J/ApJS/181/444 X-emitting stars identified from the RASS/SDSS (Agueros+, 2009)
X-ray-emitting stars identified from the ROSAT All-Sky Survey and
the Sloan Digital Sky Survey.
Agueros M.A., Anderson S.F., Covey K.R., Hawley S.L., Margon B.,
Newsom E.R., Posselt B., Silvestri N.M., Szkody P., Voges W.
<Astrophys. J. Suppl. Ser., 181, 444-465 (2009)>
=2009ApJS..181..444A 2009ApJS..181..444A
ADC_Keywords: Cross identifications ; Photometry, SDSS ; Surveys ; X-ray sources
Stars, late-type
Keywords: surveys - X-rays: stars
Abstract:
The ROSAT All-Sky Survey (RASS) was the first imaging X-ray survey of
the entire sky. Combining the RASS Bright and Faint Source Catalogs
(Cat. IX/10, 1RXS and IX/29) yields an average of about three X-ray
sources per square degree. However, while X-ray source counterparts
are known to range from distant quasars to nearby M dwarfs, the RASS
data alone are often insufficient to determine the nature of an X-ray
source. As a result, large-scale follow-up programs are required to
construct samples of known X-ray emitters. We use optical data
produced by the Sloan Digital Sky Survey (SDSS) to identify 709
stellar X-ray emitters cataloged in the RASS and falling within the
SDSS Data Release 1 footprint. Most of these are bright stars with
coronal X-ray emission unsuitable for SDSS spectroscopy, which is
designed for fainter objects (g>15[mag]). Instead, we use SDSS
photometry, correlations with the Two Micron All Sky Survey and other
catalogs, and spectroscopy from the Apache Point Observatory 3.5m
telescope to identify these stellar X-ray counterparts. Our sample of
707 X-ray-emitting F, G, K, and M stars is one of the largest
X-ray-selected samples of such stars. We identify 17 new
X-ray-emitting DA (hydrogen) WDs, of which three are newly identified
WDs. We report on follow-up observations of three candidate cool
X-ray-emitting WDs (one DA and two DB (helium) WDs); we have not
confirmed X-ray emission from these WDs.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 63 12 The CVs and WDs among the RASS/SIMBAD matches
table3.dat 134 52 RASS sources with multiple candidate counterparts
table4.dat 556 709 Full RASS/SDSS catalog
table5.dat 94 27 New X-ray-emitting SDSS DA WDs
table6.dat 92 8 X-ray-emitting SDSS non-DA WDs
table7.dat 74 20 RASS/SIMBAD class II, III, IV, and A stars
table8.dat 101 41 SIMBAD stars with Apache Point Obs. (APO) spectra
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See also:
III/210 : Spectroscopically Identified White Dwarfs (McCook+, 1999)
IX/10 : ROSAT All-Sky Bright Source Catalogue (1RXS) (Voges+ 1999)
IX/32 : ROSAT Bright Survey (Fischer+, 1998-2000)
IX/29 : ROSAT All-Sky Survey Faint Source Catalog (Voges+ 2000)
J/ApJS/117/319 : Northern RASS X-ray sources catalog (Appenzeller+ 1998)
J/A+AS/131/197 : F, G and K stars BVRI photometry (Metanomski+ 1998)
J/A+A/406/535 : Hamburg/RASS Cat. of optical ident. V3.0 (Zickgraf+, 2003)
J/ApJS/149/29 : ROSAT North Ecliptic Pole Survey (Gioia+, 2003)
J/A+A/427/387 : QORG catalog of radio/X-ray sources (Flesch+, 2004)
http://www.sdss.org : SDSS Home page
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- 1RXS 1RXS designation (HHMMSS.s+DDMMSS)
17- 21 F5.3 s-1 Cts ROSAT count rate
23- 27 F5.3 s-1 e_Cts Error on Counts
29- 39 A11 --- XID Counterpart name in Simbad (WD or V*)
41- 44 F4.1 arcsec Offset Offset between X-ray source and optical
counterpart
46- 50 F5.2 mag Bmag ?=- Simbad B-band magnitude
52- 56 F5.2 mag Vmag ?=- Simbad V-band magnitude
58- 63 A6 --- Type Object type (1)
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Note (1): "P" indicates that CV is a polar and "DN" that it is a dwarf nova.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- 1RXS Name (HHMMSS.s+DDMMSS)
17- 21 F5.3 s-1 Cts ? ROSAT counts rate
23- 27 F5.3 s-1 e_Cts ? Error on Counts
29- 46 A18 --- SDSS Name (HHMMSS.ss+DDMMSS.s)
48- 51 F4.1 arcsec Offset Offset between X-ray source and SDSS counterpart
53- 57 F5.2 mag gmag SDSS g-band magnitude
59- 63 F5.2 mag e_gmag Error on gmag
65- 69 F5.2 mag Jmag ?=- 2MASS J-band magnitude
71- 74 F4.2 mag e_Jmag ? Error on Jmag
76- 80 F5.2 [-] FX/FJ Log ratio of RASS X-ray to 2MASS J band fluxes
81 A1 --- f_FX/FJ [b] FX/FV ratio (1)
83- 85 A3 --- SpA Spectral Type (from Apache Point Obs.)
87-113 A27 --- XID Simbad counterpart
116-120 F5.2 mag Vmag ? Simbad V-band magnitude
122-126 F5.2 [-] FX/FV ? Corresponding Simbad log(FX/FV)
128-129 A2 --- SpT Simbad spectral type
131-133 A3 --- ObT Simbad object type
134 A1 --- f_XID [a] Problem with position in Simbad (2)
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Note (1): b = log(Fx/FV). There is no 2MASS detection of this QSO.
Note (2): a = the given SIMBAD position is offset by 37", but this appears
to be the SDSS star.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- 1RXS RASS Name (HHMMSS.s+DDMMSS +1RXS J)
17- 26 F10.6 deg RAdeg RASS Right Ascension in decimal degrees
(J2000)
28- 37 F10.6 deg DEdeg RASS Declination in decimal degrees (J2000)
39- 40 I2 arcsec e_Pos RASS position uncertainty (1)
42 I1 --- f_1RXS Flag on RASS (2)
44- 50 F7.5 ct/s CRate RASS count rate
52- 58 F7.5 ct/s e_CRate Uncertainty in CRate
60- 63 I4 s Exp RASS exposure time
65- 69 F5.2 --- HR1 First hardness ratio (3)
71- 74 F4.2 --- e_HR1 Uncertainty in HR1
76- 80 F5.2 --- HR2 Second hardness ratio (3)
82- 85 F4.2 --- e_HR2 Uncertainty in HR2
87- 88 I2 arcsec Ext Source extent
90 I1 --- EL Extent likelihood (See Voges et al., 1999,
Cat. IX/10)
92- 94 I3 --- DL Detection likelihood (See Voges et al., 1999,
Cat. IX/10)
96-113 A18 --- SDSS SDSS identification (HHMMSS.ss+DDMMSS.s)
115-124 F10.6 deg RA2deg SDSS Right Ascension in decimal degrees
(J2000)
126-135 F10.6 deg DE2deg SDSS Declination in decimal degrees (J2000)
137-141 F5.2 arcsec offS-R Offset from SDSS and RASS positions
143-148 F6.3 mag umag SDSS u band PSF magnitude
150-155 F6.3 mag e_umag Uncertainty in umag
157-162 F6.3 mag gmag SDSS g band PSF magnitude
164-169 F6.3 mag e_gmag Uncertainty in gmag
171-176 F6.3 mag rmag SDSS r band PSF magnitude
178-184 F7.3 mag e_rmag Uncertainty in rmag
186-191 F6.3 mag imag ?=0.0 SDSS i band PSF magnitude
193-198 F6.3 mag e_imag Uncertainty in imag
200-205 F6.3 mag zmag ?=0.0 SDSS z band PSF magnitude
207-212 F6.3 mag e_zmag Uncertainty in zmag
214-228 A15 --- f_SDSS Flags on SDSS (4)
230-245 A16 --- 2MASS 2MASS identification (HHMMSSss+DDMMSSs)
247-256 F10.6 deg RA3deg 2MASS Right Ascension in decimal degrees
(J2000)
258-267 F10.6 deg DE3deg 2MASS Declination in decimal degrees (J2000)
269-272 F4.2 arcsec offS-2 Offset from SDSS and 2MASS positions
274-279 F6.3 mag Jmag 2MASS J band magnitude
281-285 F5.3 mag e_Jmag ? Uncertainty in Jmag
287-292 F6.3 mag Hmag 2MASS H band magnitude
294-298 F5.3 mag e_Hmag Uncertainty in Hmag
300-305 F6.3 mag Ksmag ? 2MASS KS band magnitude
307-311 F5.3 mag e_Ksmag ? Uncertainty in Ksmag
313-315 A3 --- q_2MASS Quality flags on 2MASS (5)
317-321 F5.2 [-] FX/FJ Log ratio of RASS X-ray to 2MASS J band fluxes
323-326 F4.2 mag KsMAG ? Synthetic absolute KS band magnitude
328-333 F6.2 mag e_KsMAG ? Uncertainty in KsMAG
335-340 F6.2 pc Dist ? Star distance (corresponding to KsMAG)
342-347 F6.2 pc e_Dist ? Uncertainty in Dist
349-356 E8.2 10-7W LX ? RASS X-ray luminosity in erg/s
358-365 E8.2 10-7W e_LX ? Uncertainty in LX
367-370 I4 yr Obs.Y ? Year of the APO observation (6)
372-374 A3 --- Obs.M Month of the APO observation (6)
376-377 I2 d Obs.D ? Day of the APO observation (6)
379-386 A8 --- Type Source spectral type
388-414 A27 --- Simbad Simbad identification
416-425 F10.6 deg RA4deg ? Simbad Right Ascension in decimal degrees
(J2000)
427-436 F10.6 deg DE4deg ? Simbad Declination in decimal degrees
(J2000)
438-442 F5.2 arcsec offS-Si ? Offset from SDSS and Simbad positions
444-448 F5.2 mag Bmag ? Simbad B band magnitude
450-454 F5.2 mag Vmag ? Simbad V band magnitude
456-460 F5.2 [-] FX/FV ? Log ratio of RASS X-ray to Simbad V band
fluxes
462-467 A6 --- Class Simbad classification (7)
469-556 A88 --- Note Additional note(s) (8)
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Note (1): This is the total positional error (1σ error) and includes
a 6 arcsec systematic error.
Note (2): Summary of RASS flags. When = 0, the following are NOT true:
* nearby sources affecting SASS flux determination;
* possible problem with position determination;
* source extended beyond SASS extraction radius;
* complex diffuse emission pattern (see Voges et al., 1999, Cat. IX/10).
Note (3): The hardness ratios are defined by HR1=(B-A)/(B+A), where
A = count-rate in PHA range 11-41(∼0.1-0.4keV) and
B = count-rate in PHA range 52-201(∼0.5-2.0keV)
and HR2=(D-C)/(D+C), where
C = count-rate in PHA range 52-90(∼0.5-0.9keV) and
D = count-rate in PHA range 91-201(∼0.9-2.0keV)
(PHA = Pulse Height Amplitude; see Voges et al., 1999, Cat. IX/10).
Note (4): SDSS flags written in hexadecimal, full description available at
http://cas.sdss.org/astro/en/help/browser/enum.asp?n=PhotoFlags
(or see the SDSS Photometric Catalog, Cat. II/294)
Note (5): Three character flag, one per band [JHK], that provides a summary
of the net quality of the photometry in each band, as derived from the
Read Flag, measurement uncertainties ([jhk]cmsig), scan
signal-to-noise ratios ([JHK]snr), frame-detection statistics, and
profile-fit reduced chi-squared values:
X = There is a detection at this location, but no valid brightness
estimate can be extracted using any algorithm. The default magnitude
is null.
U = Upper limit on magnitude. Source is not detected in this band, or it is
detected, but not resolved in a consistent fashion with other bands.
E = This category includes detections where the goodness-of-fit quality of
the profile-fit photometry was very poor, or detections where psf fit
photometry did not converge and an aperture magnitude is reported, or
detections where the number of frames was too small in relation to the
number of frames in which a detection was geometrically possible.
A = Detections in any brightness regime where valid measurements were made
with [JHK]snr>10 AND [JHK]cmsig<0.10857.
B = Detections in any brightness regime where valid measurements were made
with [JHK]snr>7 AND [JHK]cmsig<0.15510.
C = Detections in any brightness regime where valid measurements were made
with [JHK]snr>5 AND [JHK]cmsig<0.21714.
D = Detections in any brightness regime where valid measurements were made
with no [JHK]snr OR [JHK]cmsig requirement.
Note (6): For stars observed more than once, the data listed are that of the
first APO observation.
Note (7): Object types as follows:
** = double or multiple star system;
*i* = star in double system;
* = star;
PM* = high proper-motion star;
WU* = W UMa-type eclipsing binary;
LM* = low-mass star (<1M☉);
BY* = BY Dra-type variable;
Al* = Algol-type binary;
V* = variable star;
X = X-ray source;
bL* = beta Lyr-type eclipsing binary;
SB* = spectroscopic binary;
Rad = radio source;
RR* = RR Lyrae star;
*iC = star in a cluster;
EB* = eclipsing binary.
Note (8): Includes the spectral type derived from APO observations for stars
with types listed in SIMBAD and/or the Flesch & Hardcastle (2004,
Cat. J/A+A/427/387) or Parejko et al. (2008AJ....135...10P 2008AJ....135...10P)
classification for the source counterpart.
RM = a random match between the Flesch & Hardcastle (2004,
Cat. J/A+A/427/387) source catalogs is most likely in this case;
SX = a stellar source;
SX? = a probable stellar source;
X = an unclassified X-ray source;
G = a galaxy;
R = a radio source;
U = the source is an unclassifiable galaxy in the Parejko et al. catalog
(2008AJ....135...10P 2008AJ....135...10P);
T = a transition object;
HII = a star-forming galaxy;
E = an emission galaxy;
UE = the emission is unclassified;
CC = close companion (≲5") star.
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Byte-by-byte Description of file: table[56].dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- SDSS SDSS designation (HHMMSS.ss+DDMMSS.s)
19 A1 --- f_SDSS [bc] Individual notes (1)
21- 26 I6 K Teff ?=- Effective temperature
28- 31 I4 K e_Teff ? Error on Teff
32 A1 --- u_Teff Uncertainty flag on Teff
34- 48 A15 --- 1RXS Name (HHMMSS.s+DDMMSS)
50- 53 F4.1 arcsec Offset Offset between SDSS and X-ray sources
55- 59 F5.3 s-1 Cts Counts
61- 65 F5.3 s-1 e_Cts Error on counts
67- 71 F5.2 [-] FX/FG Log ratio of RASS X-ray to SDSS g-band fluxes
72 A1 --- f_FX/FG [a] Flag on Log(FX/FG) (2)
74- 80 A7 --- Type Type (for Table 6)
82- 92 A11 --- XID McCook & Sion (1999, Cat. III/210) WD
designation
94 A1 --- f_XID [u] uncertain identifications (3)
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Note (1): Flag as follows:
b = Post-DR4 WD.
c = SDSS J0936 (in Table 5) is listed as a DQ WD by McCook & Sion (1999,
Cat. III/210). However, the SDSS spectrum does not show the carbon
absorption lines typical of DQs, and it seems that this is indeed a DA WD.
Note (2): a = g photometry is flagged in SDSS (for Table 5 only).
Note (3): u = tentative identifications requiring further observations,
on the contrary, lack of "u" means highly secure RASS counterpart
identifications (for Table 5 only).
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Byte-by-byte Description of file: table7.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- 1RXS Name (HHMMSS.s+DDMMSS)
17- 21 F5.3 s-1 Cts Counts
23- 27 F5.3 s-1 e_Cts Error on counts
29- 46 A18 --- Name HD, BD, CCDM or V* designation
48- 52 F5.2 arcsec Offset Offset between X-ray source and optical
counterpart
54- 58 F5.2 mag Vmag V-band magnitude
60- 64 F5.2 [-] FX/FV Log ratio of RASS X-ray to Simbad V band
fluxes
66- 70 A5 --- SpType Spectral type
72- 74 A3 --- OType Object type (1)
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Note (1): "**" or "*i*" indicates a double or multiple star system,
"RR*" an RR Lyrae star, and "Al*" an Algol-type binary.
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Byte-by-byte Description of file: table8.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 A15 --- 1RXS Name (HHMMSS.S+DDMMSS)
17- 34 A18 --- SDSS Name (HHMMSS.ss+DDMMSS.s)
35 A1 --- f_SDSS [f] Possibly several counterparts (1)
37- 40 F4.1 arcsec off1 Offset between RASS & SDSS positions
42- 68 A27 --- XID Counterpart Simbad name
70- 72 A3 --- f_XID [abcdegh, ] Flag on Simbad name (2)
74- 76 F3.1 arcsec off2 Offset between SDSS & Simbad positions
78- 84 A7 --- SpT2 Published spectral type
86- 95 A10 "YYYY/MM/DD" ObsDate First APO observation date
97- 99 A3 --- SpA Apache Point Obs. Spectral type
101 A1 --- f_1RXS [c] Non-secure Fx/Fopt estimation (3)
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Note (1): f = One of two possible counterparts to this source (see Table 3).
This star was not included in the flux ratio calculations discussed in
Section 4.1.1.
Note (2): Flag as follows:
a = X-ray source identified by Schwope et al. (2000AN....321....1S 2000AN....321....1S).
b = X-ray source identified by Appenzeller et al. (1998, Cat.
J/ApJS/117/319).
c = X-ray source identified by Zickgraf et al. (2003, Cat. J/A+A/406/535).
d = X-ray source identified by Metanomski et al. (1998, Cat. J/A+AS/131/197)
e = X-ray source identified by Fischer et al. (1998, Cat. IX/32).
g = X-ray source identified by Gioia et al. (2003, Cat. J/ApJS/149/29).
h = APO target is not the same star.
Note (3): Stars without "c" are those for which choosing the APO or the
SIMBAD spectral class does not impact (FX/Fopt) calculations.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 22-Oct-2009