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J/ApJ/348/253  Late type giants and supergiants in X-Ray     (Maggio+, 1990)

EINSTEIN Observatory magnitude-limited X-ray survey of late-type giant and supergiant stars. Maggio A., Vaiana G.S., Haisch B.M., Stern R.A., Bookbinder J., Harnden F.R.Jr, Rosner R. <Astrophys. J. 348, 253 (1990)> =1990ApJ...348..253M (SIMBAD/NED BibCode)
ADC_Keywords: Stars, giant ; Stars, supergiant; Stars, atmospheres ; X-ray sources Mission_Name: Einstein Keywords: stars: coronae - stars: X-rays - X-rays: sources Abstract: Results are presented of an extensive X-ray survey of 380 giant and supergiant stars of spectral types from F to M, carried out with the Einstein Observatory. It was found that the observed F giants or subgiants (slightly evolved stars with a mass M less than about 2 solar masses) are X-ray emitters at the same level of main-sequence stars of similar spectral type. The G giants show a range of emission more than 3 orders of magnitude wide; some single G giants exist with X-ray luminosities comparable to RS CVn systems, while some nearby large G giants have upper limits on the X-ray emission below typical solar values. The K giants have an observed X-ray emission level significantly lower than F and F giants. None of the 29 M giants were detected, except for one spectroscopic binary. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file giants.dat 143 380 EO Survey of Late-type Giant and Supergiant Stars
See also: J/ApJ/315/687 : X-Ray emission from solar-type stars: F and G J/ApJ/325/798 : Einstein Survey of Hyades-cluster Region 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: giants.dat
Bytes Format Units Label Explanations
2- 5 I4 --- HR ?=0 HR (Bright Star Catalog) number (1) 7- 12 I6 --- HD HD (Henry Draper Catalog) number (1) 14- 26 A13 --- Name Other name (1) 28- 44 A17 --- Sp Spectral Type (2) 46 A1 --- class [GS] Giant/Supergiant Luminosity Class (2) 48- 52 F5.2 mag B-V ?=99.9 B-V color index (3) 54- 58 F5.2 mag Vmag Visual magnitude (apparent) (3) 60- 63 F4.1 mag Mabs ?=99.9 Absolute magnitude (3) 65- 70 F6.3 arcsec plx ?=99.99 Trigonometric Parallax (4) 72 A1 --- mult [SMVR] Single/Multiple System Classification (5) 74 A1 --- f_Vmag [* ] "*" indicates star with Vmag < 6.3 (5) 76- 80 I5 --- Seqno IPC sequence number (6) 82- 84 A3 --- obscode Observer code (7) 86 I1 --- nobs Number of observations (8) 88 A1 --- f_fx [01] "1" if flux is an upper limit (9) 90- 95 F6.1 10-16W/m2 fx X-ray Flux in the 0.16-4.0 keV band (10) 97-100 F4.1 10-16W/m2 e_fx Error on X-ray Flux (10) 102 A1 --- f_fx/fv [01] "1" if fx/fv is an upper limit (9) 104-107 F4.1 --- fx/fv log of X-ray to visual flux ratio (11) 109 A1 --- f_logLx [01] "1" if logLx is an upper limit (9) 111-114 F4.1 [10-7W] logLx Log of X-ray Lum. in the 0.16-4.0 keV band (12) 116 A1 --- l_Vsini [ <] Upper limit flag to Vsini (13) 117-122 A6 km/s Vsini ? Rotational velocity (13) 124 I1 --- r_Vsini Reference for rotational velocity (13) 126-127 I2 h RAh Right Ascension (B1950) (hour) 129-130 I2 min RAm Right Ascension (B1950) (min) 132-133 I2 s RAs Right Ascension (B1950) (sec) 135 A1 --- DE- Declination sign (B1950) 136-137 I2 deg DEd Declination (B1950) (deg) 139-140 I2 arcmin DEm Declination (B1950) (arcmin) 142-143 I2 arcsec DEs Declination (B1950) (arcsec)
Note (1): These columns give the HR (Bright Star Catalog) number, the HD (Henry Draper Catalog) number, and other name of the star. A single five or six digit number in the "Name" column indicates the SAO Catalog number. Note (2): These columns give the spectral type and optical class of the star. A "G" in the "class" column indicates that the star is a Giant (luminosity classes III-IV, II, and II-III). An "S" in the "class" column indicates that the star is a Supergiant (luminosity classes II, II-I, and I). Note (3): These columns give optical information about the star; the B-V color index, apparent visual magnitude, and absolute magnitude are listed. Unknown values are set to 99.9 Note (4): This column gives the trigonometric parallax, in arcseconds. Unknown values are set to 99.99 Note (5): The "mult" column classifies a source as single ("S"), multiple ("M"), or RS CVn-like ("R"). An asterisk ("*") flags the star (in the "f_Vmag" column) as having mv < 6.3. The importance of careful discrimination between single stars and multi-component systems is clear if one wants to use the luminosity or rotational velocity with confidence. It is possible that more of the objects may belong in the RS CVn category, but further observations are needed to confirm this. We have classified a system as multiple if one of the following is indicated: (a) confirmed or suspected spectroscopic binaries (88 objects), (b) stars with either a physical or visual companion nearer than 2' (56 objects), because of the photon collecting area we used (see Maggio, et al. 1990ApJ...348..253M for details), (c) stars with variable radial velocity, unless a companion is known at more than 2' (32 objects), (d) 10 more objects with three or more components for which we cannot judge the distance of the nearest companion. Note (6): The "Seqno" column gives the Einstein sequence number, a two to five digit number which uniquely identifies the observation. The numbers were assigned at the time of proposal submission. Note (7): The observer listed in this column is the observer code from the "Yellow Book" (Seward and Martenis), the corresponding names are listed below. Observer Code Observers ------------- --------- S Serendipitous CfA stellar survey 0 Harvard-Smithsonian Center for Astrophysics stellar team 1 Columbia Astrophysical Laboratory 2 MIT 3 Goddard Space Flight Center 34 J. Nelson and F. Cordova, U. of California, Berkeley 54 C. Bowyer, F. Walter, and P. Charles, U. of California, Berkeley 97 R. Stern, J. Underwood, and S. Antiochos, JPL 99 C. Zwaan, A. Brinkman, and R. Mewe, Sonnenborgh Obs. 128 T. Ayres, B. Haisch, and J. Linsky, U. of Colorado 179 T. Snow and W. Cash, U. of Colorado 208 J. Linsky and T. Ayres, U. of Colorado 222 C. Bowyer and F. Walter, U. of California, Berkeley 227 H. Zirin, Hale Observatory 254 J. Linsky, R. Stencel, and G. Basri, U. of Colorado 255 G. Wallerstein and L. Willson, U. of Washington 265 D. Gibson, New Mexico Tech 288 S. Catalano, C. Blanco, E. Marilli, G. Peres, and S. Serio, U. of Catania 322 H. Johnson, Lockheed Research Laboratory 341 B. Haisch and T. Simon, Lockheed Research Laboratory 381 L. Hartmann and A. Dupree, Harvard College Obs. 385 C. Zwaan, A. Boggende, A. Brinkman, and R. Mewe, Sonnenborgh Observatory 398 A. Michalitsianos, M. Kafatos, and R. Hobbs, Goddard Space Flight Center 427 G. Riegler, R. Stern, and J. Underwood, JPL 445 C. Bowyer, F. Walter, and P. Charles, U. of California, Berkeley 449 T. Simon, R. Stencel, M. Giampapa, and J. Linsky, U. of Colorado 480 C. Bowyer, B. Bopp, and F. Walter, U. of California, Berkeley 501 E. Bohm-Vitense and S. Parson, U. of Heidmann, NRAO-VA 519 R. Stern, J. Underwood, and S. Antiochos, JPL 626 T. Simon and R. Stencel, U. of Colorado 994 H. Johnson, Lockheed Research Laboratory Note (8): The "nobs" column lists the total number of observations for each star. In the case of multiple observations we quote, for conciseness, only the sequence with the longest exposure time. Note (9): These columns are marked with a one ("1") if the quantities which follow (the X-ray flux density, the log of fx/fv, and the X-ray luminosity) are upper limits. 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). Only three multiply-observed stars failed to be detected in each repeated exposure: for these three stars, the derived upper limits are consistent with the X-ray fluxes derived from the detections. Note (10): These columns list the X-ray flux density (* E-13 erg/cm2/s) at the Earth and the corresponding statistical errors. X-ray fluxes were computed at Earth in the energy range 0.16-4.0 keV, using a constant conversion factor of 2.0E-11 erg/ct/cm2 times the IPC count rate. This value assumes a thermal spectrum (continuum + lines), from a plasma with solar abundances at a temperature log T=6.5. In computing an effective count rate for each source, the standard Rev-1 processing applies corrections, for mirror scattering and vignetting and for the IPC point response, and flags possible shadowing by the support structure of the IPC entrance aperture through the use of a so-called rib and edge code. However, due to a spectral dependence of these corrections (especially the point response correction), they are only approximate for sources whose spectra are dissimilar to those assumed in computing the corrections. Because the detection cell for the broad band is relatively small for the rather soft stellar sources, only ∼70% of stellar source counts fall inside the cell, a fraction about 25% smaller than assumed in computing the standard correction factors. Therefore, for local, obscured X-ray detections, and for all map detections, we have increased the standard (corrected) values by this factor of ∼25%, and for all local, unobscured X-ray detections we have computed net source counts from a circle of 3' radius centered at the source position and background counts in a concentric annulus width inner and outer radii of 5' and 6'. This same 25% correction has been applied to the upper bounds (which are only evaluated using the local method). When more than one observation was available for a given star, we adopted the following procedure (see Micela, et al. 1988ApJ...325..798M for details): 1. For detections, we computed a weighted (by inverse square of statistical error) mean count rate, preferring unobscured measurements to those for which shadowing was possible. 2. For upper bounds, we selected the lowest unobscured value, if available, and otherwise conservatively retained the largest value. Taking into account a conversion factor error of ∼50%, statistical errors of ≲40%, and systematic errors in the instrument calibrations of ≲10%, we estimate the overall error in the quoted X-ray fluxes to be ≲70%. Note (11): This column lists the log of the X-ray to visual flux ratio, computed as log fx/fv = log fx + mv/2.5 + 5.47 This distance- and radius-independent parameter is very useful in our survey because of the large percentage of stars with unknown parallax. Note (12): This column gives the log of the X-ray luminosity. In the computation of luminosities, a large source of error can be introduced by uncertainties in the individual stellar distances (as much as a factor of 2 or more); for this reason, we have computed X-ray luminosities only for stars with available trigonometric parallaxes greater than 0.01. Note (13): These columns list the radial velocity, when available, and the reference from which the radial velocity was taken. Upper limits are denoted by a '<' in the column 'l_Vsini'. The used references are: 1 Hoffleit, D. and Jaschek,C. 1982, The Bright Star Catalogue (New Haven: Yale University Press). (See Cat. V/50) 2 Gray, D.F. (1982ApJ...262..682G) 3 Herbig, G. and Spalding, J. (1955ApJ...121..118H) 4 Gray, D.F. and Toner, C.G. (1986ApJ...310..277G) 5 Gray, D.F. and Nagar, P. (1985ApJ...298..756G)
History: Prepared from the tables available at the "ADS Catalogue Service" (CfA, Harvard-Smithsonian Center for Astrophysics, Cambrigde MA)
(End) Patricio Ortiz [CDS] 21-Apr-1999
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