gemini spectra, and Hγ λ4342, He ii λ4687, Hβ, and He i λ5877 as variable for LJT spectra. The software uses the I Zwicky 1 (I Zw 1) template model (Véron-Cetty et al. 2001) to fit Fe ii emission in the mean spectrum. PrepSpec is not designed to handle gaps in spectra or extremely large flux values, e.g., from cosmic-ray hits. Therefore, chip gaps and artifacts from cosmic-ray correction or sky subtraction in the Gemini spectra were replaced by median or simulated data (see Section 3.1.3 for details) during spectral reduction.

In the PrepSpec modeling stage, we first corrected the Gemini and LJT spectra for pixel shifts relative to the [O iii] λ5008 line and then modeled the spectra with a composite model. We observed small pixel shifts (<6 pixels) while aligning the spectra along the wavelength axis. The model components were jointly fit starting with a single component and then adding components up to the ACWFB composite model for both the Gemini and the LJT spectra. PrepSpec determines the best-fitting model by accessing the Bayesian information criterion and reduced χ² (${\chi }_{\nu }^{2}$, where ν stands for degrees of freedom) statistics. The goal of the fitting process is to use the fewest possible parameters to describe the data while penalizing the model for the number of parameters used. A good model yields ${\chi }_{\nu }^{2}\sim 1$. Figure 3 displays the final model (dark blue curve) passing through the black mean spectrum (panel (a)) and the model (dark gray curve) to the residual rms (rmsx) spectrum (panel (b)) for the 64 narrow-slit Gemini spectra. The rms spectrum shows that the spectra are noisier at the bluer end.

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Figure 4 shows the final model (panel (a)) along with the residuals (in the units of σ; panel (b)) in grayscale for the Gemini spectra. The best-fit model yielded a ${\chi }_{\nu }^{2}$ value of 0.782, which indicates overfitting of the data, possibly indicating inaccurate error bars larger than the scatter in the data. The dark regions in the model highlight the prominent emission-line features of Hβ λ4861 and [O iii] λλ4960, 5008. The weak fluctuations blueward of ∼4700 Å indicate more noise in that region as compared to the red end of the spectra. The residuals in grayscale display horizontal wiggles that are strongly evident in some spectra. We noted that the wiggles appear in the spectral regions replaced by simulated data to correct for residual features either from cosmic-ray correction or sky subtraction. The replacement with simulated data may have resulted in a lower performance of the model in those regions. Another probable reason for the wiggles is the use of a higher-order spline during flat-fielding in the spectral reduction process (refer Section 3.1.3 for details). However, we visually inspected all spectra processed through PrepSpec and observed no anomalous behavior in the regions with wiggles. Therefore, the spectra were considered valid for further analysis.

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PrepSpec modeling of LJT spectra yielded nearly even residuals with a ${\chi }_{\nu }^{2}$ value of 0.791. The region redward of 6300 Å in LJT spectra comprises several blended narrow-line features, which resulted in a suboptimal performance of the PrepSpec model. Therefore, we excluded the red side of the LJT spectra (λ > 6300 Å) during PrepSpec processing.

4.2. Spectral Modeling in Sherpa

We modeled the continuum and emission lines in the Gemini and LJT spectra in Sherpa ¹⁵ (Freeman et al. 2001; Burke et al. 2018) v4.10.0 with a Python wrapper script. We first corrected the Gemini and LJT spectra for Galactic reddening using E(B − V) = 0.015 (Schlafly & Finkbeiner 2011). Averaging the two narrow-slit Gemini exposures from every night into a single spectrum per epoch (with exceptions for spectra from epochs 11, 25, and 28, where we only used single exposures) yielded a total of 33 Gemini spectra. Together with the 69 LJT spectra, we modeled a total of 102 Mrk 142 spectra.

We developed a composite model with the goal of performing a clean extraction of the Hβ and He i emission lines from the Gemini and LJT spectra. We included a power-law fit to the continuum, three Gaussians to model each of the Hβ, He i, and He ii emission lines, and a single Gaussian for each of the [O iii] doublet lines. We adopted the I Zw 1 template model from Boroson & Green (1992) as a pseudo-continuum to trace the Fe ii emission-line features. We also experimented with the Fe ii template from Véron-Cetty et al. (2001). However, it failed to suitably trace the sharp Fe ii features in Mrk 142. With the Boroson & Green (1992) Fe ii template model, the fits yielded lower (${{\chi }_{\nu }}^{2}$) values than with the Véron-Cetty et al. (2001) template. Following the procedure in Hu et al. (2015), we added single Gaussian profiles for each of the six coronal lines (Fe vii λ5160, Fe vi λ5177, Ca v λ5311, Fe vii λ5278, Fe vii λ5722, and Fe vii λ6088; see Figure 2). In addition, we included the host-galaxy template with 11 Gyr at z = 0.05 from the 2013 updated version of Bruzual & Charlot (2003) galaxy templates. The host-galaxy template, affecting the redder part of the spectrum more than the bluer, contributed greatly in producing a good fit to the He i emission-line region. The fit in the Hβ region was less sensitive to host-galaxy emission. We referred to the Vanden Berk et al. (2001) rest wavelengths for setting the positions of all emission lines.

4.2.1. Gemini Spectral Analysis

Our goal of spectral fitting was to accurately estimate the Hβ, [O iii], and He i profiles in the Gemini spectra. We aimed at finding a robust and flexible set of parameters that fit the structure in the spectra over all epochs. Figure 5 shows the composite model fit to a single-epoch Gemini spectrum.

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We describe the fitting process as follows. The Gaussian used for each of the [O iii] doublet lines traces the systemic narrow-line emission peaks. While fitting the Gemini spectra, the position, FWHM, and flux of the [O iii] λ5008 emission line were freed. However, we fixed the position of the [O iii] λ4960 line relative to the [O iii] λ5008 line and the flux in the [O iii] λ4960 line to a factor of 1/3 compared to the [O iii] λ5008 flux. We chose Gaussians over Lorentzians to appropriately trace the narrower wings of the [O iii] lines. We fixed the positions of the narrow components of Hβ, He i, and He ii relative to the position of the [O iii] λ5008 line, and their widths equal to the [O iii] λ5008 FWHM. Spectral fitting in Sherpa takes into account the scaling of the FWHM for a given line relative to the calibrator line, which is the [O iii] λ5008 line for this work. The position and flux parameters of the two broad components of both Hβ and He i were freed. The width of only one of the Hβ Gaussians was allowed to vary while the second Gaussian was fixed at twice the width of the first. On the other hand, the widths of the He i broad components were fixed at factors of 1 and 6 of the FWHM of the flexible, broad Hβ component. We determined the above FWHM ratios for the broad Hβ and He i emission lines from the mean spectrum. The insets in Figure 5 show a closer view of the two Regions of Interest—Hβ and He i. A single broad component of He ii with position fixed relative to the flexible, broad Hβ component and width equal to the FWHM of the same component proved insufficient to trace the broader emission around ∼4650 Å, indicating a plausible blueshifted broad component of He ii. Adding another blueshifted Gaussian 1.5 times the width of the flexible, broad Hβ component with flux equal to that of the first broad He ii component significantly improved the fit in that region. Table 3 lists the emission-line parameters along with their settings as used during spectral fitting.

Table 3. Emission-line Fitting Parameters for Gemini and LJT Spectra

Line	Parameter	Fixed	Ratio Relative to the Fixed Line
		Relative to Line a	Gemini	LJT
	Position	⋯	⋯	⋯
[O iii] λ5008	FWHM	⋯	⋯	⋯
	Flux	⋯	⋯	⋯
	Position	[O iii] λ5008	0.990	0.990
[O iii] λ4960	FWHM	[O iii] λ5008	1.000	1.000
	Flux	[O iii] λ5008	0.333	0.333
	Position	[O iii] λ5008	0.971	0.971
Narrow Hβ λ4861	FWHM	[O iii] λ5008	1.000	1.000
	Flux	[O iii] λ5008	⋯	0.293
	Position	⋯	⋯	⋯
Narrower broad Hβ λ4861	FWHM	⋯	⋯	⋯
	Flux	⋯	⋯	⋯
	Position	⋯	⋯	⋯
Broader broad Hβ λ4861	FWHM	Narrower broad Hβ λ4861	2.000	2.500
	Flux	⋯	⋯	⋯
	Position	[O iii] λ5008	1.174	1.174
Narrow He i λ5877	FWHM	[O iii] λ5008	1.000	1.000
	Flux	[O iii] λ5008	⋯	0.034
	Position	⋯	⋯	⋯
Narrower broad He i λ5877	FWHM	Narrower broad Hβ λ4861	1.200	1.000
	Flux	⋯	⋯	⋯
	Position	⋯	⋯	⋯
Broader broad He i λ5877	FWHM	Narrower broad Hβ λ4861	6.000	6.000
	Flux	⋯	⋯	⋯
	Position	[O iii] λ5008	0.936	0.936
Narrow He ii λ4687	FWHM	[O iii] λ5008	1.000	1.000
	Flux	⋯	⋯	⋯
	Position	Narrower broad Hβ λ4861	0.964	0.964
Narrower broad He ii λ4687	FWHM	Narrower broad Hβ λ4861	1.000	1.000
	Flux	⋯	⋯	⋯
	Position	Narrower broad Hβ λ4861	0.956	0.956
Blueshifted broad He ii λ4687	FWHM	Narrower broad Hβ λ4861	1.500	1.500
	Flux	Narrower broad He ii λ4687	1.000	1.000

Note.

^a Parameter settings with no data indicate that the parameter was kept flexible during spectral fitting.

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We followed the Fe ii template fitting procedure described in Hu et al. (2015), where the Fe ii emission is defined by a convolution of the Boroson & Green (1992) template with a Gaussian. We applied the Gaussian as a 1D point-spread function with a fixed FWHM, and the amplitude of the convolved Fe ii model was set as a flexible parameter while fitting. Although the Fe ii model successfully traces the sharp Fe ii features in most parts of the spectrum, it performs suboptimally near the Fe ii emission at the red wing of the [O iii] λ5008 line, thus resulting in larger residuals in that region. Further, the model overestimates the emission between the two [O iii] lines due to the broader wing of Fe ii from the template model.

Modeling individual coronal lines in the spectra considerably improved the fit in the Fe ii emission region from ∼5150 to ∼5350 Å. In this region, the Fe coronal lines appeared to be slightly redshifted (≤0.003) with respect to their rest wavelengths. We set the coronal-line widths to 1.5 times the [O iii] λ5008 line width and their flux values to specific fractions of the [O iii] λ5008 flux, as determined from the fit to the Gemini mean spectrum.

From spectral modeling, we derived, at each epoch, the total FWHM and flux values of the Hβ, He i, and [O iii] lines. We measured the FWHM of the broad and total (including both the broad and the narrow components) Hβ and He i lines empirically by subtracting all other model components from the spectra including the narrow lines. To calculate the contribution from the broad-line and total (again, including both the broad- and the narrow-line) flux in the Hβ and He i emission profiles, we simply added the contribution from each of their components. Tables 4–6 provide emission-line measurements for the Gemini spectra from 33 epochs. For epoch 11, the model failed to constrain the broad Hβ emission as the region blueward of the Hβ line appeared noisier compared to the other epochs. We therefore excluded epoch 11 from further analysis. Also, due to improper flux calibration at the location of the Hβ line in epoch 25, the line appeared unusually broader and brighter than at the other epochs. We therefore excluded the spectrum from epoch 25 as well.

Table 4. [O iii] λ5008 Emission-line Measurements for Gemini Spectra

Epoch	Position[O iii]λ5008	FWHM[O iii]λ5008	F[O iii]λ5008	${\chi }_{\nu }^{2}$ a
	(Å)	(km s−1)	(10−15 erg s−1 cm−2)
1	5008.21 ± 0.04	313 ± 5	15.7 ± 0.2	1.07
2	5008.19 ± 0.05	318 ± 9	15.8 ± 0.3	1.06
3	5008.12 ± 0.04	325 ± 6	16.1 ± 0.2	1.23
4	5008.19 ± 0.04	303 ± 9	15.7 ± 0.3	1.21
5	5008.18 ± 0.05	320 ± 5	16.2 ± 0.3	0.99
6	5008.20 ± 0.04	325 ± 3	16.1 ± 0.2	1.08
7	5008.23 ± 0.03	311 ± 4	15.5 ± 0.2	1.18
8	5008.15 ± 0.04	322 ± 5	16.1 ± 0.2	1.22
9	5008.15 ± 0.05	336 ± 7	16.1 ± 0.3	0.97
10	5008.11 ± 0.04	326 ± 5	16.0 ± 0.3	1.04
11	5008.11 ± 0.07	317 ± 9	15.6 ± 0.5	0.99
12	5008.16 ± 0.06	333 ± 10	16.3 ± 0.4	1.08
13	5008.19 ± 0.04	304 ± 6	15.6 ± 0.3	1.12
14	5008.16 ± 0.04	317 ± 5	15.8 ± 0.2	1.24
15	5008.20 ± 0.04	319 ± 4	15.9 ± 0.2	1.20
16	5008.19 ± 0.04	311 ± 5	15.6 ± 0.2	1.26
17	5008.22 ± 0.04	315 ± 4	16.0 ± 0.2	1.27
18	5008.14 ± 0.04	338 ± 6	16.1 ± 0.2	1.33
19	5008.22 ± 0.04	312 ± 2	15.8 ± 0.2	1.10
20	5008.21 ± 0.03	292 ± 6	15.5 ± 0.2	1.17
21	5008.23 ± 0.04	313 ± 6	16.0 ± 0.2	1.28
22	5008.18 ± 0.03	308 ± 6	15.8 ± 0.2	1.21
23	5008.20 ± 0.03	304 ± 4	15.6 ± 0.2	1.24
24	5008.15 ± 0.04	320 ± 3	15.8 ± 0.2	1.18
25	5008.20 ± 0.05	307 ± 5	15.9 ± 0.3	1.11
26	5008.20 ± 0.05	310 ± 7	15.9 ± 0.3	1.19
27	5008.21 ± 0.04	302 ± 5	15.5 ± 0.2	1.24
28	5008.34 ± 0.05	301 ± 2	15.3 ± 0.3	1.07
29	5008.18 ± 0.04	323 ± 7	16.1 ± 0.3	1.19
30	5008.24 ± 0.04	321 ± 4	15.9 ± 0.2	1.35
31	5008.27 ± 0.03	306 ± 5	15.7 ± 0.2	1.16
32	5008.25 ± 0.04	321 ± 6	16.0 ± 0.3	1.10
33	5008.22 ± 0.05	328 ± 4	16.4 ± 0.2	1.05

Note.

^a Reduced χ², ${\chi }_{\nu }^{2}={\chi }^{2}/\nu$, where ν indicates 3897 degrees of freedom, gives the model statistic for individual epochs.

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Table 5. Hβ λ4861 Emission-line Measurements for Gemini Spectra

Epoch	FWHMHβ,b	FHβ,b	FWHMHβ,n	FHβ,n	FWHMHβ,t	FHβ,t
	(km s−1)	(10−15 erg s−1 cm−2)	(km s−1)	(10−15 erg s−1 cm−2)	(km s−1)	(10−15 erg s−1 cm−2)
1	1777 ± 72	112.2 ± 2.4	312 ± 5	5.3 ± 0.4	1445 ± 52	117.5 ± 2.4
2	1681 ± 109	106.3 ± 4.3	317 ± 8	5.5 ± 0.6	1324 ± 83	111.8 ± 4.3
3	1703 ± 69	115.8 ± 5.1	325 ± 5	5.1 ± 0.4	1412 ± 73	120.9 ± 5.1
4	1745 ± 83	110.5 ± 2.7	303 ± 9	4.5 ± 0.4	1478 ± 67	115.0 ± 2.7
5	1555 ± 80	107.5 ± 3.4	319 ± 4	3.1 ± 0.6	1466 ± 96	110.6 ± 3.4
6	1830 ± 77	109.3 ± 3.7	324 ± 3	5.1 ± 0.5	1524 ± 80	114.4 ± 3.7
7	1797 ± 69	112.2 ± 2.2	310 ± 3	4.5 ± 0.4	1525 ± 56	116.7 ± 2.2
8	1697 ± 62	106.5 ± 2.3	321 ± 4	3.5 ± 0.4	1447 ± 62	110.0 ± 2.4
9	1499 ± 83	100.2 ± 3.1	336 ± 6	5.1 ± 0.6	1379 ± 58	105.4 ± 3.2
10	1593 ± 77	103.4 ± 2.7	326 ± 4	5.0 ± 0.4	1328 ± 55	108.4 ± 2.8
11 a	1637 ± 132	104.3 ± 3.3	317 ± 9	5.7 ± 0.8	1235 ± 165	110.1 ± 3.4
12	1732 ± 120	101.5 ± 5.8	332 ± 10	5.9 ± 0.7	1322 ± 81	107.3 ± 5.8
13	1628 ± 88	101.3 ± 2.5	303 ± 6	3.7 ± 0.5	1354 ± 77	105.0 ± 2.5
14	1707 ± 69	109.1 ± 2.6	316 ± 5	4.2 ± 0.4	1384 ± 56	113.3 ± 2.7
15	1672 ± 104	108.8 ± 2.7	319 ± 3	4.9 ± 0.4	1341 ± 30	113.7 ± 2.7
16	1780 ± 76	103.2 ± 2.3	311 ± 5	4.4 ± 0.4	1412 ± 73	107.6 ± 2.3
17	1623 ± 65	108.4 ± 3.0	315 ± 4	3.8 ± 0.4	1402 ± 60	112.2 ± 3.0
18	1712 ± 72	105.6 ± 2.4	337 ± 5	4.6 ± 0.5	1477 ± 64	110.2 ± 2.4
19	1579 ± 91	106.1 ± 4.2	311 ± 1	6.1 ± 0.5	1348 ± 64	112.2 ± 4.2
20	1558 ± 62	115.2 ± 2.1	291 ± 5	3.4 ± 0.4	1473 ± 42	118.7 ± 2.1
21	1604 ± 43	112.6 ± 2.1	312 ± 5	3.6 ± 0.4	1446 ± 71	116.2 ± 2.1
22	1698 ± 62	109.3 ± 2.8	307 ± 5	4.4 ± 0.4	1442 ± 55	113.7 ± 2.8
23	1590 ± 57	108.3 ± 2.1	304 ± 3	3.7 ± 0.4	1416 ± 52	112.0 ± 2.2
24	1668 ± 77	110.9 ± 2.7	319 ± 3	4.3 ± 0.5	1391 ± 54	115.2 ± 2.7
25 b	1672 ± 73	140.4 ± 3.6	307 ± 5	5.9 ± 0.7	1603 ± 83	146.3 ± 3.7
26	1655 ± 95	107.0 ± 2.6	309 ± 7	4.9 ± 0.4	1297 ± 50	111.9 ± 2.6
27	1649 ± 48	103.4 ± 3.9	301 ± 5	4.6 ± 0.4	1356 ± 59	108.0 ± 3.9
28	1678 ± 96	102.6 ± 3.2	300 ± 2	3.9 ± 0.6	1459 ± 148	106.5 ± 3.3
29	1713 ± 76	94.9 ± 3.1	322 ± 7	4.3 ± 0.4	1410 ± 66	99.2 ± 3.1
30	1754 ± 96	102.7 ± 3.7	321 ± 4	5.5 ± 0.5	1395 ± 92	108.2 ± 3.8
31	1816 ± 81	109.4 ± 4.3	306 ± 5	6.1 ± 0.4	1489 ± 96	115.5 ± 4.3
32	1682 ± 79	109.6 ± 2.3	321 ± 5	4.9 ± 0.4	1423 ± 47	114.5 ± 2.4
33	1699 ± 58	110.0 ± 5.0	328 ± 4	3.8 ± 0.5	1515 ± 78	113.8 ± 5.0

Notes. The second and the third columns providing the FWHM and flux values, respectively, for the broad ("b") Hβ component include contributions from both the broad Gaussians defined for the line. The FWHM of the narrow ("n") Hβ is equal to the FWHM of the [O iii] λ5008 (see Table 4, third column). The total ("t") FWHM and flux include contributions from both the broad and the narrow components (t = b + n).

^a Because the noisy region blueward of the Hβ emission line was unable to well constrain the broad, blue wing of Hβ, this epoch was excluded from further analysis. ^b Due to a calibration issue at the location of the Hβ emission line, the Hβ profile appeared unusually broader and brighter than in other spectra. Therefore, this epoch was excluded from further analysis.

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Table 6. He i λ5877 Emission-line Measurements for Gemini Spectra

Epoch	FWHMHe i,b	FHe i,b	FWHMHe i,n	FHe i,n	FWHMHe i,t	FHe i,t
	(km s−1)	(10−15 erg s−1 cm−2)	(km s−1)	(10−15 erg s−1 cm−2)	(km s−1)	(10−15 erg s−1 cm−2)
1	47 ± 37	34.4 ± 0.8	312 ± 5	0.7 ± 0.1	47 ± 95	35.1 ± 0.8
2	53 ± 37	33.4 ± 1.0	317 ± 8	0.6 ± 0.2	53 ± 36	34.0 ± 1.0
3	90 ± 44	41.3 ± 0.9	325 ± 5	0.7 ± 0.1	90 ± 41	42.0 ± 0.9
4	36 ± 25	36.0 ± 0.9	303 ± 9	0.8 ± 0.1	36 ± 20	36.8 ± 0.9
5	335 ± 70	35.2 ± 1.1	319 ± 4	0.3 ± 0.2	335 ± 71	35.5 ± 1.1
6	46 ± 36	35.1 ± 0.9	324 ± 3	0.6 ± 0.1	46 ± 35	35.7 ± 0.9
7	136 ± 170	39.7 ± 0.8	310 ± 3	0.6 ± 0.1	1962 ± 312	40.3 ± 0.8
8	49 ± 65	39.1 ± 0.7	321 ± 4	0.5 ± 0.1	49 ± 59	39.6 ± 0.7
9	34 ± 43	33.1 ± 0.9	336 ± 6	0.7 ± 0.2	34 ± 46	33.7 ± 0.9
10	92 ± 53	36.3 ± 0.8	326 ± 4	0.7 ± 0.2	92 ± 52	37.0 ± 0.8
11 a	153 ± 39	36.6 ± 1.4	317 ± 9	0.4 ± 0.2	153 ± 38	37.1 ± 1.4
12	92 ± 51	31.4 ± 1.3	332 ± 10	0.5 ± 0.2	92 ± 52	32.0 ± 1.3
13	1419 ± 90	35.9 ± 0.9	303 ± 6	0.0 ± 0.2	1419 ± 108	35.9 ± 0.9
14	83 ± 51	41.0 ± 0.8	316 ± 5	0.8 ± 0.1	83 ± 55	41.8 ± 0.8
15	66 ± 41	38.4 ± 0.8	319 ± 3	0.5 ± 0.1	66 ± 41	38.9 ± 0.8
16	152 ± 225	38.8 ± 0.8	311 ± 5	0.6 ± 0.1	1758 ± 497	39.4 ± 0.8
17	1825 ± 303	38.8 ± 0.9	315 ± 4	0.3 ± 0.1	1528 ± 415	39.1 ± 0.9
18	37 ± 32	37.2 ± 0.8	337 ± 5	0.4 ± 0.1	37 ± 181	37.6 ± 0.9
19	1828 ± 42	35.4 ± 0.9	311 ± 1	0.7 ± 0.1	1806 ± 41	36.1 ± 0.9
20	1862 ± 357	42.0 ± 0.7	291 ± 5	0.4 ± 0.1	1829 ± 631	42.4 ± 0.7
21	1798 ± 399	38.4 ± 0.8	312 ± 5	0.9 ± 0.1	1651 ± 647	39.3 ± 0.8
22	1870 ± 654	41.9 ± 0.8	307 ± 5	0.4 ± 0.1	1870 ± 682	42.2 ± 0.8
23	38 ± 189	40.2 ± 0.8	304 ± 3	0.5 ± 0.1	1873 ± 336	40.7 ± 0.8
24	54 ± 84	41.1 ± 0.9	319 ± 3	0.5 ± 0.1	54 ± 132	41.7 ± 0.9
25 b	137 ± 43	38.3 ± 1.3	307 ± 5	0.6 ± 0.2	137 ± 45	38.9 ± 1.3
26	61 ± 53	36.9 ± 0.8	309 ± 7	0.5 ± 0.1	61 ± 110	37.4 ± 0.8
27	114 ± 180	38.7 ± 0.9	301 ± 5	0.5 ± 0.1	1935 ± 389	39.3 ± 0.9
28	81 ± 60	55.6 ± 1.1	300 ± 2	0.1 ± 0.2	81 ± 52	55.7 ± 1.1
29	181 ± 100	36.0 ± 0.8	322 ± 7	0.4 ± 0.1	181 ± 96	36.4 ± 0.8
30	34 ± 86	40.0 ± 1.0	321 ± 4	0.5 ± 0.1	34 ± 125	40.5 ± 1.0
31	66 ± 268	44.6 ± 0.9	306 ± 5	0.9 ± 0.1	66 ± 627	45.5 ± 0.9
32	294 ± 50	41.2 ± 0.9	321 ± 5	0.9 ± 0.1	1631 ± 160	42.1 ± 0.9
33	1537 ± 161	35.3 ± 0.9	328 ± 4	0.3 ± 0.1	1528 ± 267	35.6 ± 0.9

Notes. The second and the third columns providing the FWHM and flux values, respectively, for the broad ("b") He i component include contributions from both the broad Gaussians defined for the line. The FWHM of the narrow ("n") He i is equal to the FWHM of the [O iii] λ5008 (see Table 4, third column). The total ("t") FWHM and flux include contributions from both the broad and the narrow components (t = b + n).

^a Excluded from further analysis. See corresponding note in Table 5. ^b Excluded from further analysis. See corresponding note in Table 5.

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4.2.2. LJT Spectral Analysis

We fit the 69 LJT spectra with the same goal of modeling the Hβ, [O iii], and He i lines accurately. Figure 6 shows the fit to a single-epoch LJT spectrum.

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We adopted the same model as for the Gemini spectra with small modifications to the ratios of certain fixed parameters. We determined the flux ratios for the coronal lines relative to the [O iii] λ5008 line flux from the fit to the mean LJT spectrum. The width of the fixed broad Hβ Gaussian was fixed at a factor of 2.5 (instead of 2 for the Gemini spectra). A factor of 2 for this second Hβ Gaussian in LJT spectra was insufficient to trace the broad wing of Hβ, which also affected the fit to the blended Fe ii feature at ∼4923 Å. Therefore, a broader Hβ component was required to generate a good fit in that region. This indicates an interplay between the broad Hβ and Fe ii line emission in the fitting process. Similarly, the [O iii] λ5008 appears to be blended with the Fe ii emission feature at its red wing. This is caused by the instrumental broadening in LJT spectra that further resulted in wider [O iii] FWHM measurements than typically expected for [O iii] in NLS1 objects. To contain the effect of the "broader" [O iii] FWHM measurements on the Hβ and He i line measurements, we fixed the narrow-line flux ratios of Hβ to [O iii] λ5008 and He i to [O iii] λ5008 from the Gemini spectral measurements (see Table 3). Tables 7–9 provide emission-line measurements for the LJT spectra from 69 epochs.

Table 7. [O iii] λ5008 Emission-line Measurements for LJT Spectra

Epoch	Position[O iii]λ5008	FWHM[O iii]λ5008	F[O iii]λ5008	${\chi }_{\nu }^{2}$ a
	(Å)	(km s−1)	(10−15 erg s−1 cm−2)
1	5007.25 ± 0.09	718 ± 9	16.6 ± 0.2	2.27
2	5007.22 ± 0.13	754 ± 22	17.5 ± 0.4	1.45
3	5007.25 ± 0.13	741 ± 13	17.2 ± 0.3	2.00
4	5007.40 ± 0.12	787 ± 19	17.8 ± 0.4	2.03
5	5007.33 ± 0.10	716 ± 18	16.1 ± 0.4	2.07
6	5007.43 ± 0.13	740 ± 21	16.4 ± 0.4	1.71
7	5007.44 ± 0.16	880 ± 6	19.6 ± 0.4	1.60
8	5007.46 ± 0.06	691 ± 13	16.9 ± 0.3	2.56
9	5007.42 ± 0.10	679 ± 19	17.1 ± 0.3	1.68
10	5007.51 ± 0.17	707 ± 27	17.4 ± 0.6	1.28
11	5007.43 ± 0.14	742 ± ⋯	17.6 ± 0.3	1.51
12	5007.26 ± 0.09	713 ± 10	16.7 ± 0.3	2.19
13	5007.41 ± 0.20	716 ± 27	17.2 ± 0.6	1.51
14	5007.49 ± 0.12	757 ± 13	16.8 ± 0.3	1.67
15	5007.57 ± 0.14	737 ± 22	16.8 ± 0.4	1.42
16	5007.53 ± 0.10	682 ± 16	17.4 ± 0.3	1.66
17	5007.44 ± 0.10	682 ± 2	15.7 ± 0.2	1.98
18	5007.46 ± 0.15	736 ± 27	16.3 ± 0.5	1.20
19	5007.65 ± 0.14	752 ± 15	16.6 ± 0.3	1.93
20	5007.45 ± 0.15	727 ± 28	17.2 ± 0.6	1.24
21	5007.53 ± 0.14	758 ± 17	17.1 ± 0.4	1.40
22	5007.67 ± 0.17	802 ± 16	17.1 ± 0.4	1.47
23	5007.16 ± 0.23	772 ± 26	17.7 ± 0.7	1.21
24	5007.56 ± 0.10	674 ± 17	16.5 ± 0.3	1.74
25	5007.57 ± 0.11	700 ± 26	16.9 ± 0.4	1.66
26	5007.55 ± 0.11	733 ± 14	17.1 ± 0.3	1.77
27	5007.45 ± 0.09	680 ± 4	16.8 ± 0.3	2.02
28	5007.66 ± 0.14	801 ± 6	16.9 ± 0.3	1.45
29	5007.48 ± 0.10	785 ± 16	18.6 ± 0.3	1.96
30	5007.60 ± 0.14	742 ± 22	17.7 ± 0.5	1.34
31	5007.46 ± 0.10	707 ± 11	16.1 ± 0.3	2.25
32	5007.38 ± 0.08	699 ± 5	16.3 ± 0.4	1.32
33	5007.48 ± 0.13	684 ± 17	16.5 ± 0.4	1.80
34	5007.52 ± 0.11	683 ± 17	17.1 ± 0.4	1.76
35	5007.38 ± 0.11	776 ± 15	16.8 ± 0.3	2.82
36	5007.39 ± 0.06	681 ± 2	16.5 ± 0.2	4.36
37	5007.44 ± 0.09	682 ± 0	16.5 ± 0.2	2.13
38	5007.66 ± 0.13	810 ± 9	17.3 ± 0.4	1.47
39	5007.65 ± 0.24	719 ± 49	17.2 ± 1.0	2.02
40	5007.63 ± 0.12	719 ± 16	16.9 ± 0.4	1.71
41	5007.56 ± 0.08	728 ± 9	16.9 ± 0.2	4.65
42	5007.61 ± 0.09	688 ± 2	16.9 ± 0.2	3.74
43	5007.41 ± 0.14	713 ± 27	17.2 ± 0.5	1.52
44	5007.48 ± 0.16	712 ± 45	17.4 ± 0.9	1.63
45	5007.51 ± 0.13	745 ± 18	18.3 ± 0.4	1.53
46	5007.47 ± 0.10	731 ± 14	16.8 ± 0.3	1.98
47	5007.57 ± 0.22	744 ± 36	16.5 ± 0.7	1.05
48	5007.60 ± 0.12	685 ± 26	16.1 ± 0.5	2.26
49	5008.33 ± 0.21	857 ± 30	18.8 ± 0.6	2.06
50	5007.51 ± 0.09	691 ± 31	17.1 ± 0.5	3.21
51	5007.76 ± 0.08	726 ± 11	16.7 ± 0.2	3.28
52	5007.64 ± 0.12	686 ± 31	16.1 ± 0.5	1.61
53	5007.44 ± 0.11	707 ± 19	17.1 ± 0.4	1.82
54	5007.64 ± 0.11	679 ± 15	16.6 ± 0.4	1.59
55 b	5007.50 ± 0.23	670 ± 26	14.5 ± 0.6	1.97
56	5007.40 ± 0.12	646 ± 31	15.8 ± 0.4	1.53
57	5007.39 ± 0.08	634 ± 1	16.1 ± 0.2	2.55
58	5007.55 ± 0.08	711 ± 8	17.4 ± 0.2	3.54
59	5007.62 ± 0.08	724 ± 12	17.7 ± 0.3	3.37
60	5007.57 ± 0.16	726 ± 21	17.5 ± 0.5	1.48
61	5007.39 ± 0.14	668 ± 27	17.2 ± 0.6	1.50
62	5007.60 ± 0.13	750 ± 14	18.6 ± 0.3	2.58
63	5007.68 ± 0.09	659 ± 14	16.4 ± 0.3	2.02
64	5007.32 ± 0.08	660 ± 11	16.4 ± 0.3	3.39
65	5007.70 ± 0.08	727 ± 12	17.4 ± 0.2	3.46
66	5007.55 ± 0.09	681 ± 12	17.1 ± 0.3	2.27
67	5007.63 ± 0.10	709 ± 14	17.0 ± 0.3	2.03
68	5007.70 ± 0.10	756 ± 3	17.4 ± 0.3	1.73
69	5007.59 ± 0.17	752 ± 25	17.3 ± 0.4	1.78

Notes.

^a Reduced χ², ${\chi }_{\nu }^{2}={\chi }^{2}/\nu$, where ν indicates 1071 degrees of freedom, gives the model statistic for individual epochs. ^b This spectrum appeared very noisy likely due to some disturbance in the field of view at the time of observation. Therefore, we excluded this epoch from further analysis.

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Table 8. Hβ λ4861 Emission-line Measurements for LJT Spectra

Epoch	FWHMHβ,b	FHβ,b	FWHMHβ,n	FHβ,n	FWHMHβ,t	FHβ,t
	(km s−1)	(10−15 erg s−1 cm−2)	(km s−1)	(10−15 erg s−1 cm−2)	(km s−1)	(10−15 erg s−1 cm−2)
1	1912 ± 52	83.5 ± 1.5	718 ± 9	4.85 ± 0.07	1660 ± 42	88.3 ± 1.5
2	1933 ± 73	82.7 ± 3.5	754 ± 22	5.13 ± 0.13	1702 ± 46	87.8 ± 3.5
3	1951 ± 38	83.3 ± 1.6	741 ± 13	5.03 ± 0.09	1748 ± 48	88.3 ± 1.6
4	1901 ± 52	84.9 ± 2.8	787 ± 19	5.22 ± 0.11	1700 ± 69	90.1 ± 2.8
5	1881 ± 46	80.3 ± 3.8	716 ± 18	4.72 ± 0.10	1706 ± 46	85.0 ± 3.8
6	1958 ± 85	82.2 ± 3.1	740 ± 21	4.80 ± 0.12	1708 ± 47	87.0 ± 3.1
7	2055 ± 86	82.6 ± 2.3	880 ± 6	5.74 ± 0.11	1750 ± 69	88.3 ± 2.3
8	1956 ± 54	81.3 ± 2.4	691 ± 13	4.95 ± 0.09	1804 ± 71	86.3 ± 2.4
9	1884 ± 63	78.3 ± 1.5	679 ± 19	5.02 ± 0.10	1618 ± 33	83.4 ± 1.5
10	1988 ± 85	85.2 ± 4.7	707 ± 27	5.10 ± 0.17	1742 ± 82	90.3 ± 4.7
11	1985 ± 102	78.2 ± 4.9	742 ± ⋯	5.17 ± 0.09	1647 ± 54	83.3 ± 4.9
12	1924 ± 44	82.1 ± 1.8	713 ± 10	4.90 ± 0.08	1703 ± 46	87.0 ± 1.8
13	1981 ± 87	84.8 ± 7.0	716 ± 27	5.03 ± 0.18	1848 ± 48	89.8 ± 7.0
14	2041 ± 64	80.2 ± 1.5	757 ± 13	4.93 ± 0.10	1779 ± 58	85.1 ± 1.5
15	2004 ± 57	78.5 ± 4.3	737 ± 22	4.94 ± 0.12	1684 ± 77	83.4 ± 4.3
16	2017 ± 83	82.3 ± 1.5	682 ± 16	5.11 ± 0.10	1630 ± 61	87.4 ± 1.5
17	1928 ± 64	81.8 ± 1.9	682 ± 2	4.61 ± 0.07	1702 ± 41	86.4 ± 1.9
18	1904 ± 79	82.9 ± 4.6	736 ± 27	4.77 ± 0.14	1678 ± 55	87.7 ± 4.6
19	2024 ± 63	83.0 ± 2.2	752 ± 15	4.87 ± 0.09	1782 ± 52	87.9 ± 2.2
20	1961 ± 91	81.3 ± 4.0	727 ± 28	5.05 ± 0.17	1657 ± 70	86.4 ± 4.0
21	1999 ± 68	77.6 ± 2.0	758 ± 17	5.02 ± 0.12	1696 ± 92	82.7 ± 2.0
22	1878 ± 92	76.6 ± 2.2	802 ± 16	5.01 ± 0.12	1685 ± 55	81.6 ± 2.2
23	1904 ± 60	77.1 ± 13.0	772 ± 26	5.18 ± 0.21	1755 ± 59	82.3 ± 13.0
24	1933 ± 44	77.7 ± 1.5	674 ± 17	4.83 ± 0.09	1653 ± 57	82.6 ± 1.5
25	1885 ± 73	76.8 ± 2.5	700 ± 26	4.96 ± 0.11	1647 ± 61	81.8 ± 2.5
26	2037 ± 49	78.9 ± 1.8	733 ± 14	5.02 ± 0.09	1816 ± 70	83.9 ± 1.8
27	1968 ± 76	79.7 ± 1.6	680 ± 4	4.92 ± 0.08	1735 ± 41	84.6 ± 1.6
28	1976 ± 77	76.7 ± 2.0	801 ± 6	4.94 ± 0.08	1764 ± 58	81.7 ± 2.0
29	1984 ± 45	78.0 ± 3.0	785 ± 16	5.46 ± 0.10	1742 ± 47	83.4 ± 3.0
30	1862 ± 89	75.4 ± 2.7	742 ± 22	5.18 ± 0.14	1698 ± 62	80.6 ± 2.7
31	2007 ± 39	80.2 ± 1.9	707 ± 11	4.71 ± 0.08	1744 ± 42	84.9 ± 1.9
32	2058 ± 96	81.3 ± 2.3	699 ± 5	4.77 ± 0.11	1741 ± 63	86.0 ± 2.3
33	1912 ± 56	82.9 ± 2.1	684 ± 17	4.84 ± 0.11	1688 ± 73	87.7 ± 2.1
34	1936 ± 39	84.7 ± 2.9	683 ± 17	5.00 ± 0.10	1726 ± 50	89.7 ± 2.9
35	1964 ± 29	81.9 ± 1.2	776 ± 15	4.91 ± 0.09	1730 ± 67	86.9 ± 1.2
36	1919 ± 32	84.6 ± 1.0	681 ± 2	4.85 ± 0.05	1702 ± 29	89.5 ± 1.0
37	1895 ± 76	85.5 ± 1.7	682 ± 0	4.82 ± 0.07	1654 ± 34	90.3 ± 1.7
38	1922 ± 72	84.5 ± 1.7	810 ± 9	5.08 ± 0.11	1708 ± 50	89.6 ± 1.7
39	1869 ± 69	85.1 ± 21.5	719 ± 49	5.05 ± 0.29	1655 ± 33	90.1 ± 21.5
40	1911 ± 50	87.1 ± 3.9	719 ± 16	4.94 ± 0.11	1670 ± 68	92.1 ± 3.9
41	1866 ± 45	88.7 ± 0.7	728 ± 9	4.96 ± 0.06	1641 ± 31	93.6 ± 0.7
42	1933 ± 47	87.3 ± 1.9	688 ± 2	4.96 ± 0.06	1682 ± 45	92.2 ± 1.9
43	1836 ± 74	91.0 ± 6.8	713 ± 27	5.03 ± 0.16	1700 ± 34	96.0 ± 6.8
44	1919 ± 58	87.2 ± 8.9	712 ± 45	5.10 ± 0.27	1686 ± 45	92.3 ± 8.9
45	1888 ± 66	86.5 ± 3.0	745 ± 18	5.36 ± 0.12	1676 ± 57	91.8 ± 3.0
46	1943 ± 46	85.2 ± 2.8	731 ± 14	4.94 ± 0.09	1663 ± 43	90.1 ± 2.8
47	1809 ± 133	80.0 ± 4.8	744 ± 36	4.85 ± 0.21	1606 ± 79	84.9 ± 4.8
48	1937 ± 54	82.2 ± 3.2	685 ± 26	4.71 ± 0.13	1700 ± 62	86.9 ± 3.2
49	2129 ± 115	80.4 ± 2.7	857 ± 30	5.51 ± 0.17	1702 ± 127	85.9 ± 2.7
50	2032 ± 39	87.9 ± 1.9	691 ± 31	5.02 ± 0.14	1773 ± 45	92.9 ± 1.9
51	1996 ± 36	85.7 ± 1.8	726 ± 11	4.89 ± 0.07	1749 ± 40	90.6 ± 1.8
52	1921 ± 51	81.7 ± 2.6	686 ± 31	4.73 ± 0.15	1665 ± 56	86.5 ± 2.6
53	1857 ± 43	81.6 ± 1.9	707 ± 19	5.00 ± 0.11	1667 ± 48	86.6 ± 1.9
54	1846 ± 71	80.3 ± 3.6	679 ± 15	4.87 ± 0.11	1627 ± 53	85.1 ± 3.6
55 a	2051 ± 101	98.8 ± 3.2	670 ± 26	4.24 ± 0.17	1837 ± 91	103.0 ± 3.2
56	1900 ± 60	84.4 ± 3.3	646 ± 31	4.64 ± 0.12	1657 ± 35	89.1 ± 3.3
57	1855 ± 32	84.3 ± 1.5	634 ± 1	4.71 ± 0.06	1673 ± 36	89.0 ± 1.5
58	1873 ± 45	85.1 ± 1.1	711 ± 8	5.11 ± 0.06	1648 ± 35	90.3 ± 1.1
59	1880 ± 33	83.1 ± 1.2	724 ± 12	5.18 ± 0.07	1683 ± 33	88.3 ± 1.2
60	1831 ± 79	82.8 ± 4.3	726 ± 21	5.13 ± 0.14	1674 ± 49	87.9 ± 4.3
61	1802 ± 71	79.5 ± 7.3	668 ± 27	5.04 ± 0.17	1536 ± 60	84.5 ± 7.3
62	1943 ± 57	78.1 ± 2.9	750 ± 14	5.44 ± 0.09	1724 ± 43	83.6 ± 2.9
63	1934 ± 51	79.9 ± 2.3	659 ± 14	4.81 ± 0.09	1639 ± 39	84.7 ± 2.3
64	1852 ± 36	77.7 ± 1.7	660 ± 11	4.82 ± 0.07	1653 ± 37	82.5 ± 1.7
65	1893 ± 33	81.0 ± 1.1	727 ± 12	5.11 ± 0.07	1682 ± 46	86.2 ± 1.1
66	1930 ± 47	82.6 ± 1.5	681 ± 12	5.01 ± 0.09	1706 ± 32	87.6 ± 1.5
67	1877 ± 35	83.7 ± 2.2	709 ± 14	4.98 ± 0.09	1695 ± 56	88.7 ± 2.2
68	1838 ± 47	81.5 ± 2.4	756 ± 3	5.11 ± 0.09	1651 ± 43	86.6 ± 2.4
69	1893 ± 67	81.3 ± 3.0	752 ± 25	5.05 ± 0.11	1696 ± 35	86.3 ± 3.0

Notes. The second and the third columns providing the FWHM and flux values, respectively, for the broad ("b") Hβ component include contributions from both the broad Gaussians defined for the line. The FWHM of the narrow ("n") Hβ is equal to the FWHM of the [O iii] λ5008 (see Table 7, third column). The total ("t") FWHM and flux include contributions from both the broad and the narrow components (t = b + n).

^a Excluded from further analysis. See note a in Table 7.

A machine-readable version of the table is available.

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Table 9. He i λ5877 Emission-line Measurements for LJT Spectra

Epoch	FWHMHe i,b	FHe i,b	FWHMHe i,n	FHe i,n	FWHMHe i,t	FHe i,t
	(km s−1)	(10−15 erg s−1 cm−2)	(km s−1)	(10−15 erg s−1 cm−2)	(km s−1)	(10−15 erg s−1 cm−2)
1	3321 ± 340	56.5 ± 1.3	718 ± 9	0.56 ± 0.01	3233 ± 310	57.0 ± 1.3
2	4215 ± 487	54.0 ± 1.9	754 ± 22	0.59 ± 0.01	3719 ± 432	54.6 ± 1.9
3	2677 ± 393	53.4 ± 1.5	741 ± 13	0.58 ± 0.01	2640 ± 335	54.0 ± 1.5
4	3526 ± 460	51.2 ± 1.6	787 ± 19	0.61 ± 0.01	3472 ± 439	51.8 ± 1.6
5	3672 ± 430	50.7 ± 1.5	716 ± 18	0.55 ± 0.01	2955 ± 380	51.2 ± 1.5
6	4021 ± 559	53.0 ± 1.7	740 ± 21	0.56 ± 0.01	3358 ± 509	53.6 ± 1.7
7	2800 ± 413	56.6 ± 1.9	880 ± 6	0.67 ± 0.01	2652 ± 370	57.3 ± 1.9
8	2393 ± 429	59.9 ± 1.8	691 ± 13	0.57 ± 0.01	2390 ± 356	60.5 ± 1.8
9	3007 ± 395	51.5 ± 1.5	679 ± 19	0.58 ± 0.01	3002 ± 377	52.1 ± 1.5
10	3440 ± 567	57.7 ± 2.4	707 ± 27	0.59 ± 0.02	3384 ± 534	58.3 ± 2.4
11	3742 ± 464	50.2 ± 2.0	742 ± ⋯	0.60 ± 0.01	3336 ± 414	50.8 ± 2.0
12	3707 ± 394	52.6 ± 1.3	713 ± 10	0.57 ± 0.01	3234 ± 349	53.1 ± 1.3
13	2031 ± 523	58.0 ± 3.7	716 ± 27	0.58 ± 0.02	2020 ± 440	58.6 ± 3.7
14	4636 ± 499	54.8 ± 1.7	757 ± 13	0.57 ± 0.01	3448 ± 477	55.3 ± 1.7
15	3570 ± 482	51.3 ± 2.1	737 ± 22	0.57 ± 0.01	3392 ± 451	51.9 ± 2.1
16	3777 ± 455	52.6 ± 1.6	682 ± 16	0.59 ± 0.01	2817 ± 387	53.2 ± 1.6
17	3086 ± 433	55.4 ± 1.5	682 ± 2	0.53 ± 0.01	3061 ± 378	55.9 ± 1.5
18	2644 ± 473	49.8 ± 2.2	736 ± 27	0.55 ± 0.02	2584 ± 432	50.4 ± 2.2
19	3681 ± 401	54.9 ± 1.5	752 ± 15	0.56 ± 0.01	3607 ± 366	55.4 ± 1.5
20	3500 ± 533	52.3 ± 2.2	727 ± 28	0.59 ± 0.02	3260 ± 504	52.9 ± 2.2
21	2511 ± 515	45.0 ± 1.9	758 ± 17	0.58 ± 0.01	2479 ± 447	45.6 ± 1.9
22	4378 ± 683	57.8 ± 2.1	802 ± 16	0.58 ± 0.01	3636 ± 586	58.4 ± 2.1
23	3628 ± 556	53.8 ± 3.7	772 ± 26	0.60 ± 0.02	3230 ± 523	54.4 ± 3.7
24	3526 ± 399	52.0 ± 1.4	674 ± 17	0.56 ± 0.01	3148 ± 367	52.6 ± 1.4
25	3227 ± 518	51.5 ± 1.7	700 ± 26	0.58 ± 0.01	3101 ± 485	52.1 ± 1.7
26	3575 ± 504	53.0 ± 1.6	733 ± 14	0.58 ± 0.01	3365 ± 459	53.5 ± 1.6
27	4302 ± 565	53.1 ± 1.4	680 ± 4	0.57 ± 0.01	4133 ± 484	53.6 ± 1.4
28	3591 ± 602	52.1 ± 1.7	801 ± 6	0.57 ± 0.01	3578 ± 529	52.6 ± 1.7
29	3724 ± 551	49.4 ± 1.5	785 ± 16	0.63 ± 0.01	3287 ± 540	50.0 ± 1.5
30	2501 ± 565	53.2 ± 2.1	742 ± 22	0.60 ± 0.02	2342 ± 479	53.8 ± 2.1
31	4400 ± 518	50.7 ± 1.4	707 ± 11	0.55 ± 0.01	4224 ± 445	51.3 ± 1.4
32	3186 ± 487	57.9 ± 2.0	699 ± 5	0.55 ± 0.01	3123 ± 437	58.4 ± 2.0
33	3456 ± 555	58.8 ± 1.8	684 ± 17	0.56 ± 0.01	3362 ± 519	59.3 ± 1.8
34	2880 ± 373	57.8 ± 1.9	683 ± 17	0.58 ± 0.01	2793 ± 302	58.4 ± 1.9
35	3257 ± 410	55.0 ± 1.3	776 ± 15	0.57 ± 0.01	3217 ± 374	55.6 ± 1.3
36	3778 ± 482	55.3 ± 0.9	681 ± 2	0.56 ± 0.01	3648 ± 431	55.8 ± 0.9
37	3369 ± 351	57.0 ± 1.4	682 ± 0	0.56 ± 0.01	3007 ± 302	57.5 ± 1.4
38	3024 ± 428	52.6 ± 2.0	810 ± 9	0.59 ± 0.01	3009 ± 400	53.2 ± 2.0
39	2901 ± 389	53.0 ± 4.1	719 ± 49	0.59 ± 0.03	2809 ± 349	53.5 ± 4.1
40	3124 ± 489	57.3 ± 1.8	719 ± 16	0.57 ± 0.01	3069 ± 431	57.9 ± 1.8
41	4761 ± 506	57.8 ± 1.0	728 ± 9	0.58 ± 0.01	3452 ± 380	58.4 ± 1.0
42	3699 ± 399	61.1 ± 1.2	688 ± 2	0.58 ± 0.01	3664 ± 382	61.7 ± 1.2
43	2720 ± 318	56.2 ± 2.4	713 ± 27	0.58 ± 0.02	2658 ± 296	56.8 ± 2.4
44	3220 ± 447	51.5 ± 2.4	712 ± 45	0.59 ± 0.03	3184 ± 440	52.1 ± 2.4
45	3481 ± 491	53.9 ± 2.0	745 ± 18	0.62 ± 0.01	3422 ± 444	54.5 ± 2.0
46	3367 ± 428	50.9 ± 1.4	731 ± 14	0.57 ± 0.01	3317 ± 417	51.5 ± 1.4
47	3618 ± 841	54.1 ± 3.2	744 ± 36	0.56 ± 0.02	3612 ± 762	54.6 ± 3.2
48	2302 ± 454	51.5 ± 1.7	685 ± 26	0.55 ± 0.02	2300 ± 404	52.0 ± 1.7
49	3621 ± 1008	56.9 ± 2.6	857 ± 30	0.64 ± 0.02	3598 ± 876	57.6 ± 2.6
50	3405 ± 461	55.3 ± 1.4	691 ± 31	0.58 ± 0.02	2868 ± 423	55.9 ± 1.4
51	2974 ± 379	50.9 ± 1.1	726 ± 11	0.57 ± 0.01	2512 ± 286	51.4 ± 1.1
52	3095 ± 465	49.0 ± 1.6	686 ± 31	0.55 ± 0.02	3061 ± 412	49.6 ± 1.6
53	3560 ± 386	55.2 ± 1.5	707 ± 19	0.58 ± 0.01	2853 ± 361	55.8 ± 1.5
54	4011 ± 529	54.9 ± 1.8	679 ± 15	0.56 ± 0.01	3867 ± 475	55.4 ± 1.8
55 a	1713 ± 519	56.2 ± 2.9	670 ± 26	0.49 ± 0.02	1708 ± 510	56.6 ± 2.9
56	3026 ± 343	50.5 ± 1.7	646 ± 31	0.54 ± 0.01	2986 ± 363	51.0 ± 1.7
57	3362 ± 424	49.0 ± 1.2	634 ± 1	0.55 ± 0.01	2803 ± 397	49.6 ± 1.2
58	3533 ± 224	52.5 ± 1.1	711 ± 8	0.59 ± 0.01	3401 ± 203	53.1 ± 1.1
59	4223 ± 565	51.4 ± 1.1	724 ± 12	0.60 ± 0.01	2775 ± 415	52.0 ± 1.1
60	2515 ± 545	50.3 ± 2.4	726 ± 21	0.60 ± 0.02	2515 ± 480	50.8 ± 2.4
61	3274 ± 521	50.4 ± 2.2	668 ± 27	0.59 ± 0.02	3129 ± 497	51.0 ± 2.2
62	3352 ± 421	51.9 ± 1.7	750 ± 14	0.63 ± 0.01	3337 ± 419	52.5 ± 1.7
63	3756 ± 487	53.0 ± 1.4	659 ± 14	0.56 ± 0.01	3257 ± 447	53.6 ± 1.4
64	4127 ± 1067	49.8 ± 1.2	660 ± 11	0.56 ± 0.01	3030 ± 761	50.3 ± 1.2
65	4321 ± 452	57.7 ± 1.2	727 ± 12	0.59 ± 0.01	3535 ± 420	58.3 ± 1.2
66	5320 ± 693	57.0 ± 1.4	681 ± 12	0.58 ± 0.01	3285 ± 608	57.6 ± 1.4
67	3695 ± 507	56.9 ± 1.5	709 ± 14	0.58 ± 0.01	3549 ± 504	57.5 ± 1.5
68	3375 ± 481	52.8 ± 1.7	756 ± 3	0.59 ± 0.01	2925 ± 432	53.4 ± 1.7
69	3431 ± 465	53.3 ± 1.7	752 ± 25	0.59 ± 0.01	2660 ± 385	53.9 ± 1.7

Notes. The second and the third columns providing the FWHM and flux values, respectively, for the broad ("b") He i component include contributions from both the broad Gaussians defined for the line. The FWHM of the narrow ("n") He i is equal to the FWHM of the [O iii] λ5008 (see Table 7, third column). The total ("t") FWHM and flux include contributions from both the broad and the narrow components (t = b + n).

^a Excluded from further analysis. See note a in Table 7.

A machine-readable version of the table is available.

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We used the Mrk 142 Gemini and LJT spectral measurements to generate light curves for the broad Hβ and He i emission-line profiles. We obtained the total broad-line light curves by integrating the flux under the two broad components (see green dashed Gaussians for Hβ and pink dashed Gaussians for He i in Figures 5 and 6) for the two emission lines.

We scaled the broad Hβ light curve from Gemini to the broad Hβ light curve from LJT to generate an inter-calibrated light curve. The Hβ light curves from Gemini and LJT were offset by ∼25% from each other although they displayed similar fluctuations in their patterns. The offset can be attributed to various factors—different seeing conditions at Gemini and LJT or even the difference in the calibrations from the two telescopes. Because we are interested in measuring a time shift in the pattern with reference to the continuum variations, scaling and combining the light curves is valid for our purpose. Figure 7 shows the scaled broad Hβ light curve plotted with the original Gemini and LJT light curves. We then inter-calibrated the original Hβ light curve from LJT and the scaled Hβ light curve from Gemini with PyROA (see Section 5.1) to use the combined light curve to determine the time lag between the continuum and emission-line variability.

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5.1. Cross-correlation Time Lags

We cross-correlated the broad Hβ Gemini+LJT inter-calibrated light curve with the UVW2 light curve from Swift to measure the reverberation lag of the BLR response to the continuum variability from the accretion disk, which is at smaller size scales than the BLR. Following Cackett et al. (2020), we chose the UVW2 because we aim to measure the response of Hβ line-emitting gas to the UV continuum and the UVW2 was the shortest wavelength available from the photometric monitoring of Mrk 142. During cross-correlation, we also included the LCO+Zowada+Liverpool/g, the inter-calibrated 5100 Å continuum from Gemini and LJT data, and the LJT broad Hβ light curves to use maximum available information for a reliable measurement of the variability pattern.

We employed Python-based running optimal average (PyROA; Donnan et al. 2021) to calculate cross-correlation time lags. PyROA ¹⁶ uses a running optimal average (ROA) calculated with a window function (defined by a Gaussian by default) of a certain width to estimate light-curve behavior while fitting all input light curves simultaneously. The width of the window function controls the flexibility of the model in deriving the driving light curve—a narrower window function traces the fluctuating pattern of a highly variable light curve more appropriately than a wider window, which behaves more rigidly. The code uses priors to initiate the modeling process, and the performance of the model is evaluated using the Bayesian information criterion. PyROA offers a robust treatment for outliers with an extra variance parameter and a standard deviation threshold. The extra variance adds in quadrature to the nominal uncertainties of the input light curves, and the threshold set by the user allows for further inflation of the uncertainties to mitigate the influence of large outliers. Figure 8 shows the cross-correlation results with reference to the Swift/UVW2 band.

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In addition to the Hβ time lag for the Gemini+LJT inter-calibrated light curve (${8.68}_{-0.72}^{+0.75}$ days), PyROA provided lag measurements for other input light curves (${0.73}_{-0.10}^{+0.10}$ days for LCO+Zowada+Liverpool/g, ${0.79}_{-0.29}^{+0.27}$ days for Gemini+LJT/5100 Å, and ${8.14}_{-0.80}^{+0.82}$ days for LJT/Hβ) with reference to the Swift/UVW2 band. With respect to the shorter-wavelength UVW2 emission, we expect to measure positive lags for the longer-wavelength emission in the g band, at 5100 Å, and for the Hβ emission line. We thus modeled the distribution of time lags as a log-Gaussian function that imposes positive lags with reference to UVW2, whose lag is fixed at 0.00 day (see Figure 8). In addition to measuring the time shift in the light-curve pattern, the width of the Log-Gaussian model also accounts for the amount of blurring applied to the reference light curve (here, UVW2) to match the response in the echo light curves. This becomes important for BLR RM, where the emission-line variations, emerging farther away from the central engine and from a more spatially extended structure (size scale ∼1 pc) than the accretion disk, are smoother compared to the continuum variations closer to the center. In PyROA, the width of the time-lag distribution quantifies the blurring determined for each of the echo light curves: ${0.28}_{-0.18}^{+0.19}$ days for LCO+Zowada+Liverpool/g, ${0.88}_{-0.48}^{+0.62}$ days for Gemini+LJT/5100 Å, ${4.88}_{-0.90}^{+1.16}$ days for LJT/Hβ), and ${5.47}_{-0.89}^{+1.06}$ days for Gemini+LJT/Hβ. We also performed light-curve analysis with the interpolated cross-correlation function (ICCF; Gaskell & Sparke 1986; Gaskell & Peterson 1987) and Just Another Vehicle for Estimating Lags In Nuclei (JAVELIN; Zu et al. 2011, 2013, using a top-hat time-lag distribution function) for comparison with the PyROA results. Table 10 displays the time-lag measurements with all three methods.

Table 10. Time-lag Measurements

Time Lag (days)	PyROA a	ICCF	JAVELIN
UVW2-to-g	${0.73}_{-0.10}^{+0.10}$	${0.7}_{-0.2}^{+0.2}$	${0.54}_{-0.08}^{+0.08}$
UVW2-to-5100 Å	${0.79}_{-0.29}^{+0.27}$	${1.7}_{-1.2}^{+1.8}$	${0.78}_{-0.38}^{+0.42}$
UVW2-to-Hβ, LJT	${8.14}_{-0.80}^{+0.82}$	${8.8}_{-3.5}^{+2.5}$	${6.95}_{-0.46}^{+0.69}$
UVW2-to-Hβ, Gemini+LJT	${8.68}_{-0.72}^{+0.75}$	${8.7}_{-9.1}^{+4.2}$	${11.38}_{-4.49}^{+0.51}$

Note.

^a We consider these as the most robust time-lag measurements of the three methods. See Section 6 for further details.

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5.2. He i Light Curves

The peculiar, asymmetrical shape of the He i line—narrow-line emission and a broad, asymmetrical component (modeled by a Gaussian six times the width of the broad Hβ line in our spectra fitting procedure)—is clearly evident in the high-S/N Gemini mean spectrum. The asymmetry in the broad component due to the stronger blueshifted emission feature likely indicates a wind component in the BLR. However, the cause of such a disk-wind component is not clear. Leighly (2004) performed CLOUDY simulations to model 10 high- and low-ionization emission lines observed in NLS1s. She suggested that the blueshifted emission evident in the high-ionization lines in NLS1s arises from a wind moving toward us. Interestingly, the plausible broad, blueshifted component for He ii in the spectral model may also be a result of such a wind emission. Further analysis of the He ii line is needed to draw firm inferences in this regard. In addition to the blueshifted wind, Leighly (2004) found that the high-ionization Lyα was dominated by emission in the accretion-disk atmosphere or at the low-velocity base of the broad-line wind. The very broad, flattened emission feature in He i may be indicative of a disk-wind feature as noted for Lyα. Furthermore, Leighly (2004) derived a small covering fraction for the BLR. She argued that in an object with a small black hole mass, as in the case of Mrk 142 (M_• = 3.89 × 10⁶ M_⊙ ¹⁷ ), a small covering fraction can result from an emission-line region closer to the plane of the disk. Li et al. (2018) performed velocity-resolved RM of Mrk 142, where the authors concluded that the two-zone BLR model (Wang et al. 2014b) best fit the Mrk 142 BLR with an opening angle (θ) of 10°–30° (representing a disk-like BLR). Estimating the covering fraction from the opening angle as θ/90° yields a value of 0.1–0.3 for the covering fraction; however, these small values do not confirm the presence of a disk wind in Mrk 142. To understand the components that form the atypical Mrk 142 BLR system or the kind of BLR geometry in a super-Eddington that can show a broad, blueshifted emission feature similar to the He i line feature, we would need further investigation of BLR models and data for super-Eddington AGNs.

Although the LJT rms spectrum of Mrk 142 shows a weak variable feature for He i, the variability is not usefully quantifiable given the timescale and S/N of our current Gemini+LJT spectroscopic campaigns. Figure 9 displays the individual and total broad-line components of He i emission from both the Gemini and the LJT observations. The offset observed in the narrower broad component is similar to that observed in the broad Hβ, where the light curve from Gemini appears at higher flux values than the LJT light curve. Interestingly, the broader broad component is brighter in LJT than in Gemini likely resulting from the blueshifted disk-wind component broadened due to the wider slit used for LJT data.

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We present the first results on the lag of the broad Hβ line with respect to the UV continuum in Mrk 142 from optical spectroscopic observations from Gemini+LJT with simultaneous monitoring in the photometric Swift/UVW2 and LCO+Zowada+Liverpool/g bands.

We applied a spectral model with same number of components but different parameter settings to the Gemini and LJT spectra to derive Hβ and He i light curves. We noted that a profile composed of one narrow + two broad Gaussians sufficiently traced both the Hβ and the He i lines, where the widths and positions of the narrow components were tied to those of the [O iii] λ5008 line. The use of Gaussians for fitting broad lines such as Hβ in our data does not comply with the Wang et al. (2014b) line-profile predictions for a super-Eddington AGN, where self-shadowing effects due to a slim-disk structure in super-Eddington AGNs could result in the broad-line profiles appearing more Lorentzian than Gaussian. We recognize that our Mrk 142 spectral fitting model does not align with that of Wang et al. (2014b); however, our results are not sufficient evidence to rule out the self-shadowing hypothesis. A detailed analysis of spectral line profiles for a larger sample of super-Eddington AGNs is required to build a robust understanding of how the accretion-disk behavior affects the observed broad-line profiles in these objects. We employed fixed narrow-line flux ratios F_Hβ /F_{[O iii] λ5008} and F_{He i} /F_{[O iii] λ5008} for the LJT spectral model (determined from flexible flux ratios for the Gemini spectra) due to the instrumental broadening in the LJT spectra affecting emission-line measurements. Although the LJT rms spectrum shows a weak feature at the He i location, PrepSpec modeling and light-curve analysis suggested that there is no adequate variability in the line that is measurable with the current Gemini+LJT data. However, we acknowledge that the He i emission line shows a peculiar profile evident from the high S/N of the Gemini spectra. The broader Gaussian used for the line indicates stronger blueshifted emission than the redshifted side of the line. Also, the He ii line specifically required a broad, blueshifted component to accurately trace the emission in that region. Followed by spectral analysis, we empirically measured the FWHM values as well as calculated the narrow- and broad-line flux values of the Hβ and He i lines to obtain their light curves.

Applying PyROA, we performed cross-correlation analysis with continuum (Swift/UVW2, LCO+Zowada+Liverpool/g, and Gemini+LJT/5100 Å) and broad Hβ light curves (LJT and Gemini+LJT inter-calibrated) with a goal of determining reverberation time lag for the Gemini+LJT inter-calibrated Hβ light curve. PyROA provided an improvement in quantifying the uncertainties compared to previous studies. Most early RM studies have extensively applied the ICCF method for time-lag measurements, which makes it a good comparison standard. However, ICCF struggles with nonuniformly sampled data, which is true for our Gemini+LJT campaigns similar to most other studies, and uses linear interpolation to estimate the light-curve behavior in the regions with data gaps. Consequently, the uncertainties reported for ICCF-based measurements are typically conservative compared to JAVELIN and PyROA, as noted in this work for the 5100 Å continuum as well as the Hβ emission from LJT and Gemini+LJT inter-calibrated data (see Table 10). In the context of the uncertainties on time-lag measurements, JAVELIN has been shown to perform better. For instance, Edelson et al. (2019) reported uncertainties from ICCF to be twice as large as those from JAVELIN, which is also evident from the results in this work (see Table 10). JAVELIN uses damped random walk (DRW) to estimate the light-curve pattern in the regions where data are not available. DRW closely characterizes the variability observed in AGNs, plausibly leading to smaller uncertainties in the final lag measurements. However, JAVELIN requires a good estimation of uncertainties in data. For suboptimally calibrated uncertainties, JAVELIN can sometimes fail to deliver reliable lag measurements (Donnan et al. 2021). This is likely the reason the LJT/Hβ and Gemini+LJT/Hβ emission-line light curves, which have larger calibrated uncertainties than the continuum light curves, show time-lag measurements differing from those reported by PyROA. PyROA offers an improvement over JAVELIN—the ROA along with a robust error treatment not only prevents the outlier points from disrupting the estimation of the driving light curve but also applies a valid algorithm for resolving data gaps.

We measured a time lag of ${8.68}_{-0.72}^{+0.75}$ days for the Gemini+LJT inter-calibrated Hβ emission with reference to the UVW2 continuum. We also obtained a lag of ${0.79}_{-0.29}^{+0.27}$ days for the 5100 Å continuum with reference to the UVW2 band (that is consistent, within uncertainties, with the time lag–wavelength relationship in Cackett et al. 2020), and a lag of 7.89 ± 0.80 days for the Hβ emission with respect to the 5100 Å continuum. From here, we report a black hole mass of $\mathrm{log}({M}_{\bullet }/{M}_{\odot })$ = 6.28 ± 0.29 derived using Equation (1),

$$\begin{eqnarray}&&{M}_{\bullet }=\displaystyle \frac{f\,c\,{\tau }_{{\rm{H}}\beta }\,{V}_{\mathrm{FWHM},{\rm{H}}\beta }^{2}}{G}\end{eqnarray} \tag{ 1 }$$

where we used a $\mathrm{log}(f)$ value of $-{0.36}_{-0.54}^{+0.33}$ from the dynamical modeling of the Mrk 142 BLR by Li et al. (2018). It is possible that the value of $\mathrm{log}(f)$ has a large uncertainty, which depends on the BLR's dynamical model or the calibration using the M–σ_* relation for classical bulges and pseudobulges (e.g., Ho & Kim 2014; Li et al. 2018; Yu et al. 2020). For V_FWHM, we used the mean Hβ FWHM of 1680 ± 14 km s⁻¹ from the Gemini spectra. Here, we chose the Gemini spectra due to their higher resolution providing a more reliable measurement of the narrower Hβ broad-line profile than the LJT spectra. We also considered the mean FWHM from the spectra as against the Hβ rms profiles as the rms spectra from Gemini were noisier blueward of the blue wing of the Hβ line. We further measured mean luminosities of $\mathrm{log}({L}_{{UVW}2})=43.832\pm 0.001$, $\mathrm{log}({L}_{5100})=43.643\pm 0.002$, and $\mathrm{log}({L}_{{\rm{H}}\beta })=41.621\pm 0.002$. For the L₅₁₀₀ and L_Hβ measurements, we adopted the mean flux value from our Gemini+LJT inter-calibrated light curves as their respective Gemini light curves alone were insufficient to provide a reliable flux scale due to the shorter observing timescale.

Our results agree with previously published measurements of Mrk 142 (Du et al. 2015; Li et al. 2018). From the previous 6 month SEAMBH campaign, Du et al. (2015) reported a time lag of ${7.9}_{-1.1}^{+1.2}$ days for Hβ with reference to 5100 Å. We measured an optical lag of 7.89 ± 0.80 days for Hβ in agreement with the Du et al. (2015) value within uncertainties. Furthermore, the derived black hole mass for Mrk 142 in this work, $\mathrm{log}({M}_{\bullet }/{M}_{\odot })$ = 6.28 ± 0.29, agrees with the value reported in the recent velocity-resolved RM analysis by Li et al. (2018), ${6.23}_{-0.45}^{+0.26}$, within uncertainty limits. Table 11 summarizes the measured quantities in this work and shows their comparison with the values from previous studies.

Table 11. Comparison of Measurements to Previous SEAMBH Studies

Measured Quantity	This Work	Value From Previous SEAMBH Studies
τUVW2-to-Hβ a	${8.68}_{-0.72}^{+0.75}$ days	⋯
τ5100 Å-to-Hβ	7.89 ± 0.80 days	${7.9}_{-1.1}^{+1.2}$ days (Du et al. 2015)
$\mathrm{log}({M}_{\bullet }/{M}_{\odot })$	6.28 ± 0.29	${6.23}_{-0.45}^{+0.26}$ (Li et al. 2018)
$\mathrm{log}({L}_{\mathrm{UVW}2})$*	43.832 ± 0.001	⋯
$\mathrm{log}({L}_{5100})$	43.643 ± 0.002	43.56 ± 0.06 (Du et al. 2015)
$\mathrm{log}({L}_{{\rm{H}}\beta })$	41.621 ± 0.002	43.56 ± 0.06 (Du et al. 2015)

Note.

^a New measurements.

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To visualize our results in the broader context of reverberation-mapped AGNs, we placed the measured size of the Hβ line-emitting region on various R–L scaling relations. Comparisons are discussed below.

Figure 10 shows the R_Hβ –L₅₁₀₀ (panel (a)) and R_Hβ –L_Hβ (panel (b)) relations with the red star representing the Mrk 142 measurements from this work. In agreement with the findings from previous SEAMBH campaigns (black circles in Figure 10; see references in the figure caption), the red Mrk 142 star appears to depart from the general trend observed for typical RM objects, especially in the R_Hβ –L₅₁₀₀ relation (green circles, panel (a); see the entire reference list in the figure caption). Comparatively, the departure of Mrk 142 from the Kaspi et al. (2005) best-fit relation (panel (b)) is less obvious. We quantified these Mrk 142 departures in terms of time lag (along the vertical axis) relative to the standard deviation of the departures of the typical RM sample from both best-fit relations (${\sigma }_{\mathrm{departure}}$). While the departure of Mrk 142 from the Bentz et al. (2013) relation (15.7 lt-day) is $1.15{\sigma }_{\mathrm{departure}}$ (where ${\sigma }_{\mathrm{departure}}=13.7$ lt-day), its departure from the Kaspi et al. (2005) relation (4.08 lt-day) is ≪1${\sigma }_{\mathrm{departure}}$ (where ${\sigma }_{\mathrm{departure}}=26.8$ lt-day). The latter implies that R_Hβ –L_Hβ is a tighter relationship for AGNs than R_Hβ –L₅₁₀₀. The position of Mrk 142 in the R_Hβ –L₅₁₀₀ relationship (panel (a)), considerably below the best-fit line, reiterates the characteristic of super-Eddington AGNs exhibiting smaller BLR sizes in contrast to the sub-Eddington population at the same luminosities (Du et al. 2016b). Du et al. (2015) tested this deviation of high accretion-rate AGNs from the R_Hβ –L₅₁₀₀ relationship. Studying the differences in the BLR sizes for AGNs with low ($\dot{M}/{\dot{M}}_{\mathrm{Edd}}\lt 3$) and high ($\dot{M}/{\dot{M}}_{\mathrm{Edd}}\geqslant 3$) mass-accretion rates, Du et al. (2015) inferred that $\dot{M}$ influences the size scales observed in super-Eddington AGNs, while such a correlation is absent in the low mass-accretion-rate objects.

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Figure 11 shows the R_Hβ –L₅₁₀₀ and R_Hβ –L₁₃₅₀ scaling relations for NGC 5548 over time with optical lag measurements for Hβ, and luminosities at 5100 and 1350 Å (L₁₃₅₀) from Eser et al. (2015). Again, the red star in both panels represents the Mrk 142 point from this work. Eser et al. (2015) formulated a conversion from L₅₁₀₀ to L₁₃₅₀ for NGC 5548 (see their Equation (4)) from all RM campaigns of the object from 1988–2008 (Peterson et al. 2002; Bentz et al. 2007, 2009b; Denney et al. 2010). We applied that conversion to calculate L₁₃₅₀ for NGC 5548 and generated the R_Hβ –L₁₃₅₀ plot (Figure 11, panel (b)). Here, we extrapolated the Cackett et al. (2020) UV/optical imaging data—mean flux densities—in different bands assuming power-law behavior to estimate a luminosity of $\mathrm{log}({L}_{1350})=44.13\pm 0.03$ for Mrk 142 in this work (see Figure 12). The shift in the position of Mrk 142 from panels (a)–(b), closer to the R–L scaling relation in the UV, indicates that the UV emission is a better proxy for the ionizing continuum than the 5100 Å optical emission.

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To further understand the comparison between the R_Hβ –L₁₃₅₀ relations of Mrk 142 (a super-Eddington Seyfert 1 galaxy) and NGC 5548 (a normal Seyfert 1 galaxy), we compared their SEDs from the National Aeronautics and Space Administration/Infrared Processing and Analysis Center (NASA/IPAC) Extragalactic Database (NED) and recent studies, including Cackett et al. (2020). Figure 12 shows the SEDs for the above two AGNs from NED along with the derived optical-to-X-ray spectral slope (α_ox) of –1.35 ± 0.01 for Mrk 142 from the Cackett et al. (2020) observations (purple triangles representing mean flux densities in different bands). To derive the α_ox value, we: (1) fit the local SED around the 2500 Å data point assuming power-law behavior, (2) calculated the dereddened X-ray flux density at 2 keV, and (3) used Equation (1) for α_ox from Just et al. (2007). For NGC 5548, Merritt (2022) obtained an α_ox of –1.30 ± 0.04 from simultaneous X-ray/UV/optical observations. A less negative α_ox for NGC 5548 compared to Mrk 142 suggests a harder ionizing SED for the normal Seyfert 1 galaxy, likely due to the soft X-ray excess observed in the object (e.g., Mehdipour et al. 2015), than the super-Eddington AGNs. However, the soft excess in NGC 5548 was not evident in 2013, when an obscurer heavily absorbed its soft X-ray flux (Mehdipour et al. 2015). Most Seyferts/quasars have some sort of soft X-ray excess; the debate for years has been over the origin (ionized disk reflection, warm Comptonized emission, a mixture, or both). The implication from Tortosa et al. (2023) is that for super-Eddington AGNs, ionized disk reflection can model the soft excess in this class of AGNs well. It is interesting to witness that despite their distinct types, the SED shapes of Mrk 142 and NGC 5547 are similar, as their α_ox values agree within uncertainties—a plausible explanation for the tighter R_Hβ –L₁₃₅₀ correlation than R_Hβ –L₅₁₀₀ noted in both the objects. Future accretion-disk modeling efforts can help understanding such comparisons of R–L relationships between normal and super-Eddington AGNs.

If UV emission is closer to the driving continuum as seen in Figure 11, this will affect the black hole mass of Mrk 142 derived from the 5100 Å to Hβ time lag. Recently, Cackett et al. (2020) performed the accretion-disk RM analysis for Mrk 142 with data from Swift, LCO, Zowada, Liverpool, and other ground-based observatories, simultaneous to the Gemini+LJT data taken as a part of the same broader RM campaign. Cackett et al. (2020) pointed that if the UVW2 band represents the driving continuum, then the black hole mass derived from the Hβ optical lag is underestimated by ∼10%. We used the UVW2 to Hβ time lag result from this work to calculate the black hole mass in Mrk 142. We obtained a mass of $\mathrm{log}({M}_{\bullet }/{M}_{\odot })$ = 6.32 ± 0.29 based on the UVW2 to Hβ time lag. This value is ∼10% greater than the black hole mass derived by assuming 5100 Å as the driving continuum band, and thus verifies the discrepancy estimated by Cackett et al. (2020). This discrepancy would be as high as ∼40% if X-rays, instead of UV, were the driving continuum (Cackett et al. 2020). However, our work does not propose any new implications to the accretion-disk structure of Mrk 142. A robust Hβ lag measurement with reference to the X-ray continuum from future studies will help understand how X-rays play a role in driving the continuum variability in Mrk 142 and shape its inner accretion disk.

We performed BLR RM analysis of Mrk 142 with medium- and low-resolution optical spectra from Gemini and LJT, simultaneous to the Swift and LCO+Zowada+Liverpool photometric campaigns reported by Cackett et al. (2020) to measure the UV lag for Hβ emission line. With PrepSpecanalysis, we corrected calibration discrepancies for both the Gemini and the LJT spectra individually. From spectral modeling in Sherpa, we measured FWHM and fluxes for [O iii] λλ4960, 5008; Hβ λ4861; and He i λ5877 emission lines. To combine the 5100 Å and Hβ light curves from Gemini and LJT, we inter-calibrated the respective light curves from the two telescopes in PyROA. Applying PyROAfor time-lag analysis, we measured a UV time lag for Hβ and further derived refined black hole masses. Placing our results on various R–L scaling relations, we verified that our results are consistent with previously published values for Mrk 142. We summarize our main findings below.

• 1.  
  PyROA, using the Bayesian information criterion to evaluate model performance along with a rigorous treatment of uncertainties, provided a robust method for measuring cross-correlation time lags. This project is one of the early works employing the PyROA technique for measuring RM time lags with real data. In this process, the longer timescale of LJT spectra nicely complemented the gaps in the Gemini observations.
• 2.  
  We measured, for the first time, a UV time lag of ${8.68}_{-0.72}^{+0.75}$ days for Hβ in Mrk 142, with simultaneous photometry in the Swift/UVW2 band and optical spectroscopy with Gemini and LJT. Assuming the UV continuum as the primary driver of the observed variability, we derived a black hole mass of $\mathrm{log}({M}_{\bullet }/{M}_{\odot })$ = 6.32 ± 0.29.
• 3.  
  We obtained a 5100 Å to Hβ time lag of 7.89 ± 0.80 days, consistent with the measured value from previous SEAMBH campaigns (Du et al. 2015). From this lag measurement, we also derived a black hole mass for Mrk 142 of $\mathrm{log}({M}_{\bullet }/{M}_{\odot })$ = 6.28 ± 0.29, in agreement with the mass reported by Li et al. (2018).
• 4.  
  We placed the 5100 Å to Hβ time lag with measured L₁₃₅₀ on the R_Hβ –L₁₃₅₀ relation for NGC 5548 (Eser et al. 2015). Mrk 142 falls closer to the R_Hβ –L₁₃₅₀ scaling relation than the R_Hβ –L₅₁₀₀ relation indicating that the UV is closer to the "true" driving continuum as opposed to the 5100 Å band.

In addition, we also recorded supplementary results. Our spectral analysis indicated blueshifted, broad components for the He i and He ii emission lines suggestive of wind components in these higher-ionization lines. To infer the cause of such disk+wind components, we need more higher-resolution data and BLR modeling efforts for super-Eddington AGNs. We intend to study the He i and He ii lines in further detail in future work. Furthermore, BLR RM analysis with the concurrent X-ray data available from Swift can better inform our understanding of the measured Hβ time lags with respect to the UV continuum. We aim to explore this in future study.

We recognize the support of Rick Edelson in taking the g-band data from Las Cumbres Observatory. V.C.K. acknowledges the support of Joel Roediger and the Gemini Observatory staff during the planning of observations and reduction of the Gemini data. V.C.K. thanks T. A. Boroson, who provided the Fe ii template to C.H. for the spectral modeling process. We acknowledge the support of the Natural Sciences and Engineering Research Council of Canada (NSERC), Discovery Grant RGPIN/04157. V.C.K. acknowledges the support of the Ontario Graduate Scholarships. E.M.C. gratefully acknowledges support for analysis of the Swift data from NASA through grant 80NSSC19K0150, and support for analysis of the Zowada Observatory data from the NSF through grant AST-1909199. C.H. acknowledges support from the National Science Foundation of China (12122305). The research of V.C.K. was partially supported by the New Technologies for Canadian Observatories, an NSERC CREATE program. V.C.K. also acknowledges Jonathan Trump, Martin Houde, Stanimir Metchev, and Charles McKenzie for their valuable feedback and discussions.

This research was based on observations obtained at the Gemini Observatory (processed using the Gemini IRAF package), which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation on behalf of the Gemini Observatory partnership: the National Science Foundation (United States), National Research Council (Canada), Agencia Nacional de Investigación y Desarrollo (Chile), Ministerio de Ciencia, Tecnología e Innovación (Argentina), Ministério da Ciência, Tecnologia, Inovações e Comunicações (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea). This work was enabled by observations made from the Gemini North telescope, located within the Maunakea Science Reserve and adjacent to the summit of Maunakea. We are grateful for the privilege of observing the Universe from a place that is unique in both its astronomical quality and its cultural significance.

This research used observations from the Lijiang 2.4 m Telescope funded by the Chinese Academy of Sciences (CAS) and the People's Government of Yunnan Province. We acknowledge the support of the National Key R&D Program of China No. 2021YFA1600404, and the National Science Foundation of China (11833008, 11973029, 11991051, 11991054).

The Liverpool Telescope is operated on the island of La Palma by Liverpool John Moores University in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias with financial support from the UK Science and Technology Facilities Council.

Facilities: Gemini:Gillett - , YAO:2.4m - , Swift - , FTN - , Zowada - , Liverpool:2m - .

Software: IRAF, Gemini IRAF, Python, Astropy (Astropy Collaboration et al. 2013), PrepSpec, Sherpa (Freeman et al. 2001; Burke et al. 2018), PyROA (Donnan et al. 2021), ICCF (Gaskell & Sparke 1986; Gaskell & Peterson 1987), JAVELIN (Zu et al. 2011, 2013).

This Section describes the special cases from the spectral reduction of the Mrk 142 Gemini Spectra that were either treated differently or discarded due to calibration issues.

• 1.  
  Epoch 11 narrow-slit standard star spectra: The extracted spectrum from exposure 1 appeared to drop in flux and flatten shorter than (blueward of) ∼4740 Å, whereas the exposure 2 spectrum was flat on both ends. While it was possible to recover the flat region of the exposure 1 spectrum, the one from exposure 2 was not suitable for further analysis and hence was discarded. Because the shape of the spectrum blueward of ∼4740 Å was not evident from the exposure 2 spectrum, we recovered the region from ∼4520 to ∼4740 Å with reference to the mean wide-slit standard star spectrum (used as the reference to correct for slit losses). Consequently, only the region longer than (redward of) ∼4740 Å was corrected for slit losses with the spline fitting procedure. The former and the latter were then concatenated to obtain only one slitloss-corrected spectrum for epoch 11 from exposure 1. Note that the standard star spectrum from exposure 1 was later used to calibrate the narrow-slit science spectrum from exposure 2.
• 2.  
  Epoch 11, exposure 1 wide-slit standard star spectrum: Two bumps with bad data were recovered redward of ∼5900 Å with reference to the spectrum from exposure 2. However, the recovery is not reliable, as the two spectra had slightly different count levels.
• 3.  
  Discarded wide-slit standard star spectra: the wide-slit standard star spectra from exposures 1, 1, and 2 of epochs 21, 22, and 25, respectively, showed bump-like features, which could not be recovered as the standard star spectra from the other exposure of the same epochs had different count levels. Therefore, the epochs/exposures listed here were discarded.
• 4.  
  Correction of affected pixels or recovery of bump-like regions on or close to the emission lines of interest: a few science spectra showed bumpy features on or close to the emission lines of interest, He i λ5877 and Hβ λ4861. We attempted to recover the "true" shape of such regions with reference to the other exposure taken with the same slit on the same night. In most cases, the two exposures had similar count levels. However, spectral measurements from the recovered spectra with different count levels are less reliable and must be considered carefully. What follows is a list of the specific cases.Epoch 13, exposure 2 narrow-slit spectrum: A large, downward bump with bad data from ∼5545 Å until the red wing of the He i emission line was recovered with reference to the exposure 1 spectrum. Spectra from both exposures had similar count levels.Epoch 16 narrow-slit spectra: Spectra from both exposures showed partially overlapping bump-like features in the region blueward of the Hβ emission line. Because neither of the exposures could be used to recover the shape of the spectrum in the affected region, we recovered the shapes of both the spectra with reference to the mean wide-slit science spectrum (used as the reference to correct for slit losses). In the exposure 2 spectrum, the recovery extended until the blue wing of Hβ. Spectra from both exposures had similar count levels.Epoch 21, exposure 2 narrow-slit spectrum: the bumpy region from ∼4325 to ∼4740 Å was recovered with reference to exposure 1 with similar count levels. The recovered region extended until the tail end of the blue wing of Hβ.Epoch 27, exposure 1 narrow-slit spectrum: A small bumpy region from until the blue wing of Hβ was recovered with reference to exposure 2 with similar count levels.Epoch 28, exposure 1 narrow-slit spectrum: A 17-pixel wide region residual from sky subtraction on the blue wing of Hβ was replaced by simulated data values after linear interpolation in that region. However, this correction was affecting Hβ line measurements and hence was excluded from the analysis.Epoch 30 narrow-slit spectra: Spectra from both exposures showed overlapping bump-like features in the region from ∼4370 to ∼4685 Å that were recovered with reference to the mean wide-slit science spectrum. In the exposure 1 spectrum, another bumpy feature from the red wing of the [O iii] emission line at ∼5008 Å was recovered with reference to the exposure 2 spectrum with similar count levels.Epoch 3, exposure 1 wide-slit spectrum: A bumpy feature on the blue wing of the He i line was recovered with reference to the exposure 2 spectrum, where both spectra had similar count levels. This is one of the brighter wide-slit spectra. However, it was not used to generate the mean wide-slit spectrum for slitloss correction.Epoch 11, exposure 1 wide-slit spectrum: A spike, possibly residual of sky subtraction, on the blue side of the [O iii] peak at ∼5008 Å was replaced by simulated data after linear interpolation in the affected region.Epoch 14, exposure 2 wide-slit spectrum: A huge bump-like feature with bad data was replaced by simulated data after linear interpolation until the blue wing of Hβ.Epoch 24, exposure 2 wide-slit spectrum: A huge bump with bad data extended from the region blueward of the He i line until the red end of the line. This affected region was recovered with reference to the exposure 1 spectrum, which was at slightly lower count levels than the exposure 2 spectrum.Epoch 32, exposure 2 wide-slit spectrum: A bump-like feature from the blueward region of the He i line until the blue side of the He i peak was recovered with reference to the exposure 1 spectrum. Spectra from both exposures had similar count levels.
• 5.  
  Epoch 25, exposure 2 narrow-slit science spectrum: The region on the blue side of He i λ5877 emission line shows a large bumpy feature with bad data. Because the region redward of ∼5320 Å has lower count levels overall as compared to the spectrum from exposure 1, the affected region in spectrum 2 was not recovered. Therefore, this exposure was discarded.
• 6.  
  Epoch 22, exposure 2 wide-slit science spectrum: The red end of the spectrum from ∼6320 to ∼6400 Å was recovered with reference to the spectrum from exposure 1. However, the exposure 2 spectrum had slightly higher count levels than exposure 1.