J/ApJ/697/1695 The Chandra survey of the SMC "Bar". II. (Antoniou+, 2009)
The Chandra survey of the Small Magellanic Cloud "Bar".
II. Optical counterparts of X-ray sources.
Antoniou V., Zezas A., Hatzidimitriou D., McDowell J.C.
<Astrophys. J., 697, 1695-1716 (2009)>
=2009ApJ...697.1695A 2009ApJ...697.1695A
ADC_Keywords: Magellanic Clouds ; Binaries, X-ray ; Cross identifications
Photometry, UBV ; Stars, Be
Keywords: Magellanic Clouds - pulsars: general - stars: early-type -
stars: emission-line, Be - stars: formation - X-rays: binaries
Abstract:
We present the most likely optical counterparts of 113 X-ray sources
detected in our Chandra survey of the central region of the Small
Magellanic Cloud (SMC) based on the OGLE-II and Magellanic Clouds
Photometric Survey catalogs. We estimate that the foreground
contamination and chance coincidence probability are minimal for the
bright optical counterparts (corresponding to OB type stars; 35 in
total). We propose here for the first time 13 high-mass X-ray
binaries, of which four are Be/X-ray binaries (Be-XRBs), and we
confirm the previous classification of 18 Be-XRBs. We estimate that
the new candidate Be-XRBs have an age of ∼15-85Myr, consistent with
the age of Be stars.
Description:
We initiated a Chandra survey, consisting of five observations of the
central part of the SMC performed between 2002 May and October with
the Chandra ACIS-I detector. The survey covers an area of
1280arcmin2 along the central, most actively star forming, region of
the SMC (also referred to as the SMC "Bar"). In this paper we have
used the Chandra survey of the SMC (Zezas et al. 2003lgal.conf..111Z),
and searched for optical counterparts of the X-ray sources included in
this survey.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 98 392 Optical counterparts of X-ray sources in Chandra
fields 3-7
table4.dat 150 228 Additional optical info
table7.dat 162 71 Summary of optical and X-ray properties for
bright sources
refs.dat 93 70 References
notes.dat 80 276 Notes on individual sources
--------------------------------------------------------------------------------
See also:
I/315 : UCAC3 Catalogue (Zacharias+ 2009)
B/denis : The DENIS database (DENIS Consortium, 2005)
VII/234 : DENIS catalog of galaxies (Paturel+, 2003)
I/284 : The USNO-B1.0 Catalog (Monet+ 2003)
II/236 : UBVR CCD survey of the Magellanic clouds (Massey+, 2002)
I/271 : The Guide Star Catalog, Version 2.2 (GSC2.2) (STScI, 2001)
II/228 : DENIS Catalogue toward Magellanic Clouds (DCMC) (Cioni+ 2000)
I/221 : The Magellanic Catalogue of Stars - MACS (Tucholke+ 1996)
J/MNRAS/388/1198 : Be/X-ray binaries in Small Magellanic Cloud (McBride+, 2008)
J/AcA/54/1 : OGLE II SMC eclipsing binaries (Wyrzykowski+, 2004)
J/MNRAS/353/705 : OGLE Variables in Magellanic Clouds (Ita+, 2004)
J/AJ/127/1632 : UBVR(UIT) photometry of O and OB stars in SMC (Oey+, 2004)
J/MNRAS/353/601 : 2dF survey of the Small Magellanic Cloud (Evans+, 2004)
J/PASJ/55/161 : ASCA sources in the SMC (Yokogawa+, 2003)
J/AcA/48/147 : OGLE SMC BVI photometry (Udalski+ 1998)
J/AcA/48/563 : Photometry of OGLE SMC eclipsing binaries (Udalski+, 1998)
J/AcA/51/317 : OGLE DIA. Catalog of LMC and SMC images (Zebrun+, 2001)
J/A+AS/147/75 : ROSAT HRI catalogue of SMC X-ray sources (Sasaki+, 2000)
J/A+AS/142/41 : SMC X-ray sources ROSAT PSPC catalogue (Haberl+, 2000)
J/MNRAS/311/741 : SMC emission-line objects (Murphy+, 2000)
J/ApJS/101/41 : SMC and Bridge extended catalog (Bica+ 1995)
J/A+AS/102/451 : Emission-line stars and PNe in the SMC (Meyssonnier+ 1993)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- XSrc X-ray source identification (G1)
6- 7 A2 --- f_XSrc [*dfc ] Flag on Src (1)
9- 12 F4.2 arcsec XRad Search radius
14- 25 A12 --- OSrc Optical counterpart source identification (G2)
27- 28 A2 --- f_OSrc Flag on OSrc (2)
30- 31 I2 h RAh ? Hour of Right Ascension of optical source
(J2000)
33- 34 I2 min RAm ? Minute of Right Ascension of optical source
36- 40 F5.2 s RAs ? Second of Right Ascension of optical source
42 A1 --- DE- Sign of optical source Declination (J2000)
43- 44 I2 deg DEd ? Degree of Declination of optical source
46- 47 I2 arcmin DEm ? Arcminute of Declination of optical source
49- 52 F4.1 arcsec DEs ? Arcsecond of Declination of optical source
54- 57 F4.2 arcsec Off ? Optical/X-ray positional offset
59- 63 F5.2 mag Vmag ? The V band magnitude (3)
65- 69 F5.2 mag e_Vmag ? Error in Vmag (3)
71- 75 F5.2 mag B-V ? The (B-V) color index (3)
77- 81 F5.2 mag e_B-V ? Error in B-V (3)
83- 87 F5.2 mag U-B ? The (U-B) color index (3)
89- 93 F5.2 mag e_U-B ? Error in U-B color (3)
95- 98 A4 --- Note Additonal notes (4)
--------------------------------------------------------------------------------
Note (1): Sources without OGLE-II coverage (thus no available finding charts),
and any MCPS counterpart(s): 3_6, 3_8, 3_10, 3_11, 3_13, 3_16, 3_20,
3_21, 3_23 to 3_25, 3_27, 3_28, 4_9, 4_38, 5_5, 5_11, 5_17, 5_19,
5_20, 5_35, 7_8, and 7_14. Flag as follows:
* = source with OGLE-II coverage (and available finding chart) but no
counterpart(s) either in the OGLE-II or MCPS catalogs.
** = source without OGLE-II coverage (thus no available finding chart)
but with counterpart(s) in the MCPS catalog.
d = OGLE-II detected two sources instead of one star (suggested by the
visual inspection of the finding chart).
fc = The finding chart of Chandra source 6_18 also includes the nearby
source 6_15.
Note (2): Flag as follows:
b = Most likely counterpart.
) = unclear match of the MCPS source to the OGLE-II source(s) listed
just above.
s = same source detected in two neighboring OGLE-II fields.
o = Just outside the search radius there is another OGLE-II source
(not listed in this table) that is most likely related to the detected
MCPS source within it.
Note (3): These data are taken directly from the original catalogs without
applying any reddening or zero-point correction.
Note (4): Flag as follows:
u = unable to uniquely identify an optical counterpart;
c = additional comments for this source in section 8.3;
n = new candidate counterpart for the X-ray source.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- XSrc X-ray source identification (G1)
6- 35 A30 --- Type Source type (1)
37- 51 A15 --- r_Type Reference(s) for Type (see refs.dat file)
53- 87 A35 --- OSrc Optical source identification (G2)
89-112 A24 --- r_OSrc Reference(s) for OSrc (see refs.dat file)
114-140 A27 --- Other Other sources within 1.5"
142-150 A9 --- r_Other Reference(s) for Other (see refs.dat file)
--------------------------------------------------------------------------------
Note (1): Source type as follows:
Be? = Hα emission-line object as possible counterpart, no optical
spectrum available in the literature;
HMXB? = HMXB candidate;
P = pulsar;
Be/X? = very promising candidate for Be-XRBs;
Be-XBP = Be-XRB pulsar.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table7.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- XSrc X-ray source identification (G1)
6- 15 A10 --- OSrc Optical counterpart source identification (G2)
16 A1 --- f_OSrc [dfs] Flag on OSrc (1)
18- 26 A9 --- OSrc2 Optical counterpart source identification (G2)
28- 29 A2 --- r_OSrc2 ? Reference for OSrc2
31- 35 F5.2 mag Vmag V-band magnitude
37- 40 F4.2 mag e_Vmag Error in Vmag
42- 46 F5.2 mag B-V ? The (B-V) color index
48- 51 F4.2 mag e_B-V ? Error in B-V
53- 57 F5.2 mag U-B ? The (U-B) color index
59- 62 F4.2 mag e_U-B ? Error in U-B color index
64- 67 F4.2 arcsec Off ? Optical/X-ray positional offset
69- 78 A10 --- Spec Spectrum band (2)
80- 87 A8 --- SXP X-ray pulsar identification (3)
89- 90 A2 --- r_SXP ? Reference for SXP
92- 97 F6.2 10-17W/m2 Flux ? Absorbed flux in the 2.0-10.0keV energy
band calculated from net counts
(expressed in 10-14erg/cm2/s)
99-102 F4.2 10-17W/m2 E_Flux ? Positive error on Flux
104-107 F4.2 10-17W/m2 e_Flux ? Negative error on Flux
109-113 F5.2 --- xi ? X-ray to optical "color index", ξ (4)
115-118 F4.2 --- E_xi ? Positive error on xi
120-123 F4.2 --- e_xi ? Negative error on xi
125-128 I4 --- [MA93] ? Identified from the catalog of Meyssonnier &
Azzopardi (1993, Cat. J/A+AS/102/451)
129 A1 --- u_[MA93] Uncertainty flag for [MA93]
131-133 F3.1 arcsec Sep ? Offset for [MA93]
135-145 A11 --- Class This work object classification (5)
146 A1 --- f_Class [h] confirmed Class (6)
148-161 A14 --- Classp Previous classification
162 A1 --- f_Classp [eg] Flag on Classp (6)
--------------------------------------------------------------------------------
Note (1): Flag as follows:
d = Sources with hard (or possibly hard) X-ray spectra and early-type
counterparts (O or B) between the 1σ and 2σ search radii. For
more details see Section 1.1 in the Appendix.
f = These sources are discussed in Section 8.3. For Chandra source 4_11 more
details can be found in Section A.4, and for source 5_35 in Section A.6.
s = similar identifications for the source
Note (2): A "?" following the hard or soft X-ray spectrum indicates a
possibly hard or soft spectrum, respectively (due to the small number
of X-ray counts).
Note (3): SXP stands for SMC X-ray pulsars followed by the pulse period in
seconds to three significant figures
(http://www.astro.soton.ac.uk/~mjc/). A "?" denotes candidate X-ray
pulsars from the work of Laycock et al. (2010ApJ...716.1217L 2010ApJ...716.1217L).
Note (4): The X-ray to optical "color index," ξ=B0+2.5log(FX) (where
B0 is the reddening-corrected apparent B magnitude and FX is the
2.0-10.0keV X-ray flux in uJy), introduced by van Paradijs and
McClintock (1995xrbi.nasa...58V), is another standard means of
classifying X-ray sources, as HMXBs have lower values of ξ than the
LMXBs.
Note (5): Classification as follows:
New HMXB? = candidate new HMXB (early-type counterpart but no information
about the X-ray spectrum and or pulsations);
Be-XBP = Be-XRB pulsar;
fg star = foreground star;
Unclass. = sources with a soft X-ray spectrum or unavailable spectral
information or without an early-type counterpart - cannot be
classified without further information (e.g., optical
spectroscopy, X-ray timing, or spectral analysis).
The references for the previously classified sources are given
in r_Type of Table 4.
Note (6): Flags as follows:
h = Confirmed classification by optical follow-up spectroscopy of selected
targets from our Chandra survey (Antoniou et al. 2009ApJ...707.1080A 2009ApJ...707.1080A)
e = Unclassified: sources of uncertain nature (Shtykovskiy & Gilfanov,
2005MNRAS.362..879S 2005MNRAS.362..879S)
g = More details are given in Section A.2.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: refs.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- Ref Reference code
13- 31 A19 --- BibCode Bibcode
33- 55 A23 --- Aut Author's name
57- 93 A37 --- Note Catalog reference in VizieR
--------------------------------------------------------------------------------
Byte-by-byte Description of file: notes.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- XSrc X-ray source identification (G1)
6- 80 A75 --- Note Text of note
--------------------------------------------------------------------------------
Global Notes:
Note (G1): Following the format F_NN where F is the Chandra field number and
NN is the source ID in the field (from Zezas et al. 2009, in prep).
--------------------------------------------------------
Chandra field RA (J2000) DE Detected sources
--------------------------------------------------------
3 00 56 46.14 -72 18 10.78 28
4 00 49 30.74 -73 16 52.34 38
5 00 53 11.45 -72 26 29.91 37
6 00 53 04.40 -72 42 18.22 28
7 00 49 25.09 -72 44 22.80 27
---------------------------------------------------------
Note (G2): OGLE-II sources are named as OFNNNNNN, where F and NNNNNN are
the field and optical source number, respectively (from Udalski et al.
1998, Cat. J/AcA/48/147, in Simbad), while MCPS
sources are named as Z_NNNNNN where NNNNNN is the line number of the
source in Table 1 of Zaritsky et al. (2002, Cat. J/AJ/123/855).
--------------------------------------------------------------------------------
History:
From electronic version of the journal
References:
McDowell et al. 2003AAS...202.4003M 2003AAS...202.4003M
Zezas et al. 2004RMxAC..20..205Z 2004RMxAC..20..205Z
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 31-May-2011