RADIAL VELOCITY STUDIES OF CLOSE BINARY STARS. XIII^*

The variability of EG Cep was discovered by Strohmeier (1958). Photoelectric light curves and their solutions have been presented by several investigators; for references, see Erdem et al. (2005). The system shows a β Lyrae-type light curve with minima of about 1.0 and 0.3 mag deep. Etzel & Olson (1993) determined the projected rotational velocity of the primary as 146 ± 20 km s⁻¹. A photometric analysis of the system was performed by Kaluzny & Semeniuk (1984) who used a grid search to find the mass ratio q_ph = 0.45–0.50 and a semi-detached configuration for the system. Chochol et al. (1998) discussed the long-term period change in the system and also arrived at the semi-detached configuration with the less massive component filling its Roche lobe and the mass ratio q_ph = 0.47. The new analysis of Erdem et al. (2005) led to a similar mass ratio. No spectroscopic orbit of the system has been published so far.

In view of discrepancies between the spectroscopic and photometric mass ratios previously noted in our DDO series, it is surprising, but also encouraging, that all photometric investigations have led to a mass ratio close to our spectroscopic value, q_sp = 0.464(5). This is in spite of the semi-detached configuration which has weaker photometric constraints than the contact configuration in the light-curve solution. The agreement must result from the high orbital inclination angle, ≈86° (Chochol et al. 1998), and the presence of the total eclipses.

The intrinsic color of the system was estimated at about (B − V)₀ = 0.197 (Kaluzny & Semeniuk 1984) indicating the spectral type of the primary component of A7. The Tycho-2 color index B − V = 0.24 is consistent with our A7V classification and requires a slight reddening. The J − K = 0.19(4) color indicates the A9V–F2V spectral type which may reflect the stronger contribution of the secondary component. EG Cep was not included in the Hipparcos astrometric measurements.

The variability of the contact binary V1191 Cyg (GSC 3159-1512, V_max = 10.82, V_min = 11.15) was detected by Mayer (1965) while observing the nearby star V1187 Cyg. Since then the system was rather neglected with the only thorough photometric analysis of Pribulla et al. (2005), who found that the orbital period of the system increases at a record rapid (for contact binaries) rate of ΔP/P = 2.12 × 10⁻⁶ yr⁻¹. The system is totally eclipsing so the geometric elements derived through a light-curve solution, i = 80.4°, q = 0.094, and f = 0.46, were well defined in the solution of Pribulla et al. (2005). The deeper minimum is flat; hence, the system was classified as a W-type contact binary. The authors determined (B − V) = 0.62 (uncorrected for the interstellar absorption). No spectroscopic study of the system has been published yet.

We found V1191 Cyg to be a rather difficult spectroscopic target due to its relative faintness, the short orbital period of P = 0.3134 days, and the weakness of the Mg i triplet lines. As a solution, we took 129 spectra evenly covering all phases; the extracted BFs were subsequently smoothed in the phase domain (the phase step of 0.02) in the way previously described in Rucinski et al. (2005).

The spectroscopic lower conjunction of the more massive component occurs during the primary minimum; hence, V1191 Cyg is a W-type system. The spectroscopic mass ratio, q_sp = 0.107 ± 0.005, is consistent with the photometric determination. The system is, however, very unusual: (1) it is of a rather late spectral type for such a small mass ratio, (2) its mass ratio is unusually small for a W-type system, (3) the orbital period is short for the mid-F spectral type implying smaller, more compact components than for typical solar-type contact binaries. The 2MASS color, J − K = 0.318, corresponds to the F6V spectral type which is exactly what we see in the classification spectra. The Tycho-2 color, B − V = 0.39 ± 0.10, is too uncertain to draw any firm conclusions.

The variability of this system was found by the Hipparcos satellite. It is described there as a periodic variable of an unspecified variability type with the period P = 0.246, 661 days. Later, Duerbeck (1997) suggested that it is a contact binary with the orbital period twice the original Hipparcos value. Analysis of photometric observations of the binary is complicated by the rather low amplitude, ΔV = 0.09. In the ASAS-3 survey (Pojmanski 2002), the system appears with an undefined variability type and the best period of 21.846 days; however, the same observations, when phased with the double of the Hipparcos period, show a light curve with the minima of similar depths, a feature which is typical for contact binaries. Rather noisy observations can be found in the Northern Sky Variability Survey (NSVS) database (NSVS 11074663, http://skydot.lanl.gov/nsvs/nsvs.php). Except for those fragmentary observations, no other photometric or spectroscopic observations of V1003 Her are available.

Our spectroscopic observations show that V1003 Her is indeed a close binary, most likely of the W Ursae Majoris (W UMa) type, but—because of the very small photometric amplitude—a full description and classification of the system are impossible at this point and would require a high-precision photometry. The projected total mass of the system, (M₁ + M₂)sin³i = 0.672 ± 0.009 M_☉, the low photometric amplitude, the early spectral type (A7), and the absence of any third light all indicate a very low inclination angle. The Hipparcos parallax, π = 4.64 ± 1.66 mas, is of limited use because of its low relative accuracy. Our spectral-type estimate, A7V, is consistent with the 2MASS infrared color, J − K = 0.234, but the Tycho-2 color index B − V = 0.38 indicates a substantial reddening in the direction of V1003 Her, E(B − V) ≈ 0.19.

Variability of BD+7°3142 was detected during the analysis of the ASAS data (Pojmanski 2002). It was classified as an eclipsing binary with the following ephemeris: HJD = 2, 452, 383.92 + 0.275, 277 × E for the primary minima. No photometric or spectroscopic observations of the system have yet been published. Simultaneous photometry during our spectroscopic observations has led to the determination of one light minimum at HJD = 2, 454, 188.8663(1), which occurred at the phase 0.8366 of the ASAS prediction. Our spectroscopic conjunction agrees with this newly observed minimum.

The spectroscopic observations show BD+7°3142 as a triple system with a third component stationary in RVs. The light contribution of the third component is L₃/(L₁ + L₂) = 0.50 at the brightness maximum of the eclipsing pair; its signature is narrow with Vsin i ⩽ 15 km s⁻¹, which is close to the resolution of our spectroscopy. After approximating the third peak by a Gaussian and its removal from the BFs, we obtained well-defined BFs of the eclipsing pair. The RV of the third component, RV₃ = −69.2 ± 1.4 km s⁻¹, was found to be close to the center-of-mass velocity of the eclipsing pair, V₀ = −64.1 ± 0.8 km s⁻¹; hence, the third component appears to be a physical member of the system. The small difference of velocities is, very probably, a result of a slow mutual revolution. The system is not listed in the Washington Double Star (WDS) catalog as a previously recognized visual double (Mason et al. 2001).

The parallax of the system is unknown, but its absolute visual magnitude can be estimated using the calibration of Rucinski & Duerbeck (1997) and the K2 spectral type ((B − V)₀ = 0.74) at M_V = 4.84. A correction of the maximum visual magnitude of the combined system, V = 9.89, for the contribution of the third component results in V₁₂ = 10.33 and then the distance d = 97 pc.

By combining the proper motion of BD+7°3142 adopted from the Tycho-2 Catalogue (Høg et al. 2000) with the systemic RVs and the estimated distance, one obtains a large space velocity of 88 km s⁻¹. The 2MASS color of BD+7°3142, J − K = 0.591, and the Tycho-2 B − V = 0.92 agree with our spectral type of K2V and is consistent with the very short period of the system.

The variability of V357 Peg (HD222994) was discovered during the Hipparcos mission. The system was correctly classified as a contact binary. The first photometry of V357 Peg, published by Yasarsoy et al. (2000), shows a typical W UMa-type light curve. The photometric amplitude is about 0.48 mag so the eclipses cannot be far from total (assuming our q_sp = 0.40). No photometric or spectroscopic study of the system has yet been published in spite of a fairly large brightness of V_max = 9.06.

Our spectroscopic observations show that V357 Peg is a contact binary of the A type with the mass ratio of q = 0.401 which is moderately large for this type. The total projected mass of the system (M₁ + M₂)sin³i = 2.112 M_☉ is probably not far from the true total mass. Our spectra taken in 2005 August and September showed a dark photospheric spot on the secondary component which became visible just after the secondary minimum (Figure 5). In addition to the main series of observations in 2005, V357 Peg had been shortly observed in 1997. These observations do not show any indication of the photospheric spots. All RVs are listed in Table 1, but the 1997 data were not used in the orbital solution given in Table 2 to avoid any influence of the possibly imprecisely-known or variable period. An orbit based on the 1997 data (V₀ = −10.8 km s⁻¹, K₁ = 93.8 km s⁻¹, K₂ = 234.1 km s⁻¹, T₀ = 2, 450, 748.7496(12) for the spectroscopic conjunction) is consistent with the 2005 results.

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The trigonometric parallax of the system, π = 6.00 ± 1.56 mas, is too imprecise to reliably determine its absolute magnitude. Our estimate of the spectral type, F2V, agrees with both the 2MASS color, J − K = 0.178, and the Tycho-2 color, B − V = 0.33.

V407 Peg (BD+14°5016; V_max = 9.28) was found to be a variable during the Semi-Automatic Variability Search program at the Piwnice Observatory close to Toruń, Poland (Maciejewski et al. 2002). The authors presented a moderate-precision BV photometry and the first ephemeris for the primary minima HJD = 2, 452, 558.1703 + 0.636, 889 × E. The light curve of V407 Peg was that of a contact binary.

Later, Maciejewski & Ligeza (2004) published 13 RV determinations based on spectra taken at the DDO and processed using the BF formalism. Unfortunately, about a half of the available spectra were taken close to the orbital conjunctions making the derived spectroscopic elements (V₀ = 22.1 ± 5.9 km s⁻¹, K₁ = 54.7 ± 3.8 km s⁻¹, and K₂ = 233.9 ± 5.6 km s⁻¹) rather uncertain and in fact very different from our orbit which is based on 63 spectra. The most substantial difference is in the 8.7% larger sum of the semi-amplitudes resulting in the 29% larger total (projected) mass.

The star was not included in the Hipparcos mission. Its J − K color in the 2MASS catalog (Skrutskie et al. 2006) is 0.181 corresponding to the F1 spectral type, which is consistent with (B − V) = 0.35 determined by Maciejewski et al. (2002). Our spectral classification is F0V.

The variability of V1123 Tau (visual double WDS 03350+1743) was discovered during the Hipparcos satellite mission. In the Hipparcos Variable Stars Annex, the star is classified as a β Lyrae-type eclipsing binary with the ephemeris for the primary minimum: HJD = 2, 458, 500.3570 + 0.399, 957 × E. The binary is accompanied by a fainter companion (ρ = 4.3'', θ = 136°, and ΔV = 1.77). The large error of the Hipparcos trigonometric parallax, π = 6.82 ± 3.03 mas, suggests that it was most likely corrupted by the presence of the visual companion.

Özdarcan et al. (2006) published the first ground-based photometry of the system. Based on the observed color of the system, (B − V) = 0.684, the authors estimated the spectral type to be G6V which is much later than our direct classification of G0V. The rather red color and the wavelength-dependent depths of the minima were very probably a result of the neglected contribution of the late-type companion which was almost certainly entering the diaphragm of the photoelectric photometer. The third light of the visual companion appears to have caused the amplitudes of the system to be color dependent: while in the U filter the full amplitude of the light curve was 0.413 mag, it was only 0.352 mag in the R filter.

The light of the visual companion partially entered the spectrograph slit during periods of the poor seeing; it was however marginally visible in the extracted BFs with the relative contribution not larger than typically 0.02–0.03. Its RV, V₃ = 29 km s⁻¹, was constant during our observing run and was fairly close to the center-of-mass velocity of the eclipsing pair, V₀ = 25.2 ± 0.6 km s⁻¹.

In addition to the recent observations reported here (2005 September–2007 March), V1123 Tau was also observed in 2002 using the older CCD chip (see previous papers of this series) and the 1800 lines mm⁻¹ grating. The resulting RVs, listed in Table 1, were not used in the orbital solution given in Table 2 due to the long interval between the two data sets. The orbit based on the 2002 data (V₀ = 24.6 km s⁻¹, K₁ = 69.3 km s⁻¹, K₂ = 258.2 km s⁻¹, T₀ = 2, 452, 558.4581(8) for the spectroscopic conjunction) is consistent with the results from the new, better-defined data.

The lower conjunction of the more massive component corresponds to the time of the secondary minimum as given in the online database of ephemerides of eclipsing binary stars (see http://www.as.ap.krakow.pl/ephem/, and Kreiner 2004); therefore, V1123 Tau is a W-type contact binary.

V1128 Tau (visual double WDS 03495+1255) is another Hipparcos discovery. Originally, it was classified as a β Lyrae-type eclipsing binary with a 0.304,3732 day orbital period. The eclipsing pair forms a relatively wide visual double with BD+12°511B, separated by 14 arcsec. The visual companion at the position angle θ = 196° did not enter our spectrograph slit which is permanently oriented in the east–west direction. The high-precision photometry of Tas et al. (2003) showed that the system is a totally eclipsing contact binary, with the totality lasting about 16 min. Subsequent light-curve modeling led to q_ph = 0.48 and the high orbital inclination angle of i = 85°. The light-curve asymmetry, with the maximum following the primary minimum being brighter, was interpreted in terms of a cool spot on the cooler component.

Our spectroscopic mass ratio, q_sp = 0.534(6), is in a reasonable but not perfect consistency with the photometric estimate. However, we could not see any evidence of dark photospheric spots on either of the components in our BFs. The lower conjunction of the more massive component coincides with the deeper eclipse so that V1128 Tau is definitely a W-type contact binary.

In addition to our recent observations reported here (2005 December–2007 March), V1128 Tau had been shortly observed in 1997 and in 2003 using the old CCD detector and the 1800 lines mm⁻¹ grating. The resulting RVs, listed in Table 1, were not used in the orbital solution given in Table 2. The corresponding orbit (V₀ = −14.5 km s⁻¹, K₁ = 127.1 km s⁻¹, K₂ = 243.4 km s⁻¹, T₀ = 2, 451, 119.0927(5) for the spectroscopic conjunction) is consistent with the results from the new data.

The presence of the visual companion to the contact binary makes the Hipparcos parallax, π = 1.71 ± 6.27 mas, rather uncertain (see Pribulla & Rucinski 2006). There is a disparity between J − K = 0.454, as determined from the 2MASS survey, implying a spectral type later than G6V, and our spectral-type estimate, F8V; this disparity is probably caused by the late-type visual companion.

The photometric variability of HH UMa was discovered by the Hipparcos mission where it was classified as a periodic variable with P = 0.187, 747 days. On the basis of the color–period relation, Duerbeck (1997) concluded that it is very probably a genuine contact binary with twice the Hipparcos period. The ground-based observations of Pribulla et al. (2003) supported the contact binary nature of HH UMa; they also gave an improved ephemeris: HJD = 2, 452, 368.3979 + 0.375, 4937 × E. Due to the partial eclipses, the mass ratio could not be reliably determined and was estimated as q_ph ≈ 0.35–0.45.

Our spectroscopy definitely shows a contact-binary nature of HH UMa and gives q_sp = 0.295(3). The low projected total mass, (M₁ + M₂)sin³i = 0.826 M_☉, together with low amplitude of the light curve, 0.17 mag, supports the low inclination angle, as found in the photometric analysis.

The trigonometric parallax of the system, π = 4.50 ± 1.78 mas, is too imprecise to draw any conclusions on its absolute magnitude. The 2MASS color of the system, J − K = 0.572, agrees fairly well with our estimate of the spectral type, F5V. The Tycho-2 B − V = 0.50 corresponds to the F7V spectral type.

PY Vir (GSC 4961-667) was found on Stardial images to be a variable of the W UMa type (Wils & Dworak 2003). The system is also known as an X-ray source (1RXS J131032.4-040934). No photometric or spectroscopic analysis of PY Vir has yet been published. A minimum observed photometrically in parallel with the spectroscopic observations (HJD = 2, 554, 201.7944) was used for a preliminary improvement of the ephemeris used for phasing of our spectroscopy.

The BFs of PY Vir based on the 2007 observations show the presence of a third component with a constant RV, V₃ = −32.9 ± 4.1 km s⁻¹; this velocity is rather different from the systemic velocity of the contact binary, V₀ = −14.66 km s⁻¹. A few additional, low-quality spectra of PY Vir taken under poor-weather conditions in 2008 February 19 (not listed in Table 1) give V₃ = −23.3 ± 3.7 km s⁻¹ (at the mean HJD = 2,454,515.883) so that we have an indication of a change in V₃. The velocities of the close binary from these additional observations are not precise enough to see if the motion of the third component is reflected in systemic RVs of the eclipsing pair. The third component may be a binary itself; otherwise, the velocity changes may result from its low mass and a relatively fast orbital motion in a tight triple system. We consider the latter possibility as a relatively probable and more exciting one, but its verification would require observations over several seasons.

PY Vir has not been known to be a multiple system; it is also not listed in the WDS catalog. A lunar occultation of the system in 1984 July did not reveal the presence of any visual companion (Evans et al. 1985); hence, the separation of components is probably very small. Moreover, the light contribution of the third component is fairly small, only about L₃/(L₁ + L₂) = 0.08, at the maximum light of the eclipsing pair.

The 2MASS color of the system, J − K = 0.572, indicates the K2V spectral type, which is consistent with our spectral classification. The orbital period of the system, 0.311 days, is rather long for such a late spectral type (it would be more consistent with late F) so that the system may be close but detached. The shape of the BF (see Figure 4) with a gap between the two peaks is not inconsistent with this possibility. The Tycho-2 (B − V) color is rather uncertain to draw any conclusions, B − V = 0.80 ± 0.06.