J/A+A/418/509 Chandra observation of M67 (Van Den Berg+, 2004)
A Chandra observation of the old open cluster M67.
Van Den Berg M., Tagliaferri G., Belloni T., Verbunt F.
<Astron. Astrophys., 418, 509-523 (2004)>
=2004A&A...418..509V 2004A&A...418..509V
ADC_Keywords: Clusters, open ; X-ray sources
Mission_Name: Chandra
Keywords: stars: activity - stars: binaries: general - stars: blue stragglers -
open clusters and associations: individual: M67 - X-rays: binaries
Abstract:
We present the results of a 47-ks Chandra/ACIS observation of
the old open cluster M67. We detected 25 proper-motion cluster members
(including ten new sources) and 12 sources (all new) that we suspect
to be members from their locations close to the main sequence
(1<B-V<1.7). Of the detected members, 23 are binaries.
Description:
table1.dat summarizes the X-ray properties of the 158 sources
detected by Chandra, and lists the ROSAT (Belloni et al.,
1998A&A...335..517B 1998A&A...335..517B) and optical (candidate) counterparts.
table4.dat gives the estimated positions of fifteen faint candidate
optical counterparts that were identified by eye in a deep ESO Imaging
Survey (EIS) V-band image of M67. These sources are not included in
the corresponding EIS source catalogue (Momany et al.,
2001A&A...379..436M 2001A&A...379..436M).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 114 158 Catalogue of Chandra sources in the field of M67
notes.dat 69 33 Individual notes
table4.dat 71 15 Estimated positions of faint optical counterparts
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See also:
V/52 : Photometry and Proper Motions in M67 (Frolov+ 1986)
II/123 : UBV Photometry of Faint Stars (V>14.5) in M67 (Frolov+ 1986)
J/AJ/106/181 : CCD photometry of open cluster M67 (Montgomery+ 1993)
J/AJ/112/628 : BATC Color Survey of M67 (Fan+ 1996)
J/A+A/382/899 : BVI photometry in M67 (Stassun+, 2002)
J/BaltA/7/369 : M67 CCD photometry (Boyle+, 1998)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- CX Chandra source identification
4 A1 --- Sig Indicator of significance of detection (1)
7- 11 F5.2 arcmin Daim Distance from the telescope aimpoint
14 I1 h RAh Right ascension (J2000) (2)
16- 17 I2 min RAm Right ascension (J2000)
19- 24 F6.3 s RAs Right ascension (J2000)
26- 30 F5.3 s e_RAs Error in right ascension (2)
33 A1 --- DE- Declination sign (J2000)
34- 35 I2 deg DEd Declination (J2000) (2)
37- 38 I2 arcmin DEm Declination (J2000)
40- 44 F5.2 arcsec DEs Declination (J2000)
46- 49 F4.2 arcsec e_DEs Error in declination (2)
52- 54 I3 ct CRateb Background-corrected counts between 0.3-7keV
56- 57 I2 ct e_CRateb Error in background-corrected counts
60- 64 F5.2 ct/ks CRate Net count-rate between 0.3-7keV (3)
67 A1 --- B [SHT] Energy band of most significant
detection (4)
70- 74 F5.2 --- HR ? Hardness ratio (5)
76- 79 F4.2 --- e_HR ? Error in hardness ratio
82- 83 I2 --- X ? (Candidate) ROSAT counterpart in
Belloni et al. (1998A&A...339..431B 1998A&A...339..431B),
[BVM98] M 67 NN in Simbad
86-101 A16 --- Opt (Candidate) optical counterpart (6)
104-108 A5 --- n_CX Notes on individual sources, detailed in
notes.dat file
111-114 F4.2 arcsec dXO ? Distance between Chandra and optical source
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Note (1): An '*' indicates that the source is detected with the significance
threshold set to 10-6 but not with the threshold set to 10-7.
Note (2): Positions are derived from the 0.3-7keV band image, and are
corrected for a systematic offset 'delta' relative to the EIS
optical positions:
delta(RA)=(RA)X-(RA)opt=-0.23arcsec and
delta(DE)=(DE)X-(DE)opt=-0.20arcsec.
The errors on RA and DE in columns 7 and 12 are the 1-sigma
'wavdetect' errors including the corrections for small count numbers
(See Sect.2.3 of paper). These are often much smaller than the
uncertainty in the absolute positions, i.e. than the uncertainty in
the offset values delta(RA) and delta(DE) (about 0.3arcsec).
Note (3): Corrected for background and vignetting
Note (4): Energy bands are:
S=0.3-2keV (soft), H=2-7keV (hard), T=0.3-7keV (total)
Note (5): Hardness ratio is defined as (H'-S')/(H'+S') where S' and H'
are the number of counts between 0.5-1 and 1-7keV respectively. Only
listed if the error on the hardness ratio is less than 0.4.
Note (6): The name of the counterpart is selected from (in order of preference):
Sanders (1977A&AS...27...89S 1977A&AS...27...89S) (S),
Momany et al. (2001A&A...379..436M 2001A&A...379..436M) (E), and
Fan et al. (1996AJ....112..628F 1996AJ....112..628F) (F).
Sources that are identified by eye with objects listed in neither
catalogue are labelled with 'faint' (see table4.dat).
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Byte-by-byte Description of file: notes.dat
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Bytes Format Units Label Explanations
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1 A1 --- Code Note letter
4- 79 A76 --- Note Text of the note
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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- 3 I3 --- CX Chandra source identification
5- 6 I2 --- X ? Identification of ROSAT candidate counterpart
in Belloni+Tagliaferri (1998A&A...335..517B 1998A&A...335..517B)
7 A1 --- u_X Uncertainty flag for ROSAT identification (1)
9 I1 h RAh Right ascension (J2000)
11- 12 I2 min RAm Right ascension (J2000)
14- 18 F5.2 s RAs Right ascension (J2000)
20 A1 --- DE- Declination sign
21- 22 I2 deg DEd Declination (J2000)
24- 25 I2 arcmin DEm Declination (J2000)
27- 30 F4.1 arcsec DEs Declination (J2000)
32 A1 --- n_X Note on ROSAT identification (2)
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Note (1): Cross-identification with ROSAT source is uncertain because of
a relatively large offset between the Chandra and ROSAT positions; see
the discussion in Sect. 3.2 of the paper.
Note (2): For Chandra sources with a ROSAT counterpart, an 'N' in this
column indicates that the identification with the optical counterpart
is new and was not yet suggested by Belloni et al.
(1998A&A...339..431B 1998A&A...339..431B).
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Acknowledgements: Maureen Van den Berg
History:
* 26-Apr-2004: Original version
* 26-Jan-2007: Unit of e_RAs originally specified as "arsec", was
changed to s (seconds of time)
(End) Maureen van den Berg [CfA], Patricia Bauer [CDS] 26-Apr-2004