#  The Identification of RR Lyrae and $\delta$ Scuti stars from variable
$GALEX$ Ultraviolet Sources.

T.D. Kinman11affiliation:  NOAO is operated by AURA, Inc. under cooperative
agreement with the National Science Foundation. National Optical Astronomy
Observatory, 950 N. Cherry Avenue, Tucson, AZ 85719, USA  Warren R. Brown
Smithsonian Astrophysical Observatory, 60 Garden St., Cambridge, MA 02138, USA

###### Abstract

We identify the RR Lyrae and $\delta$ Scuti stars in three catalogs of $GALEX$
variable sources. The $NUV$ amplitude of RR Lyrae stars is about twice that in
$V$, so we find a larger percentage of low amplitude variables than catalogs
such as Abbas et al. (2014). Interestingly, the $(NUV-V)_{0}$ color is
sensitive to metallicity and can be used to distinguish between variables of
the same period but differing [Fe/H]. This color is also more sensitive to
Teff than optical colors and can be used to identify the red edge of the
instability gap. We find 8 $\delta$ Scuti stars, 17 RRc stars, 1 RRd star and
84 RRab stars in the $GALEX$ variable catalogs of Welsh et al. (2005) and
Wheatley et al. (2008). We also classify 6 $\delta$ Scuti stars, 5 RRc stars
and 18 RRab stars among the 55 variable $GALEX$ sources identified as “stars”
or RR Lyrae stars in the catalog of Gezari et al. (2013). We provide
ephemerides and light curves for the 26 variables that were not previously
known.

###### Subject headings:

stars: RR Lyrae. stars: $\delta$ Scuti, stars: variable. stars: red horizontal
branch.

††slugcomment: AJ accepted

##  1\. Introduction

The $Galaxy~{}Evolution~{}Explorer$ ($GALEX$) (Martin et al. 2005) has imaged
the whole sky in the $FUV$ ($\lambda\lambda$ 1350 – 1750 Å) and $NUV$
($\lambda\lambda$ 1750 – 2750 Å) wavebands, opening the door to studying
variable stars in the ultraviolet. One of the most important classes of
variable stars are RR Lyraes, evolved horizontal branch stars that have
intrinsic luminosities that correlate with pulsation amplitude and period.
$\delta$ Scuti stars (DSCT111These pulsating variables (spectral types A0 to
F5) have $V$ amplitudes in the range 0.03 to 0.90 mag.; those with $V$
amplitudes greater than 0.20 are often called High Amplitude $\delta$ Scuti
stars.) are a different class of pulsators with colors and pulsation periods
comparable to RR Lyraes; they are discussed in the appendix (Sec. A).
Importantly, the ultraviolet ($UV$) amplitudes of RR Lyrae stars are much
larger in $GALEX$ wavebands than in optical wavebands (Wheatley et al. 2003).
What remains unexplored are complete samples of $UV$ variables.

Interestingly, detailed observations of several bright RR Lyrae stars show
that their $UV$–optical colors correlate with metallicity. Wheatley et al.
(2012) fit model light-curves to the $FUV$ and $NUV$ photomtery of six well-
observed bright RR Lyrae stars. They find that the $FUV$ and $NUV$ light-
curves, which primarily reflect temperature changes during the pulsation
cycle, also depend on metallicity. We also find that $(NUV-V)$ depends on
metallicity.

To date, candidate variable $GALEX$ sources have been cataloged by Welsh
(2005) (Catalog 1) and by Wheatley et al. (2008) (Catalog 2). During the
course of this work, a third catalog of over a thousand variable $GALEX$
sources was published by Gezari et al. (2013); this catalog exclusively uses
$NUV$ magnitudes. Few of these $UV$ variables have optical identifications.
Only 25% of the 84 sources in Catalog 1 and less than a third of the 410
sources in Catalog 2 are matched to optical objects of known type. Most of the
$UV$ variables with optical identifications are extragalactic objects. Less
than 10% of the $UV$ variables in the catalog of Gezari et al. (2013) have
identifications with known types of stars.

The goal of this paper is to identify all of the Galactic stars in the $GALEX$
variable catalogs in a complete and systematic way, with a particular focus on
RR Lyrae variables. We investigate the $(NUV-V)_{0}$ color index as a possible
diagnostic for identifying variable types: in Sec. 4.5 and Appendix B, we
address the problem of distinguishing between type c RR Lyrae stars and
contact binaries (Kinman & Brown 2008). We base our analysis on $NUV$
magnitudes, because $NUV$ magnitudes are more accurate than $FUV$ magnitudes
and are available for a larger number of objects. The use of the $(FUV-NUV)$
color could provide additional constraint (see for example, Smith et al. 2014)
but would limit the sample.

Figure 1.— $V$-magnitude light curves for 4 newly identified RRc and 4 newly
identified RRab variables presented in Table 2.  Figure 2.—  $V$-magnitude
light curves for 8 new identified RRab variables presented in Table 2.  Figure
3.—  $V$-magnitude light curves for 7 newly identified $\delta$ Scuti stars
and one EW variable presented in Table 2. The periods of the lowest amplitude
$\delta$ Scuti stars are quite uncertain.  Figure 4.—  $V$-magnitude light
curves for 2 newly identified Algol (EA) variables presented in Table 2. The
period of J221657.3$-$000633.0 is uncertain.

Our approach is to use the VizieR search tool and the JAAVS variable star
catalog (VSX, Watson 2006) to identify known variables, such as those
identified by Drake et al. (2012) in the Catalina Surveys, by Palaversa et al.
(2013) in the LINEAR Survey, and by Abbas et al. (2014) in their search of the
combined SDSS, Pan-STARRS1 and Catalina Surveys222The Abbas et al. Catalog was
published only shortly before this paper was completed and so it has only been
possible to make limited use of it.. We look at every object in Catalog 1 and
in Catalog 2, and the subset of objects identified as “stars” in the larger
Gezari catalog. If we are unable to classify an object with the variable star
catalogs, we then use data from the Catalina Survey Data Release 2 (Drake et
al. 2009) to measure the object’s mean $V$ magnitude and, if possible, its
variability. Period-finding with the Catalina Survey data (e.g. using the NASA
Exoplanet Archive Periodogram Service) becomes difficult for objects with $V$
$>$ 17 and for objects with $V$ amplitudes $\lesssim$0.2 magnitudes;
consequently, the types we assign to such variables are less certain. We also
review the 38 objects previously identified as RR Lyrae stars in the Gezari
catalog.

This paper presents the RR Lyrae and $\delta$ Scuti stars that we identify,
and describes how $GALEX$ magnitudes can assist in their identification. The
$(NUV-V)_{0}$ color is particularly sensitive for detecting the temperature
changes that come from pulsations, and for detecting the onset of this
instability as a function of parameters such as Teff. The identification of
other types of stars and variables from the $GALEX$ variability catalogs will
be discussed elsewhere.

##  2\. The identification of RR Lyrae and $\delta$ Scuti Stars in the first
two $GALEX$ variability Catalogs.

Table 1 presents 110 RR Lyrae and $\delta$ Scuti stars that we identify from
the first two catalogs of $GALEX$ variables; these stars constitute 22% of all
the sources in these catalogs. Our list comprises 8 $\delta$ Scuti stars, 17
RRc stars, 1 RRd star and 84 RRab stars. References to the sources of the
$GALEX$ magnitudes and the optical data are given in columns 4 and 10
respectively. The $(NUV-V)_{0}$ colors given in col. 8 refer to mean
magnitudes 333The mean $NUV$ magnitude is the mean of the maximum and minimum
values. The mean $V$ magnitude is the arithmetic mean of all the observations
given by the Catalina DataRelease 2. For brighter variables not in this
survey, the mean was estimated from the maximum and minimum magnitudes using
the formula given in the appendix of Preston et al. (1991). and their largest
source of uncertainty lies in the estimation of the mean $NUV$ from the
available data; this uncertainty increases with the $NUV$ amplitude and is
therefore largest for the RRab variables. We assumed the galactic extinction
A$(NUV)$ = 8.90E$(B-V)$ (Rey et al. 2007). The E$(B-V)$ were taken from the
MAST archive of $GALEX$ objects. Only 6 stars have E$(B-V)$ $>$ 0.100 so the
uncertainty in the correction for extinction (Peek & Schiminovich, 2013) is
probably significant only for these stars. The periods given in column 9 are
those taken from the literature in the case of previously known variables;
otherwise, the periods were determined by us.

We discover 2 new $\delta$ Scuti stars, 3 RRc stars and 10 RRab stars among
the 110 variable stars. We present the ephemerides of the new variables in
Table 2, and plot their light curves in Figures 1, 2, 3 & 4\. One of these RRc
and one of these RRab were later found in the catalog of Drake et al, (2014)
but with differing periods; these differences are discussed in Sec. 4.6.

Figure 5.—  Distribution of known RR Lyrae stars from Dambis et al. (2013) in
plots of the de-reddened $(NUV-V)_{0}$ color versus period (upper panel) and
versus [Fe/H] (lower panel). The filled circles, crosses, and open circles
denote halo RRab, disk RRab, and RRc variables, respectively. There are
significant differences in $(NUV-V)_{0}$ between the disk RRab stars ([Fe/H]
$\geq-0.40$), the halo RRab stars ([Fe/H] $\leq-0.80$), and the RRc stars.

We investigate trends between $(NUV-V)_{0}$ color and stellar properties by
studying a well-defined sample of known RR Lyrae stars. We begin by
calculating $(NUV-V)_{0}$ for 150 nearby RR Lyrae stars using the recent
compilation by Dambis et al. (2013), a sample for which we could easily obtain
the necessary data. For this sample, we plot $(NUV-V)_{0}$ against period for
RRc and for $halo$ and $disk$ RRab (Fig 5, upper panel), and against [Fe/H]
(Fig 5, lower panel).

There is a significant difference in $(NUV-V)_{0}$ between the RRc and RRab
that reflects the average temperature difference between the two types. There
is also a significant difference in $(NUV-V)_{0}$ between the $disk$ and
$halo$ RRab that reflects the metallicity difference between the two types as
expected from Wheatley et al. (2012).

We also investigate trends between the $(NUV-V)_{0}$ color and stellar
properties for a sample of known high-amplitude $\delta$ Scuti stars (HADS)
taken from McNamara (1997) and $\delta$ Scuti of lower amplitude taken from
Suveges et al. (2012). The results are shown in the plot of $(NUV-V)_{0}$
$vs.$ Period given in Fig. 6. The blue open circles, black open triangles and
black filled triangles are respectively the RRc (both Catalogs), RRab from
Catalog 1 and RRab from Catalog 2 in Table 1. The horizontal solid blue,
dotted black and dashed red lines show the mean values of $(NUV-V)_{0}$ for
the RRc, halo RRab, and disk RRab respectively; their associated vertical
lines show the $r.m.s.$ standard errors of these means. There is good
agreement between these mean values and the $(NUV-V)_{0}$ of our program
stars. The observed increase in this color with increasing period is nicely
matched to the $(NUV-V)_{0}$ location of the blue edge of the instability gap
(Kinman et al. 2007), shown by the heavy blue vertical line at a period of 0.2
days in Fig. 6.

Figure 6.—  De-reddened $(NUV-V)_{0}$ color versus pulsation period for our
program stars from Table 1. The stars are plotted as: high-amplitude $\delta$
Scuti stars (green solid circles), RRc (blue open circles), RRab from Catalog
1 (black open triangles) and RRab from Catalogue 2 (black filled triangles).
The blue (solid), black (dotted) and red (dashed) horizontal lines show mean
values of $(NUV-V)_{0}$ for known RRc, halo RRab, and disk RRab variables,
respectively. Two samples of known high-amplitude $\delta$ Scuti stars
variables are plotted with black x’s (McNamara 1997) and encircled black x’s
(Suveges et al. 2012). The heavy blue vertical line shows the range of
$(NUV-V)_{0}$ for blue horizontal branc stars at the blue edge of the
instability gap (Kinman et al. 2007).  Table 1Identifications of $\delta$
Scuti (DCST) and RR Lyrae Stars in Catalogs 1 and 2. [Available in full in the
Online Journal]

Star aa$GALEX$ identification of source. |  $NUV_{max}$ bb$NUV$ magnitude at maximum. |  $NUV_{amp}$ ccAmplitude of $NUV$ magnitude.  | Ref ddReference for $GALEX$ source. | E$(B-V)$ |  $V_{max}$ ee$V$ magnitude at maximum. |  $V_{amp}$ ffAmplitude of $V$ magnitude. |  $(NUV-V)_{0}$ ggDifference beteween mean $NUV$ and $V$ magnitudes corrected for galactic extinction. | Period hhPeriod in days. | Refs iiReferences for optical data. | Notes
---|---|---|---|---|---|---|---|---|---|---
DCST: |  |  |  |  |  |  |  |  |  |
J004347.9+421654.9 | 13.02 | 0.63 | 1,2 | 0.084 | 09.19 | 0.27 | 3.692 | 0.1249078 | 13 | 1
J004347.7–445130.7 | 16.78 | 0.84 | 2 | 0.009 | 14.45 | 0.50 | 2.457 | 0.0574790 | 20 | 2
J033715.2–283238.1 | 15.51 | 0.94 | 2 | 0.011 | 13.20 | 0.65 | 2.397 | 0.0561380 | 11 |
J104647.6+591445.5 | 19.86 | 0.93 | 2 | 0.008 | 17.40 | 0.80 | 2.480 | 0.1231520 | 20 | 3
J133757.1+401610.8 | 20.00 | 0.91 | 1 | 0.006 | 18.00 | 0.50 | 2.177 | 0.0641760 | 16 |
J160608.8+530519.0 | 18.76 | 1.53 | 2 | 0.014 | 13.53 | 0.55 | 5.647 | 0.1027590 | 20 | 2
J164106.8+404225.2 | 15.70 | 0.87 | 2 | 0.008 | 13.40 | 0.55 | 2.419 | 0.0512960 | 13 | 4
J171250.9+582748.6 | 18.51 | 0.63 | 2 | 0.044 | 15.70 | 0.30 | 2.749 | 0.0803930 | 16,7 | 5
RRc: |  |  |  |  |  |  |  |  |  |
J033546.0–290209.8 | 16.09 | 0.90 | 2 | 0.008 | 13.45 | 0.50 | 2.797 | 0.2773379 | 18 |
J051855.0–492606.1 | 17.59 | 0.84 | 2 | 0.026 | 14.85 | 0.45 | 2.806 | 0.3822732 | 20 | 2
J103720.9+591653.8 | 18.31 | 0.62 | 2 | 0.008 | 15.70 | 0.40 | 2.679 | 0.3132750 | 10,21,22 |
J103759.4+581213.5 | 19.67 | 1.03 | 2 | 0.008 | 16.90 | 0.40 | 3.038 | 0.4023800 | 21 | 2
J105044.4+045115.9 | 19.51 | 0.97 | 2 | 0.027 | 16.80 | 0.45 | 2.813 | 0.2827820 | 16,19.22 |
J143823.9+635329.9 | 19.23 | 0.76 | 2 | 0.016 | 16.34 | 0.36 | 2.998 | 0.3559790 | 10,21 |
J144033.3–781914.6 | 17.09 | 0.79 | 2 | 0.108 | 13.80 | 0.70 | 2.789 | 0.3281820 | 13 | 6
J154550.8–124936.8 | 19.51 | 0.62 | 2 | 0.146 | 15.96 | 0.28 | 2.970 | 0.2935940 | 20,22 | 2, 45
J155800.6+535233.6 | 18.06 | 0.87 | 2 | 0.012 | 15.12 | 0.36 | 3.124 | 0.3284030 | 16,10,21,22 |
J160759.9+535209.9 | 19.20 | 0.90 | 2 | 0.012 | 16.52 | 0.44 | 2.841 | 0.3806390 | 12,22 |
J171008.9+585112.9 | 20.06 | 0.92 | 2 | 0.031 | 17.25 | 0.50 | 2.842 | 0.2821010 | 16,21,22 |
J203922.4–010346.0 | 16.88 | 0.81 | 2 | 0.084 | 13.57 | 0.40 | 3.089 | 0.3703490 | 14,7,22 | 7
J204024.3–010950.0 | 19.06 | 0.72 | 2 | 0.079 | 15.68 | 0.34 | 3.170 | 0.3626603 | 14,7,21 | 8
J204042.8–003717.3 | 20.28 | 0.72 | 2 | 0.159 | 17.12 | 0.40 | 3.023 | 0.2865740 | 14,21 |
J221444.8–182639.3 | 20.00 | 0.96 | 2 | 0.026 | 17.40 | 0.55 | 2.654 | 0.2862060 | 20 | 2
J223601.0+134711.5 | 19.16 | 0.91 | 2 | 0.068 | 15.80 | 0.40 | 3.271 | 0.3760710 | 16,7,22 | 9
J224029.0+120056.3 | 17.56 | 0.85 | 2 | 0.050 | 14.60 | 0.50 | 2.877 | 0.2786230 | 16,7,21,22 | 10
RRd: |  |  |  |  |  |  |  |  |  |
J130204.5+463533.7 | 18.01 | 1.45 | 1 | 0.014 | 15.45 | 0.60 | 2.959 | 0.3509191 | 12 | 11
RRab: |  |  |  |  |  |  |  |  |  |
J001611.6–392721.5 | 16.16 | 2.02 | 2 | 0.015 | 13.50 | 1.00 | 3.420 | 0.5316009 | 11 |
J003043.0–422747.7 | 17.25 | 1.48 | 2 | 0.007 | 14.00 | 0.90 | 3.747 | 0.6973440 | 9 |
J004047.4–434948.9 | 18.20 | 1.95 | 2 | 0.016 | 15.30 | 0.95 | 3.633 | 0.4941930 | 20 | 2
J004548.2–435509.1 | 16.00 | 1.38 | 1 | 0.001 | 13.00 | 0.70 | 3.565 | 0.5898310 | 11 |
J011010.9–452431.3 | 18.84 | 1.85 | 2 | 0.009 | 15.90 | 0.85 | 3.697 | 0.5897626 | 13 | 12
J011805.2–751126.1 | 18.61 | 1.41 | 2 | 0.055 | 15.60 | 1.20 | 3.032 | 0.480 | 13 | 13
J013642.0–062743.1 | 19.70 | 0.63 | 2 | 0.028 | 16.35 | 0.25 | 3.483 | 0.7775660 | 16,7,22 | 14
J022521.8–050017.4 | 19.42 | 1.57 | 2 | 0.027 | 16.90 | 0.80 | 3.012 | 0.6212419 | 3,21 |
J033500.4–272854.8 | 16.98 | 1.63 | 2 | 0.009 | 14.20 | 0.80 | 3.415 | 0.6975764 | 18 |
J042832.3+165821.6 | 19.30 | 1.64 | 2 | 0.377 | 14.42 | 1.00 | 3.288 | 0.6229220 | 20,7 | 2,15
J051728.7–481712.8 | 18.60 | 1.42 | 2 | 0.027 | 15.70 | 0.80 | 3.291 | 0.6614350 | 20 | 2
J052307.7–490336.1 | 18.17 | 2.13 | 2 | 0.030 | 15.47 | 1.10 | 3.397 | 0.5139700 | 20 | 2
J081226.4+033320.5 | 18.95 | 1.95 | 2 | 0.023 | 16.08 | 0.72 | 3.677 | 0.5555151 | 6,7 | 16
J093026.0+071221.6 | 15.83 | 0.97 | 1 | 0.058 | 12.08 | 0.79 | 3.666 | 0.6028494 | 13 | 17
J100133.2+014328.5 | 17.21 | 1.98 | 2 | 0.019 | 14.40 | 1.00 | 3.521 | 0.5423741 | 3,10,19,21 |
J100358.9–270001.4 | 18.26 | 1.43 | 1 | 0.079 | 13.78 | 0.84 | 4.556 | 0.6311440 | 20 | 2
J102002.7+611538.9 | 16.71 | 1.62 | 1 | 0.007 | 14.34 | 0.81 | 3.005 | 0.6428627 | 5,3,10,21 |
J102641.8+572858.7 | 18.78 | 1.84 | 2 | 0.011 | 15.80 | 0.85 | 3.719 | 0.6636605 | 10,21 |
J103538.2+581549.1 | 15.53 | 1.92 | 2 | 0.008 | 12.87 | 1.02 | 3.384 | 0.5242549 | 13,7 | 18
J104707.6+053349.2 | 17.78 | 2.25 | 2 | 0.024 | 15.00 | 1.00 | 3.642 | 0.5369295 | 10,19,21 |
J104803.1+554209.9 | 18.32 | 2.14 | 2 | 0.008 | 15.70 | 1.05 | 3.476 | 0.5065280 | 10,21 |
J104844.2+581538.6 | 18.47 | 2.49 | 2 | 0.011 | 16.10 | 1.30 | 3.317 | 0.4748198 | 3,21 |
J105130.9+043801.7 | 17.74 | 2.03 | 2 | 0.033 | 15.00 | 1.00 | 3.403 | 0.5243170 | 16,10,19,21 |
J105513.8+564747.7 | 17.09 | 2.24 | 2 | 0.007 | 14.65 | 0.75 | 3.519 | 0.5417451 | 16,10 |
J105622.3+570522.1 | 17.09 | 2.27 | 2 | 0.009 | 14.70 | 0.90 | 3.402 | 0.5016290 | 3,10,21 |
J105926.1–005927.9 | 19.53 | 2.09 | 1 | 0.042 | 16.72 | 1.43 | 3.246 | 0.4499016 | 13,3,42 | 19
J111147.3+510549.4 | 18.12 | 1.50 | 1 | 0.014 | 15.10 | 0.85 | 3.514 | 0.6449104 | 3 |
J112334.9+474014.6 | 19.45 | 1.07 | 1 | 0.014 | 16.18 | 1.10 | 3.353 | 0.5224715 | 3,10,21 |
J113340.3+502328.0 | 16.71 | 2.93 | 1 | 0.014 | 14.70 | 1.10 | 3.333 | 0.4976910 | 13,21 | 20
Truncated for display |  |  |  |  |  |  |  |  |  |

References. — (1) Welsh+(2005)(The $GALEX$ Ultraviolet Variability Catalog);
(2) Wheatley+(2008)(The Second $GALEX$ Ultraviolet Varaiability Catalog); (3)
Drake+(2013); (4) Keller+(2008); (5) Kinemuchi+(2006); (6) Kraus+(2007); (7)
Li+(2011); (8) Miceli+(2008); (9) Norton+(2007); (10) Palaversa+(2013); (11)
Pojmanski(2002)(ASAS Catalogue); (12) Poleski(2013); (13) Samus+(2012)(Gen.
Cat. Variable Stars); (14) Sesar+(2010); (15) Vivas+(2004)(QUEST Survey); (16)
Watson+(2006)(AAVSO VSX Catalog); (17) Wils+(2006); (18) Wils(2010)(Data in
VSX Catalog); (19) Zinn+(2014)(Extension of QUEST Survey); (20) This Paper
(New Identification). (21) Abbas+ (2014); (22) Drake+ (2014).

Note. — (1) CC And. (2) New identification. Ephemeris in Table 2. (3) New
Identification. Type and period uncertain. (4) v1209 Her (SX Phe type). (5) Sp
Type A (7) (6) v344 Aps. (7) Sp Type A (7) (8) Sp Type F (7) (9) Sp Type A (7)
(10) Sp Typ A (7) (11) Period is first overtone. (12) UU Phe. (13) BG Tuc, B
magnitude. (14) Sp Typ A (7) (15) Sp Typ F (7) (16) Sp Typ F (7) (17) WW Leo.
(18) v341 Uma;Sp Type A (7). (19) IX Leo. (20) CZ Uma.

Table 2 Positions, Types and Ephemerides of New† Variables.

Star aa$GALEX$ identification of source. | R.A. bbRight Ascension in decimal degrees. | Dec. ccDeclination in decimal degrees. | Type ddVariable Type. | HJD(max) eeHeliocentric Julian Date of Maximum. | Period ffPeriod in days. | $V_{max}$ gg$V$ magnitude at maximum. | $V_{min}$ hh$V$ magnitude at minimum.
---|---|---|---|---|---|---|---
| (2000) | (2000) |  | 2450000.0+ | (days) | (mag.) | (mag.)
CATALOGS 1 and 2: |  |  |  |  |  |  |
J004347.7$-$445130.7 | 010.9488 |  $-$44.8586 | DCST | 3556.1599 | 0.057479 | 14.45 | 14.95
J160608.8$+$530519.0 | 241.5371 |  $+$53.0890 | DCST | 3656.5589 | 0.102759 | 13.53 | 13.64
J051855.0$-$492606.1 | 079.7293 |  $-$49.4349 | RRc | 3578.5038 | 0.382273 | 14.85 | 15.30
J154550.8$-$124936.8‡ | 236.4618 |  $-$12.8269 | RRc | 3523.4753 | 0.293594 | 15.96 | 16.24
J221444.8$-$182639.3 | 333.6870 |  $-$18.4444 | RRc | 3583.6795 | 0.286206 | 17.40 | 17.95
J004047.4$-$434948.9 | 010.1981 |  $-$43.8301 | RRab | 3555.8138 | 0.494193 | 15.30 | 16.25
J042832.3$+$165821.6 | 067.1349 |  $+$16.9726 | RRab | 3469.5764 | 0.622922 | 14.45 | 15.45
J051728.7$-$481712.8 | 079.3700 |  $-$48.2869 | RRab | 3576.4696 | 0.661435 | 15.70 | 16.50
J052307.7$-$490336.1 | 080.7823 |  $-$49.0599 | RRab | 3576.4712 | 0.513970 | 15.47 | 16.57
J100358.9$-$270001.4 | 150,9955 |  $-$27.0002 | RRab | 3694.8098 | 0.631144 | 13.78 | 14.62
J122836.9$-$064230.0‡ | 187.1540 |  $-$06.7085 | RRab | 3496.5066 | 0.501648 | 17.50 | 18.60
J132546.5$-$425141.3 | 201.4437 |  $-$42.8615 | RRab | 3556.7107 | 0.451759 | 15.25 | 16.25
J165153.4$-$223952.2 | 252.9728 |  $-$22.6644 | RRab | 3599.5306 | 0.613432 | 13.80 | 14.75
J213856.4$-$240234.6 | 324.7351 |  $-$24.0430 | RRab | 3597.8294 | 0.594016 | 15.80 | 16.55
J214038.1$-$233642.7 | 325.1592 |  $-$23.6118 | RRab | 3638.7051 | 0.564344 | 17.25 | 17.90
Gezari et al. (2013): |  |  |  |  |  |  |
J022709.0$-$032420.6 | 036.7872 |  $-$03.4058 | DCST | 3648.7343 | 0.1685980 | 16.60 | 16.69
J221812.8$+$004839.0 | 334.5535 |  $+$00.8106 | DCST | 3507.9368 | 0.0413220 | 17.35 | 17.50
J160552.5$+$540825.0 | 241.4690 |  $+$54.1404 | DCST | 3880.8828 | 0.0587400 | 17.70 | 18.10
J160905.7$+$534712.2‡ | 242.2740 |  $+$53.7866 | DCST | 3505.5268 | 0.1697210 | 16.50 | 16.85
J021838.1$-$041951.0 | 034.6589 |  $-$04.3304 | DCST | 3627.8700 | 0.0759360 | 17.70 | 17.80
J022121.9$-$033040.0‡ | 035.3413 |  $-$03.5109 | RRc | 3627.5444 | 0.3438110 | 17.90 | 18.30
J095632.9$+$011706.0 | 149.1372 |  $+$01.2850 | RRab | 3464.1026 | 0.7711330 | 16.60 | 16.69
J160348.2$+$545841.0 | 240.9508 |  $+$54.9780 | RRab | 3880.6148 | 0.5418940 | 17.25 | 18.05
J095945.7$+$005912.1 | 149.9400 |  $+$00.9866 | EW | 3464.4354 | 0.2874170 | 14.62 | 14.75
J221657.3$-$000633.0 | 334.2392 |  $-$00.1091 | EA | 3502.9800 | 18.32325 | 18.30 | 20.:
J022411.7$-$052501.6‡ | 036.0485 |  $-$05.4172 | EA | 3627.8052 | 0.8254050 | 13.95 | 14.3:

$\dagger$$\dagger$footnotetext: All stars in this table had not been
identified as variables prior to 2014 May 29.

$\ddagger$$\ddagger$footnotetext: These stars were identified as variables by
Drake et al. (2014).

Table 3 Data for the Variable Stars identified by Gezari et al. (2013) .

R.A. aa Right Ascension in decimal degrees. | Dec. bb Declination in decimal degrees. | $NUV_{amp}$ cc Amplitude of $NUV$. | LCdd Light curve type: V = Stochastic; F = Flaring (Gezari et al., 2013). | $(NUV-V)_{0}$ ee Difference between mean $NUV$ and $V$ magnitudes corrected for galactic extinction. | Period ff Period in days. | $V$gg Mean $V$ corrected for extinction. | $(B-V)$ hh Mean $(B-V)$ corrected for extinction. | Type ii Variable type from color (Gezari et al., 2013). | Type jj Variable type (Gezari et al., 2013); RR = RR Lyrae, BHB = blue HB star. | Type kk Variable type (This paper). EA are Algol-type eclipsing systems. EW are W Ursa Majoris-type eclipsing systems. | Notes
---|---|---|---|---|---|---|---|---|---|---|---
(2000) | (2000) | (mag.) |  | (mag.) | (days) | (mag.) | (mag.) |  |  |  |
212.2576 | +53.1997 | 0.24 | V | 3.298 | $\cdots$ | 16.39 | +0.52 | RR | RR | $\cdots$ |
36.7721 | –03.7063 | 0.36 | V | 1.896 | $\cdots$ | 16.54 | +0.26 | RR | RR | $\cdots$ |
36.7872 | –03.4058 | 0.37 | V | 2.103 | 0.1685980 | 15.51 | +0.32 | RR | RR |  $\delta$ Scuti | (1)(18)
36.4632 | –04.8917 | 0.43 | V | 1.912 | $\cdots$ | 16.73 | +0.19 | RR | RR | $\cdots$ |
334.5535 | +00.8106 | 0.45 | V | 1.728 | 0.0413220 | 17.30 | +0.21 | RR | RR |  $\delta$ Scuti | (1)
150.0513 | +01.0615 | 0.46 | V | 3,361 | $\cdots$ | 17.19 | +0.49 | RR | RR | $\cdots$ |
150.0909 | +01.2796 | 0.49 | V | 4.477 | 0.3162890 | 14.82 | +0.61 | RR | RR | EW | (2)(22)
34.6594 | –04.3309 | 0.51 | V | 2.280 | 0.0759360 | 17.72 | +0.26 | RR | RR |  $\delta$ Scuti | (1)
332.9349 | –00.4230 | 0.63 | V | 1.782 | $\cdots$ | 17.42 | +0.50 | RR | RR | $\cdots$ |
149.1372 | +01.2850 | 0.73 | V | 3.359 | 0.7711330 | 16.69 | +0.37 | RR | RR | RRab | (1)
149.6863 | +02.5218 | 0.79 | V | 3.553 | 0.6468498 | 17.61 | +0.47 | RR | RR | RRab | (3)
241.4690 | +54.1404 | 0.80 |  | 2.376 | 0.0587400 | 17.96 | +0.32 | RR | RR |  $\delta$ Scuti | (1)
242.2740 | +53.7866 | 0.89 |  | 3.882 | 0.1697210 | 16.61 | +0.54 | RR | RR |  $\delta$ Scuti | (1)(23)
241.9999 | +53.8693 | 0.95 | V | 2.619 | 0.3806406 | 16.71 | +0.20 | RR | RR | RRab | (4,5)
35.3413 | –03.5109 | 0.95 | V | 2.820 | 0.3438094 | 18.04 | +0.29 | RR | RR | RRc | (1,7,22)
333.3199 | –00.5376 | 0.95 |  | 2.114 | 0.3365870 | 16.66 | –0.45 | RR | RR | RRc | (6,21,22)
333.5874 | +01.3271 | 0.96 |  | 4.347 | $\cdots$ | 17.22 | +0.55 | RR | RR | $\cdots$ |
332.4833 | –00.6473 | 0.99 | V | 2.290 | 0.3016423 | 16.05 | +0.22 | RR | RR | RRc | (8,9,21,22)
215.9569 | +52.6509 | 1.00 | V | 0.961 | $\cdots$ | 20.30 | +0.53 | RR | RR | $\cdots$ |
150.2291 | +01.3947 | 1.00 | V | 2.651 | 0.3210413 | 15.75 | +0.36 | RR | RR | RRc | (2,21,22)
216.3439 | +52.7295 |  $>$1.04 | F |  $>$3.263 | $\cdots$ | 19.42 | +0.46 | RR | RR | $\cdots$ |
214.0191 | +52.4641 | 1.11 | V | 3.532 | 0.5825432 | 16.41 | +0.51 | RR | RR | RRab | (2,3)
333.8419 | +00.5817 | 1.18 | V | 0.960 | $\cdots$ | 20.07 | +0.26 | RR | RR |  $\delta$ Scuti ? | (10)
212.8810 | +53.5101 | 1.29 |  | 3.375 | 0.5807728 | 16.54 | +0.41 | RR | RR | RRab | (11,21,22)
150.5272 | +01.3757 | 1.41 | V | 3.271 | 0.7289104 | 16.28 | +0.50 | RR | RR | RRab | (2,3,21)
332.8058 | –00.3874 | 1.55 | V | 2.612 | 0.5807727 | 16.98 | +0.33 | RR | RR | RRab | (2,21)
242.8745 | +53.7296 | 1.57 | V | 3.052 | 0.5838609 | 16.07 | +0.52 | RR | RR | RRab | (2,4,12,21)
334.4712 | –00.0933 | 1.71 | V | 2.876 | 0.6556452 | 13.93 | +0.37 | RR | RR | RRab | (13)
241.8077 | +55.8589 | 1.85 |  | 3.286 | 0.5464062 | 15.92 | +0.18 | RR | RR | RRab | (2,3,4,21)
241.2133 | +54.1410 | 1.89 |  | 2.997 | 0.5161044 | 16.55 | +0.13 | RR | BHB | RRab | (2,3)
334.2392 | –0.1091 |  $>$1.91 | F |  $>$2.754 | 18.32325 | 18.20 | +0.24 | RR | RR | EA | (1,14)
150.3887 | +01.7245 | 1.93 | V | 3.047 | 0.5423790 | 14.91 | +0.26 | RR | RR | RRab | (2,3,4,21)
36.3486 | –05.5392 | 2.07 | V | 2.832 | 0.5363961 | 16.79 | +0.46 | RR | RR | RRab | (3,20,21)
240.9508 | +54.9780 | 2.11 | V | 3.465 | 0.5418940 | 17.71 | +0.24 | RR | RR | RRab | (1)
36.3409 | –05.0050 | 2.30 | V | 2.888 | 0.6212305 | 17.27 | +0.46 | RR | RR | RRab | (3,21)
150.1707 | +01.3682 |  $>$2.70 | V |  $>$3.115 | 0.4888790 | 18.55 | +0.16 | RR | BHB | RRab | (3)
332.9690 | 0.6330 | 2.91 | V | 2.633 | 0.5053500 | 16.73 | +0.31 | RR | RR | RRab | (3,21)
333.0054 | –0.0571 | 2.92 | V | 2.680 | 0.5030960 | 17.42 | +0.32 | QSO | RRab | RRab | (6)
36.0485 | –05.4172 | 1.03 | F | 5.38 | 0.8254050 | 13.94 | 0.89 | $\cdots$ | Star | EA | (1,15,24)
150.8023 | +00.9722 | 1.00 | F | 3.74 | 0.6061280 | 16.08 | 0.55 | $\cdots$ | Star | RRab | (3)(19)
333.0985 | +00.0828 | 0.96 | V | 2.18 | 0.3505063 | 15.85 | 0.17 | $\cdots$ | Star | RRc | (6,22)
149.9732 | +03.2086 | 0.72 | V | 4.91 | 0.2738640 | 15.12 | 0.69 | $\cdots$ | Star | EA | (2,22)
215.2242 | +54.4815 | 0.61 |  | 5.24 | 0.3586440 | 13.92 | 0.58 | $\cdots$ | Star | EW | (16,22)
35.5465 | –03.1702 | 0.57 | V | 4.63 | 0.4051308 | 13.14 | 0.60 | $\cdots$ | Star | EW | (17.15,22)
149.9400 | +00.9866 | 0.27 | V | 4.44 | 0.2874170 | 14.63 | 0.66 | $\cdots$ | Star | EW | (1)

Note. — (1) New Identification (this paper). (2) Palaversa et al. (2013). (3)
Drake et al. (2012). (4) Wheatley et al. (2008) Second $GALEX$ catalogue of
variables. (5) Drake et al. (2014) give type and period. Poleski (2014) gives
same period. (6) Sesar et al. (2010). (7) Radial velocity –154$\pm$2 km s-1
(SDSS DR 9). (8) Sesar et al. (2012). (9) Radial velocity –213$\pm$1 km s-1
(SDSS DR 9). (10) New Identification. Possible HADS but period uncertain. (11)
CL Boo. (12) Radial velocity –302$\pm$2 km s-1 (SDSS DR 9). (13) GG Aqr. (14)
Faint object: Period and depth of minima uncertain. Drake et al. (2014) give
Period of 2.23825 days. Radial velocity +29$\pm$5 km s-1 (SDSS DR 9). (15)
X-ray source (Flesch, 2010) (16) KM Boo. (17) Pojmanski (2002). (18) $(B-V)$ =
0.28; [Fe/H] =–1.56; Radial Velocity = –14$\pm$14 (Brown et al., 2008). (19)
Radial velocites +76$\pm$6 & +159$\pm$3 (SDSS DR 9). (20) [C/Fe] = +3.4
(Christlieb et al., 2008). (21) Abbas et al. (2014). (22) Drake et al. (2014).
(23) Drake et al. (2014) give type as EW and period of 0.339 days. See Sec.
4.6 for discussion. (24) Drake et al. (2014) give same type and period of
0.583 days. See Sec. 4.6 for discussion.

We discover three new RRab of particular interest. J100358.9-270001.4 has the
largest $(NUV-V)_{0}$ color and is the only object to lie in the color domain
of the disk RR Lyrae stars. Yet at a heliocentric distance of roughly 5 kpc,
it must be about 2 kpc above the galactic plane. Its proper motion of 8$\pm$2
mas y-1 (Girard et al., 2011) corresponds to a velocity of 200$\pm$50 km s-1.
This velocity and its relatively long pulsation period (0.6311 days) suggest
that J100358.9-270001.4 is not a disk star, but a halo star. Spectroscopic
radial velocity and metallicity measurements are needed to establish its
origin. The two RRab stars with the smallest $(NUV-V)_{0}$ colors are
J165153.4-223952.2 and J214038.1-233642.7. J165153.4-223952.2 has the largest
E$(B-V)=0.419$ and therefore the most uncertain extinction correction of the
sample, while J214038.1-233642.7 has an unusually low $V$ amplitude for its
period and is possibly multiperiodic.

The high amplitude $\delta$ Scuti stars in Table 1 are shown by green filled
circles in Fig. 6 and lie within the domain of the known $\delta$ Scuti stars
which show a wide range in $(NUV-V)_{0}$. We note that the star SS Psc, which
has a conflicting RRc classification in the GCVS and a $\delta$ Scuti star
classification by McNamara (1997), is clearly in the $\delta$ Scuti star
domain.

##  3\. The identification of RR Lyrae and $\delta$ Scuti Stars in the Gezari
et al. (2013) Catalog.

In Table 3 we present updated classifications and period measurements for 28
of the 38 RR Lyraes stars identified by Gezari et al. (2013). We find that 16
are RRab, 4 are RRc, 6 are $\delta$ Scuti stars and 2 are eclipsing systems.
The main reason that we could not obtain acceptable light-curves for the
remaining objects was because their visual amplitudes were comparable to the
observational errors of their magnitudes. A fuller discussion is given in Sec.
4.6.

Interestingly, Gezari et al. (2013) provide a “light curve type” (LC) which is
either Stochastic (V) or Flaring (F) (col. 4, Table 3). We would expect that
RR Lyrae and $\delta$ Scuti stars to have “Stochastic” light curves, but two
of the variables that Gezari et al. type as RR Lyrae have “Flaring” light
curves in $NUV$.

Another 17 variables in the Gezari catalog are identified simply as “Stars.”
We are able to make detailed classifications for 7 of these objects, listed at
the end of Table 3. We identify 1 RRab, 1 RRc and 5 eclipsing systems. Five of
the “Stars” from the Gezari catalog have “Flaring” light curves: 1 is an RRab,
2 are eclipsing systems and 2 are of unknown type.

We provide ephemerides for the eleven newly identified variables from the
Gezari catalog in Table 2.

Figure 7.—  The relation between the $NUV$ amplitude and the $V$ amplitude for
84 type RRab variables. The line corresponds to the case where the $NUV$
amplitude is twice the $V$ amplitude. The variables from Catalog 1 (open
circles) lie preferentially below the line while those from Catalog 2 (filled
circles) are more equally above and below the line.

##  4\. Discussion

We investigate the stellar properties of our sample of $UV$-selected
variables. We compare $NUV$ pulsation amplitudes with optical $V$ amplitudes,
with the distribution of pulsation periods, and with the distribution of non-
variable stars. We explore the completeness of the $UV$-selected sample, the
problem of distinguishing between contact binaries and pulsating stars and
finally with a comparison of periods obtained in this paper with those
independently obtained in a contemporous compilation by Drake et al. (2014).

###  4.1. The relation between the $NUV$ and $V$ amplitudes.

We begin by exploring the distribution of $NUV$ and $V$ pulsation amplitudes
of the $GALEX$ variables. For context, consider the five RRab variables with
well-observed $NUV$ light curves from Wheatley et al. (2012). The mean of the
ratio of the $NUV$ amplitudes to the corresponding $V$ amplitudes (taken from
the literature) for these five RRab stars is 2.15$\pm$0.18. The [Fe/H] of
these stars range from $-1.5$ to $-1.7$ (mean $-1.64$), which means they are
typical halo RR Lyrae stars.

In Figure 7 we plot the $NUV$ amplitude $vs.$ the $V$ amplitude for the 84
RRab variables in Table 1. The variables from Catalog 1 are plotted as open
circles and those from Catalog 2 by filled circles. The line represents the
case where the $NUV$ amplitude is twice that of the $V$ amplitude. In this
figure, 11 of the RR Lyrae from Catalog 1 lie above the line and 24 below; 26
of the variables from Catalog 2 lie above the line and 23 below. The Catalog 1
variables lie preferentially below the line (5% level of significance) while
those from Catalog 2 are more equally spaced. Thus the $NUV$ amplitudes for
the RRab derived from Catalog 1 are on average lower than those from Catalog
2; the latter are generally derived from more observations and approximate
more closely to the true amplitudes. The scatter in Fig. 7 is large so that
the correlation between the $NUV$ and $V$ amplitudes is not strong. It is
clear, however, that on average the RRab $NUV$ amplitudes are twice as large
as their $V$ amplitudes.

###  4.2. The $\log$ period-amplitude relation for $NUV$ and $V$ amplitudes.

Next we explore the period-amplitude relation of the variables. In Figure 8 we
plot the distribution of $\log$(period) versus $NUV$ amplitudes (left panel)
and $V$ amplitudes (right panel). For reference, the curve shows the relation
for Oosterhoff Type I RRab variables observed in the globular cluster M3
(Cacciari et al. 2008). The curve refers to monoperiodic variables; curves
with secondary periods such as RRd or those with Blazhko effect will have
smaller amplitudes and lie below the line in this plot. In the right hand
plot, the variables with periods shorter than 0.56 days ($\log$ P $\leq$
–0.25) lie mainly below the curve; those with longer periods lie increasingly
above the curve with increasing period. We suspect that our $V$ amplitudes
(derived by visual inspection from light-curves largely derived from Catalina
Survey data (Drake et al., 2009) or in a few cases LINEAR Survey data (Sesar
et al., 2013)) are systematically too small and that the admixture of higher
amplitude variables with periods greater than 0.56 days comes from a
population of Oosterhoff type II variables. The errors in the amplitudes are
too great for a clean separation of the two types. A similar interpretation
holds for the $NUV$ amplitudes in the left plot in Fig. 8 although the scatter
is larger.

Two stars of interest are J013642.0-062743.1 and J171251.8+185452.4, which
have periods 0.7775660 and 0.8111936 days, respectively, and amplitudes less
than 0.4 mag. Schmidt (2002) has studied stars with periods between 0.60 and
1.0 days and explored the various types of variables in this range. He finds 6
RRab with periods greater than 0.75 days and only 4 with periods greater than
0.80 days. None of these stars have amplitudes less than 0.50 mag. A new
survey by Abbas et al. (2014) finds $\sim$ 20 RRab with periods greater than
0.80 days. Most of these stars have $V$ amplitudes between 0.4 and 0.6
magnitudes, and constitute about 0.03% of their total sample. Here, we find
two RRab with smaller amplitudes in this period range, the aforementioned
J013642.0-062743.1 and J171251.8+185452.4. These two RRab constitute $\sim$ 2%
of our sample, suggesting that the use of $GALEX$ magnitudes (where observed
amplitudes are larger) facilitates the discovery of such low ampltiude stars.

Figure 8.—  Amplitude $vs.$ $\log$ period relation for the $NUV$ amplitude
(left panel) and $V$ amplitude (right panel) for the 84 RRab variables from
Catalog 1 (open circles) and Catalog 2 (solid circles). The curve is the
relation found for the Oosteroff type 1 variables in the globular cluster M3
given by Cacciari et al. (2008); the amplitude of the curve has been doubled
for the $NUV$ amplitudes in the left panel.  Figure 9.—  $(NUV-V)_{0}$ color
versus spectroscopic effective temperature Teff for a selection of red
horizontal branch (RHB) stars. Colors indicate metallicity: [Fe/H] $>-0.80$
are shown by red filled circles, $-0.8>$ [Fe/H] $>-1.70$ are blue open
circles, and [Fe/H] $<-1.70$ are green filled circles. The two measurements
for HD 119516 are joined by a dotted line. Four stars are optical variables
and are indicated by encircled symbols (bottom left). The red and green
horizontal lines show the mean values of$(NUV-V)_{0}$ for disk and halo RRab
variables (as shown in Fig. 6). The data and notes on individual stars are
presented in Table A3 in the Appendix.

###  4.3. The Red Horizontal Branch (RHB) stars.

In the plot of $(NUV-V)_{0}$ against period, the hottest RR Lyrae stars (type
RRc) are coterminous with the blue horizontal branch stars at the blue edge of
the instability gap. The stars near this blue edge are nearly all metal-poor;
thick disk blue horizontal branch stars are rare (Kinman et al. 2009).

We now consider the non-variable horizontal branch stars on the cool side of
the instability gap: the red horizontal branch (RHB) stars. Fig. 9 plots
$(NUV-V)_{0}$ against effective temperature (Teff) for these stars. The
sources for the data in this plot are given in the Appendix (Sec. C). We see
that the hottest metal-poor RHB stars have $(NUV-V)_{0}$ colors similar to the
halo RR Lyrae stars. Indeed, we find that some of the hottest metal-poor RHB
candidates are actually RR Lyrae stars.

For Teff less than about 5200 K, most of these RHB stars are metal-rich
([Fe/H] $>$ -0.8) and have larger $(NUV-V)_{0}$ than the metal-poor RHB,
similar to the trend seen in the RRab stars. We do not find any metal-rich RHB
stars hotter than this limit. As we discuss in Appendix C, this is likely an
observational selection effect; there are few constraints on hot metal-rich
RHB stars at fainter magnitudes ($V$ $>$ 10.5). We cannot rule out, however,
that hot metal-rich RHB stars may be scarce in the field even though they are
found in the metal-rich globular clusters like 47 Tuc.

The change in $(NUV-V)_{0}$ color with effective temperature is much larger
compared with the change in optical color indices. Stars like BD 18∘ 2757 and
BPS CS 22875-029 have similar metallicity but differ in Teff by $\sim$1250 K.
Their difference in $(B-V)_{0}$ and $(J-K)_{0}$ are 0.32 and 0.15 mag,
respectively, while their difference in $(NUV-V)_{0}$ is over 2 mag. This
makes the $(NUV-V)_{0}$ color particularly sensitive for detecting the
temperature changes that come from pulsations and, in particular, for
detecting the onset of this instability as a function of other parameters
(such as Teff).

Figure 10.—  The distribution of the RRab in Table 3 versus their $V$
magnitude at minimum light (panel a). The distribution versus $(NUV)$
magnitude at minimum light for Catalog 2 (panel b) and Catalog 1 (panel c).

###  4.4. The Completeness of the Samples.

We explore the magnitude limits of our samples in Figure 10. Fig. 10(a) plots
the distribution of the minimum $V$ magnitudes for the 84 RRab variables in
Table 1. There is a steep fall-off in the distribution at $V$ $\sim$ 17.5.
Fig. 10(b) and Fig. 10(c) plot the distribution of the faintest observed $NUV$
of the RRab in Catalogs 2 and 1, respectively. There is a steep fall-off at
about $(NUV)$ = 21.0. These two magnitude limits are consistent with the
$3.4\leq(NUV-V)\leq 3.8$ mag RRab colors observed by Wheatley et al. (2012);
most of the RRab in Table 1 are also in this range.

A $V$=17.5 magnitude corresponds to a distance limit of about 25 kpc for our
sample of RRab. Most of the stars in our sample are at a sufficiently high
galactic latitude that the correction for interstellar extinction is small,
E$(B-V)$ $\leq$ 0.04 for which E$(NUV-V)$ $\leq$ 0.23.

The mean $(NUV-V)$ for RRc is somewhat smaller than that of the RRab, and they
have lower amplitudes. Consequently, RRc stars will have a fainter $V$
magnitude for a given $NUV$, and their identification will necessarily be less
complete than for the RRab. The $NUV$ light curve minima in the Gezari catalog
are all fainter than 20.0 and so, neglecting extinction, the RRc will have $V$
$>$ 17 and will generally be less easy to detect with existing optical data
without the use of new techniques.

The 17 RRc and 48 RRab corresponds to $\sim$0.40 variables per square degree
for Catalog 2. This is comparable to the 0.455 RR Lyrae per square degree
found by Abbas et al. (2014) in a survey of somewhat greater depth (28 kpc)
and which they find has a completeness of $\sim$50%. This suggests that
$GALEX$ has detected only half of the RRab to $V$=17.5, or else Catalog 2 is
itself only about half complete for these variables.

Catalog 2 contains the variables whose $NUV$ amplitudes are greater or equal
to 0.6 mag. The survey covered 169 fields; each field (radius 0.∘55) was
visited from between 10 and 187 times. Table 4 shows that that variables were
only discovered in about 20% of the fields when the number of visits was 20 or
less but this percentage rose to about 40% when there were over 30 visits. The
field centered on AE Aqr is also in the well studied SDSS Stripe 82; three RRc
and 2 RRab were found in this field but three RRc of comparable brightness
that lie within this field were missed. There were 31 visits to this field but
the number of actual detections of the RRc variables ranged from 19 for a 13th
mag star to 5 for one at 17th mag. Thus the completeness will vary from field
to field depending on the number of visits. In the 19 fields that were visited
more than 50 times, eleven RR Lyrae variables were found and only two were
missed. It is therefore only in these fields (that comprise only 11% of the
total) that the Catalog 2 survey is reasonably complete.

###  4.5. Contact Binaries.

Contact binaries can be confused with RRc variables that have half their
periods; see discussions by Kinman & Brown (2010) and Drake et al. (2014).
Table 2 in the appendix (Sec. B) gives the $UV$ colors for a sample of bright
contact binaries and these are plotted against period in Fig. 11.

Drake et al. (2014) use a variety of parameters to distinguish between RRc and
contact binaries and conclude that misidentification is most likely to occur
among the longer-period bluer contact binaries which are the brightest among
such variables; misidentification is therefore not a serious problem for faint
surveys. Misidentification apart, the cause of the spread in $(NUV-V)_{0}$
among contact binaries needs further investigation. It is unlikely to be
caused by a spread in metallicity because the range of metallicity in these
objects is small (Rucinski et al. 2013). The presence of companions is a more
likely cause since it is known that multiplicity is very common among contact
binaries (Pribulla & Rucinski 2008). Smith et al. (2014) consider the effect
of companion stars on $GALEX$ colors in their discussion of stars in the
Kepler field. $(NUV-V)_{0}$ may therefore be a useful diagnostic in searching
for such companion stars.

Figure 11.—  $(FUV-NUV)_{0}$ (upper panel) and $(NUV-V)_{0}$ (lower panel) plotted against the half-periods of a sample of bright contact binaries (black filled circles). Two of these objects (SW Ret and v1643 Sgr) that are shown encircled, are actually RRc variables. The blue horizontal lines in both figures show the location of RRc variables. Our program RRc variables are plotted as blue filled circles using the full periods in the lower figure.  Figure 12.—  Comparison of the light-curves of J022411.7-052501.6, J1222837.9-064230.0, J154550.8-124936.8 and 160905.7+534712.2 obtained in this paper (on the left) and those given by Drake et al. (2014) on the right.  Table 4 Discovery rate of RR Lyrae stars as a function of number of visits per field for Catalog 2. Visits per Field | No. of Fields with this | Number of Fields in which
---|---|---
| range of visits | variables were found
(1) | (2) | (3)
10 to 20 | 86 | 18
21 to 30 | 39 | 14
31 to 50 | 25 | 11
$>$ 51 | 19 | 8

###  4.6. Uncertainties in determining Variable Type and Period.

Five of our new variables (Table 2) are also found in a new catalogue of
periodic variables from the Catalina Surveys (Drake et al. 2014, hereafter
D14). The first star is J022121.9-033040.0, for which D14 find the same
variable type and period as we do. Thus we do not discuss this star further.
For the other four stars, we obtain repeat periodograms using the Lomb-Scargle
(LS) and Plavchan (PL) routines in the NASA Exoplanet Archive Periodogram
Service. Fig. 12 presents the light curves for these four variables. For each
variable, the left-hand panel plots the data folded on our period, and the
right-hand panel plots the data folded on the D14 period.

With the exception of J154550.8-124936.8, identifying the correct period and
type by visual inspection is difficult because of period alias uncertainties.
The discrepant results described below illustrate the difficulty in
identifying the nature of low-amplitude variables.

J022411.7-052501.6. We identify this as an Algol variable with a period of
0.8254050 days. D14 give the same type with a period of 0.583802 days. The LS
routine gives neither of these periods. The PL routine gives both periods; the
D14 period has more power in the PL routine and is likely correct.

J122837.9-064230.0. We identify this as an RRab with a period of 0.501648
days. D14 give the same type with a period of 0.333755 days, but call this
period “inexact.” The LS and PL routines give both periods, however our period
has more power and is likely correct.

J154550.8-124936.8. We identify this as an RRc with a period of 0.293594 days.
D14 give the same type with a period of 0.416068 days. Both the LS and PL
routines give more power to our period than to the one at 0.416 days, and our
period gives a better looking light curve (Fig. 12).

J160905.7+534712.2. We identify this as a $\delta$ Scutiwith a period of
0.1697210 days. D14 identify it with an EW with a period of 0.339438 days. The
LP routine gives our period. The PL routine gives both periods with marginally
more power to our period. However, the D14 identification is likely correct
because the $(g-r)=0.32$ color of the variable is probably too red for a
$\delta$ Scuti.

##  5\. Summary

We make as complete an identification as possible of unclassified variable
stars in existing $GALEX$ variable source catalogs. We present newly
identified $\delta$ Scuti, RRc and RRab stars found in what we refer to as
Catalog 1 (Welsh et al. 2005) and Catalog 2 (Wheatley et al., 2008). We also
examine the sources identified either as “stars” or RR Lyrae stars in the
larger catalog of variable $GALEX$ sources of Gezari et al. (2013).

We identify 8 $\delta$ Scuti stars, 17 RRc stars, 1 RRd star and 84 RRab stars
in Catalogs 1 and 2. These 110 pulsating variables account for 22% of the
sources in these Catalogs. Sixteen of these variables were not previously
known; their ephemerides and light curves are given in Table 2 and Figures 1,
2, 3 and 4 respectively.

In Table 3 we present new classifications and period measurements for 28 of
the 38 variable $GALEX$ sources that Gezari et al (2013) identify as RR Lyrae
stars: 16 are RRab stars, 4 are RRc stars, 6 are $\delta$ Scuti stars and 2
are eclipsing systems. We also classify 7 of the 17 $GALEX$ sources that
Gezari et al. identify as “stars”: 1 is a RRab star, 1 is a RRc star and 5 are
eclipsing systems. The classification of these objects depends on our ability
to recognize their variability type from optical data in the Catalina Surveys
Data Release 2. This becomes difficult for low-amplitude variables with
$V>17.5$. Thus classifications are less complete for the Gezari catalog
because the catalog contains lower amplitude variables ($NUV$ amplitude $\geq$
0.2 mag compared with $\geq$ 0.6 mag for Catalog 2). The light-curves of the
variables in Table 2 from the Gezari Catalog are given in Figures 1, 2, 3 and
4.

We find that the $(NUV-V)_{0}$ color of low metallicity halo RRab stars is
smaller than that of the higher-metallicity $disk$ RRab stars. The $NUV$
pulsation amplitude of RR Lyrae stars is roughly twice that of their $V$
amplitude (as found earlier by Wheatley et al. (2012)). This allows us to
detect low-amplitude variables such as J013642.0-062743.1 and
J171251.8+185452.4 which have $V$ amplitudes of 0.25 and 0.38 mag,
respectively. A larger number might be found if the Catalogs were more
complete. At a rough estimate, the overall completeness of Catalog 2 is
similar to that of the catalog of Abbas et al. (2014) which they estimate as
50%. The completeness of Catalog 2 varies from field to field depending on the
number of observations made per field.

$(NUV-V)_{0}$ is more sensitive than optical colors to changes in Teff (such
as those that occur in stellar pulsation). Four stars that have been described
in the literature as RHB stars are actually RR Lyrae stars (e.g. BPS CS
22940-070 which is called non-variable by For et al., (2010)). A plot of
$(NUV-V)_{0}$ against Teff shows that the metal-poor RHB stars merge into the
RR Lyraes at Teff $\sim$ 6000 K which agrees with other estimates of the red
edge of the instability gap. Existing surveys such as Afsar et al. (2012) do
not show any metal-rich (disk) RHB stars hotter than Teff $\sim$ 5200 K
whereas such stars are known in the metal-rich globular cluster 47 Tuc. We
suggest that hotter metal-rich RHB stars could be found by deeper surveys.

We find a large range in both $(NUV-V)_{0}$ and $(FUV-NUV)_{0}$ colors in a
sample of bright contact binaries that have twice the periods of RRc stars and
which may therefore be confused with them. These $UV$ colors do not allow a
clear distinction between the two types, but may be of value in detecting
companions to the contact binaries.

We acknowledge use of the International Variable Star Index (VSX) database
operated at AAVSO, Cambridge, MA, USA. Also the LINEAR survey (available on
the SkyDOT website) and funded by NASA at MIT Lincoln Laboratory under Air
Force Contract FA8721-05-0002. Also the Catalina Surveys (Data Release 2) that
is supported by NASA under grant NNG05GF22G and NSF grants AST-0909182 and
AST-1313422, We used the VizieR catalogue access tool, CDC, Strasbourg,
France. We acknowledge using data from the SDSS funded by the Alfred P. Sloan
Foundation, the Participating Institutions, the NSF and the US D.O.E.. We also
used the MAST (Multimission Archive at the STSci which is operated for NASA by
AURA), the SIMBAD database (operated at the CDS, Strasbourg, France), ADS (the
NASA Astrophysics Data System), and the arXiv e-print server. We also used the
NASA Exoplanet Archive which is operated by the California Institute of
Technology under contract with NASA.

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##  Appendix A High-Amplitude $\delta$ Scuti Stars (HADS).

The High-Amplitude $\delta$ Scuti stars are radially pulsating stars with
periods in the range 0.04 to 0.30 days that are largely monoperiodic. They
show some overlap in period with the RRc variables but can usually be
distinguished from them by having more asymmetric light curves. Table A1 gives
the $(NUV-V)_{0}$ for a sample of these stars drawn from the compilations of
McNamara (1997) and Suveges et al. (2012). The HADS are well separated from
the RRc variables in the $(NUV-V)_{0}$ $vs.$ Period plot (Fig. 6); this is
clearly the case for SS Psc (which is marked in this figure). This is of
interest because Ferro et al. (2013) were unable to classify this star from
their Stromgren photometry. The revised Hipparcos parallax of SS Psc is 5.26
$\pm$ 1.99 (van Leeuwen, 2007) gives an Mv of between +3.5 and +5.2 which is
in the expected range for HADS (Peterson & Hog, 1998).

Table 2$(NUV-V)_{0}$ for $\delta$ Scuti Stars.

R.A. aaRight Ascension in decimal degrees. | Dec. bbDeclination in decimal degrees. | Ref ccReference for identification as $\delta$ Scuti star. |  $(NUV-V)_{0}$ ddDereddened difference beteween mean $NUV$ and $V$ magnitudes. | Period eePeriod in days. | GCVS IDffIdentification in General Catalogue of Variable Stars.
---|---|---|---|---|---
(deg.) | (deg) |  | (mag.) | (days) |
(1) | (2) | (3) | (4) | (5) | (6)
144.2216 | +44.0668 | 1 | 3.330 | 0.0860100 | AE UMa
231.0294 | +36.8670 | 1 | 3.118 | 0.1040900 | YZ Boo
238.2908 | +06.0907 | 1 | 3.193 | 0.1891500 | CW Ser
013.8256 | +23.1637 | 1 | 2.461 | 0.0786800 | GP And
337.5121 | –08.1075 | 1 | 3.912 | 0.1683800 | GV Aqr
247.8249 | +11.9979 | 1 | 3.392 | 0.1486300 | DY Her
247.5682 | +16.9185 | 1 | 2.550 | 0.0946800 | v1116 Her
357.1914 | –08.1457 | 1 | 3.767 | 0.1978230 | BS Aqr
146.4452 | –12.9940 | 1 | 3.226 | 0.2233891 | VX Hya
020.2182 | +21.7287 | 1 | 3.898 | 0.2877928 | SS Psc
270.6644 | +62.7186 | 2 | 3.393 | 0.1969000 | v395 Dra
278.0269 | +40.5991 | 2 | 2.790 | 0.1021400 | v593 Lyr
240.7758 | +26.2396 | 2 | 4.357 | 0.1924460 | BY CrB
237.4137 | –76.4219 | 2 | 2.182 | 0.0638630 | v360 Aps
343.0172 | –0.8690 | 3 | 3.214 | 0.0495655 |
320.2203 | +0.2755 | 3 | 2.067 | 0.0500164 |
319.3871 | +0.8267 | 3 | 2.813 | 0.0493681 |
318.9853 | –0.8594 | 3 | 2.472 | 0.0512525 |
044.3292 | –0.6536 | 3 | 2.323 | 0.0482597 |
037.4992 | +1.2482 | 3 | 2.380 | 0.0509957 |
341.6031 | +1.1892 | 3 | 2.754 | 0.0502367 |
338.5538 | +0.7835 | 3 | 2.794 | 0.0537832 |
322.4356 | +1.0480 | 3 | 2.421 | 0.0596027 |
320.6782 | +0.7816 | 3 | 2.386 | 0.0538881 |
313.7465 | –0.1246 | 3 | 2.024 | 0.0515025 |
312.4206 | –0.3539 | 3 | 2.749 | 0.0931453 |
322.4695 | –1.1719 | 3 | 2.989 | 0.0805862 |
321.1715 | +0.0444 | 3 | 2.451 | 0.0452487 |
043.1488 | +0.2955 | 3 | 2.480 | 0.0550160 |
355.3285 | +0.7152 | 3 | 3.247 | 0.1198865 |
323.7998 | +0.6225 | 3 | 2.782 | 0.0872579 |
313.1301 | –0.5333 | 3 | 2.554 | 0.0530346 |
305.7112 | –0.1257 | 3 | 2.468 | 0.0521552 |
320.1692 | +0.9076 | 3 | 1.698 | 0.0742401 |
316.8586 | +1.1715 | 3 | 3.410 | 0.0678054 |
310.7717 | +0.0367 | 3 | 2.386 | 0.0457611 |
310.3194 | +0.5634 | 3 | 2.739 | 0.0663556 |
357.0749 | +0.9069 | 3 | 2.562 | 0.0607696 |
314.2421 | +1.0685 | 3 | 2.722 | 0.0702984 |
304.6618 | +1.0123 | 3 | 3.566 | 0.0457270 |
346.1327 | +0.4127 | 3 | 2.390 | 0.0565413 |
002.3078 | –0.1846 | 3 | 2.426 | 0.0519909 |
338.6537 | +0.3735 | 3 | 2.625 | 0.0530301 |
320.8264 | +0.8867 | 3 | 2.186 | 0.0706932 |
045.7345 | –0.6974 | 3 | 2.804 | 0.0581344 |

References. — (1) McNamara (1997); (2) Samus et al. (2012), (General Catalogue
of Variable Stars); (3) Suveges et al. (2012).

##  Appendix B Contact Binaries

Table A2 gives the $(NUV-V)_{0}$ and $(FUV-NUV)_{0}$ for a sample of bright
contact binaries with half-periods between 0.19 and 0.44 days (primarily taken
from Malkov et al., 2006). We excluded variables at low galactic latitudes
($\mid$b$\mid<$ 14∘) in order to minimize errors in the corrections for
extinction. The extinction correction used to derive $(FUV-NUV)_{0}$ is less
than that for $(NUV-V)_{0}$, but $FUV$ is available for fewer stars. The data
from Table A2 is plotted in Fig. 11.

The $(NUV-V)_{0}$ of the 17 RRc that we found in Catalogs 1 and 2 range from
2.65 to 3.17 ($\sigma$ = 0.14 mag) while in a sample of 50 RRc from the Abbas
et al. catalog, the range is from 2.36 to 3.52 ($\sigma$ = 0.26 mag). The
$mean$ $NUV$ in the former case were derived from multiple values of $NUV$
whereas in the latter case only a single value was usually available; this may
well explain the greater spread of $(NUV-V)_{0}$ found for the RRc in the
Abbas et al. catalog.

Half the contact binaries in Table A2 have $(NUV-V)_{0}$ within the range that
we find for the RRc. Two of these stars with low $(NUV-V)_{0}$ are actually RR
Lyrae stars: SW Ret is an RRd (Szczgiel & Fabrycky 2007) and v1643 Sgr is an
RRc (Dvorak 2004). The more recent catalog of Avvakumova et al. (2013)
continues to identify v1643 Sgr as a contact binary. The mean $(FUV-NUV)_{0}$
of 16 RRc variables is +2.59$\pm$0.14. In Table A2, EK Aqr, AG Vir, v941 Her
and the RRc v1643 Sgr are within the range of $(FUV-NUV)_{0}$ occupied by RR
Lyraes; AG Vir is known to have an infra-red excess (Nichols et al. 2010).

Table 3 UV colors for bright Contact Binaries.

R.A. aaRight Ascension in decimal degrees. | Dec. bbDeclination in decimal degrees. | b ccGalactic Latitude. |  $(NUV-V)_{0}$ ddDereddened difference beteween mean $NUV$ and $V$ magnitudes. |  $(FUV-NUV)_{0}$ eeDereddened difference beteween mean $FUV$ and $NUV$ magnitudes. | X-ray ffGiven as X-ray source by Flesch (2010). | P0.5 ggHalf of period in days. | GCVS IDhhIdentification in General Catalogue of Variable Stars.
---|---|---|---|---|---|---|---
(deg.) | (deg) | (deg.) | (mag.) | (mag) |  | (days) |
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8)
130.0071 | +18.9998 | +32.17 | 4.72 | 4.83 | X | 0.1914 | TX Cnc
150.6998 | +01.0945 | +41.94 | 3.83 | 4.17 | … | 0.2099 | Y Sex
258.4909 | +16.3502 | +28.73 | 4.48 | 3.73 | X | 0.2108 | AK Her
077.8104 | –08.5569 | –26.13 | 4.98 | … | X | 0.2117 | ER Ori
141.6710 | –13.7518 | +25.68 | 4.71 | … | … | 0.2248 | EZ Hya
234.1083 | +15.5317 | +50.1 | 2.95 | 3.67 | … | 0.2580 | CC Ser
299.2000 | +01.1000 | –14.0 | 3.10 | 3.77 | … | 0.2588 | v0724 Aql
052.0838 | –64.9772 | –44.8 | 2.68 | 3.82 | … | 0.2614 | SW Ret$\dagger$
126.1351 | –16.4032 | +12.04 | 3.92 | 5.32 | … | 0.2782 | AV Pup
079.9754 | –35.9017 | –33.2 | 2.50 | 3.73 | … | 0.2826 | RZ Col
354.8175 | –09.1534 | –65.2 | 2.58 | 2.67 | … | 0.3065 | EK Aqr
160.1383 | +13.5669 | +56.59 | 3.23 | 3.75 | … | 0.3090 | UZ Leo
180.2646 | +13.0083 | +71.61 | 4.60 | 1.24 | … | 0.3213 | AG Vir
143.0766 | –28.6278 | +16.61 | 4.51 | … | … | 0.3242 | S Ant
277.4200 | +31.0003 | +17.9 | 3.26 | … | … | 0.3266 | IY Lyr
296.4417 | –40.9383 | –27.3 | 2.94 | 3.07 | … | 0.3398 | v1643 Sgr$\dagger$
212.3643 | –15.5816 | +43.3 | 4.01 | 4.23 | … | 0.3730 | CX Vir
119.5459 | +72.7643 | +30.7 | 3.39 | 4.17 | … | 0.3821 | CD Cam
311.6156 | –71.9495 | –34.5 | 3.98 | … | … | 0.3974 | MW Pav
274.2226 | +27.6628 | +19.3 | 3.07 | 4.06 | … | 0.4340 | MS Her
252.3800 | +47.1080 | +39.9 | 3.92 | 2.59 | … | 0.4386 | v921 Her

Note. — $\dagger$ Both SW Ret and v1643 Sgr are RR Lyrae stars.

##  Appendix C  Red Horizontal Branch (RHB) Stars.

Fig. 9 (Sec. 4.3) shows the trend of $(NUV-V)_{0}$ with effective temperature
(Teff) for RHB stars in three metallicity ([Fe/H]) ranges. The data used in
this plot are given in Table A3. We take all stars with the type RHB in Table
2 of Behr (2003), and we also take NSV 4256 (HD 82590), which Behr lists as
RR?, because its Teff (6094 K) is near the red edge of the instability gap.
The classification of NSV 4256 is uncertain but it is likely to be one of the
lowest amplitude RR Lyrae stars known; both Corben et al. (1972) and Alfonzo-
Garzon et al. (2012) give NSV 4256 a $V$ amplitude of 0.06 mag. Further data
were taken from: Preston et al. (2006), For & Sneden (2010) and Afsar et al.
(2012). We expect that errors in Teff are about $\pm$150 K. To illustrate this
uncertainty, we provide data for HD 119516 from two different sources in Table
A3, and plot the points separately (joined by a dotted line) in Fig. 9.

Behr (2003) place the red edge of the instability strip at Teff=6000 K (as
plotted in Fig. 9). Preston et al. (2006) and For & Sneden (2010) give 6310
$\pm$ 145 K and 5900 K, respectively, for this quantity. These temperatures
are appropriate for the lowest metallicity stars (plotted in green in Fig 5.).
Bearing in mind the uncertainties in Teff, these estimates for the red edge of
the instability strip are in reasonable agreement with our data. We find that
$(NUV-V)_{0}$ increases with increasing metallicity at a given Teff.

There is, however, a large gap in Teff between the hottest metal-rich RHB
stars that we have found in the literature and the Teff of the metal-rich disk
RR Lyrae stars. We estimate the latter to have Teff $\geq$ 6500 K based on the
$(V-K)$ of a small sample of these stars. The blue tip of red horizonal branch
of the metal-rich globular cluster 47 Tuc (Salaris et al. 2007) has $J-K$
$\sim$ 0.40 to 0.45, whereas the hottest of our metal-rich RHB stars has $J-K$
= 0.53. We therefore suspect that the lack of hotter stars among our sample of
metal-rich RHB stars is an observational selection effect. The faintest 15 of
the 76 stars studied by Afsar et al. (2012) have $V$ between 9.0 and 10.5,
which for Mv = +0.8 corresponds to distances between 436 and 870 pc. Thus, as
they point out, their sample strongly favors thin disk stars. A search for
thick disk RHB stars must be made at significantly fainter magnitudes.

Table 4$(NUV-V)_{0}$, [Fe/H] and Teff for a sample of RHB stars.

Identification |  $(NUV-V)_{0}$ aaDereddened difference beteween mean $NUV$ and $V$ magnitudes. | [Fe/H] | Teff | Ref. | Notes
---|---|---|---|---|---
| mag. |  |  $\deg$ K |  |
(1) | (2) | (3) | (4) | (5) | (6)
HIP 62325 | 8.117 | –0.06 | 4710 | (6) |
BD 25∘2459 | 7.101 | –0.28 | 4743 | (1) |
HIP 115839 | 6.285 | –0.40 | 5000 | (6) |
BD 34∘2371 | 7.262 | –0.41 | 5005 | (1) |
HIP 3031 | 8.058 | –0.53 | 5020 | (6) |
BD 29∘2294 | 6.411 | –0.55 | 5132 | (1) |
BD 29∘2231 | 7.076 | –0.65 | 4756 | (1) |
HIP 45412 | 6.870 | –0.68 | 5080 | (6) |
BD 25∘2436 | 7.041 | –0.76 | 4847 | (1) |
BD 36∘2303 | 7.860 | –0.77 | 4705 | (1) |
HIP 5104 | 6.335 | –0.86 | 5100 | (6) |
HD 110930 | 6.854 | –0.94 | 4934 | (1) |
HIP 4960 | 5.516 | –1.02 | 5260 | (6) |
HD 112030 | 7.111 | –1.12 | 4699 | (1) |
HD 202573 | 6.706 | –1.21 | 4853 | (1) |
BD 27∘2057 | 7.246 | –1.25 | 4695 | (1) |
HD 6229 | 5.516 | –1.35 | 5200 | (1) |
HD 97 | 5.678 | –1.42 | 5272 | (1) |
BPS CS 22940-070 | 3.024 | –1.47 | 6100 | (2) | (1)
HD 82590 | 3.893 | –1.50 | 6094 | (1) | (2)
HD 105546 | 5.437 | –1.67 | 5299 | (1) |
HD 63791 | 6.735 | –1.72 | 4954 | (1) |
BD 18∘2890 | 5.334 | –1.78 | 5347 | (1) |
HD 119516 | 4.224 | –1.92 | 5689 | (1)(4) |
BD 10∘2495 | 5.040 | –2.07 | 5275 | (1) |
BD 17∘3248 | 4.480 | –2.08 | 5398 | (1) |
BPS CS 22886-043 | 3.631 | –2.15 | 6000 | (2) |
HD 119516 | 4.233 | –2.16 | 5400 | (3) |
BPS CS 22888-047 | 3.487 | –2.35 | 6000 | (2) | (3)
BD 18∘2757 | 5.527 | –2.43 | 4741 | (1) |
BPS CS 22882-001 | 3.483 | –2.54 | 5950 | (3) |
BPS CS 22875-029 | 3.391 | –2.66 | 6000 | (3) |
BPS CS 22191-029 | 3.417 | –2.72 | 6000 | (3) |
BPS CS 22881.039 | 3.178 | –2.73 | 6100 | (3) | (4)
BPS CS 22186-005 | 3.318 | –2.77 | 6200 | (3) | (5)
BPS CS 30317-056 | 3.441 | –2.85 | 6000 | (5) | (6)

;

References. — (1) Behr (2003); (2) Preston et al. (2006); (3) For & Sneden
(2010). (4) Ishigaki et al. (2013); (5) Hansen et al. (2011). (6) Afsar et al.
(2012).

Note. — (1) RRab variable; Period = 0.5103 days; $V_{amp}$$\sim$ 0.9 mag.
(this paper) (2) NSV 4526; $V_{amp}$ $\sim$0.06 mag. (Corben et al. 1972;
Alfonzo-Garzon et al. , 2012); type uncertain. (3) [C/Fe] = 1.4 (Christlieb et
al., 2008). (4) RRab variable, Period = 0.66876 days; $V_{amp}$$\sim$0.8 mag.
(Hansen et al., 2011); [C/Fe] = 2.0 (Christlieb et al., 2008) (5) [C/Fe] =
+1.0 (Christlieb et al., 2008) 6 RRab variable, Period = 0.74851 days;
$V_{amp}$$\sim$0.35 mag. (Hansen et al., 2011)