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 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:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
giants.dat 143 380 EO Survey of Late-type Giant and Supergiant Stars
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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
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Bytes Format Units Label Explanations
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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)
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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 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
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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 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 1982ApJ...262..682G)
3 Herbig, G. and Spalding, J. (1955ApJ...121..118H 1955ApJ...121..118H)
4 Gray, D.F. and Toner, C.G. (1986ApJ...310..277G 1986ApJ...310..277G)
5 Gray, D.F. and Nagar, P. (1985ApJ...298..756G 1985ApJ...298..756G)
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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