THE ALLWISE MOTION SURVEY, PART 2

The essence of the scientific method is to observe nature, make a testable hypothesis to explain the observations, perform experiments to test the theory, analyze the results, revise the hypothesis if necessary, and repeat. After myriad cycles of this process, scientific methodology helps us develop general theories while allowing us to build an understanding of our surroundings with increasingly greater detail.

Each scientific discipline has its own mechanisms for achieving this. A chemist, for example, might use earlier observations and tested theory to hypothesize what the chemical reaction between two newly created compounds might be. To test this, the chemist need only mix the compounds and observe the result. In this case, the experiment is a tactile process; the chemist is an active participant.

Astronomy, on the other hand, is generally quite different. Unlike chemists, astronomers have their hands figuratively tied behind their backs. They are unable to force the experiment. There is no picking up of test tubes to bring chemicals into contact. The laboratory itself is even far removed—light minutes or light years away. The astronomer is left merely to witness, not participate. Nevertheless, the cosmos is continually performing experiments all around us. The astronomer's challenge is in recognizing these experiments and realizing how they can be used in the scientific method. The satisfaction resulting from this forced ingenuity is, in fact, one of the joys of astronomical research.

Basic observations provide the insight needed to devise new experiments. It was Halley (1718) who first showed that three bright stars—Arcturus, Sirius, and Palilicium (known now as Aldebaran)—exhibited their own, small motions across the sky, as shown by the fact that their positions had changed dramatically with respect to other stars since the measurements made by Timocharis, Aristyllus, Hipparchus, and Claudius Ptolemy 1600–1800 years previously.¹⁰ However, it was not until Herschel (1783) concluded that the motion of such objects may indicate proximity to the Sun that astronomers realized they had a new tool for distinguishing the nearest stars from the countless points of light in the background. Thereafter, surveys began in earnest to search for proper motion objects whose distances might be measurable through a tool that the earth's yearly orbit about the Sun provides us: trigonometric parallax (e.g., Bessel 1838; Henderson 1839). Modern astronomy owes its underpinnings to the successes of these early motion surveys—from the establishment of the bottom rungs of the "distance ladder" (e.g., convergent point analysis of the Hyades cluster; Boss 1908) to the discovery of degenerate states of matter (via the identification of hot but very low luminosity stars now known as white dwarfs; Bond 1862; Adams 1914, 1915; van Maanen 1917).

By performing the AllWISE2 Motion Survey, we continue this time-honored tradition. In AllWISE2 we identify nearby objects useful as "test particles" for various experiments:

• 1.  
  In one experiment, we identify motion stars located within or behind nearby molecular clouds. As these stars move, their flux variations along the line of sight can probe the clumpiness of the cloud material itself since the stars have spectral types appropriate for use as standard candles (Section 4.2).
• 2.  
  In a second experiment, we select spectroscopically verified M dwarfs from our follow-up list to hunt for previously missed young objects in the solar vicinity. In this case, we use positional alignments of our motion sources with detections by X-ray and ultraviolet all-sky surveys to identify candidates with high levels of magnetic activity, which can often be tied to youth (Section 4.3.1). Young M dwarfs sometimes host young, low-mass brown dwarf companions that can be used as proxies for exoplanet atmospheric studies.
• 3.  
  In a third experiment, we search for objects having both unusual colors and higher-than-average motions for their brightness to identify old, low-metallicty late-M and L (sub)dwarfs. The identification of a large collection of such objects spanning the stellar/substellar break will eventually allow us to measure directly the brown dwarf cooling rates at very old ages (Section 4.6).
• 4.  
  In a fourth experiment, we search for widely separated common-proper motion binaries having vastly different spectral types in order to constrain physical parameters of the system (Section 5). As one example, we identify a system consisting of a normal M subdwarf and a carbon dwarf. The metallicity of the carbon dwarf, presumably polluted by a close but unseen white dwarf neighbor, can be measured directly using the metallicity of the M subdwarf companion, the first such system where this is possible (Section 4.6.5 and Section 5.4).
• 5.  
  In a fifth experiment, we look for outliers in color–color space to identify unresolved proper motion systems with disparate types. In one example, discussed in S. Fajardo-Acosta et al. (2016, in preparation), an examination of the infrared colors led to the discovery of what we believe is a cold and unique white dwarf member in an unresolved system with a late-M dwarf.
• 6.  
  In a sixth experiment, discussed in K. Kellogg et al. (2016, in preparation), we comb our list of motion candidates for objects detected by WISE but not by surveys at shorter wavelengths. The goal is to uncover other very cold brown dwarfs, such as the 250 K object WISEA J085510.74−071442.5 (Luhman 2014b), that might have escaped color selection techniques. These cold atmospheres provide much needed empirical data points in the temperature regime just hotter than Jupiter (T_eff ≈ 135 K; Aitken & Jones 1972).

This paper is organized as follows. In Section 2 we describe our new motion search using AllWISE and show a number of color–color and color–magnitude diagrams to aid in the characterization of the motion sources. In Section 3 we describe our spectroscopic observations and reductions on selected objects. In Section 4 we discuss spectral classification and analysis on the resulting spectra, divided into subsections by type: white dwarfs (Section 4.1), stars with types ≤K5 (Section 4.2), mid-K through late-M dwarfs (Section 4.3), L dwarfs (Section 4.4), T dwarfs (Section 4.5), and subdwarfs (Section 4.6). In Section 5 we discuss the search for common-proper-motion systems, with special emphasis on systems having L or T dwarf members (Section 5.1), systems with white dwarf members (Section 5.2), systems with large magnitude differences (Section 5.3), and systems identified serendipitously (Section 5.4). Conclusions are given in Section 6.

Section 5 of Kirkpatrick et al. (2014) shows that 80% of the objects found by Luhman (2014a), but missed by the AllWISE1 Motion Survey, were lost because of the criterion ${rchi}2/{rchi}2\_{pm}\gt 1.03$, where rchi2 is the reduced ${\chi }^{2}$ value for the stationary fit and rchi2_pm is the reduced ${\chi }^{2}$ value for the motion fit. This criterion was used by AllWISE1 under the assumption that the reduced ${\chi }^{2}$ value would be significantly lower for the motion fit relative to the stationary fit if the object were truly moving. For the AllWISE2 Motion Survey, we have used the same criteria used for AllWISE1—discussed in Section 4.1 of Kirkpatrick et al. (2014)—except that the reduced ${\chi }^{2}$ criterion has been changed to ${rchi}2/{rchi}2\_{pm}\leqslant 1.03$. That is, the combination of AllWISE1 and AllWISE2 drops the ${rchi}2/{rchi}2\_{pm}$ check entirely.

An unfortunate consequence of this new criterion, and the reason it was not implemented originally, is the large number of new candidates it produces—another 1,409,845 of them. To scrutinize these, we created finder charts showing a 2 × 2 arcmin region around each candidate's AllWISE coordinates as imaged by WISE (in the W1, W2, W3, and W4 bands) and by previous large-area surveys: the Digitized Sky Survey 1 (B and R bands), the Digitized Sky Survey 2 (B, R, and I bands), the Two Micron All Sky Survey (J, H, and K_s bands), and, when available, the Sloan Digital Sky Survey (u, g, r, i, and z bands). See Figure 1 as an example.

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After scrutinzing the first 491,031 charts, sampling different Galactic environments covering 35.8% of the sky, we found that only 2.2% of the candidates were valid motion objects. This accrued knowledge allowed us to create additional criteria to further winnow the remaining candidate list. Objects were removed from further consideration if an object from the USNO-B1 catalog (Monet et al. 2003) was found within 1 arcsec of the candidate's AllWISE position or if both $w1{nm}/w1m$ and $w2{nm}/w2m$ fall below 0.8. The first criterion was imposed because many spurious candidates were found to be either not moving at all between USNO-B1 and WISE or were barely moving objects whose motions were overestimated in AllWISE. (The ∼10 year time baseline between the USNO-B1 proper moved positions and the AllWISE positions means that this criterion eliminates any legitimate motion objects with $\mu \lt 0.1$ arcsec/year.) The second criterion was imposed to eliminate false source detections from AllWISE: $w1{nm}$ and $w2{nm}$ give the number of individual exposures on which the source was detected with the profile-fit measurement in band W1 and W2, respectively, whereas $w1m$ and $w2m$ give the total number of individual exposures available in bands W1 and W2. Spurious sources occurring in just a handful of frames are readily tossed out if both $w1{nm}/w1m$ and $w2{nm}/w2m$ are significantly less than 1. Running these additional criteria on the original list of 1,409,845 candidates reduces the list to 333,345 objects.

These criteria were then run on the 35.8% of the sky already scrutinized to see how many valid motion objects would be erroneously eliminated. Only 54 of the 10,598 confirmed motion objects (0.5% of the total) were rejected by the additional criteria. These sources are listed in Table 1.¹¹ Of these 54, 51 were rejected because they had a USNO-B1 source lying within 1 arcsec, but this source is a non-moving background object that nearly coincides with the position of the WISE source. In these cases, the USNO-B1 criterion has unfortunately eliminated a valid motion object. For the remaining three objects (WISE 1222−5629, WISE 2046+3358, and WISE 2245+3026)¹² , both of the $w1{nm}/w1m$ and $w2{nm}/w2m$ values fall below 0.8. All three of these are very bright, heavily saturated sources—W1 magnitudes of 3.9, −1.8, and 4.0 mag, respectively—and their low $w1{nm}/w1m$ and $w2{nm}/w2m$ values are indicative of the fact that very few usable pixels were available for the profile-fit measurement. The mean coverage per pixel was less than 7 for these objects, so measurements were not possible with >80% frequency.

Table 1.  Valid Motion Objects Not Included in Table 2

WISEA Designation	2MASS J	2MASS H	2MASS Ks	W1	W2	AllWISE	AllWISE	Computed	Computed	Flagb
	(mag)	(mag)	(mag)	(mag)	(mag)	R.A. Motion	decl. Motion	${\mu }_{\alpha }$ a	μδa
						(mas/year)	(mas/year)	(mas/year)	(mas/year)
J000624.35−141309.4	13.395 ± 0.030	12.732 ± 0.029	12.447 ± 0.025	12.275 ± 0.023	12.098 ± 0.024	200 ± 56	−229 ± 55	199.8 ± 7.4	−79.0 ± 5.9	1
J001207.46−122714.3	12.686 ± 0.023	12.089 ± 0.024	11.917 ± 0.026	11.796 ± 0.024	11.722 ± 0.022	27 ± 52	−330 ± 52	15.6 ± 7.4	−141.0 ± 6.6	1
J001936.92+492103.2	12.803 ± 0.023	12.202 ± 0.021	11.918 ± 0.021	11.689 ± 0.023	11.487 ± 0.021	155 ± 29	−57 ± 29	140.5 ± 6.1	−59.5 ± 6.0	0
J002539.83−643630.6	11.418 ± 0.022	10.779 ± 0.021	10.564 ± 0.023	10.363 ± 0.023	10.230 ± 0.020	5 ± 35	−287 ± 36	136.9 ± 7.3	−184.3 ± 6.5	0
J002545.47+730127.9	13.502 ± 0.029	12.881 ± 0.033	12.555 ± 0.025	12.358 ± 0.024	12.185 ± 0.023	235 ± 44	137 ± 43	127.1 ± 9.3	−1.5 ± 8.4	0
J002952.26+584548.8	10.108 ± 0.025	9.528 ± 0.026	9.269 ± 0.016	9.123 ± 0.022	9.013 ± 0.020	−51 ± 24	−134 ± 23	−34.1 ± 6.0	−162.9 ± 6.0	1
J010352.45−155508.3	13.226 ± 0.022	12.636 ± 0.026	12.279 ± 0.024	12.023 ± 0.024	11.833 ± 0.022	−30 ± 54	−274 ± 52	103.7 ± 8.0	−21.7 ± 7.9	0
J012245.03+530105.2	9.261 ± 0.021	8.636 ± 0.022	8.499 ± 0.020	8.394 ± 0.023	8.439 ± 0.020	134 ± 25	−33 ± 24	172.8 ± 5.9	−60.4 ± 5.9	1
J012304.83−691842.2	11.979 ± 0.021	11.429 ± 0.025	11.164 ± 0.023	11.030 ± 0.023	10.862 ± 0.020	191 ± 36	31 ± 38	237.7 ± 6.6	29.5 ± 5.9	1
J013218.26−120302.7	11.013 ± 0.023	10.469 ± 0.025	10.168 ± 0.026	10.017 ± 0.023	9.827 ± 0.020	244 ± 39	−128 ± 38	426.1 ± 13.7	−42.3 ± 7.0	1
J013535.39−721427.1	14.026 ± 0.024	13.512 ± 0.021	13.250 ± 0.041	13.070 ± 0.024	12.840 ± 0.023	203 ± 48	−144 ± 45	99.8 ± 9.9	−21.6 ± 6.9	0
J020837.11−650516.7	11.541 ± 0.024	10.853 ± 0.024	10.663 ± 0.021	10.527 ± 0.022	10.459 ± 0.020	219 ± 34	29 ± 35	216.4 ± 6.5	−10.4 ± 6.6	1
J021025.03+622501.8	11.300 ± 0.023	10.660 ± 0.023	10.392 ± 0.016	10.249 ± 0.023	10.222 ± 0.021	208 ± 36	−76 ± 35	80.7 ± 6.3	−91.8 ± 6.2	0
J030338.48−395537.6	11.840 ± 0.022	11.235 ± 0.021	11.027 ± 0.021	10.932 ± 0.023	10.820 ± 0.020	184 ± 26	58 ± 26	219.6 ± 6.4	39.8 ± 6.3	1
J032816.37+575436.0	9.471 ± 0.021	8.797 ± 0.016	8.613 ± 0.019	8.473 ± 0.022	8.495 ± 0.019	134 ± 34	−140 ± 32	147.3 ± 6.1	−93.4 ± 6.0	1
J033223.47−820014.0	11.069 ± 0.021	10.391 ± 0.021	10.196 ± 0.023	10.118 ± 0.023	10.115 ± 0.020	140 ± 29	90 ± 38	107.8 ± 8.5	89.8 ± 7.7	0
J033253.99−213219.7	11.114 ± 0.026	10.523 ± 0.025	10.393 ± 0.023	10.333 ± 0.024	10.387 ± 0.020	137 ± 26	19 ± 25	150.2 ± 9.1	4.1 ± 8.1	1
J033952.94−374326.8	13.064 ± 0.028	12.515 ± 0.027	12.258 ± 0.024	12.148 ± 0.023	11.982 ± 0.022	109 ± 26	−85 ± 26	145.6 ± 6.7	−71.3 ± 6.6	0
J040131.59−771032.8	14.267 ± 0.032	13.727 ± 0.038	13.421 ± 0.039	13.149 ± 0.023	12.919 ± 0.024	230 ± 43	−94 ± 48	86.9 ± 6.2	−84.4 ± 6.2	0
J040506.16−114423.7	14.828 ± 0.038	14.297 ± 0.045	13.952 ± 0.051	13.683 ± 0.025	13.412 ± 0.032	363 ± 87	−307 ± 92	238.7 ± 6.9	−261.0 ± 6.8	0
J041949.59−224727.0	13.850 ± 0.026	13.281 ± 0.029	13.069 ± 0.033	12.874 ± 0.041	12.709 ± 0.044	158 ± 91	−547 ± 94	151.4 ± 11.5	−615.4 ± 7.7	1
J045721.97−720717.3	11.842 ± 0.024	11.217 ± 0.025	10.959 ± 0.026	10.845 ± 0.023	10.761 ± 0.021	99 ± 29	133 ± 31	105.3 ± 7.5	167.9 ± 6.1	0
J052552.76−624320.6	14.723 ± 0.038	14.028 ± 0.037	13.767 ± 0.054	13.543 ± 0.024	13.342 ± 0.024	33 ± 29	191 ± 28	39.0 ± 7.1	193.5 ± 6.3	0
J053528.69−640321.6	11.346 ± 0.024	10.757 ± 0.024	10.477 ± 0.021	10.381 ± 0.023	10.237 ± 0.020	14 ± 22	137 ± 22	14.3 ± 6.1	140.2 ± 6.0	0
J060433.86−371659.7	13.318 ± 0.028	12.738 ± 0.029	12.408 ± 0.025	12.230 ± 0.023	12.023 ± 0.022	159 ± 51	−246 ± 52	78.2 ± 7.0	−197.4 ± 6.9	0
J070424.11−490017.1	13.704 ± 0.026	13.099 ± 0.031	12.847 ± 0.027	12.628 ± 0.023	12.449 ± 0.022	172 ± 39	−187 ± 39	93.5 ± 6.7	−190.7 ± 6.7	1
J101437.19−061934.4	13.188 ± 0.027	12.551 ± 0.026	12.329 ± 0.029	12.211 ± 0.022	12.105 ± 0.022	101 ± 52	−286 ± 54	93.9 ± 10.1	−218.0 ± 6.2	1
J111050.12−732726.0	11.327 ± 0.024	10.735 ± 0.023	10.459 ± 0.021	10.319 ± 0.023	10.168 ± 0.020	42 ± 32	189 ± 33	115.8 ± 8.5	104.6 ± 7.8	1
J114033.30−685844.1	13.347 ± 0.027	12.591 ± 0.024	12.363 ± 0.027	12.216 ± 0.024	12.088 ± 0.024	−248 ± 43	7 ± 43	−183.6 ± 8.1	−1.8 ± 7.3	0
J115435.82+273806.7	12.466 ± 0.022	11.866 ± 0.022	11.593 ± 0.020	11.383 ± 0.023	11.215 ± 0.021	−14 ± 43	−275 ± 43	−66.0 ± 6.4	−172.7 ± 6.4	1
J121148.08−732828.5	12.009 ± 0.023	11.473 ± 0.025	11.203 ± 0.023	11.052 ± 0.023	10.864 ± 0.022	−246 ± 37	45 ± 37	−158.5 ± 8.7	24.7 ± 7.1	1
J121510.28−821830.5	11.104 ± 0.023	10.560 ± 0.025	10.336 ± 0.021	10.176 ± 0.023	10.037 ± 0.021	−219 ± 31	27 ± 31	−214.4 ± 7.6	−69.0 ± 6.9	1
J122258.48−562952.0	11.502 ± 0.022	10.975 ± 0.027	10.719 ± 0.021	10.635 ± 0.022	10.479 ± 0.020	−154 ± 26	−60 ± 25	−160.6 ± 6.4	−21.8 ± 6.4	0
J122833.29−562430.4	4.860 ± 0.242	4.167 ± 0.210	4.117 ± 0.264	3.947 ± 0.399	3.637 ± 0.218	−183 ± 27	50 ± 27	−258.7 ± 16.2	−242.3 ± 16.3	1
J130223.85−363400.4	14.791 ± 0.045	14.042 ± 0.039	13.627 ± 0.049	13.411 ± 0.025	13.183 ± 0.028	−240 ± 45	−35 ± 48	−287.8 ± 6.8	−80.1 ± 6.8	0
J130701.48−734518.9	11.853 ± 0.023	11.244 ± 0.026	11.020 ± 0.021	10.865 ± 0.024	10.786 ± 0.021	−171 ± 33	−64 ± 34	−118.7 ± 19.8	−111.4 ± 7.8	0
J131220.16−174836.9	13.455 ± 0.026	12.905 ± 0.024	12.689 ± 0.030	12.529 ± 0.024	12.337 ± 0.025	−238 ± 34	−72 ± 35	−216.7 ± 9.6	−85.2 ± 6.6	1
J132231.09−272252.6	12.840 ± 0.026	12.224 ± 0.023	12.086 ± 0.027	11.950 ± 0.023	11.839 ± 0.022	−208 ± 34	−134 ± 34	−202.7 ± 6.5	−122.4 ± 6.4	1
J143840.48+262512.9	14.615 ± 0.036	14.134 ± 0.042	13.843 ± 0.045	13.767 ± 0.025	13.482 ± 0.029	−259 ± 52	−102 ± 55	−259.8 ± 25.0	−125.6 ± 8.3	1
J150752.98−692400.7	11.580 ± 0.022	10.918 ± 0.024	10.720 ± 0.023	10.649 ± 0.023	10.630 ± 0.021	−195 ± 41	−153 ± 40	−111.0 ± 7.0	−79.4 ± 7.0	0
J152709.00−242601.2	12.317 ± 0.026	11.801 ± 0.021	11.563 ± 0.027	11.428 ± 0.024	11.237 ± 0.021	−242 ± 47	−137 ± 46	−175.1 ± 6.8	−95.7 ± 6.0	1
J152814.16−663149.6	12.464 ± 0.025	11.935 ± 0.023	11.636 ± 0.026	11.498 ± 0.023	11.345 ± 0.021	−275 ± 45	−30 ± 47	−143.0 ± 16.4	−127.2 ± 7.1	0
J160056.49−714144.2	11.767 ± 0.024	11.236 ± 0.027	10.951 ± 0.021	10.772 ± 0.023	10.609 ± 0.020	−258 ± 35	−100 ± 38	−143.8 ± 7.9	−154.0 ± 6.9	0
J161321.81−412331.3	12.932 ± 0.024	12.450 ± 0.025	12.190 ± 0.025	11.985 ± 0.024	11.834 ± 0.023	−302 ± 54	−28 ± 55	−134.7 ± 7.3	−6.7 ± 7.1	0
J164154.48−345205.4	13.284 ± 0.027	12.818 ± 0.026	12.533 ± 0.035	12.392 ± 0.023	12.231 ± 0.025	−336 ± 63	−19 ± 70	−269.2 ± 6.7	11.5 ± 6.7	0
J170016.84−510421.7	12.212 ± 0.024	11.571 ± 0.022	11.422 ± 0.023	11.135 ± 0.021	11.110 ± 0.021	−63 ± 46	−325 ± 46	−47.8 ± 6.5	−159.0 ± 6.4	0
J170551.78−515449.2	12.325 ± 0.024	11.808 ± 0.024	11.474 ± 0.023	11.226 ± 0.024	11.060 ± 0.021	−201 ± 47	−146 ± 46	−99.9 ± 6.6	−131.5 ± 6.5	0
J174549.22−361257.9	11.351 ± 0.023	10.766 ± 0.021	10.494 ± 0.025	10.349 ± 0.025	10.258 ± 0.023	−153 ± 47	−229 ± 47	−9.9 ± 6.3	−139.3 ± 6.2	0
J174639.95+225834.7	11.494 ± 0.021	10.823 ± 0.019	10.691 ± 0.023	10.607 ± 0.023	10.606 ± 0.020	−15 ± 40	−220 ± 39	−2.7 ± 6.5	−286.4 ± 6.3	1
J174805.58−450851.9	13.479 ± 0.024	13.030 ± 0.027	12.765 ± 0.029	12.626 ± 0.025	12.419 ± 0.025	−150 ± 74	−381 ± 75	−69.2 ± 6.8	−185.3 ± 6.8	0
J193231.49+403052.2	11.089 ± 0.025	10.441 ± 0.022	10.268 ± 0.020	10.107 ± 0.023	10.086 ± 0.020	−119 ± 32	−152 ± 31	−76.7 ± 5.8	−173.2 ± 5.7	1
J204612.98+335816.2	0.641 ± 0.218	0.104 ± 0.160	−0.007 ± 0.204	−1.763 ±  NaN	−0.936 ±  NaN	−446 ± 67	−149 ± 82	357.2 ± 26.9	312.9 ± 27.1	1
J205135.26−253238.2	12.103 ± 0.027	11.484 ± 0.026	11.384 ± 0.025	11.295 ± 0.023	11.333 ± 0.021	−172 ± 47	−251 ± 48	−135.0 ± 6.0	−258.4 ± 5.9	1
J224534.23+302629.5	5.113 ± 0.246	4.427 ± 0.196	4.497 ± 0.320	4.002 ± 0.445	3.526 ± 0.170	−839 ± 41	61 ± 46	−298.4 ± 25.1	−332.3 ± 25.2	1

Notes.

^aThis is the motion measured between the 2MASS and AllWISE epochs. ^bIf the source is a motion discovery unique to AllWISE, this column is "0". For previous discoveries the column is "1."

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As noted in Table 1, 27 of these 54 objects are new discoveries. Extrapolating to the remaining 64.2% of the sky means that our additional criteria could potentially eliminate ∼100 valid motion objects, roughly 50 of which would be new discoveries. This loss was deemed acceptable since the additional criteria reduce the number of remaining candidates by a factor of ∼5. Thus, for the remaining 64.2% of sky, the additional criteria were employed. In the remainder of this paper, only those objects meeting the full set of criteria are discussed.

Table 2 gives the AllWISE coordinates, W1 and W2 magnitudes, and AllWISE-measured motions for all 27,846 verified motion objects from the AllWISE2 survey along with 2MASS J, H, and K_s magnitudes¹³ and our measurement of the 2MASS-to-AllWISE proper motion. This table includes 11,287 new discoveries as well as 16,559 previously identified motion objects¹⁴ , the distinction between which can be found in the Flag column.

Table 2.  Motion Objects Identified by the AllWISE2 Motion Survey

WISEA Designation	2MASS J	2MASS H	2MASS Ks	W1	W2	AllWISE	AllWISE	Computed	Computed	Flagb
	(mag)	(mag)	(mag)	(mag)	(mag)	R.A. Motion	decl. Motion	${\mu }_{\alpha }$ a	μδa
						(mas/year)	(mas/year)	(mas/year)	(mas/year)
(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)	(11)
J000003.89+341118.1	7.249 ± 0.017	6.940 ± 0.016	6.885 ± 0.017	6.851 ± 0.062	6.871 ± 0.019	−231 ± 36	15 ± 34	−224.7 ± 7.4	−69.1 ± 6.6	1
J000004.53+335248.8	12.712 ± 0.023	12.096 ± 0.023	11.867 ± 0.019	11.745 ± 0.024	11.619 ± 0.021	231 ± 46	−89 ± 46	170.7 ± 11.4	7.1 ± 8.9	1
J000005.54+134759.5	12.332 ± 0.026	11.760 ± 0.028	11.549 ± 0.025	11.298 ± 0.023	11.112 ± 0.021	200 ± 45	−229 ± 45	207.9 ± 7.4	−109.1 ± 7.3	1
J000012.91−545452.7	10.722 ± 0.020	10.475 ± 0.025	10.449 ± 0.023	10.383 ± 0.023	10.379 ± 0.021	208 ± 38	−75 ± 37	249.3 ± 7.3	−89.8 ± 6.5	1
J000015.91−481258.5	9.015 ± 0.029	8.593 ± 0.033	8.583 ± 0.023	8.493 ± 0.024	8.551 ± 0.020	196 ± 36	−102 ± 35	161.7 ± 7.9	−49.1 ± 7.8	0
J000017.32+203312.5	13.426 ± 0.027	12.878 ± 0.035	12.578 ± 0.026	12.443 ± 0.023	12.272 ± 0.023	243 ± 59	−224 ± 60	144.5 ± 9.1	−46.0 ± 7.4	0
J000018.94+495447.2	13.263 ± 0.025	12.631 ± 0.024	12.361 ± 0.023	12.220 ± 0.023	12.005 ± 0.021	172 ± 32	88 ± 32	138.7 ± 6.1	77.0 ± 6.1	1
J000021.98+314939.9	10.705 ± 0.020	10.119 ± 0.015	9.863 ± 0.020	9.747 ± 0.023	9.649 ± 0.020	275 ± 43	−22 ± 41	279.3 ± 6.6	−35.7 ± 6.5	1
J000022.32−050305.3	9.860 ± 0.026	9.478 ± 0.025	9.410 ± 0.025	9.337 ± 0.022	9.404 ± 0.019	84 ± 39	−204 ± 37	34.1 ± 11.4	−92.4 ± 7.9	1
J000022.88+375803.2	11.006 ± 0.022	10.402 ± 0.031	10.139 ± 0.023	9.924 ± 0.022	9.774 ± 0.020	186 ± 40	−119 ± 39	258.7 ± 7.2	−66.5 ± 7.1	1
J000023.39+534126.8	11.357 ± 0.023	10.731 ± 0.023	10.552 ± 0.021	10.465 ± 0.023	10.444 ± 0.020	38 ± 26	−161 ± 25	65.1 ± 6.7	−186.1 ± 5.9	1
J000024.05+395157.0	12.053 ± 0.022	11.504 ± 0.030	11.304 ± 0.022	11.167 ± 0.023	11.004 ± 0.021	193 ± 33	−12 ± 32	229.1 ± 7.4	5.0 ± 6.5	1
J000028.26−360909.7	13.653 ± 0.024	13.105 ± 0.029	12.865 ± 0.029	12.707 ± 0.024	12.494 ± 0.024	−207 ± 56	−258 ± 56	−137.3 ± 7.5	−103.2 ± 6.6	0
J000029.88+334822.6	12.195 ± 0.022	11.595 ± 0.021	11.343 ± 0.023	11.198 ± 0.024	11.062 ± 0.021	−209 ± 47	−134 ± 46	−119.7 ± 12.1	−77.4 ± 9.7	0
J000032.33−565009.7	8.575 ± 0.024	7.968 ± 0.031	7.867 ± 0.024	7.767 ± 0.027	7.853 ± 0.020	−181 ± 32	−69 ± 31	−45.7 ± 7.3	−118.1 ± 7.3	1
J000032.37−244231.3	7.981 ± 0.027	7.484 ± 0.047	7.383 ± 0.024	7.248 ± 0.035	7.387 ± 0.020	220 ± 36	15 ± 35	104.5 ± 7.9	−58.0 ± 7.9	1
J000033.07−532606.9	12.641 ± 0.023	12.051 ± 0.026	11.719 ± 0.023	11.522 ± 0.023	11.335 ± 0.021	86 ± 43	−291 ± 43	169.8 ± 8.1	−133.1 ± 7.1	1
J000035.38−011248.8	13.822 ± 0.030	13.226 ± 0.022	12.899 ± 0.027	12.724 ± 0.024	12.506 ± 0.024	−256 ± 64	−251 ± 66	−24.9 ± 9.9	−246.1 ± 8.2	0
J000035.78−451506.2	11.798 ± 0.026	11.212 ± 0.022	11.112 ± 0.023	11.040 ± 0.023	11.048 ± 0.020	248 ± 42	12 ± 40	176.5 ± 6.5	−11.7 ± 6.4	1
J000040.37+162804.4	14.061 ± 0.031	13.519 ± 0.041	13.159 ± 0.037	12.985 ± 0.024	12.738 ± 0.026	383 ± 72	−34 ± 73	441.2 ± 7.7	−27.8 ± 6.8	1
J000040.56+031339.3	13.711 ± 0.026	13.212 ± 0.031	12.964 ± 0.030	12.849 ± 0.024	12.618 ± 0.026	−20 ± 70	−414 ± 71	167.5 ± 12.7	−307.3 ± 8.2	1
J000043.95−270016.2	10.094 ± 0.023	9.466 ± 0.021	9.292 ± 0.019	9.220 ± 0.023	9.188 ± 0.020	63 ± 40	−212 ± 42	67.6 ± 7.9	−161.6 ± 7.8	1
J000047.16−351007.1	9.117 ± 0.029	8.480 ± 0.040	8.282 ± 0.027	8.109 ± 0.022	8.072 ± 0.021	218 ± 34	−119 ± 33	343.2 ± 7.7	−111.5 ± 6.8	1
J000048.67+295109.0	8.987 ± 0.023	8.597 ± 0.027	8.519 ± 0.021	8.464 ± 0.023	8.511 ± 0.020	−64 ± 36	198 ± 35	−7.7 ± 8.1	115.4 ± 6.5	1
J000050.33+624625.8	14.513 ± 0.035	14.090 ± 0.051	13.801 ± 0.053	13.567 ± 0.024	13.438 ± 0.027	245 ± 44	44 ± 44	162.3 ± 8.6	−9.9 ± 7.0	1
J000051.18−163804.3	13.104 ± 0.023	12.556 ± 0.024	12.171 ± 0.023	12.012 ± 0.023	11.798 ± 0.023	−209 ± 51	−220 ± 52	−74.8 ± 6.9	−87.5 ± 6.1	0
J000056.18+385206.3	13.543 ± 0.024	12.993 ± 0.035	12.842 ± 0.023	12.779 ± 0.024	12.792 ± 0.027	337 ± 65	−123 ± 62	153.3 ± 7.7	−63.3 ± 6.9	1
J000102.21−224639.9	6.924 ± 0.018	6.459 ± 0.033	6.357 ± 0.020	6.337 ± 0.081	6.289 ± 0.025	237 ± 37	31 ± 36	63.0 ± 6.4	−87.9 ± 6.4	1
J000103.04+610219.1	13.904 ± 0.026	13.303 ± 0.036	13.084 ± 0.032	12.860 ± 0.023	12.718 ± 0.025	170 ± 36	−87 ± 35	134.9 ± 7.6	−38.1 ± 6.8	0
J000104.01−064310.4	13.190 ± 0.031	12.606 ± 0.021	12.296 ± 0.024	12.064 ± 0.025	11.839 ± 0.023	−190 ± 56	−275 ± 57	−104.2 ± 6.1	−193.2 ± 6.1	1
J000104.97−350502.6	11.515 ± 0.023	10.931 ± 0.025	10.725 ± 0.023	10.586 ± 0.023	10.500 ± 0.020	−145 ± 36	−202 ± 36	−39.4 ± 8.8	−72.1 ± 6.9	0
J000107.62−811038.6	13.402 ± 0.028	12.879 ± 0.025	12.633 ± 0.031	12.465 ± 0.023	12.244 ± 0.023	250 ± 44	−151 ± 45	225.0 ± 20.1	−57.6 ± 6.9	0

Notes.

^aThis is the motion measured between the 2MASS and AllWISE epochs. ^bIf the source is a motion discovery unique to AllWISE, this column is "0." For previous discoveries the column is "1."

Only a portion of this table is shown here to demonstrate its form and content. A machine-readable version of the full table is available.

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Because they were not published in Kirkpatrick et al. (2014), the 16,628 re-discovered motion objects found as part of our previous AllWISE1 survey¹⁵ are listed in Table 3.¹⁶ These two tables, together with the list of 3525 new discoveries from Kirkpatrick et al. (2014) (their Table 3) and WISEA J085510.74−071442.5 (their Table 4), represent exactly 48,000 verified motion objects identified by the AllWISE1+AllWISE2 surveys. In addition to these, a small number of possible AllWISE motion objects lacking DSS and 2MASS counterparts are discussed separately in K. Kellogg et al. (2016, in preparation).

Table 3.  Previously Known Motion Objects Identified by the AllWISE1 Motion Survey

WISEA Designation	2MASS J	2MASS H	2MASS Ks	W1	W2	AllWISE	AllWISE	Computed	Computed
	(mag)	(mag)	(mag)	(mag)	(mag)	R.A. Motion	decl. Motion	${\mu }_{\alpha }$ a	μδa
						(mas/year)	(mas/year)	(mas/year)	(mas/year)
(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
J000010.31+412141.3	12.506 ± 0.022	11.990 ± 0.031	11.750 ± 0.021	11.624 ± 0.022	11.446 ± 0.022	221 ± 32	−6 ± 32	239.0 ± 6.6	−17.6 ± 6.5
J000015.37+390251.1	9.264 ± 0.024	8.872 ± 0.032	8.763 ± 0.023	8.717 ± 0.023	8.768 ± 0.019	236 ± 35	176 ± 33	207.7 ± 7.2	65.2 ± 6.3
J000019.27+431242.4	9.924 ± 0.020	9.412 ± 0.019	9.358 ± 0.019	9.282 ± 0.022	9.360 ± 0.020	189 ± 26	−38 ± 26	195.3 ± 6.0	−73.5 ± 5.9
J000027.09+575404.9	12.497 ± 0.024	12.010 ± 0.031	11.855 ± 0.028	11.734 ± 0.023	11.733 ± 0.023	371 ± 29	239 ± 28	381.1 ± 6.7	219.1 ± 6.7
J000028.04−412531.3	13.545 ± 0.026	12.974 ± 0.021	12.834 ± 0.032	12.685 ± 0.023	12.548 ± 0.024	508 ± 58	−78 ± 57	506.6 ± 7.4	−33.8 ± 6.6
J000028.55−124516.4	13.200 ± 0.026	12.445 ± 0.023	11.973 ± 0.023	11.707 ± 0.024	11.496 ± 0.021	−300 ± 49	−140 ± 49	−156.5 ± 7.6	−95.2 ± 6.0
J000031.00−261352.0	10.400 ± 0.029	9.753 ± 0.031	9.523 ± 0.024	9.328 ± 0.023	9.286 ± 0.020	320 ± 38	230 ± 37	297.9 ± 7.9	124.7 ± 7.8
J000031.98+650427.7	12.126 ± 0.022	11.558 ± 0.031	11.393 ± 0.021	11.285 ± 0.023	11.144 ± 0.020	290 ± 26	−92 ± 26	274.3 ± 6.5	−86.0 ± 6.5
J000034.69−365006.8	11.698 ± 0.022	11.095 ± 0.023	10.912 ± 0.023	10.809 ± 0.023	10.718 ± 0.020	391 ± 40	101 ± 38	428.0 ± 7.3	105.7 ± 7.2
J000037.12−243830.3	11.692 ± 0.023	11.119 ± 0.021	10.862 ± 0.021	10.691 ± 0.022	10.525 ± 0.020	−223 ± 42	−321 ± 41	−166.9 ± 8.9	−188.1 ± 7.9
J000037.66+420712.8	12.581 ± 0.022	11.958 ± 0.024	11.800 ± 0.024	11.682 ± 0.024	11.614 ± 0.021	340 ± 32	47 ± 31	300.2 ± 6.9	49.1 ± 6.1
J000044.53−502924.7	11.215 ± 0.030	10.726 ± 0.026	10.486 ± 0.024	10.387 ± 0.023	10.230 ± 0.020	359 ± 37	−6 ± 36	394.2 ± 7.9	6.3 ± 7.0
J000048.86+450558.8	12.225 ± 0.021	11.612 ± 0.023	11.348 ± 0.018	11.154 ± 0.024	11.005 ± 0.021	85 ± 36	−262 ± 35	147.3 ± 6.1	−184.2 ± 6.0
J000052.23+143402.2	10.014 ± 0.019	9.382 ± 0.028	9.155 ± 0.023	9.057 ± 0.024	9.009 ± 0.020	266 ± 39	−65 ± 41	345.4 ± 10.7	−60.1 ± 7.2
J000101.74−214857.3	11.671 ± 0.025	11.148 ± 0.022	10.956 ± 0.022	10.792 ± 0.022	10.592 ± 0.020	33 ± 42	−301 ± 41	71.7 ± 6.5	−218.1 ± 6.3
J000114.58+573310.6	12.705 ± 0.026	12.280 ± 0.031	12.150 ± 0.024	11.876 ± 0.022	11.770 ± 0.021	435 ± 30	−409 ± 29	397.4 ± 6.6	−449.9 ± 6.5
J000115.50+065934.5	11.286 ± 0.022	10.741 ± 0.028	10.418 ± 0.021	10.219 ± 0.023	10.042 ± 0.021	−623 ± 43	−151 ± 41	−429.6 ± 9.8	−99.6 ± 8.8
J000121.22+773801.9	7.006 ± 0.027	6.533 ± 0.071	6.417 ± 0.026	6.322 ± 0.055	6.367 ± 0.022	368 ± 25	−90 ± 30	155.1 ± 9.8	12.5 ± 9.8
J000125.11+523021.2	11.171 ± 0.022	10.631 ± 0.021	10.398 ± 0.018	10.262 ± 0.022	10.086 ± 0.020	261 ± 25	90 ± 25	301.4 ± 5.9	60.2 ± 5.9
J000133.02+430024.9	11.660 ± 0.022	11.048 ± 0.030	10.810 ± 0.019	10.651 ± 0.023	10.488 ± 0.020	360 ± 31	−140 ± 29	336.9 ± 7.4	−49.4 ± 6.5
J000144.46−352834.1	9.822 ± 0.026	9.189 ± 0.021	8.932 ± 0.023	8.799 ± 0.022	8.742 ± 0.019	456 ± 32	2 ± 32	505.8 ± 5.9	−24.6 ± 5.8
J000204.45+022140.7	12.685 ± 0.026	12.131 ± 0.030	11.891 ± 0.026	11.688 ± 0.023	11.515 ± 0.021	−254 ± 53	−170 ± 52	−140.3 ± 10.7	−107.9 ± 7.0
J000211.31−431002.6	12.597 ± 0.026	12.425 ± 0.023	12.445 ± 0.024	12.471 ± 0.024	12.515 ± 0.024	116 ± 57	−926 ± 56	607.1 ± 8.3	−668.8 ± 7.4
J000220.39+423401.4	12.357 ± 0.022	11.817 ± 0.029	11.617 ± 0.020	11.455 ± 0.023	11.266 ± 0.021	234 ± 30	148 ± 29	310.8 ± 6.7	162.4 ± 6.6
J000233.87+434315.3	12.584 ± 0.022	12.031 ± 0.029	11.877 ± 0.019	11.827 ± 0.023	11.829 ± 0.022	357 ± 35	29 ± 34	308.3 ± 7.5	68.8 ± 6.6
J000234.55−391031.2	12.711 ± 0.025	12.136 ± 0.025	11.802 ± 0.027	11.589 ± 0.022	11.384 ± 0.021	189 ± 44	−369 ± 43	287.5 ± 6.5	−159.3 ± 6.4
J000240.21−341347.6	14.117 ± 0.024	14.024 ± 0.038	13.919 ± 0.063	13.794 ± 0.025	13.732 ± 0.033	−33 ± 101	−924 ± 101	143.3 ± 6.8	−764.8 ± 6.7
J000252.49+380057.4	10.570 ± 0.022	9.891 ± 0.028	9.795 ± 0.022	9.698 ± 0.022	9.706 ± 0.020	−94 ± 38	−265 ± 36	−0.6 ± 7.3	−266.5 ± 6.4
J000303.69+564400.3	8.153 ± 0.021	7.734 ± 0.049	7.656 ± 0.017	7.575 ± 0.031	7.669 ± 0.020	199 ± 26	96 ± 26	194.4 ± 7.2	36.8 ± 6.4
J000307.25+061633.8	11.039 ± 0.021	10.533 ± 0.028	10.295 ± 0.019	10.111 ± 0.022	9.896 ± 0.020	6 ± 45	−583 ± 40	242.1 ± 10.7	−506.2 ± 8.7
J000311.05+035042.3	11.292 ± 0.027	10.723 ± 0.023	10.445 ± 0.023	10.254 ± 0.023	10.087 ± 0.021	−242 ± 42	−349 ± 40	−79.5 ± 13.4	−302.2 ± 8.7
J000313.38−171246.0	13.131 ± 0.022	12.509 ± 0.024	12.278 ± 0.024	12.059 ± 0.022	11.899 ± 0.022	138 ± 53	−238 ± 53	158.3 ± 6.1	−113.7 ± 6.1

Note.

^aThis is the motion measured between the 2MASS and AllWISE epochs.

Only a portion of this table is shown here to demonstrate its form and content. A machine-readable version of the full table is available.

Download table as:  DataTypeset image

Figure 2 shows the sky distribution of AllWISE2 discoveries along with AllWISE1 and AllWISE2 rediscoveries. These plots can be compared to those shown in Figure 14 of Kirkpatrick et al. (2014). Both sets show an overdensity of sources in the ecliptic longitude zones covered at three epochs by WISE, as well as an underdensity in the zone of high backgrounds and source confusion along the Galactic Plane, particularly on either side of the Galactic Center. More evident in the AllWISE2 plots is the overdensity of sources toward either ecliptic pole, which is the most repeatedly observed region of the sky for WISE. The discoveries in the upper plot of Figure 2 are concentrated toward the deep southern hemisphere since that area has historically seen fewer motion surveys than the rest of the sky. (For confirmation of this, see the sky distribution of sources from the New Luyten Two Tenths Catalog illustrated in the upper panel of Figure 15 of Kirkpatrick et al. 2014.)

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A comparison of AllWISE-measured motions to the 2MASS-to-AllWISE motions is shown in Figure 3 for both the AllWISE1 re-discovery list and the list of all motion sources identified by AllWISE2. There is generally good agreement between the short-baseline AllWISE measurements and the longer-baseline 2MASS-to-AllWISE measurements. A small bias is present, as expected, between the two sets, in the sense that the AllWISE measurement is slightly larger on average than the 2MASS-to-AllWISE one. This bias exists because of our selection criteria. At a given, true motion value, we preferentially choose those objects whose measurement values scatter higher than the mean because objects with measurements scattering lower than the mean may not meet our criterion for motion significance. This is the same effect noted in Figure 16 of Kirkpatrick et al. (2014).

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Furthermore, we note that the correlation between the AllWISE-measured motions and the 2MASS-to-AllWISE ones is less tight for AllWISE2 than for AllWISE1. This is also expected since AllWISE2 is preferentially selecting sources with smaller motions, which is evident in subsequent plots. For the remainder of this paper, we use our measurement of the 2MASS-to-AllWISE motion rather than the shorter baseline AllWISE-only one.

A comparison of the parameter space explored by the AllWISE and NEOWISER motion surveys is given in Figure 4, which shows the W1 magnitude and total motion distribution for all identified motion objects.¹⁷ By design, the NEOWISER survey was limited to motions exceeding ∼250 mas yr⁻¹, whereas the AllWISE1 and AllWISE2 surveys identified many thousands of objects with motions below this value. The power of the NEOWISER survey over the AllWISE1 and AllWISE2 surveys is in its extended time baseline—∼3.75 years for NEOWISER as opposed to ∼0.5 years for AllWISE1 and AllWISE2—as evidenced by the fact that the NEOWISER survey was much more adept at selecting motion objects at magnitudes fainter than W1 ≈ 14 mag.

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This point is further demonstrated in Figure 5. The only faint (W1 > 15 mag) objects identifiable by AllWISE1 or AllWISE2 are rare objects of very high motion; those identified have motions typically >1500 mas yr⁻¹. With the longer time baseline, the same motion significance corresponds to a smaller absolute motion for NEOWISER (∼500 mas yr⁻¹). Because there is a larger population of sources with motions >500 mas yr⁻¹ compared to the (very sparse) population having motions >1500 mas yr⁻¹, NEOWISER finds many more objects at these fainter magnitudes. Note also from Figure 5 that AllWISE2 identifies objects with much smaller motions on average than AllWISE1, which is the expected behavior given our ${rchi}2/{rchi}2\_{pm}\leqslant 1.03$ criterion.

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Histograms as a function of W1 magnitude and total motion are shown in Figure 6 for the discovery lists from AllWISE1, AllWISE2, Luhman (2014a), and NEOWISER. The power of the Luhman (2014a) and NEOWISER surveys is their ability to pick up new motion objects at very faint magnitudes, and this is particularly evident in NEOWISER, where the extended time baseline has made the identification of those faint motion objects easier. The power of the AllWISE1 and AllWISE2 surveys is in picking up new discoveries of smaller motion at brighter magnitudes.

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Motion objects from the combined AllWISE1 and AllWISE2 surveys are further characterized in Figure 7 through 10. Using SIMBAD, we have searched for published spectral types of previously known objects¹⁸ and supplemented these with spectral types of new discoveries provided by Kirkpatrick et al. (2014), Luhman & Sheppard (2014), and this paper. Each spectral type was assigned a different color, although the wide locus spanned by M, L and T dwarfs made it possible to divide each of these into early (e.g., M0-M4.5) and late (e.g., M5-M9.5) divisions. Colors were assigned so that the entire visible palette was covered, with O-type stars at the violet end and late-T dwarfs at the red end. (Because Y dwarfs would have required a dramatic rescaling of the axes, these are not shown.) Objects were further subdivided by luminosity or metallicity types. Objects with luminosity classes of I, II, III, or IV were grouped together as giants or other high-luminosity objects ("g+") in the figures, and classes of IV–V and V were assigned to dwarfs ("d"). Luminosity class VI was assigned to subdwarfs ("sd") as were objects with a luminosity or metallicity prefix of sd. Metallicity classes esd and usd were assigned to extreme subdwarfs ("esd"). Objects of type O through T that lacked a luminosity or metallicity class were assumed to be dwarfs of solar metallicity ("d"). White dwarfs with temperature types <6.7 ((Sion et al. 1983); ${T}_{\mathrm{eff}}\gt 7500$ K) were assigned to the "warm white dwarf" class, and those with temperature types $\geqslant 6.7$ (${T}_{\mathrm{eff}}\lt 7500$ K) were assigned to the "cool white dwarf" class. Carbon stars were assigned to either a "dwarf carbon star" class for objects like G 77-61 or an "other carbon star" class to cover carbon-enhanced metal poor stars (HE 0440−1049 and 2MASS J04442200−4513542) and the CH-enhanced star HD 26. Three objects discovered to be highly reddened G and K dwarfs (see Section 4.2) are also distinguished. Legends on each figure show the mapping between our assigned divisions and the colored symbols.

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Figure 7 shows the location of objects in the J − ${K}_{s}$ versus J – W2 diagram. The densest locus of objects, which runs redward in both colors with decreasing temperature, is composed of stars with types of F, G, K, or M. The kink near the boundary between K and M stars marks the onset of H₂O absorption at the blue side of K_s band¹⁹ (see Figure 12 of Cushing et al. 2005) and CO at W2, although the onset of CO likely occurs at a somewhat lower temperature than that of H₂O (Allard 1990; Yamamura et al. 2010; Sorahana & Yamamura 2012). From this main locus, the L dwarfs proceed redward in both colors because of decreasing temperature and the production of dust in the photosphere, the latter of which dramatically reddens the J − K_s colors (e.g., Marley et al. 2002; Tsuji et al. 2004); the reddest L dwarfs extend to values of (J – W2, J − K_s) ≈ (4.5, 2.6). As the dust clears, the later L dwarfs turn back to the blue in both colors. The appearance of CH₄ at J and K_s marks the beginning of the T dwarf sequence (Burgasser et al. 2006) starting near (J – W2, J − K_s) ≈ (3.0, 1.6) and proceeding blueward in both colors until mid-T types near (J – W2, J − K_s) ≈ (2.0, 0.4). Here, at ${T}_{\mathrm{eff}}\lt 1500\;{\rm{K}}$ (Kirkpatrick 2005), the T dwarfs change course by turning redward in J – W2 color. This effect is caused both by decreasing temperature, which causes the J-band flux to plummet since this wavelength is now on the flux-poor Wien tail of the spectral energy distribution, and by increasing absorption by H₂O and CH₄ throughout most of the near-infrared spectrum, which squeezes most of the flux through the opacity hole on which the WISE W2 band is centered (Burrows et al. 1997; Mainzer et al. 2011).

Falling below the blue end of the main locus, from (J – W2, J − K_s) = (−0.6, −0.4) to (1.0, 0.4) are the bulk of the white dwarfs, at least those bright enough to be detectable by WISE. A small number of white dwarfs, however, appear to be superimposed on the locus of normal M dwarfs; most of these are known white dwarf + M dwarf doubles.²⁰ Subdwarfs of type M and L fall below the central, most densely populated locus, with the later L subdwarfs commingling with normal T dwarfs. These objects are bluer in J − K_s than their solar-metallicity counterparts because of the increased relative importance of pressure-induced H₂ opacity (Borysow et al. 1997).

Two objects from the literature stand out as having unusual locations compared to objects of similar published type. The first of these, shown by the open green star at (J – W2,J − K_s) = (3.06, 1.93), is 2MASS J08273118−1100029 classified as M0 III by Cruz et al. (2003). This object has a motion significance of only 5.2σ and thus barely passes our test for inclusion in the motion list; because it is too faint to be seen in the DSS1 or DSS2 images, its measured motion of 47 ± 9 mas yr⁻¹ cannot be independently verified and may be fictitious. Even if it not actually moving, its colors do not match those of the other early-M giants on the figure. Interstellar reddening may explain its colors, or the Cruz et al. (2003) spectrum may be in error. This object is worthy of further follow-up. The second unusual object, at (J –W2, J − K_s) = (2.41, 0.44), is the dust-enshrouded white dwarf G 29-38 (Zuckerman & Becklin 1987; Wickramasinghe et al. 1988; Graham et al. 1990), a well known oddball in color space.

Figure 8 shows the J – W2 versus W1−W2 diagram. As with the previous figure, the densest locus of objects is composed of F, G, K, and M stars. The redward jog in W1−W2 color near the K/M boundary is probably caused by the appearance of H₂O absorption at W1 (Yamamura et al. 2010; Sorahana & Yamamura 2012), which appears somewhat earlier in the temperature sequence than the CO absorption at W2. Running redward of these types in both colors are the L dwarfs, which reach values as red as J – W2 ≈ 4.5 at mid-L types. After this point, the later L dwarfs turn back to the blue in J – W2; here, the J-band flux increases relative to W2. This J-band brightening has been the subject of much speculation (see Kirkpatrick 2005 for an overview), but is likely related to the disappearnce of photospheric dust that blankets the J-band region.²¹ At this same point in the temperature sequence, the fundamental band of CH₄ at 3.3 μm begins to depress the W1 flux (Oppenheimer et al. 1998; Noll et al. 2000; Cushing et al. 2005), first via the Q-branch at mid-L types and then with wider, deeper absorption in the P- and R-branches by mid-T. Also, as mentioned previously, blanketing by ever strengthening H₂O and CH₄ absorption creates a flux excess through the opacity hole in the W2 band. This combination of effects causes the W1−W2 colors to shift dramatically to the red. The reversal of the J – W2 color to the red at mid-T types is a consequence both of the excess flux escaping through the W2 opacity hole as well as the J-band flux plummeting as J-band falls further down the Wien tail of the flux distribution at cooler temperatures.

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Falling below the blue end of the main locus, from (W1 − W2, J – W2) = (−0.3, −0.6) to (0.2, 0.6) are the bulk of the white dwarfs. Subdwarfs of type M and L typically fall blueward in J – W2 and redward in W1−W2 of their solar-metallicity counterparts. This shift in colors is almost entirely modulated by the increased relative importance of collision-induced H₂ absorption, which is present at J, stronger at W2, and strongest at W1 (see Figures 3 and 6 of Borysow et al. 1997). Oddly, the carbon dwarfs, which are also low-metallicity, fall to the left of the main locus and differentiate themselves far better from the bulk of other objects on this diagram than in Figure 7. Absorption bands of C₂ and CN at J-band (Joyce 1998) may help to modulate what would otherwise be a blueward trend in J – W2 color by H₂ absorption alone; likewise, the expected redward trend in W1−W2 color may be pushed blueward of the main locus by an unknown carbon-bearing species dominating at W2 band.

The next plot, Figure 9, shows the J versus J – W2 diagram. Here, each spectral subtype separates out well in J – W2 color, with the exception of the L and T dwarfs which are known not to follow a monotonic relation (Figure 7 of Kirkpatrick et al. 2011). Most of the white dwarfs fall to the left and below the main sequence, at values of J – W2 < 0.6 mag. White dwarfs have colors similar to or bluer than the O, B, A, and F stars but generally fall at much fainter magnitudes, revealing their lower luminosities.

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The final plot, Figure 10, shows the H_J versus J – W2 diagram, where H_J is the reduced proper motion²² at J-band, defined by ${H}_{J}=J+5\mathrm{log}(\mu )+5$, where J is the apparent J-band magnitude and μ is the total proper motion in arcsec yr⁻¹. Here, the instrinsically fainter white dwarfs separate much more cleanly from the bulk of early-type stars than they do in Figure 9. The main locus of F, G, K, and M stars, along with the sequence of L and T dwarfs, shows a broad distribution in H_J values for a given J – W2 color, indicative of the randomness of the V_tan component of each object's space velocity. However, those random V_tan components are generally higher for old objects with high kinematics compared to solar-age field stars. Therefore, metal-poor objects of high kinematics are easy to identify on this diagram since they generally fall much lower on the diagram (larger H_J values). This plot, in concert with the color–color plots shown in Figure 7 and Figure 8, is extremely useful in selecting subdwarf candidates for follow-up.

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3.1.1. Palomar/DSpec

3.1.2. duPont/BCSpec

3.1.3. NTT/EFOSC2

3.1.4. Keck/LRIS

3.2.1. IRTF/SpeX

3.2.2. Magellan/FIRE

3.2.3. Keck/NIRSPEC

Spectra of white dwarf suspects (Figures 11 and 12) were classified using the scheme described in Sion et al. (1983). We provide only the core type—DA, DC, etc.—here and not the temperature suffix. Most of our white dwarf spectra have either poor signal-to-noise, which makes them difficult to compare to the models used in the temperature classification, and/or they lack data blueward of Hβ, which is generally needed to establish accurate temperatures.

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Spectra of the common-proper-motion double WISE 0345−0348A and WISE 0345−0348B (Figure 11) are noisy but appear to show Hα absorption, so these have tentatively been classified as DA white dwarfs. The signal-to-noise for WISE 2101−4906 (Figure 11) is much better, and while there appears to be a detection of Hα, other hydrogen lines in the Balmer series are not clearly seen. Hence, this object is only tentatively classified as DA. WISE 1028−6327 (Figure 12) shows Hα, Hβ, Hγ, and Hδ absorption along with the Ca ii H&K doublet, so this object is tenatively classified as a DAZ, pending a spectrum with higher signal-to-noise. Despite the excellent signal-to-noise in the spectrum of WISE 1747−5436 (Figure 12), no clear features are seen, leading to a classification of DC.

The remaining spectrum, that of WISE 1702+7158B (Figure 12), is extremely noisy due to the faintness of the object at optical wavelengths. The object itself was not detected by AllWISE, but its common-proper-motion primary, the M4.5 dwarf WISE 1702+7158A, was identified by AllWISE as a high motion source. Analysis of this pair can be found in Section 5. Curiously, our DA suspect WISE 2101−4906 (above) shares proper motion with another M4.5 dwarf, WISE 2101−4907, as also discussed in Section 5.

Spectra of objects with types of K5 or earlier were classified using spectral standards taken as part of the NStars project (see Appendix C of Gray & Corbally 2009). These standard spectra cover only the blue end of our spectral region (typically 3800–5600 Å) but cover a number of prominent diagnostic lines—Ca ii H&K at 3934 and 3969 Å; the δ, γ, and β Balmer lines of H i at 4102, 4340, and 4861 Å; Ca i at 4227 Å; Fe i at 4308 and 5270 Å; and the Mg i b triplet at 5167, 5173, and 5184 Å. Spectra of nine early-type objects are shown in Figures 13 and 14.

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One object, WISE 1423−1646A (Figure 14), has a peculiar spectrum best fit by the K5 standard. That is, the line strengths best match the K5 standard even though the overall continuum over our spectral range is somewhat bluer than the standard. This object has common proper motion (Section 5.4) with the normal M0.5 dwarf WISE 1423−1646B shown later. We do not know the physical cause for the peculiarity in WISE 1423−1646A, but it is not shared by the companion object.

One of the objects in Figure 13, WISE 1835−2226 is reddened relative to other objects in the G to early-K sequence. Using the IDL program FM_UNRED that dereddens an observed spectrum using the Fitzpatrick (1999) parameterization of interstellar extinction as a function of wavelength²⁵ , we find that correcting by a color excess of ${E}_{B-V}\approx 0.15$ mag gives an overall spectral shape that most closely matches that of an unreddened G8 dwarf, which matches the classification based on the depth of the spectral features alone. This color excess corresponds to a total V-band extinction of $A(V)\approx 0.47$ mag if ${R}_{V}={A}_{V}/E({B}_{V})=3.1$ is assumed (Schultz & Wiemer 1975).

Three other early-type stars are even more heavily reddened, as shown in Figures 15 and 16. WISE 1839+1249 has a continuum that is best fit to a mid-G dwarf if a color excess of ${E}_{B-V}\approx 1.9$ mag ($A(V)\approx 5.9$ mag) is assumed; the spectral type is uncertain because of the low signal-to-noise in the short-wavelength region, where only questionable detections of Na i at 5890 Å and Hα are seen. In WISE 1630−2017, the strengths of the MgH and CaH bands, as well as the Mg i, Na i, Ca i lines, are best fit by a K5 dwarf, as is the continuum if a color excess of ${E}_{B-V}\approx 1.0$ mag ($A(V)\approx 3.1$ mag) is assumed. For WISE 0418+2520, the near-infrared continuum shows metal lines throughout the J and H bands, along with CO bandheads at K, indicating a mid-K dwarf. (The CO bandheads are not strong enough for a mid-K giant; see the suite of K dwarf and giant spectra in the IRTF SpeX Spectral Library of Rayner et al. 2009.) The continuum is best fit if a color excess of ${E}_{B-V}\approx 4.7$ mag ($A(V)\approx 14.6$ mag) is assumed.

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With measured extinctions and spectral types in hand, we can calculate the distances to the four reddened stars in Figures 13, 15, and 16. Using their apparent K_s-band magnitudes from the 2MASS Point Source Catalog²⁶ , assuming ${A}_{K}=0.112{A}_{V}$ (Rieke & Lebofsky 1985), and using the absolute K_s magnitudes²⁷ corresponding to their spectral types as derived above (Pecaut & Mamajek 2013), we find the approximate distances listed in Table 6. The table also lists the tangential velocity for that distance, using our computed 2MASS-to-AllWISE proper motion values. The average tangential velocity for a disk star is 37 km s⁻¹ (Reid 1997) and for a halo star is 175–215 km s⁻¹ (Reid & Hawley 2000), suggesting the possibility that WISE 1630−2017 is a halo member. Nonetheless, these velocities are typical of stars found during motion surveys, so the derived distances appear reasonable.

Table 6.  Derived Parameters for Reddened Motion Stars

WISE	Approx.	$E(B-V)$	Dist.	vtan	Note
Object	Type	(mag)	(pc)	(km s−1)
0418+2520	K5 V	4.7	114	73	Taurus
1630−2017	K5 V	1.0	227	246	Ophiuchus
1835−2226	G8 V	0.15	282	96	⋯
1839+1249	G5 V	1.9	295	131	Hercules

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For three of the four objects, however, the total line of sight reddening measured in a beam of 5 arcmin radius²⁸ is lower than the value we measure for the motion star—only for WISE 1835−2226 is our value of $E(B-V)=0.15$ lower than the total column extinction measured by either Schlafly & Finkbeiner (2011) ($0.27\pm 0.01$) or Schlegel et al. (1998) ($0.31\pm 0.01$). For these three cases, a check of the 100 μm dust maps produced by Schlegel et al. (1998) shows that the star falls squarely along a patch of very high extinction relative to nearby areas, explaining why our values of the extinction are higher than the region average. For all three of these objects, much of the intervening dust is known to be near the Sun. At 114 pc, WISE 0418+2520 is likely moving through the Taurus Molecular Cloud, whose mean distance²⁹ is ∼140 pc (Kenyon et al. 1994). At 227 pc, WISE 1630−2017 is moving behind the Ophiuchus Cloud, whose mean distance is ∼120 pc (Lombardi et al. 2008, Schlafly et al. 2014). At 295 pc, WISE 1839+1249 is moving behind the Hercules Cloud, whose mean distance is ∼200 pc (Schlafly et al. 2014; see also Dame et al. 2001). The locations of these three objects with respect to the intervening clouds are shown in Figure 17.

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These three stars have relatively high velocities, so they are presumably middle-aged objects unrelated to the clouds themselves. The mean motions and dispersions for objects belonging to Taurus (Jones & Herbig 1979) and Ophiuchus (Makarov 2007, Mamajek 2008) preclude membership for both WISE 0418+2520 (${\mu }_{\alpha }\;=\;111.8\pm 5.7$, ${\mu }_{\delta }\;=-75.1\pm 5.6$ mas yr⁻¹) and WISE 1630−2017 (${\mu }_{\alpha }\;=-2.3\pm 9.7$, ${\mu }_{\delta }\;=\;-228.9\pm 9.1$ mas yr⁻¹). Except for occasional chromospheric activity that primarily affects the ultraviolet and blue optical bandpasses, the vast majority of middle-aged mid-G to mid-K dwarfs are free of intrinsic variability at the millimag level (Ciardi et al. 2011) and are therefore useful as standard candles. For the three stars in Figure 17, any observed variability can be attributed to line of sight variations in the dust column as the stars trek behind (or within) the cloud.

Figures 18 through 20 show examples of existing light curves for these objects. Figure 18 shows V, W1, and W2 data for WISE 0418+2520, where the V-band data come from the Catalina Sky Survey³⁰ (Drake et al. 2009) and the WISE data are the per-epoch weighted means computed using the measured magnitudes in each individual W1 and W2 frame. (A few frames with quality score of zero, which generally indicates image smearing, were eliminated prior to the computation.) WISE 0418+2520 is much fainter, by almost 10 magnitudes, in V than in W1 and W2, so the photometric errors make it difficult to discern any brightness changes at V. At W1 and W2, on the other hand, there is a trend of steady dimming, although the magnitude change over the 4.5 year baseline is only 0.03–0.04 mag in both bands. Monitoring this object at intermediate bands, such as R, J, H, and K, would be fruitful.

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The corresponding light curves for WISE 1630−2017 are shown in Figure 19. Data at the V-band are available from both the Catalina Sky Survey as well as the Siding Spring Survey.³¹ Because there appears to be a zero-point offset between the Catalina and Siding Spring calibrations, we have subtracted 0.1 mag from the Catalina values prior to plotting. The V-band light curve shows a secular brightening of about ∼0.2 mag over the course of eight years. The W1 and W2 photometry show no significant changes in magnitude over the WISE time baseline, although the second-epoch W1 point is anomalous. Having simultaneous photometry in many bands would help elucidate if anomalies such as this are just random measurement fluctuations or indications of small-scale clumpiness within the cloud.

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For WISE 1839+1249 (Figure 20), we have only WISE photometric monitoring available, which may show a barely discernible brightening over the WISE time baseline. Ongoing and future surveys will be able to provide nightly monitoring of such objects at a variety of wavelengths. Notable examples are the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS; Hodapp et al. 2004) at g, r, i, z, and y; the Large Synoptic Survey Telescope (LSST; Ivezić et al. 2014) at those same wavelengths, plus the u band; and the Zwicky Transient Facility (ZTF; Bellm 2014) at ${g}^{\prime }$ and R. Nightly monitoring is important because the light beam of each star shines through a column of intervening material that is offset between 30 au (for Taurus) and 100 au (for Ophiuchus) from the night before, providing exquisite detail on the line of sight clumpiness of these clouds. Combined with simultaneous data from multiple wavelengths, we can identify variations that run contrary to the "universal" reddening law, which will give us insight into the average grain sizes along the beam.

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Mid-K through late-M dwarfs were typed in the optical using the classification system of Kirkpatrick et al. (1991). Table 7 lists the standards employed for the classifications produced in this section. The spectrum of the M7 standard comes from the Deep Imaging Multi-object Spectrograph (DEIMOS; Faber et al. 2003) on the 10m W. M. Keck Observatory (see Table 3 of Kirkpatrick et al. 2010). All others come from the Double Spectrograph on the Palomar 5 m telescope and originated in a project described in Kirkpatrick et al. (1997), although only those spectra of type M6 and later were discussed in that paper. All of the objects in Table 7 were listed as primary (or secondary, in the case of the M9) spectral standards in Kirkpatrick et al. (1991) except for the M5 and the M8. Unlike the two M5 dwarfs originally proposed, this M5 has the advantage of being a single star lying near the celestial equator for ease of observation in both hemispheres; this M8 falls further away from the Galactic Plane than the only M8 standard listed in Kirkpatrick et al. (1991) and is less subject to contamination by background stars. For reference, a plot of these standard spectra is shown in Figure 21.

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Table 7.  Mid-K through Late-M Dwarf Spectral Standards in the Optical

Spectral	Object	Other
Type	Name	Name
K5	Gl 820A	61 Cyg A
K7	Gl 820B	61 Cyg B
M0	Gl 270	BD+33$^\circ$ 1505
M1	Gl 229A	HD 42581
M2	Gl 411	HD 95735
M3	Gl 436	Ross 905
M4	Gl 402	Wolf 358
M5	GJ 1057	LHS 168
M6	Gl 406	Wolf 359
M7	Gl 644C	vB 8
M8	LP 412-31	⋯
M9	LHS 2065	⋯

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Plots of our mid-K through M dwarfs are shown in Figure 22 through Figure 44. We used these observations to search for newly identified active M dwarfs that could be part of nearby young associations, and to identify and/or better characterize newly discovered M dwarfs within ∼20 pc of the Sun.

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4.3.1. Searching for Young, Active M Dwarfs

For F, G, and K dwarfs, there is a well established correlation between youth and magnetic activity (Hartmann & Noyes 1987). As these stars spin down with time, the activity driven by the magnetic dynamo also decreases. Hence, activity levels in the coronae and chromospheres can be used as proxies for age. These indicators, however, are not perfect bellwethers. If an old star is observed only once and during a flare, its high level of activity may be misconstrued as a sign of youth. Similarly, old stars in close binary systems can retain high levels of magnetic activity because tidal locking keeps the rotation speeds high. Nonetheless, such activity indicators can be used to identify young candidates.

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In these stars, the dynamo depends on rotational sheer and an anchor point at the interface between the radiative and convective zones within the star. This same dynamo would not, however, be able to anchor itself in the fully convective atmospheres possessed by mid- to late-M dwarfs (Reid & Hawley 2000). Although, it is unclear what the underlying physical mechanism is, the same activity/age correlations are seen in M dwarfs as in higher mass stars (Browning et al. 2010), so we can use these same youth indicators despite not fully understanding why they work.

We have considered the spectroscopically verified M dwarfs from Table 4 and Table 5 to search for previously missed, young M dwarfs in the solar neighborhood. Table 8 lists those M dwarfs with detections in X-ray, ultraviolet, and/or Hα emission. Detections in the X-ray or ultraviolet were assumed if our AllWISE object falls within 30 arcsec of a 3σ detection from the Röntgensatelit³² (ROSAT) or 20 arcsec of a 3σ detection in either the far- (FUV) or near-ultraviolet (NUV) from the Galaxy Evolution Explorer³³ (GALEX), these radii taking into account the resolution of each survey and the time span between them and AllWISE. The ROSAT count rates have been converted to fluxes using the formula ${F}_{X}\;=(\mathrm{count}\;\mathrm{rate})\times (8.31+5.30\times {HR}1)\times {10}^{-12}$ erg cm⁻² s⁻¹ from Schmitt et al. (1995), where ${HR}1=(B-A)/(B+A)$, with A being the counts in the soft channel (0.1–0.4 keV) and B being the counts in the hard channel (0.5–2.0 keV). (See also Voges et al. 1999.)

Table 8.  Measured Properties of Active M Dwarfs from Tables 4 and 5

WISE	Spec.	USNO R	USNO I	2MASS J	fJ	FJ	FX	${f}_{{\rm{FUV}}}$	${f}_{{\rm{NUV}}}$	Hα EW	Group	Memb.	d${}_{{\rm{pred}}}$
Object	Type	(mag)	(mag)	(mag)	(mJy)	(erg/cm2 s)	(erg/cm2 s)	(μJy)	(μJy)	(Å)		Prob.(%)	(pc)
(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)	(11)	(12)	(13)	(14)
0005+0209	M6	16.56	13.78	11.992 ± 0.029	25.5	8.10e-12	⋯	⋯	⋯	−10.9 ± 1.5	AB Dor	91.96	18.1 ± 1.0
0051−2251	M8	19.36	15.37	13.019 ± 0.027	9.88	3.15e-12	⋯	⋯	⋯	−20.6 ± 2.5	old field	98.76	27.3 ± 12.8
0157−0948	M4	16.03	⋯	13.064 ± 0.038	9.48	3.02e-12	⋯	⋯	47.70 ± 1.07	⋯	old field	96.37	45.0 ± 16.8
0405+3719	M5	15.01	13.39	10.915 ± 0.021	68.6	21.9e-12	⋯	⋯	14.70 ± 3.50	−6.2 ± 0.3	old field	70.88	83.4 ± 32.8
0422+0337	M4.5	14.58	10.90	9.857 ± 0.023	182	57.9e-12	18.5 ± 2.7e-13	⋯	42.29 ± 1.30	−7.0 ± 0.1	old field	79.98	51.8 ± 22.4
0447+2534	M4	14.10	11.64	10.631 ± 0.017	89.1	28.4e-12	⋯	⋯	⋯	−5.1 ± 0.4	old field	70.55	83.0 ± 33.9
0500+1916	M1	11.21	10.17	9.125 ± 0.021	357.	113.e-12	⋯	⋯	21.36 ± 4.31	⋯	old field	85.37	55.8 ± 22.0
0536−0006	M4.5	12.62	11.35	10.630 ± 0.019	89.2	28.4e-12	3.0 ± 1.0e-13	⋯	⋯	−6.0 ± 0.4	old field	63.73	34.6 ± 14.8
0546−0440	M4.5	13.89	11.58	10.366 ± 0.023	114.	36.2e-12	⋯	⋯	⋯	−3.9 ± 0.5	young field	50.46	49.8 ± 24.6
0701−0137	M4	14.24	12.52	10.613 ± 0.020	90.6	28.9e-12	⋯	⋯	⋯	−4.8 ± 0.3	old field	61.19	85.8 ± 35.7
0705−1007	M5	14.11	11.50	10.196 ± 0.021	133.	42.4e-12	⋯	⋯	⋯	−6.2 ± 0.3	old field	97.08	33.3 ± 15.6
0720−0846	M9	16.87	13.95	10.628 ± 0.023	89.4	28.5e-12	⋯	⋯	⋯	−17.7 ± 0.3	old field	49.16	52.6 ± 21.6
0852+5139	M7.5	19.23	16.10	13.984 ± 0.024	4.06	1.29e-12	⋯	⋯	⋯	−5.5 ± 1.7	old field	98.24	24.5 ± 9.0
0912+2205	M3	13.32	11.59	10.733 ± 0.017	81.1	25.9e-12	⋯	⋯	18.50 ± 0.99	−5.9 ± 0.3	old field	77.90	81.4 ± 31.6
0935−0301	M3	13.12	11.38	10.555 ± 0.025	95.6	30.4e-12	⋯	⋯	10.75 ± 2.25	−1.9 ± 0.2	old field	94.83	67.4 ± 27.4
1019+3922	M4.5	14.69	12.88	11.143 ± 0.014	55.6	17.7e-12	⋯	1.55 ± 0.12	6.16 ± 0.21	−4.3 ± 0.3	old field	98.44	42.2 ± 20.4
1029+2545	M4.5	13.48	11.31	10.358 ± 0.018	115.	36.5e-12	3.7 ± 1.2e-13	10.33 ± 2.68	20.63 ± 2.79	−7.5 ± 0.2	old field	96.27	69.0 ± 30.6
1055−5750	M4	⋯	12.60	11.424 ± 0.021	42.9	13.7e-12	⋯	⋯	⋯	−1.6 ± 0.4	old field	93.39	52.2 ± 21.6
1059+1509	M3.5	14.18	12.06	11.154 ± 0.018	55.1	17.5e-12	⋯	⋯	4.41 ± 1.38	⋯	old field	96.81	69.4 ± 28.8
1114+5703	M0	12.08	10.79	10.258 ± 0.015	126.	40.0e-12	⋯	⋯	11.63 ± 1.27	⋯	old field	93.06	56.6 ± 23.8
1140−0624	M5	15.61	13.27	11.957 ± 0.021	26.3	8.37e-12	⋯	⋯	⋯	−2.5 ± 0.5	old field	96.69	40.2 ± 15.2
1202−0111	M4	16.27	14.72	13.256 ± 0.021	7.94	2.53e-12	⋯	⋯	1.27 ± 0.42	⋯	old field	88.89	78.6 ± 30.0
1203+1810	M0	12.62	11.21	10.331 ± 0.015	118.	37.4e-12	⋯	3.54 ± 0.65	8.03 ± 0.56	⋯	old field	95.07	79.0 ± 33.5
1206+0016	M5	13.83	11.49	10.348 ± 0.023	116.	36.8e-12	⋯	2.34 ± 0.37	10.26 ± 0.87	−5.4 ± 0.4	old field	93.95	73.0 ± 29.2
1210−4612	M1	11.65	10.21	9.769 ± 0.019	197.	62.8e-12	⋯	⋯	149.14 ± 7.38	⋯	old field	98.99	24.5 ± 12.0
1218+1140	M7.5	20.18	16.65	14.185 ± 0.032	3.38	1.08e-12	⋯	⋯	6.37 ± 1.21	⋯	old field	98.73	31.7 ± 12.2
1222−8449	M3	12.04	10.45	9.721 ± 0.024	206.	65.6e-12	⋯	⋯	24.96 ± 5.23	⋯	old field	95.29	41.4 ± 19.6
1235+4450	M4.5	15.14	13.50	11.985 ± 0.018	25.6	8.16e-12	⋯	⋯	13.07 ± 2.64	⋯	old field	98.20	47.0 ± 23.2
1240+2047	M7	19.45	15.77	14.106 ± 0.024	3.63	1.16e-12	⋯	⋯	⋯	−14.1 ± 1.2a	old field	99.10	31.7 ± 13.0
1247−4344	M5	16.69	14.71	13.279 ± 0.025	7.78	2.48e-12	⋯	⋯	8.61 ± 2.45	⋯	old field	82.32	53.4 ± 20.4
1454+0053	M3	13.40	11.40	10.444 ± 0.021	106.	33.7e-12	⋯	⋯	1.60 ± 0.44	⋯	old field	90.53	37.0 ± 15.2
1516−2832	M5	14.39	12.14	10.516 ± 0.021	99.1	31.6e-12	⋯	⋯	31.57 ± 5.61	−4.7 ± 0.3	old field	76.00	14.9 ± 5.6
1546−5534	M8	16.45	12.80	10.209 ± 0.022	131.	41.9e-12	⋯	⋯	⋯	−6.1 ± 0.3	Argus	50.17	9.3 ± 0.8
1615+0336	M7	19.72	16.19	13.817 ± 0.026	4.74	1.51e-12	⋯	⋯	4.74 ± 1.40	−5.1 ± 1.2	old field	96.99	41.4 ± 15.8
1634+4827	M4	11.78	10.01	9.115 ± 0.032	360.	115.e-12	⋯	⋯	3.39 ± 0.43	⋯	old field	91.42	47.8 ± 21.2
1718−2246	M4.5	13.80	12.18	10.207 ± 0.018	132.	42.0e-12	3.6 ± 1.4e-13	⋯	18.25 ± 4.56	−7.1 ± 0.2	old field	87.69	53.0 ± 20.2
1722−6951A	M3	11.71	10.22	9.330 ± 0.021	295.	94.1e-12	13.9 ± 3.7e-13	⋯	⋯	−5.5 ± 0.3	old field	94.37	49.8 ± 18.6
1905−5434	M4	12.28	10.57	9.409 ± 0.024	275.	87.5e-12	⋯	⋯	37.81 ± 3.64	−4.7 ± 0.2	β Pic	66.68	19.7 ± 1.6
2002−4433	M8	19.37	15.80	13.528 ± 0.023	6.18	1.97e-12	⋯	⋯	⋯	−5.2 ± 1.5	old field	80.30	16.1 ± 5.6
2007+7001	M6	18.52	15.78	14.068 ± 0.034	3.76	1.20e-12	⋯	6.69 ± 2.09	⋯	⋯	old field	98.26	14.1 ± 6.4
2200−4636	M4.5	17.78	16.19	14.323 ± 0.021	2.97	9.46e-13	⋯	⋯	10.47 ± 3.13	⋯	old field	57.88	84.2 ± 35.9
2304+2111	M0.5	11.68	10.46	9.709 ± 0.022	208.	66.4e-12	⋯	⋯	10.25 ± 2.51	⋯	AB Dor	89.70	24.5 ± 1.6

Note.

^aThis measurement is for the flaring spectrum shown in Figure 38.

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To ease comparison to published sources, we also provide in Table 8 R- and I-band photometry from the United States Naval Observatory B1.0 Catalog³⁴ (USNO-B1), which has typical uncertainties of ±0.3 mag³⁵ , and J-band photometry from 2MASS³⁶ . These J-band magnitudes are also converted to J-band flux densities (f_J) and fluxes (F_J) and listed in the table for convenience. These were computed via the equations ${f}_{J}=({{f}_{J}}_{0}){10}^{-J/2.5}$ and ${F}_{J}=({f}_{J})c{\lambda }^{-2}{\rm{\Delta }}\lambda$, where ${{f}_{J}}_{0}$ is the J-band flux density at J = 0 mag, J is the J-band magnitude, c is the speed of light, λ is the central wavelength of the J-band filter, and ${\rm{\Delta }}\lambda$ is the J-band filter width. We use the values listed in the 2MASS Explanatory Supplement³⁷ of ${{f}_{J}}_{0}$ = 1594 ± 27.8 Jy, λ = 1.235 ± 0.006 μm, and ${\rm{\Delta }}\lambda$ = 0.162 ± 0.001 μm.

We have computed flux and flux density ratios, as listed in Table 9, to compare to published values in the literature. Figure 3 of Shkolnik et al. (2009) shows the ratio of X-ray to J-band flux versus I − J color (or spectral type) for old field M dwarfs and M dwarfs in younger clusters and moving groups of various ages. In order to compare our values of log(F_X/F_J) to the ones in that figure, though, it should be noted that the Shkolnik et al. (2009) values are computed with an assumed J-band filter width of 0.3 μm, almost twice the width that we used in our calculation of F_J. This translates to a difference in 0.27 dex between our computed log(F_X/F_J) values and theirs. For convenience, our Table 9 gives the modified value needed for direct comparison to their Figure 3. Also, we consider our spectral types to be a better indicator of the x-axis in this figure than the tabulated I − J color, since fainter I-band measurements from USNO-B1 can sometimes be well outside the expected 0.3 mag uncertainty envelope. With these caveats in mind, we find that one of our five M dwarfs with X-ray emission, WISE 0422+0337, shows X-ray emission well above the norm for its spectral type. Its fractional X-ray flux is higher than all of the plotted members of the β Pic moving group and most of the plotted members of the Pleiades. The other four X-ray detected M dwarfs have lower fractional X-ray fluxes. These four have values of $\mathrm{log}({L}_{X}/{L}_{\mathrm{bol}})$ that fall between −2.9 and −2.7, which are typical coronal saturation values for active field M dwarfs (see Figure 5 of Riaz et al. 2006).

Table 9.  Flux Ratios for M Dwarfs with X-ray and Ultraviolet Detections

WISE	SpType	R − J	I − J	log(FX/FJ)	Modifieda	${f}_{{\rm{FUV}}}/{f}_{J}$	${f}_{{\rm{NUV}}}/{f}_{J}$	NUV $-J$	J − Ks	NUV−W1	J – W2
Object		(mag)	(mag)	(dex)	(dex)			(mag)	(mag)	(mag)	(mag)
(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)	(11)	(12)
0157−0948	M4	2.97	⋯	⋯	⋯	⋯	0.00503	6.64 ± 0.04	0.64 ± 0.05	7.50 ± 0.03	1.08 ± 0.04
0405+3719	M5	4.10	2.48	⋯	⋯	⋯	0.00021	10.06 ± 0.26	0.87 ± 0.03	11.14 ± 0.26	1.29 ± 0.03
0422+0337	M4.5	4.72	1.04	−1.50	−1.77	⋯	0.00023	9.97 ± 0.04	0.86 ± 0.03	10.93 ± 0.04	1.11 ± 0.03
0500+1916	M1	2.09	1.05	⋯	⋯	⋯	0.00006	11.45 ± 0.22	0.82 ± 0.03	12.41 ± 0.22	0.91 ± 0.03
0536−0006	M4.5	1.99	0.72	−1.98	−2.25	⋯	⋯	⋯	0.82 ± 0.03	⋯	1.23 ± 0.03
0912+2205	M3	2.59	0.86	⋯	⋯	⋯	0.00023	10.00 ± 0.06	0.94 ± 0.03	11.07 ± 0.06	1.15 ± 0.03
0935−0301	M3	2.56	0.82	⋯	⋯	⋯	0.00011	10.76 ± 0.23	0.88 ± 0.03	11.74 ± 0.23	1.11 ± 0.03
1019+3922	M4.5	3.55	1.74	⋯	⋯	0.00003	0.00011	10.79 ± 0.04	0.82 ± 0.02	11.81 ± 0.05	1.19 ± 0.02
1029+2545	M4.5	3.12	0.95	−1.99	−2.26	0.00009	0.00018	10.25 ± 0.15	0.82 ± 0.02	11.24 ± 0.15	1.16 ± 0.03
1059+1509	M3.5	3.03	0.91	⋯	⋯	⋯	0.00008	11.14 ± 0.34	0.82 ± 0.03	12.10 ± 0.34	1.12 ± 0.03
1114+5703	M0	1.82	0.53	⋯	⋯	⋯	0.00009	10.98 ± 0.12	0.81 ± 0.03	11.92 ± 0.12	0.93 ± 0.02
1202−0111	M4	3.01	1.46	⋯	⋯	⋯	0.00016	10.38 ± 0.36	0.79 ± 0.03	11.30 ± 0.36	1.12 ± 0.03
1203+1810	M0	2.29	0.88	⋯	⋯	0.00003	0.00007	11.31 ± 0.08	0.80 ± 0.02	12.16 ± 0.08	0.89 ± 0.02
1206+0016	M5	3.48	1.14	⋯	⋯	0.00002	0.00009	11.02 ± 0.09	0.87 ± 0.03	12.09 ± 0.09	1.26 ± 0.03
1210−4612	M1	1.88	0.44	⋯	⋯	⋯	0.00076	8.70 ± 0.05	0.79 ± 0.03	9.65 ± 0.05	1.06 ± 0.03
1218+1140	M7.5	5.99	2.46	⋯	⋯	⋯	0.00188	7.70 ± 0.21	0.95 ± 0.05	8.90 ± 0.21	1.38 ± 0.04
1222−8449	M3	2.32	0.73	⋯	⋯	⋯	0.00012	10.69 ± 0.23	0.87 ± 0.03	11.66 ± 0.23	1.07 ± 0.03
1235+4450	M4.5	3.16	1.52	⋯	⋯	⋯	0.00051	9.13 ± 0.22	0.79 ± 0.02	10.06 ± 0.22	1.17 ± 0.03
1247−4344	M5	3.41	1.43	⋯	⋯	⋯	0.00111	8.28 ± 0.31	0.89 ± 0.04	9.37 ± 0.31	1.28 ± 0.03
1454+0053	M3	2.96	0.96	⋯	⋯	⋯	0.00002	12.95 ± 0.30	0.78 ± 0.03	13.87 ± 0.30	1.07 ± 0.03
1516−2832	M5	3.87	1.62	⋯	⋯	⋯	0.00032	9.63 ± 0.19	0.90 ± 0.03	10.73 ± 0.19	1.28 ± 0.03
1615+0336	M7	5.90	2.37	⋯	⋯	⋯	0.00100	8.39 ± 0.32	0.81 ± 0.04	9.44 ± 0.32	1.37 ± 0.04
1634+4827	M4	2.66	0.90	⋯	⋯	⋯	0.00001	13.45 ± 0.14	0.99 ± 0.04	14.61 ± 0.14	1.25 ± 0.04
1718−2246	M4.5	3.59	1.97	−2.07	−2.34	⋯	0.00014	10.54 ± 0.27	0.83 ± 0.03	11.53 ± 0.27	1.15 ± 0.03
1722−6951A	M3	2.38	0.89	−1.83	−2.10	⋯	⋯	⋯	0.86 ± 0.03	⋯	1.09 ± 0.03
1905−5434	M4	2.87	1.16	⋯	⋯	⋯	0.00014	10.55 ± 0.10	0.86 ± 0.03	11.61 ± 0.10	1.16 ± 0.03
2007+7001	M6	4.45	1.71	⋯	⋯	0.00178	⋯	⋯	0.61 ± 0.07	⋯	1.16 ± 0.04
2200−4636	M4.5	3.46	1.87	⋯	⋯	⋯	0.00353	7.03 ± 0.32	0.82 ± 0.04	8.31 ± 0.32	1.83 ± 0.03
2304+2111	M0.5	1.97	0.75	⋯	⋯	⋯	0.00005	11.66 ± 0.27	0.88 ± 0.03	12.62 ± 0.27	0.97 ± 0.03

Note.

^aThis is the value of log(F_X/F_J) to be used when comparing to the plots of Shkolnik et al. (2009). See the text for details.

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Figure 3 of Shkolnik et al. (2011) provides a reference for the ultraviolet fluxes of typical M dwarfs in the field versus those in younger groups such as the TW Hya Association. It should be noted that that figure actually plots the ratio of NUV to J-band flux densities, not fluxes, despite what the y-axis label implies. (For more on this, see footnote 7 of Shkolnik & Barman 2014.) Three of our X-ray detected stars—WISE 0422+0337, 1029+2545, and 1718−2246—are also detected in the ultraviolet and fall within the locus of objects typically regarded as having ages below ∼300 Myr. All three of these show clear Balmer emission in our optical spectra as well. Five other M dwarfs in Table 9 have very high fractional levels of NUV flux density (>0.0001)—WISE 0157−0948, 1218+1140, 1247−4344, 1615+0336, and 2200−4636—but none are detected in either the X-ray or the FUV. These presumably are objects caught by GALEX during a flaring event and do not maintain high levels of magnetic activity. Indeed, only one of these, the M7 dwarf WISE 1615+0336, was seen to have measurable Hα emission when our optical spectrum was acquired.

We can also identify objects having ultraviolet excesses indicative of high magnetic activity by creating colors across the GALEX, 2MASS, and WISE passbands. Four such colors are given in the final four columns of Table 9. Figure 5 of Rodriguez et al. (2011) shows the location of TW Hya Association members in the NUV $-J$ versus J − K_s plane. Roughly half of our objects in Table 9 fall in the selection region used by Rodriguez et al. (2011) to identify candidate objects with ultraviolet excesses. Similarly, Figure 1 of Rodriguez et al. (2013) shows known members of young moving groups on the NUV−W1 versus J – W2 plane. Again, roughly half of our objects fall within the selection wedge used by Rodriguez et al. (2013) to select young candidates.

Given that some of our objects have magnetic signs of youth, do any of these share kinematics consistent with young moving groups known in the solar vicinity? To answer this question, we have used v1.4 of the Bayesian analysis tool BANYAN II³⁸ (Malo et al. 2013; Gagné et al. 2014) that determines membership probabilities for young associations within 100 pc of the Sun (TW Hya, β Pic, Tucana-Horologium, Columba, Carina, Argus, and AB Dor) or for the general young or old field populations. Because we have only positions and proper motions for our objects, and no radial velocities or trigonometric parallaxes, we have input only those quantities into the tool. In the final three columns of Table 8, we list the group with the highest membership probabilty, the membership probability itself, and the object's predicted distance if the membership is real. The predicted distance (${d}_{{\rm{pred}}}$) can be compared to our spectrophotometric estimate (${d}_{{\rm{est}}}$ in Table 10; see Section 4.3.2) as an independent judge of the results.

Table 10.  Distance Estimates for M, L, and T Dwarfs from Table 4

Name	Spec.	d${}_{{\rm{est}}}$				Name	Spec.	d${}_{{\rm{est}}}$				Name	Spec.	d${}_{{\rm{est}}}$
	Type	(pc)					Type	(pc)					Type	(pc)
(1)	(2)	(3)				(1)	(2)	(3)				(1)	(2)	(3)
0005+0209	M6	23 ± 2				1055−7356	M7	5 ± 1				1615+0336	M7	41 ± 3
0006−1319	L7:	27 ± 2				1055−5750	M4	37 ± 3				1634+4827	M4	13 ± 1
0034+5513	M4.5	128 ± 8				1056−5750	M4	35 ± 3				1702+7158A	M4.5	151 ± 10
0043+2221	M8	55 ± 4				1059+1509	M3.5	44 ± 3				1712+0645	T2 pec	22 ± 2
0051−2251	M8	24 ± 2				1114+5703	M0	74 ± 5				1718−2245	M3.5	31 ± 2
0111+1211	M8	58 ± 4				1133−4140	M0.5	122 ± 8				1718−2246	M4.5	22 ± 2
0130−1047	M9	36 ± 3				1140−0624	M5	42 ± 3				1722−6951A	M3	28 ± 2
0130−3836	M5	128 ± 8				1201−1324	M9.5	40 ± 3				1722−6951B	M4	58 ± 4
0134+0525	M4.5	100 ± 7				1202−0111	M4	85 ± 6				1740−5507	M2.5	257 ± 16
0157−0948	M4	78 ± 5				1203+1810	M0	76 ± 5				1741−4234	M4	70 ± 5
0158+3231	L4.5	33 ± 2				1206+0016	M5	20 ± 2				1743+6313	M9	42 ± 3
0231+2811	M9	41 ± 3				1210−4612	M1	52 ± 4				1746+5100	L0:	43 ± 3
0309−1354	M6:	48 ± 3				1218+1140	M7.5	45 ± 3				1747+4008	M4	42 ± 3
0404−6259	M4	39 ± 3				1222−8449	M3	33 ± 2				1758−5839	M6	16 ± 1
0405+3719	M5	26 ± 2				1222−2116	L7:	25 ± 2				1800−1559	L4.5	10 ± 1
0422+0337	M4.5	18 ± 2				1223+5510	M8 pec	48 ± 3				1835−7912	M5	28 ± 2
0447+2534	M4	25 ± 2				1235+4450	M4.5	49 ± 3				1842+2104	L1.5	33 ± 2
0500+1916	M1	39 ± 3				1240+2047	M7	47 ± 3				1843−6355	M4.5	92 ± 6
0500+0442	L0.5 pec	24 ± 2				1241−2457	L2.5p	49 ± 3				1905−5434	M4	15 ± 1
0507−0342	M9 pec?	33 ± 2				1247−4344	M5	78 ± 5				1940+6346	M9.5	39 ± 3
0508+3319	L2	24 ± 2				1305−1019	M5	104 ± 7				2002−4433	M8	30 ± 2
0536−0006	M4.5	26 ± 2				1333+3744	L5	27 ± 2				2004−2637	M7.5:	71 ± 5
0546−0440	M4.5	23 ± 2				1343−1216	L4	18 ± 2				2007+7001	M6	59 ± 4
0559+5844	M9	41 ± 3				1348−4227	L2	34 ± 2				2008+7030	M7:	79 ± 5
0632+2643	M7	53 ± 4				1403−5923	M3	43 ± 3				2101−4907A	M4.5	13 ± 1
0701−0137	M4	25 ± 2				1404−5924	M3	42 ± 3				2120+2652	M7	60 ± 4
0705−1007	M5	19 ± 2				1404−4726	M6	60 ± 4				2121−6239	T2	16 ± 1
0730−6335	M4	28 ± 2				1411−1403	M9	45 ± 3				2133+7319	M4.5	246 ± 15
0826−1640	L8:	16 ± 1				1423−1646B	M0.5	54 ± 4				2135+7312	L2:	26 ± 2
0852+5139	M7.5	40 ± 3				1452+2723	L0	42 ± 3				2200−4636	M4.5	143 ± 9
0855−0233	L7	21 ± 2				1454+0053B	M9	49 ± 3				2201−4112	M4:	136 ± 9
0912+2205	M3	53 ± 3				1454+0053A	M3	46 ± 3				2230−2720	L0:	40 ± 3
0920−7557	M4.5	33 ± 2				1507+6030	L2:	56 ± 4				2249+3205	L4:	28 ± 2
0935−0301	M3	49 ± 3				1516−2832	M5	22 ± 2				2304+2111A	M0.5	54 ± 4
0949−0103	M0	81 ± 5				1539−5352	M4	39 ± 3				2304+2111B	M4.5	68 ± 5
1019+3922	M4.5	33 ± 2				1540−5101	M6.5	5 ± 1				2324+1617	M8	57 ± 4
1029+5715	L6 pec	32 ± 2				1542−1007	M7.5	49 ± 3				2344+1312	M7:	36 ± 3
1029+2545	M4.5	23 ± 2				1546−5254	M5	54 ± 4

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As the table values indicate, most of our M dwarfs are likely to be members of the old field population. This includes all of the aforementioned objects that appear to be young candidates on the Shkolnik et al. (2009, 2011) and Rodriguez et al. (2011, 2013) plots. Several other M dwarfs, on the other hand, have >50% probabilities of belonging to young associations based on the BANYAN results:

• 1.  
  The M6 dwarf WISE 0005+0209 has a high probability of belonging to the AB Dor Moving Group, but secondary checks show that this is likely a chance association. The BANYAN-predicted distance of 18.1 ± 1.0 pc differs by almost 5σ from our spectrophotomeric estimate, and the object shows only Balmer emission with no ROSAT or GALEX detections.
• 2.  
  The M4.5 dwarf WISE 0546−0440 is given a 50% chance of belonging to the young field population, but like the previous object, shows only Balmer emission with no ROSAT or GALEX detections, so it, too, is likely an older field star.
• 3.  
  The M8 dwarf SCR J1546−5534 (Figure 45), recognized as a nearby (∼6.7 pc distant) star by Boyd et al. (2011), is given a 50% probability of belonging to Argus; however, a comparison of its spectrum to an old field M8 and a young field M8 (Figure 46) shows that SCR J1546−5534 exhibits no signs of youth and therefore could not be a member of an association as young as Argus (30–50 Myr; Zuckerman et al. 2011).
• 4.  
  The M4 dwarf WISE 1905−5434 has a 67% probability of association in the β Pic Moving Group. Our distance estimate of 15 pc, however, is ∼3σ closer than the predicted one. Although this object has ultraviolet detections by GALEX, there is no ROSAT detection.
• 5.  
  The M0.5 dwarf WISE 2304+2111, which is also detected by GALEX, has a 90% probability of association in AB Dor, but our estimated distance is over 18σ away from the predicted value by BANYAN.

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None of our M dwarfs pass all four tests of youth—high X-ray flux, high ultraviolet flux, Balmer emission detections, and high probability of group membership based on kinematics. We therefore conclude that all detections of magnetic activity are likely related to chance flares rather than persistent coronal and chromospheric activity.

4.3.2. Recently Discovered M Dwarfs with d < 20 pc