Einstein Observatory magnitude-limited X-ray survey of late-type giant and supergiant stars

1990 ◽  
Vol 348 ◽  
pp. 253 ◽  
Author(s):  
A. Maggio ◽  
G. S. Vaiana ◽  
B. M. Haisch ◽  
R. A. Stern ◽  
J. Bookbinder ◽  
...  
2013 ◽  
Vol 437 (1) ◽  
pp. 108-115
Author(s):  
E. Filippova ◽  
M. Revnivtsev ◽  
E. R. Parkin

1998 ◽  
Vol 188 ◽  
pp. 217-218 ◽  
Author(s):  
S. Hubrig ◽  
T. W. Berghöfer

In the ROSAT all-sky survey 11 HgMn stars were detected as soft X-ray emitters (Berghöfer, Schmitt & Cassinelli 1996). Prior to ROSAT, X-ray observations with the Einstein Observatory had suggested that stars in the spectral range B5-A7 are devoid of X-ray emission. Since there is no X-ray emitting mechanism available for these stars (also not for HgMn stars), the usual argument in the case of an X-ray detected star of this spectral type is the existence of an unseen low-mass companion which is responsible for the X-ray emission. However, this hypothesis is not easily testable. Based on high resolution X-ray images taken with the ROSAT HRI, Berghöfer & Schmitt (1994) showed that known visual late-type companions can be disregarded in this context. In almost all cases studied so far (including two HgMn stars in our sample) the X-ray emission is associated with the primary B star.


1994 ◽  
Vol 162 ◽  
pp. 200-201
Author(s):  
Thomas W. Berghöfer ◽  
Jürgen H. M. M. Schmitt

Extensive stellar surveys with the Einstein Observatory (Chlebowski et al., 1989) and with ROSAT have clearly confirmed the presence of stellar X-ray emission over nearly the whole range of the HR diagram. In the ROSAT all-sky survey data approximately 20000 stellar X-ray sources were detected (Schmitt et al., 1992). Most of these stellar X-ray emitters are low mass late-type stars, the origin of their X-ray emission is thought to be coronal.


1999 ◽  
Vol 512 (2) ◽  
pp. 874-891 ◽  
Author(s):  
K. P. Singh ◽  
S. A. Drake ◽  
E. V. Gotthelf ◽  
N. E. White
Keyword(s):  

1983 ◽  
Vol 71 ◽  
pp. 125-129
Author(s):  
P.C. Agrawal ◽  
A.R. Rao ◽  
B.V. Sreekantan

Flare stars are a group of mostly dMe stars, which show intense flaring activity in the optical as well as in the radio and X-ray bands. These stars are characterized by the presence of chromospheric emission lines like % and Call H and K which are present even during the quiescent state. The presence of transition regions and coronae have been inferred from the detection of UV emission lines like NV, CIV, SiIV etc. with IUE and X-ray observations made with the Einstein Observatory. We report here X-ray observations of flare stars made with Einstein to measure their coronal X-ray emission during the quiescent state.


1983 ◽  
Vol 101 ◽  
pp. 281-286
Author(s):  
L. A. Higgs ◽  
T. L. Landecker ◽  
F. D. Seward

The south-eastern portion of the supernova remnant G78.2+2.1, in Cygnus, has been detected as a weak X-ray source by the Einstein Observatory. The X-ray structure is similar to that of the radio filaments in this region, and confirms that X-ray emission in this portion of the “Cygnus super-bubble” does originate in a known supernova remnant. Marginally significant variations in X-ray hardness across the mapped area have been detected and can be related to known radio and optical features of the remnant. In its X-ray properties, G78.2+2.1 resembles IC443.


1983 ◽  
Vol 101 ◽  
pp. 205-211
Author(s):  
C. R. Canizares ◽  
P. F. Winkler ◽  
T. H. Markert ◽  
C. Berg

We review results obtained with the Focal Plane Crystal Spectrometer (FPCS) on the Einstein Observatory. Clear evidence is found for departures from ionization equilibrium in the interior of Puppis A. This comes from the observed weakness of the forbidden lines relative to the resonance lines for the He - like triplets of O VII and Ne IX. However, it is shown that this departure from equilibrium does not alter our conclusion, based on previous FPCS results, that O and Ne are overabundant relative to Fe. The spectrum of N132D shows strong O VIII emission and very weak Fe emission, suggesting an even greater O/Fe abundance enhancement than in Puppis A. In the Cygnus Loop, the O to Ne abundance ratio is approximately solar; we have no information about Fe. The O VII triplet shows clear evidence for departures from ionization equilibrium in the Cygnus Loop. The spectrum of Tycho's SNR contains lines from ionization stages of Fe XVII through Fe XXIII and XXIV, indicating that a wide range of ionization conditions are present. Cas A and Kepler's SNR show relatively less emission from the higher ionization stages. For Tycho, we measured the strength of the strong Si XIII lines, and we find that a many-fold overabundance of Si relative to Fe is required regardless of the equilibrium state of the emitting plasma (confirming the Solid State Spectrometer results). On a separate topic, the completed analysis of X-ray Doppler shifts in Cas A suggests that the emitting material is concentrated in a ring that is inclined to the line of sight and is expanding at ~5000 km s−1.


2004 ◽  
Vol 215 ◽  
pp. 292-293
Author(s):  
Stefano Covino ◽  
Gianpiero Tagliaferri ◽  
José Renan de Medeiros
Keyword(s):  

We present and discuss statistical relation between rotation and X-ray activity for giant and supergiant stars.”


1983 ◽  
Vol 71 ◽  
pp. 415-427 ◽  
Author(s):  
P.A. Charles

AbstractThe discovery of X-ray emission from RS CVn systems by HEAO-1 and subsequent surveys by the Einstein Observatory have shown that these close binaries exhibit greatly enhanced coronal activity. Here we review the 3 main observational areas: (1) results of the X-ray surveys of RS CVn systems and other late-type stars which indicate how the X-ray luminosity is correlated with the binary period (and hence stellar rotation) and other coronal activity indicators. This will be discussed in the context of scaled models of the solar corona; (2) X-ray spectroscopy of the most active systems which show multitemperature spectra and line emission consistent with solar abundances of the heavy elements; (3) observations of X-ray “flare-type” activity that has been associated with several RS CVn systems.


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