J/ApJ/348/557 X-ray studies of stars in the Pleiades (Micela+, 1990)
X-ray studies of coeval star samples. II. The Pleiades cluster as observed with
the Einstein Observatory.
Micela G., Sciortino S., Vaiana G.S., Harnden F.R., Rosner R.,
Schmitt J.H.M.M.
<Astrophys. J. 348, 557 (1990)>
=1990ApJ...348..557M 1990ApJ...348..557M (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Stars, emission ; X-ray sources
Mission_Name: Einstein
Keywords: clusters: open - stars: rotation - stars: X-rays
Abstract:
Coronal X-ray emission of the Pleiades stars is investigated, and
maximum likelihood, integral X-ray luminosity functions are
computed for Pleiades members in selected color-index ranges. A
detailed search is conducted for long-term variability in the
X-ray emission of those stars observed more than once. An overall
comparison of the survey results with those of previous surveys
confirms the ubiquity of X-ray emission in the Pleiades cluster
stars and its higher rate of emission with respect to older
stars. It is found that the X-ray emission from dA and early dF
stars cannot be proven to be dissimilar to that of Hyades and
field stars of the same spectral type. The Pleiades cluster
members show a real rise of the X-ray luminosity from dA stars to
early dF stars. X-ray emission for the young, solar-like Pleiades
stars is about two orders of magnitude more intense than for the
nearby solar-like stars.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
pleiad_1.dat 110 283 EO Survey of the Pleiades: Optical Properties
and X-ray Luminosities
pleiad_2.dat 53 14 EO Survey of the Pleiades: Observation Parameters
refs.dat 80 34 Files with references
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See also:
J/ApJ/315/687 : X-Ray emission from solar-type stars: F and G
J/ApJ/348/253 : Einstein Survey of Late-type Giant and Supergiant Stars
J/ApJ/325/798 : Einstein Survey of Hyades-cluster Region
J/ApJ/351/492 : X-ray Emission in the Ursa Major Stream
Byte-by-byte Description of file: pleiad_1.dat
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Bytes Format Units Label Explanations
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2- 12 A11 --- Name Star name (1)
14- 15 I2 h RAh Right Ascension (B1950) (hour)
17- 18 I2 min RAm Right Ascension (B1950) (min)
20- 21 I2 s RAs Right Ascension (B1950) (sec)
23 A1 --- DE- Declination sign (B1950)
24- 25 I2 deg DEd Declination (B1950) (deg)
27- 28 I2 arcmin DEm Declination (B1950) (arcmin)
30- 31 I2 arcsec DEs Declination (B1950) (arcsec)
33- 37 F5.2 mag Vmag ?=99.99 Apparent Visual magnitude (2)
39- 41 A3 --- r_Vmag Reference for visual magnitude (3)
43- 47 F5.2 mag B-V B-V color index (2)
49- 58 A10 --- Sp Spectral type (2)
60- 64 A5 --- r_Sp ? Reference for spectral type (3)
66- 72 A7 km/s Vsini ? Equatorial (rotational) velocities along
line of sight (2)
74- 78 A5 --- r_Vsini ? Reference for vsini Comma separated
list (3)
80- 92 A13 --- notes Notes on the source (4)
94 A1 --- f_Lx [01] "1" if luminosity is an upper limit (5)
96-100 F5.2 [10-7W] Lx log of X-ray luminosity from 0.16-4.0 keV (5)
102-105 F4.1 % e_Lx Percentage-error on X-ray luminosity (5)
107-108 A2 --- flx_flg Flag indicating how flux was evaluated (6)
110 A1 --- reco [ Y] Ribs and Edge Code flag (7)
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Note (1): This column gives the star name(s), coded according to the
following conventions:
A: Asiago observatory flare stars
ALR: Ahmed, Lawrence and Reddish (1965)
B: Byurakan observatory flare stars
Hz: Hertzsprung (1947)
JRS: Stauffer (1984ApJ...280..189S 1984ApJ...280..189S)
MT: McCarthy and Treanor (1964) (1964RA......6..535M 1964RA......6..535M)
P: Pels (Quoted in van Leeuween, 1983)
van Leeuween, F. 1983, Ph.D. thesis, Leiden.
T: Tonantzintla flare stars (Cat.II/131)
VM: VanMaanen (1945ApJ...102...26V 1945ApJ...102...26V)
Note (2): These columns give the following optical properties of the stars:
the apparent visual magnitude, the B-V color index, the spectral
type, and the equatorial (rotational) velocity projected along
the line of sight. Optical properties are taken from the
literature (see references below). If a the spectral property or
rotational velocity is not known, a '...' appears as the entry in
the column.
Note (3): These columns list the reference used to obtain Vmag, Sp, and
Vsini.
Note (4): This column is for notes on the source. In particular, we have
noted when we believe a star is variable (var.) or binary (bin).
If there is no note on the source, a '...' appears as the entry
in the column.
Note (5): The "f_Lx" column is flagged with a "1" if the X-ray
luminosity is an upper limit. Upper limits given are 3-sigma
upper bounds for all members of the optical sample that fall
within 2' of the position of an object from the Einstein
Observatory master catalog (which includes ∼60 different
catalogs). The log of the X-ray luminosity from 0.16-4.0 keV is
presented in the "lx" column and the corresponding error (by
percentage) is listed in the "e_lx" column. If the luminosity is
an upper limit, the uncertainty is listed as 0.000.
Note (6): This column indicates how the X-ray flux is evaluated:
MB: from the "Map" cell count rate
LB: from the "Local" cell count rate
WM: from a weighted mean, for sources observed more than once
See the paper (1990ApJ...348..557M 1990ApJ...348..557M) for further details.
Note (7): This column is flagged "Y" if the X-ray luminosity is derived in
the presence of potential source shadowing. Reco is a ribs and
edge code, indicating that the source fell on or near the
detector ribs or edges. The local detect algorithm uses a
detection cell subdivided into nine central subcells (3x3) with a
background frame (around the central cell) subdivided into 16
subcells. The reco value provides an estimate of the number of
background and detection subcells potentially obscured and is
nonzero whenever a source could have any of its central or frame
subcells obscured. However, this approach necessarily employs
simplifying assumptions regarding the shape and dimensions of the
ribs, and it neglects spectral dependencies. Consequently,
although a quantitative attempt is made to correct for such
effects, the only completely reliable approach is to regard count
rates for sources with nonzero reco values (flagged "Y" here) as
indeterminate. See the paper (1990ApJ...348..557M 1990ApJ...348..557M) for more details.
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Byte-by-byte Description of file: pleiad_2.dat
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Bytes Format Units Label Explanations
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2- 6 I5 --- Seqno Sequence Number (1)
8- 9 I2 h RAh Right Ascension (B1950) (hour)
11-12 I2 min RAm Right Ascension (B1950) (min)
14-15 I2 s RAs Right Ascension (B1950) (sec)
17 A1 --- DE- Declination sign (B1950)
18-19 I2 deg DEd Declination (B1950) (deg)
21-22 I2 arcmin DEm Declination (B1950) (arcmin)
24-25 I2 arcsec DEs Declination (B1950) (arcsec)
27-38 A12 --- Date Observation Date (2)
40-43 F4.1 ks live Live Time (3)
45-53 A9 --- Obs Original Einstein Observer (2)
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Note (1): This column gives the Einstein "sequence" number of the field.
The sequence number is a two to five digit number which uniquely
identifies the observation. The numbers were assigned
sequentially at the time of proposal submission.
Note (2): These columns give the date of the observation and the original
obs of the field. The obs listed is from the "Yellow Book"
(Seward and Martenis, 1986).
Note (3): This column gives the observation live time, in kiloseconds. The
live time is the effective exposure time, a measure of the total
time the detectors were able to gather data. It excludes
intervals lost because of Earth occultation, because of passage
through the South Atlantic Anomaly, or because of unacceptable
aspect solution. The livetime has been corrected for detector
dead time, a fractional correction for the time during which the
detector is unable to record events because it is "processing" a
prior event.
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- code reference code
5-80 A76 --- reftxt reference text
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History:
Prepared from the tables available at the "ADS Catalogue Service"
(CfA, Harvard-Smithsonian Center for Astrophysics, Cambrigde MA)
References:
Ahmed, F., Lawrence, L., and Reddish, V.C. 1965, Pub. Roy. Obs. Edinburgh,
Vol. 1, No. 7.
Hertzsprung, E. 1947, Ann. Leiden Obs., Vol. 19, Pt. 1A.
McCarthy, M.F. and Treanor, P.S. 1964, Ric. Astr., 6, 535.
Seward, F.D. and Martenis, P. 1986, Einstein Observatory Catalog of
Observations (the "Yellow Book"; 5th ed.; Cambridge: Harvard-Smithsonian
Center for Astrophysics).
van Leeuween, F. 1983, Ph.D. thesis, Leiden.
(End) Patricio Ortiz [CDS] 31-Mar-1999