J/AJ/126/1455 2MASS photometry of hot subdwarf stars (Stark+, 2003)
Single and composite hot subdwarf stars in the light of 2MASS photometry.
Stark M.A., Wade R.A.
<Astron. J. 126, 1455 (2003)>
=2003AJ....126.1455S 2003AJ....126.1455S
ADC_Keywords: Stars, early-type ; Photometry, infrared ; Stars, subdwarf ;
Stars, horizontal branch
Keywords: binaries: general - infrared radiation - stars: early-type -
stars: horizontal-branch - subdwarfs
Abstract:
Utilizing the Two Micron All Sky Survey (2MASS) Second Incremental
Data Release Catalog, we have retrieved near-IR magnitudes for several
hundred hot subdwarfs (sdO and sdB stars) drawn from the Catalogue of
Spectroscopically Identified Hot Subdwarfs by Kilkenny et al.
(1988SAAOC..12....1K 1988SAAOC..12....1K). This sample size greatly exceeds that of
previous studies of hot subdwarfs. Examining 2MASS photometry alone or
in combination with visual photometry (Johnson BV or Stroemgren uvby)
available in the literature, we show that it is possible to identify
hot subdwarf stars that exhibit atypically red IR colors, which can be
attributed to the presence of an unresolved late-type companion.
Utilizing this large sample, we attempt for the first time to define
an approximately volume-limited sample of hot subdwarfs. We discuss
the considerations, biases, and difficulties in defining such a
sample. We find that, of the hot subdwarfs in Kilkenny et al.
(1988SAAOC..12....1K 1988SAAOC..12....1K), about 40% in a magnitude-limited sample have
colors that are consistent with the presence of an unresolved
late-type companion. Binary stars are overrepresented in a
magnitude-limited sample. In an approximately volume-limited sample
the fraction of composite-color binaries is about 30%.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 133 593 Updated Coordinates and Notes for All Subdwarfs
with a 2MASS 2IDR Identification (ordered by R.A.)
table2.dat 120 593 Magnitudes and Colors for All Subdwarfs
(ordered by J2000 R.A.)
notes.dat 79 26 Individual notes
--------------------------------------------------------------------------------
See also:
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- Seq Sequence number assigned by us (G1)
5 A1 --- n_Seq [*] indicates a note detailed in notes.dat
6- 22 A17 --- ID First identifier that appears in KHD
(Kilkenney et al., 1988SAAOC..12....1K 1988SAAOC..12....1K)
24- 25 I2 h RAh Hour of right ascension (J2000)
27- 28 I2 min RAm Minute of right ascension (J2000)
30- 35 F6.3 s RAs Second of right ascension (J2000)
37 A1 --- DE- Sign of the declination (J2000)
38- 39 I2 deg DEd Degree of declination (J2000)
41- 42 I2 arcmin DEm Arcminute of declination (J2000)
44- 48 F5.2 arcsec DEs Arcsecond of declination (J2000)
50- 59 A10 --- SpType MK spectral type
61- 98 A38 --- NoteID Notes about the designations of the star (2)
100-133 A34 --- SID The SIMBAD identifier (3)
--------------------------------------------------------------------------------
Note (2): Note on Seq:
#NNNN (hash sign followed by a number) indicates a duplicate entry in
KHD (Kilkenney et al., 1988SAAOC..12....1K 1988SAAOC..12....1K) (the duplicate entry is
not otherwise listed in this table).
Note (3): The identifiers are consistent with SIMBAD nomenclature.
For example, the designator CSHK 22876-35 used by KHD for star No. 8
in this table is equivalent to the SIMBAD designator BPS CS 22876-35,
and the designator PG 23595+1942 used by KHD for star No. 1527 in this
table is equivalent to the SIMBAD designator PG 2359+197. If no other
ID is given, the identifier from KHD (given in column ID) is
consistent with SIMBAD. In this way, one SIMBAD-compliant designator
is available for cross-reference. The exceptions are the "HS" star No.
390 HS 1000+4704, the "SC" star No. 1165 SC 1721-3338 from Reid et al.
(1988AJ.....96..275R 1988AJ.....96..275R), and the "LBQS" stars from Berg et al.
(1992ApJS...78..409B 1992ApJS...78..409B),
Nos. 41, 565, and 1405, which are not presently recognized by SIMBAD,
although SIMBAD does use the LBQS designator for quasars from Hewett
et al. (1995AJ....109.1498H 1995AJ....109.1498H).
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- Seq Sequence number (G1)
5 A1 --- n_Seq [*] Individual note in notes.dat file
6- 22 A17 --- ID First identifier that appears in KHD
(Kilkenney et al., 1988SAAOC..12....1K 1988SAAOC..12....1K)
25- 30 F6.3 mag Jmag The J-band magnitude
32- 36 F5.3 mag e_Jmag ? The 1 σ error in Jmag (2)
38- 43 F6.3 mag Hmag The H-band magnitude
45- 49 F5.3 mag e_Hmag ? The 1 σ error in Hmag (2)
51- 56 F6.3 mag Ksmag The Ks band magnitude
58- 62 F5.3 mag e_Ksmag ? The 1 σ error in Kmag (2)
64 A1 --- l_J-Ks Limit flag on J-Ks
66- 71 F6.3 mag J-Ks The (J-Ks) color (3)
73- 77 F5.3 mag e_J-Ks ? The 1 σ error in J-Ks
79- 84 F6.3 mag mag The Filt band magnitude
85 A1 --- Filt Filter used in mag (4)
87- 92 F6.3 mag B-mag ? The (B-mag) color
93 A1 --- u_B-mag Uncertainty flag on B-mag
95-104 A10 --- SpType MK spectral type
106-120 A15 --- Notes Individual remarks (5)
--------------------------------------------------------------------------------
Note (2): If no error is listed, then the star was not detected in that band,
and the quoted magnitude is a 95% confidence upper limit.
Note (3): The reported value is the maximum color index when an upper limit
on Kmag is reported, and it is the minimum color index for an upper
limit on Jmag.
Note (4): Johnson V band unless noted as follows:
y = Stroemgren y
P = Photographic visual magnitude
J = Photographic J magnitude
B = Photographic B magnitude
: = Uncertain magnitude
Note (5): Note on Seq as follows:
s = Reported single sdB or sdO star used to determine the single
hot subdwarf locus (see Section 3.1 and Fig. 1);
c = Reported composite sdB or sdO star used to determine the
composite hot subdwarf locus (see Section 3.1 and Fig. 1);
CC = 2MASS magnitudes listed are for a nearby companion only
(the hot subdwarf was not detected);
n = Excluded from the sample because of a "non-subdwarf" classification;
AEA = V and (B-V) from Allard et al. (1994AJ....107.1565A 1994AJ....107.1565A)
BBL = Nos. 1076 and 1095 had synthetic measurements of b and y only
(see Section 2.3);
LAN = V and (B-V) from Landolt (1992, Cat. II/183)
MEA = Nos. 320 and 1327, Stromgren uvby from Mooney et al.,
2000A&A...357..553M 2000A&A...357..553M
TYC = V and (B-V) for No. 234 are converted from Tycho magnitudes (see
Section 2.3): VT=10.194, (BT-VT)=+0.111 (ESA, 1997,
Hipparcos catalog, I/239)
WMG = V and (B-V) from Williams et al. (2001PASP..113..490W 2001PASP..113..490W)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: notes.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- Seq Sequential number
6- 79 A74 --- Note Text of the note
--------------------------------------------------------------------------------
Global notes:
Note (G1): Not intended to be used as a new designator in the literature,
but useful in navigating the KHD (Kilkenney et al.,
1988SAAOC..12....1K 1988SAAOC..12....1K) catalog and cross-referencing tables 1 and 2.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Bauer [CDS] 16-Oct-2003