J/AJ/121/337 Chandra Observation of the Pleiades (Krishnamurthi+, 2001)
Observations of the core of the Pleiades with the Chandra X-ray observatory.
Krishnamurthi A., Reynolds C.S., Linsky J.L., Martin E., Gagne M.
<Astron. J., 121, 337-346 (2001)>
=2001AJ....121..337K 2001AJ....121..337K (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; X-ray sources ; Stars, early-type ;
Stars, late-type
Mission_Name: Chandra
Keywords: Galaxy: Open Clusters and Associations: Individual: Name: Pleiades,
Stars: Activity, Stars: Early-Type, Stars: Low-Mass, Brown Dwarfs
Abstract:
We present results from a 36 ks observation of the core of the
Pleiades open cluster using ACIS-I on the Chandra X-Ray Observatory.
We have detected 57 sources, most of which do not have previously
known optical counterparts. Follow-up photometry indicates that many
of the detections are likely to be active galactic nuclei, in
accordance with extragalactic source counts, but some of the sources
may be previously undiscovered low-mass members of the Pleiades. We
discuss our data set and our findings about X-ray emission from
early-type stars, as well as very late-type stars. In particular, the
large X-ray fluxes, lack of variability, and hardness ratios of the
four Pleiades B6 IV-F4 V stars suggest a tentative conclusion that
Pleiades stars in this spectral type range are intrinsic X-ray sources
rather than previously unknown binaries in which the X-ray emission is
from a late-type companion. Also, the sensitivity of Chandra allowed
us to detect nonflare X-ray emission from late M stars.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 50 57 Sources Detected by Chandra
table2.dat 41 18 Known Optical Counterparts to ACIS Detections
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Seq Source number
4 I1 h RAh Right ascension (J2000)
6- 7 I2 min RAm Right ascension (J2000)
9- 13 F5.2 s RAs Right ascension (J2000)
15- 16 I2 deg DEd Declination (J2000)
18- 19 I2 arcmin DEm Declination (J2000)
21- 25 F5.2 arcsec DEs Declination (J2000)
27- 33 F7.2 ct Counts Source counts
35- 39 F5.2 ct e_Counts Statistical error in Counts
41- 45 F5.2 --- HR Hardness ratio (1)
47- 50 F4.2 --- e_HR Uncertainty in HR
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Note (1): HR = (hard - soft)/(hard + soft), where hard is from the 1-3keV
image and soft is from the 0-1keV image.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Seq Source number
4- 11 A8 --- Opt Optical counterpart (1)
13 A1 --- f_Opt Indicates a star has flared during the
observation. Discussion in sections
3.4 and 3.5.
15- 17 F3.1 arcsec Offset Offset from the optical counterpart
19- 22 F4.2 arcsec COffset Corrected offset from the optical counterpart
24- 27 I4 ct Counts X-ray counts
29- 33 F5.2 mag Vmag The V-band magnitude
35- 39 A5 --- SpType Spectral type
41 A1 --- Member Membership (2)
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Note (1):
HII = The second list in Hertzsprung 1947, sometimes also referred to
as Hz (see e.g. Cat. I/90)
HCG = The catalog of Haro, Chavira, & Gonzalez 1982 (Cat. II/131)
HHJ = The Hambly, Hawkins, & Jameson catalog 1991 (J/A+AS/100/607)
MHO = Objects from the Mount Hopkins survey (Stauffer et al.
1998ApJ...504..805S 1998ApJ...504..805S).
Note (2):
Y = Member;
? = Uncertain membership.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Laurent Cambresy [CDS] 17-Aug-2004