scholarly journals X-ray observations of symbiotic stars

1982 ◽  
Vol 70 ◽  
pp. 115-116
Author(s):  
David A. Allen
Keyword(s):  
Steady State ◽  
Proportional Counter ◽  
White Dwarfs ◽  
Symbiotic Stars ◽  
X Ray ◽  
The Past ◽  
Accretion Process ◽  
Einstein Observatory

AbstractObservations are reported of 19 symbiotic stars made with the imaging proportional counter of the Einstein Observatory. Three of the objects (HM Sge, V 1016 Cyg and RR Tel) were detected as soft X-ray sources. All three have shown slow-nova eruptions in the past 40 years. The data are interpreted as support of a model for slow novae involving thermonuclear events on white dwarfs which accrete from M giant companions. Symbiotic stars in their steady state, not being detected X-ray sources, are presumed to be powered by the accretion process alone.

scholarly journals X-Ray Sources of Cosmological Relevance

1983 ◽  
Vol 104 ◽  
pp. 7-18
Author(s):  
T. Maccacaro ◽  
I. M. Gioia
Keyword(s):  
Proportional Counter ◽  
Extragalactic Astronomy ◽  
X Ray ◽  
Einstein Observatory

The imaging and spectroscopic instruments onboard the Einstein Observatory (Giacconi et al. 1979) have been extensively used to study in detail the X-ray properties of a large variety of astronomical objects. In this paper we will briefly discuss some of the most relevant results on extragalactic astronomy obtained mainly with the Imaging Proportional Counter (IPC).

scholarly journals Time Resolved Circular Polarimetry of White Dwarf Pulsars

1982 ◽  
Vol 69 ◽  
pp. 399-401
Author(s):  
W. Krzeminski ◽  
J.D. Landstreet ◽  
I. Thompson
Keyword(s):  
Orbital Period ◽  
White Dwarf ◽  
White Dwarfs ◽  
Radiation Mechanisms ◽  
Time Resolved ◽  
X Ray ◽  
Rotation Periods ◽  
Accretion Process ◽  
Cataclysmic Binaries ◽  
Synchronous Rotation

There are two recognized subsets of cataclysmic binaries that contain white dwarfs: the AM Her stars, whose white dwarf components are sufficiently magnetized to ensure synchronous rotation with the orbital period, and the DQ Her stars, which do not maintain synchronism and probably have been spun up by mass accretion. Both groups of stars, recognized also as X-ray sources, are important as probes of the accretion process, and the radiation mechanisms in the vicinity of the white dwarf. So far, we know five objects belonging to the former group (AM Her, AN UMa, VV Pup, 2A 0311-227, and PG 1550+191), and seven falling into the latter: WZ Sge, AE Aqr, V533 Her, DQ Her, V1223 Sgr, H2252-035, and EX Hya, with the corresponding rotation periods of their white dwarf primaries of 28, 33, 64, 71, 794, 805, and 4020 s, respectively. While the main observational and theoretical efforts have been focussed on the AM Her class, the DQ Her binaries have been investigated to much lesser extent. This is probably because the DQ Her stars have been recognized only very recently as a homogeneous class.

scholarly journals Small-Scale Fluctuations and Anisotropies in the 1–3 keV X-Ray Background

1990 ◽  
Vol 139 ◽  
pp. 408-409
Author(s):  
X. Barcons ◽  
A. C. Fabian
Keyword(s):  
Spatial Distribution ◽  
Probability Distribution ◽  
Proportional Counter ◽  
Flux Distribution ◽  
Small Scale ◽  
X Ray ◽  
Deep Survey ◽  
X Ray Background ◽  
Einstein Observatory ◽  
Source Number

The spatial distribution of the 1–3 keV X-ray background (XRB) in five Einstein Observatory Imaging Proportional Counter fields has been analyzed. The autocorrelation function does not exceed 9% on scales ~5′. The observed count probability distribution is then used to check the source number-flux distribution at faint levels. Agreement with the Einstein Observatory deep survey is obtained. A cutoff in the number-flux distribution for a Euclidean population of sources at a flux approximately one-half of the deep survey limit, previously suggested by Hamilton and Helfand (1987), is also inferred.

X-ray observations of LMC X-3 with the monitor proportional counter aboard the HEAO 2 Einstein observatory - A comparison with Cygnus X-1

1983 ◽  
Vol 274 ◽  
pp. L65 ◽  
Author(s):  
M. C. Weisskopf ◽  
W. A. Darbro ◽  
R. F. Elsner ◽  
A. C. Williams ◽  
S. M. Kahn ◽  
...  
Keyword(s):  
Proportional Counter ◽  
X Ray ◽  
Einstein Observatory

scholarly journals X-Ray Observations of M87’s Halo

1980 ◽  
Vol 5 ◽  
pp. 689-693
Author(s):  
D. Fabricant ◽  
M. Lecar ◽  
P. Gorenstein
Keyword(s):  
Proportional Counter ◽  
Total Mass ◽  
Precise Determination ◽  
Virgo Cluster ◽  
Field Of View ◽  
Two Dimensional ◽  
X Ray ◽  
Einstein Observatory ◽  
Extended Emission

We briefly describe the soft X-ray image of M87 obtained using the imaging proportional counter aboard the Einstein Observatory. These data provide further strong evidence for the existence of a massive halo of dark matter surrounding M87 and allow a much more precise determination of its mass. Two pointing positions of the satellite were analyzed; one centered on M87, the other 63’ south and 25’ east of M87. The field of view of the imaging proportional counter is 60’ × 60’, and it attains a two dimensional spatial resolution of ˜ 1.5’ in a spectral range spanning 0.1 to 4.5 keV.As previous reports had suggested (Gorenstein et al. 1977; Fabricant et al. 1978), the present observations show M87 to be a strong, very extended, thermal X-ray source with a temperature near 2 keV, surrounded by weaker and still more extended emission from hotter gas associated with the Virgo cluster as a whole (Davison, 1978; Lawrence, 1978). We find M87 to have a total 0.5-4.5 keV X-ray luminosity of about 2 × 1043 ergs/sec, and an extrapolated 2-6 keV luminosity of approximately 1 × 1043 ergs/sec. The total mass of gas inferred from the X-ray measurement exceeds 1012 solar masses.

X-Ray Observations of Supernova Remnants from the Einstein Observatory

1980 ◽  
Vol 4 (1) ◽  
pp. 4-8 ◽  
Author(s):  
Ian R. Tuohy
Keyword(s):  
Supernova Remnants ◽  
X Ray ◽  
The Past ◽  
Optical Wavelengths ◽  
Einstein Observatory

The most extensive studies of supernova remnants (SNRs) in the past have taken place at radio and optical wavelengths.

scholarly journals Recent X-Ray Observations of Seyferts and Emission-Line Galaxies

1980 ◽  
Vol 5 ◽  
pp. 641-651 ◽  
Author(s):  
R. E. Griffiths
Keyword(s):  
Average Error ◽  
X Ray ◽  
The Past ◽  
Sky Survey ◽  
Emission Line Galaxies ◽  
Modulation Collimator ◽  
Using Data ◽  
Seyfert Nucleus ◽  
Einstein Observatory

It has been just a few years since Type 1 Seyferts were established as a class of X-ray sources with luminosities in the range 1042 - 1045 ergs s-1 by Elvis et al. (1978) using data from the sky survey instrument on Ariel V, and by Tananbaum et al. (1978) using data from UHURU.The average error-box sizes for X-ray sources identified with Type 1 Seyferts in the 2A catalog (Cooke et al. 1978) is ˜ 0.4 sq. degrees, and ˜ 1.0 sq. degrees for those in the 4U catalog (Forman et al. 1978). Improvement in these positions has been made over the past two years by the modulation collimators on board the satellites SAS-3 and HEAO-1. In particular, the HEAO-1 scanning modulation collimator has been used to position a total of 20 X-ray sources, confirming the identification in each case, with the possible exception of Mkn 279 (Dower et al. 1979, Griffiths et al. 1979a). Of the 37 X-ray sources which were discovered prior to the launch of the Einstein Observatory and which have been associated with Type 1 Seyferts, 21 have been positioned to ˜ 1 arc minute, representing an improvement by factors of ˜ 20 to 100 over the previous 2A and 4U error box sizes. Some examples of the error boxes and identifications confirmed with the HEAO-1 scanning modulation collimator are shown in figs. 1 and 2. In fig. 1 both NGC 7213 (Philips 1979) and MCG - 2 - 58 - 22 (Ward et al. 1978) were discovered to be Seyferts by optical spectroscopy of candidate objects in the error regions of the corresponding X-ray sources. NGC 7213 is a Seyfert nucleus in a galaxy of Type SO (Philips 1979). In fig. 2, NGC 931 was likewise discovered to be a Seyfert as a result of its X-ray emission (Ward and Wilson 1978).

scholarly journals X-Ray Variability of the O Star ζ Puppis

1999 ◽  
Vol 169 ◽  
pp. 203-205
Author(s):  
Thomas W. Berghöfer
Keyword(s):  
Steady State ◽  
Numerical Simulations ◽  
Two Dimensions ◽  
Stellar Winds ◽  
Dynamical Processes ◽  
X Ray ◽  
Hot Gas ◽  
Wind Flows ◽  
Einstein Observatory

X-ray surveys carried out with the Einstein Observatory (Chlebowski et al. 1989) and ROSAT (Berghöfer et al. 1996) have shown that all O stars are soft X-ray emitters. Since O star winds are opaque at soft X-ray energies the stars or their photospheres cannot be the origin of the observed X-ray emission, thus, this emission must be produced in their stellar winds. Obviously, the X-ray emission is connected to dynamical processes present in the winds of O stars; steady-state computations for O star winds which are able to explain many of the observational features cannot predict any X-ray emission.Lucy & White (1980) suggested the presence of hot gas in the stellar winds which is produced in shocks developing from the growth of instabilities in the winds; supersonic wind flows in O stars are known to be intrinsically unstable. Numerical simulations confirmed this scenario. However, so far these simulations are limited to one or two dimensions and are not able to explain for instance the observed X-ray luminosity of O stars.

scholarly journals Review of Recent Observations of Cluster X-Ray Sources Using the Einstein Observatory

1980 ◽  
Vol 5 ◽  
pp. 727-734
Author(s):  
Stephen S. Murray
Keyword(s):  
Energy Resolution ◽  
Proportional Counter ◽  
Field Of View ◽  
Clusters Of Galaxies ◽  
X Ray ◽  
Moderate Energy ◽  
Einstein Observatory

In this contribution I shall review briefly some of the recent research being carried out at the Harvard-Smithsonian Center for Astrophysics in the study of X-ray emission from clusters of galaxies. This work is being done by several of us at CFA, and I particularly wish to thank Drs. Christine Jones, William Forman, and J. Patrick Henry for permission to discuss their results. The data have been obtained from the Einstein X-ray Observatory (HEAO-2) using the imaging instruments, and in particular the Imaging Proportional Counter (IPC). This gives X-ray images with about l½ arc minute resolution over a field of view of ½° × ½° and moderate energy resolution over a band from 0.5 to 3.0 keV. (For further details see Giacconi et al. 1979).

X-ray observations of GX 1 + 4 with the monitor proportional counter on board the Einstein Observatory

1985 ◽  
Vol 297 ◽  
pp. 288 ◽  
Author(s):  
R. F. Elsner ◽  
M. C. Weisskopf ◽  
K. M. V. Apparao ◽  
W. Darbro ◽  
B. D. Ramsey ◽  
...  
Keyword(s):  
Proportional Counter ◽  
X Ray ◽  
Einstein Observatory
Sign in / Sign up

Export Citation Format

Share Document