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 (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:
FileName Lrecl Records Explanations
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
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
Bytes Format Units Label Explanations
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  "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)
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) MT: McCarthy and Treanor (1964) (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) 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) 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) for more details.
Byte-by-byte Description of file: pleiad_2.dat
Bytes Format Units Label Explanations
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)
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.
Byte-by-byte Description of file: refs.dat
Bytes Format Units Label Explanations
1- 2 A2 --- code reference code 5- 80 A76 --- reftxt reference text
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
|The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line|