J/ApJ/685/463 ChaMPlane X-ray sources in the Galactic bulge (Koenig+, 2008)
Investigating ChaMPlane X-ray sources in the Galactic bulge with Magellan LDSS2
spectra.
Koenig X., Grindlay J.E., van den Berg M., Laycock S., Zhao P., Hong J.,
Schlegel E.M.
<Astrophys. J., 685, 463-477 (2008)>
=2008ApJ...685..463K 2008ApJ...685..463K
ADC_Keywords: Photometry, VRI ; Spectral types ; Surveys ; X-ray sources ;
Stars, dwarfs
Keywords: Galaxy: stellar content - novae, cataclysmic variables -
stars: activity - stars: late-type - surveys - X-rays: stars
Abstract:
We have carried out optical and X-ray spectral analyses on a sample of
136 candidate optical counterparts of X-ray sources found in five
Galactic bulge fields included in our Chandra Multiwavelength Plane
Survey. We use a combination of optical spectral fitting and quantile
X-ray analysis to obtain the hydrogen column density toward each
object, and a three-dimensional dust model of the Galaxy to estimate
the most probable distance in each case. We present the discovery of a
population of stellar coronal emission sources, likely consisting of
pre-main-sequence, young main-sequence, and main-sequence stars, as
well as a component of active binaries of RS CVn or BY Dra type. We
identify one candidate quiescent low-mass X-ray binary with a subgiant
companion; we note that this object may also be an RS CVn system. We
report the discovery of three new X-ray-detected cataclysmic variables
(CVs) in the direction of the Galactic center (at distances ≲2kpc).
This number is in excess of predictions made with a simple CV model
based on a local CV space density of ≲10-5pc-3, and a scale
height ∼200pc. We discuss several possible reasons for this observed
excess.
Description:
X-ray data for this paper come from three ACIS-I and one ACIS-S
Chandra pointings use in the ChaMPlane survey (Hong et al.,
2005ApJ...635..907H 2005ApJ...635..907H).
Targets for optical spectral follow-up were selected following
observations made in 2000 March with the Mosaic camera on the CTIO 4m
telescope in V,R,I, and Hα filters to identify candidate
counterparts. The target list was used for the observing runs in
2001-2002 with the Low Dispersion Survey Spectrograph 2 (LDSS2) on the
6.5m Baade Magellan telescope.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table5.dat 134 136 Combined results for 2σ optical matches
--------------------------------------------------------------------------------
See also:
B/cb : Cataclysmic Binaries, LMXBs, and related objects (Ritter+, 2010)
http://hea-www.harvard.edu/ChaMPlane/ : ChaMPlane survey home page
Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- Field Field identification
7- 25 A19 --- ChOPS ChOPS identification: JHHMMSS.ss+DDMMSS.s (1)
27- 40 A14 --- SpType Spectral type classification (2)
42- 43 A2 --- Class Special source classification type (3)
45- 48 I4 ct Cts Background subtracted 0.3-0.8keV net counts
50 A1 --- f_Cts [*] * for source with SNR<3
52- 53 I2 ct e_Cts Uncertainty in Cts
55 A1 --- l_NH Limit flag on NH
56- 61 F6.3 10+22/cm2 NH Hydrogen column density from spectral fit (4)
63 A1 --- f_NH [d] NH estimated from QCCD analysis (5)
65- 66 I2 10+21/cm2 e_NH ? Uncertainty in NH
68 A1 --- l_X/R Limit flag on Fx/FR
69- 72 F4.1 [-] X/R ? log(Fx/Fr) of unabsorbed 0.5-2keV X-ray to
unreddened R band flux (in ergs/cm2/s/100nm)
74- 76 F3.1 [-] e_X/R ? Uncertainty in Fx/FR
78 A1 --- l_Dist Limit flag on Dist
79- 82 F4.1 kpc Dist ? Heliocentric distance; error about 60%
84 A1 --- l_VMAG Limit flag on VMAG
85- 90 F6.2 mag VMAG ? Absolute V band magnitude
92- 93 I2 dmag e_VMAG ? Uncertainty in VMag (in 0.1mag)
95 A1 --- l_logLx Limit on logLx
97-101 F5.2 [10-7W] logLx ? Log of 0.5-2keV X-ray luminosity
103-105 F3.1 [10-7W] e_logLx ? Uncertainty in logLx
107-112 F6.3 mag Rmag R band magnitude
114 I1 cmag e_Rmag Uncertainty in Rmag (in 0.01mag)
116 I1 --- Nm Number of optical matches (6)
118-122 F5.3 arcsec Srch Combined 95% X-ray and optical position
error circle (7)
124-128 F5.3 arcsec off Positional offset between X-ray and
optical position
130-134 F5.3 --- PRn Random match probability (8)
--------------------------------------------------------------------------------
Note (1): ChaMPlane IDs have prefix ChOPS (<ChOPS JHHMMSS.ss+DDMMSS.s> in
Simbad).
Note (2): Spectral type classifications:
MidM = M4-M6 spectral range, with Teff=3000±500K, MV=13.2±2.0
LateG = G6-G8 spectral range, with Teff=5200±500K, MV=5.3±0.5
MidG = G4-G6 spectral range, with Teff=5400±500K, MV=4.9±0.5
EarlyG = G2-G4 spectral range, with Teff=5600±500K, MV=4.6±0.4
F/G = F8-G2 spectral range, with Teff=5950±500K, MV=4.3±0.7
LateF = F6-F8 spectral range, with Teff=6200±500K, MV=3.8±0.4
EarlyA = A2-A4 spectral range, with Teff=9100±500K, MV=1.8±0.4
See Table 4 of paper for further details of spectral type classification.
Note (3): Object classification for 19 special sources as follows:
q = qLMXB (quiescent low-mass X-ray binary system) candidate;
by = BY Dra candidate;
rs = RS CVn candidate;
tt = T Tauri;
cv = Cataclysmic Variable.
Note (4): True value may be higher by ∼0.2, see text.
Note (5): Objects with "?" spectral type and CVs, which have NH estimated
from X-ray quantile color-color diagram (QCCD) analysis.
Note (6): Found within 95% confidence (2σ) error circle of this X-ray
source.
Note (7): Used to search for optical matches.
Note (8): Given error circle size and measured local optical projected
surface density.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 13-Dec-2010