Optical study of F, G and K stars in the ROSAT all-sky survey [Elektronische Ressource] / vorgelegt von Agnès D.F. Metanomski

Sujets

• Astronomie

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• Publié par: ruprecht-karls-universitat_heidelberg
• Publié le: 01 janvier 2004
• Nombre de lectures: 15
• Langue: Deutsch
• Poids de l'ouvrage: 1 Mo

Extrait

INAUGURAL{DISSERTATION
zur
Erlangung der Doktorwurde
der
Naturwissentschaftlich{Mathematischen
Gesamtfakultat
der
Ruprecht{Karls{Universitat
Heidelberg
vorgelegt von
Dipl.{Phys. Agnes D.F. Metanomski
aus Paris
Tag der mundl. Prufung: 22. April 1998Optical study of F, G and K stars
in the ROSAT All-Sky Survey
Gutachter: Herr Prof. Dr. Joachim Krautter
Herr Prof. Dr. Reiner WehrseZusammenfassung
Ich untersuche eine Stichprobe von 107 Sudhimmels-Sternen von Spektraltyp
A bis K. Diese Sterne sind als die optischen Gegenstuc ke zu R ontgen-Quellen,
die der ROSAT Satellit w ahrend seines All-Sky Survey (RASS) entdeckte, iden-
ti ziert wurden. Die Untersuchung wird mit Hilfe optischen Beobachtungen,
sowohl photometrischer als auch spektroskopischer, durchgefuhrt. Verschiedene
Parameter werden fur die untersuchten Objekte bestimmt, wie z.B. Spektraltyp
und Leuchtkraftklasse, absolute Helligkeit, Entfernung, Radialgeschwindigkeit,
projezierte Rotationsgeschwindigkeit, E ektivtemp eratur, Lithium H au gk eit.
Ich vergleiche die R ontgen-Parameter meiner Stichproben-Sterne mit denen
aus einer ahnlic hen Stichprobe von Sternen, die vomEinstein Observatory w ahrend
dessen Medium Sensitivity Survey (EMSS) entdeckt wurden. Ich suche auch nach
Korrelationen zwischen verschiedenen Parametern, die fur meine Stichproben-
Sterne bestimmt wurden und vergleiche die Ergebnisse mit denen, die fur die
EMSS Stichprobe erhalten wurden, sowie mit den Ergebnissne anderer, fruherer
Studien.
Abstract
I analyze a sample of 107 southern stars of spectral types A to K, which
were identi ed as the optical counterparts of X-ray sources detected by ROSAT
during its All-Sky Survey. The study is conducted using optical observations,
photometric as well as spectroscopic (high-resolution). Various parameters are
determined for the sample objects, mainly spectral types and luminosity classes,
absolute magnitudes, distances, radial velocities, projected rotational velocities,
e ectiv e temperatures, Lithium abundances.
I compare the X-ray parameters of my sample stars with those of a similar
sample, detected by the Einstein Observatory during its Medium Sensitivity Sur-
vey (EMSS). I also look for correlations between the di eren t stellar parameters
determined for my sample, and compare those results to those obtained for the
EMSS sample, and also to some results obtained from other, earlier studies.Contents
1 Introduction 1
1.1 Stellar X-ray emission . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1.1 Pre-Einstein Era . . . . . . . . . . . . . . . . . . . . . . . 1
1.1.2 Einstein Era . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2 Results from the Einstein Observatory . . . . . . . . . . . . . . . 2
1.3 Dissertation project . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2 The ROSAT All-Sky Survey 7
2.1 The survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.2 The sample . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3 Observations 10
3.1 Photometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.2 High-resolution spectroscopy . . . . . . . . . . . . . . . . . . . . . 12
4 Analysis 14
4.1 Photometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
4.1.1 Spectral classi cation . . . . . . . . . . . . . . . . . . . . . 14
4.1.2 The (U B) colour index . . . . . . . . . . . . . . . . . . 14
4.1.3 E ectiv e temperature . . . . . . . . . . . . . . . . . . . . . 17
4.1.4 Absolute magnitude, distance and X-ray luminosity . . . . 18
4.1.5 Hipparcos data . . . . . . . . . . . . . . . . . . . . . . . . 20
4.2 Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
4.2.1 Radial and rotational velocity . . . . . . . . . . . . . . . . 20
4.2.2 Lithium abundance . . . . . . . . . . . . . . . . . . . . . . 25
5 Results 29
5.1 Distribution of spectral types . . . . . . . . . . . . . . . . . . . . 29
5.2 X-ray luminosity as a function of spectral type . . . . . . . . . . . 30
5.3 Luminosity function . . . . . . . . . . . . . . . . . . . . . . . . . 36
5.4 Distribution with distance . . . . . . . . . . . . . . . . . . . . . . 43
5.5 Lithium abundances . . . . . . . . . . . . . . . . . . . . . . . . . 53
5.6 Rotational velocity . . . . . . . . . . . . . . . . . . . . . . . . . . 59
6 Discussion 61
A X-ray data of the sample 70
B Stellar parameters 75C Spectroscopic Data 84
D Standards 89
E Northern Sample 95
2List of Figures
1.1 Representation of X-ray activity on the Hertzsprung-Russel diagram. 3
1.2 Comparison of the Einstein spectrum of Ori with the shock model
of Lucy (1982). The best t to the observations requires strong,
but infrequent shocks (image taken from Cassinelli and Swank 1983). 4
1.3 The relation between X-ray luminosity and projected rotation rate. 5
2.1 Schematic view of the ROSAT satellite and X-ray telescope. . . . 8
2.2 Location of the elds studied in the southern and northern identi-
cation programs. . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.1 Color-color plots for the southern sample. . . . . . . . . . . . . . . 15
4.2 Spectrum, solar template and cross-correlation function with t,
for a slow rotating single star, RXJ 1121.8-2411, v sin i = 5 km/s. . 21
4.3 Spectrum, solar template and function with t,
for a single fast rotator, RXJ 0135.8-3956, v sin i = 33 km/s. . . . 22
4.4 Spectrum, solar template and cross-correlation function with t,
for one of the triple systems in the sample, RXJ 2331.4-4209. . . . 23
4.5 The ts for the rotaional velocity determination. . . . . . . . . . . 24
4.6 Examples of synthetic spectra. . . . . . . . . . . . . . . . . . . . . 27
5.1 log(L =L ) vs. the (B V ) color index. . . . . . . . . . . . . . . 31X V
5.2 Luminosity distribution for the single stars and binaries. . . . . . 31
5.3y for the RASS sample, by spectral type. . 33
5.4 Luminosity for the RASS, EMSS and EXOSAT samples. 33
5.5y function for the RASS single stars and binaries. . . . . 37
5.6 Luminosity functions for the southern sample. . . . . . . . . . . . 37
5.7 X-ray luminosity as a function of distance for the RASS and EMSS
samples. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
5.8 Histrogram of the distance distribution for the RASS and EMSS
samples. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
5.9 Histogram of the distance for single stars and binaries. 45
5.10 Lithium abundances for single stars as a function of e ectiv e tem-
perature. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
5.11 Lithium for the binaries and multiple systems as a
function of e ectiv e temperature. . . . . . . . . . . . . . . . . . . 47
5.12 Lithium abundance vs rotational velocity. . . . . . . . . . . . . . . 47
5.13 vs X-ray luminosity for the single stars. . . . 49
5.14 Lithium abundance vs. rotational velocity for the single stars, by
spectral type. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
5.15 X-ray luminosity vs. rotational velocityfor the single stars. . . . . 51
5.16 X-rayy vs. velocity for the multiple systems. . 51
5.17 X-ray luminosity vs. radius. . . . . . . . . . . . . . . . . . . . . . 57List of Tables
3.1 Observing periods, for photometry. . . . . . . . . . . . . . . . . . 11
3.2 The ESO Cousins lters. . . . . . . . . . . . . . . . . . . . . . . . 11
3.3 The references used for the brightest sources in the sample. . . . . 11
3.4 Observing periods, for spectroscopy. The observing period be-
tween Sept. 23d abd 29th corresponds to reserved time for the 1.4
m CAT and CES. . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
4.1 The sources of the southern sample for which Hipparcos data was
found. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
5.1 Distribution of the X-ray sources among the spectral types studied,
for my sample, the EMSS sample (Stocke et al. 1991) and the
EXOSAT sample (Cutispoto et al. 1996) . . . . . . . . . . . . . . 29
25.2 Results of the tests for the X-ray luminosity distributions. . . . 36
25.3 of the tests for the distance distributions. . . . . . . . 44
5.4 Results of the correlation tests Pearson’s r and Spearman’s r testss
for the lithium abundance. . . . . . . . . . . . . . . . . . . . . . . 56
5.5 Results of the correlation tests Pearson’s r and Spearman’s r testss
for correlations between the X-ray luminosity and the rotational
velocity or the radius. . . . . . . . . . . . . . . . . . . . . . . . . . 59
A.1 ROSAT X-ray data for the sources in the studied southern sample. 71
B.1 Data for the counterparts of the sample sources. . . . . . . . . . . 76
C.1 Velocities, Li abundances for the southern hemisphere sample. . . 85
D.1 The photometric standards from the E-regions used in the pho-
tometry for the southern sample. Data from Vogt et al. (1981) . . 89
D.2 The open clusters used for standard stars in the photometry for
the northern sample. The standards from the clusters and their
colors are taken from: 1: Christian et al. (1985), 2: Odewahn et
al. (1992). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
D.3 The radial velocity standards used for the southern sample. The
standards were taken from 1: Duquennoy and Mayor (1991) 2:
The Astronomical Almanach (1996) .