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J/ApJ/325/798  Einstein survey of stars in the Hyades       (Micela+, 1988)

The Einstein Observatory survey of stars in the Hyades cluster region. Micela G., Sciortino S., Vaiana G.S., Schmitt J.H.M.M., Stern R.A., Harnden F.R.Jr, Rosner R. <Astrophys. J. 325, 798 (1988)> =1988ApJ...325..798M (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Stars, emission ; X-ray sources Mission_Name: Einstein Keywords: clusters: open stars ; stars X-rays Abstract: The paper reports the results of an extensive X-ray study of the Hyades region and improves on previous studies by using refined X-ray source detection algorithms and the complete set of Einstein Observatory IPC exposures covering the Hyades cluster region (a total of 63 1 x 1 deg images). Maximum likelihood integral X-ray luminosity functions were computed for the Hyades stars for given color index (B-V) ranges. The present results agree substantially with a previous survey about the ubiquity of the stellar activity in the Hyades cluster, especially among solar-type stars. The result of Stern et al. (1981ApJ...249..647S) that stellar X-ray emission is dependent on stellar age is confirmed. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file hyades_1.dat 61 63 EO Survey of Hyades Region: Observation Parameters hyades_2.dat 241 131 EO Survey of Hyades Stars: Optical Properties and X-ray Luminosities refs.dat 80 40 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/348/557 : Einstein Survey of the Pleiades Cluster J/ApJ/351/492 : X-ray Emission in the Ursa Major Stream Byte-by-byte Description of file: hyades_1.dat
Bytes Format Units Label Explanations
2- 6 I5 --- Seqno Sequence number (1) 8 A1 --- f_Seqno [ a] "a" indicates data is merged (1) 10- 11 I2 h RAh Right Ascension (B1950) (hour) 13- 14 I2 min RAm Right Ascension (B1950) (min) 16- 20 F5.2 s RAs Right Ascension (B1950) (sec) 22 A1 --- DE- Declination sign (B1950) 23- 24 I2 deg DEd Declination (B1950) (deg) 26- 27 I2 arcmin DEm Declination (B1950) (arcmin) 29- 32 F4.1 arcsec DEs Declination (B1950) (arcsec) 34- 44 A11 "MMM:DD:YYYY" StartDate Start of observation (2) 46- 56 A11 "MMM:DD:YYYY" StopDate End of observation (2) 58- 61 F4.1 ks livetime Live time of observation (3)
Note (1): The first column gives the IPC sequence number, a two to five digit number which uniquely identifies the observation. The numbers were assigned sequentially at the time of proposal submission. The 'f_Seqno' is flagged with an "a" if the data has been merged from data acquired at epochs spanning months. It is blank otherwise. Note (2): The start and stop date of the observation are given in these columns in the form: month-day-year. Note (3): This column gives the observation livetime, in kiloseconds. The livetime 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: hyades_2.dat
Bytes Format Units Label Explanations
2- 89 A88 --- Name Star name (1) 91- 92 I2 h RAh Right Ascension (B1950) (hour) 94- 95 I2 min RAm Right Ascension (B1950) (min) 97- 98 I2 s RAs Right Ascension (B1950) (sec) 100 A1 --- DE- Declination sign (B1950) 101-102 I2 deg DEd Declination (B1950) (deg) 104-105 I2 arcmin DEm Declination (B1950) (arcmin) 107-108 I2 arcsec DEs Declination (B1950) (arcsec) 110-114 F5.2 mag Vmag Apparent visual magnitude (2) 116-120 F5.2 mag B-V B-V color index (2) 122 I1 --- r_B-V ? Reference for mv and/or B-V (2) 124-135 A12 --- Sp Spectral type (3) 137-142 A6 --- r_Sp Reference for spectral type, comma separated (3) 144-154 A11 km/s Vsini Equatorial (rotational) velocities along line of sight (more than one value) (4) 156-169 A14 --- r_Vsini Reference for vsini. comma separated list (4) 171-206 A36 --- Notes Notes 208 A1 --- status [AB] "A" if Certainty about Hyades membership; "B" if "Potential" (9) 210-218 A9 --- VName Star name (first name found in Name) (1) 220 A1 --- f_Lx [01] Flagged "1" if Lx is an upper limit (5) 222-228 E7.2 10-7W Lx X-ray luminosity from 0.16-4.0 keV (6) 230-236 E7.2 10-7W e_Lx Error for luminosity (6) 238-239 A2 --- flux_flg Flag indicating how flux was evaluated (7) 241 A1 --- reco Ribs and Edge Code flag (8)
Note (1): This column lists the star name. We use the following naming conventions. EG -- Eggen and Greenstein (1965ApJ...141...83E, 1965ApJ...142..925E) GH -- Gichas, et al. (1962) GY -- Gyllenberg (1931) H -- Hanson (1975AJ.....80..379H) Ho -- Holmberg (1944) Hz -- Hertzsprung (1947) HTK -- Luyten as quoted by Herbig (1962) HZ -- Humason and Zwicky (1947ApJ...105...85H) J -- Johnson, et al. (1962ApJ...136...75J) KA -- Kapteyn and de Sitter (1904) L -- Pels, et al. (1975A&A....43..423P) LP -- Luyten, et al. (1981) MLC -- Murray, et al. (1966) O -- Osvald (1954) Ra -- Ramberg (1941) VA -- van Altena (1969AJ.....74....2V) VB -- van Bueren (1952) VR -- van Rhijn and Raymond (1934) VYS -- Vyssotsky (1956AJ.....61..201V) WOR -- Worley (1962AJ.....67..396W) Note (2): These columns give the apparent visual magnitude, the B-V color, and the reference for mv and/or B-V. Note (3): These columns give the spectral type and the reference for the spectral type. This is a comma separated list, an asterisk '*' indicates that Spectral types computed from Color Index or rotational velocity inferred from modulation of chromospheric emission. Note (4): These columns give the equatorial rotational velocity, projected along the line of sight, and the reference for the rotational velocity. Note (5): This 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) and Herbig and Rao (1972ApJ...174..401H). Note (6): The X-ray luminosity from 0.16-4.0 keV is presented in the "Lx" column and the corresponding statistical uncertainties in the "e_Lx" column (one sigma). If the luminosity is an upper limit, the uncertainty is listed as 0.000. The conversion factor from count rate to luminosity, assuming a common distance of 45 parsecs (Hanson 1975AJ.....80..379H) for all cluster members, is 4.860 *1030 ergs/count. The estimated overall error in the X-ray luminosities is a factor of ∼2 and consists of statistical errors (less than 40% for the 2.5 sigma sources), systematic errors in instrument calibrations (≲10%, Harnden, et al. 1984), errors due to the individual cluster member distance (<100%), and systematic errors in converting count to flux due to the assumed source temperature (≲40%). Note (7): This column indicates how the flux was calculated. We use the following abbreviations: MB = from "Map" cell count rate, increased by 25% LC = from "Local" count rate in a 3'-radius circle LB = from "Local" cell count rate, increased by 25% WM = weighted mean for source observed more than once Count rates were increased by 25% before their conversion to flux when they were partially obscured and detected with the "map" method or when they were detected only with the "map" method. They were also increased by 25% for upper limits. See the appendices of the paper for complete details. Note (8): 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 appendix A of the paper for more details. Note (9): The "status" column lists an "A" if the star is one of the 121 "Certain" Hyades members, or a "B" if the star is one of 10 "Potential" Hyades members whose Hyades membership has been rejected by Hanson (1975AJ.....80..379H).
Byte-by-byte Description of file: refs.dat
Bytes Format Units Label Explanations
1- 2 I2 --- code reference code 5- 80 A76 --- reftxt bibcode (if any) and reference text
History: Prepared from the tables available at the "ADS Catalogue Service" (CfA, Harvard-Smithsonian Center for Astrophysics, Cambrigde MA) References: Blanco, V.M., Demers, S., Douglass, G.C., and Fitzgerald, M.P. 1970, U.S. Naval Observatory Photoelectric Catalog (USNO Pub., Vol. 21). Buscombe, W. 1977, MK Spectral Classifications. Third General Catalogue (Evans ton: Northwestern University). Buscombe, W. 1980, MK Spectral Classifications. Fourth General Catalogue (Evanston: Northwestern University). Buscombe, W. 1981, MK Spectral Classifications. Fifth General Catalogue (Evanston: Northwestern University). Cowley, A., et al. 1969, A.J., 141, 83. Gichas, H., Burnham, R., Jr., and Thomas, N. 1962, Lowell Obs. Bull., 5, 257. Gyllenberg, W. 1931, Medd. Lund. Astr. Obs., Ser. II, No. 57 Harnden,, F.R., Jr., Fabricant, D.G., Harris, D.E., and Schwarz, J. 1984, Smithsonian Ap. Obs. Spec. Rept., No. 393. Hoffleit, D. and Jasheck, C. 1982, The Bright Star Catalogue (New Haven: Yale University Observatory). Cat. V/50 Hoffleit, D., Saladiga, M., and Wlansk, P. 1984, A Supplement to the Bright Star Catalogue (New Haven: Yale University Observatory). Cat. V/36 Holmberg, E. 1944, Lund. Medd., Ser. II, No. 113. Hertzsprung, E. 1947, Leiden Ann., 19, Pt. 1A. Kapteyn, J.C. and de Sitter, W. 1904, Pub. Kapteyn Astr. Lab. Groningen, No 14. Luyten, W.J., Hill, G., and Morris, S. 1981, Proper Motion Survey With The 48-I nch Schmidt Telescope. LIX. A Catalogue of 929 Possible Candidates for Hyades Membership (Minneapolis: University of Minnesota). Murray, C.A., Lowne, C.M., and Clements, E.D. 1966, Roy. Obs. Bull., No. 108. Osvald, V.V. 1954, Astr. Nach., 281, 193. Pesch, P. 1968, Ap.J., 151, 605. Ramberg, J.M. 1941, Stockhold Ann., 13, No. 9. Stern, R.A., Underwood, J.M., and Antiochos, S.C. 1983, in Second Workshop on Cool Stars Stellar System and the Sun, ed. M.S. Giampapa and L. Golub, Smithsonian Ap. Obs. Spec. Rept. No. 392), Vol. 2, p. 101. van Bueren, H.G. 1952, Bull. Astr. Inst. Netherlands, 11, 385. van Rhijn, P.J. and Raymond, J.J 1934, Pub. Kapteyn Astr. Lab. Groningen, No. 35.
(End) Patricio Ortiz [CDS] 31-Mar-1999
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