摘要:

Three outbursts of the x‐ray binary system A 0535+262 have been detected in the 20–120 keV energy range by the BATSE instrument onboard the Compton Gamma Ray Observatory. The system orbital parameters have been determined by a pulse timing analysis during data from these outbursts. ©1994 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.46032

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

We present the results of six Main‐On observations of Her X‐1, obtained by HEXE between 7/87 and 10/88 in hard x‐rays. Pulse period measurements confirm the long term spin‐up trend. A 16–60 keV pulse profile of excellent quality is given. The pulse‐minus‐off‐pulse spectrum is best represented by a power‐law with exponential cut‐off and a cyclotron absorption line (Ecycl=34.1±2.5 keV). ©1994 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.45988

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

Hercules X‐1 was observed by the Large Area Counters (LAC) on the Ginga satellite during several periods in 1988 and 1989. The spectrum of Her X‐1 was measured on a timescale of several minutes, and the flux measured on a timescale of a few seconds. Large changes in flux and in spectral shape were observed, on short and on long timescales. The spectrum has been modeled consistently using a model with two continuum components plus iron emission line and absorption by cold matter. Spectral parameters are derived for pre‐eclipse absorption dips and for eclipse ingress. The changes in spectral parameters are given a physical interpretation in terms of the emission region around the neutron star and in terms of the absorbing matter in the system. ©1994 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.45989

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

EXOSAT observations of three absorption dips in Hercules X‐1 are presented. A partial covering model is employed, and qualitative differences between the three dips are highlighted. The behavior of the pulse profile during the dips is discussed. A transition between different phase states of the absorbing medium is observed within one dip, consistent with the cooling and condensation of an ionized cloud into discrete absorbing clumps. ©1994 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.46035

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

Using BATSE observations of Her X‐1 for the entire CGRO mission to date, a correlation is observed between the hard x‐ray pulsed flux at the peak of the main‐on portion of the 35d cycle and the spin frequency derivative, a measure of the torque acting on the neutron star. An apparent correlation is also found between the 35 day cycle start times and the pulsed flux. Orbital parameters are also obtained, with evidence for orbital decay with a timescale slightly less than reported in Deeteretal. (1991). ©1994 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.45990

出版商:AIP    

年代:1994

数据来源: AIP

ISSN:0094-243X    

DOI:10.1063/1.45924

出版商:AIP    

年代:1994

数据来源: AIP

ISSN:0094-243X    

DOI:10.1063/1.45925

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

We present a summary of the Southampton/Valencia/Caltech/SAAO campaign for long‐term, multiwavelength monitoring of high mass x‐ray binaries. A number of sources have been observed in unusual states, including detailed studies of the Be/x‐ray transients X Persei (4U0352+309: disk loss state, 1988–1990), 3A1118‐616 (transient outburst, Jan. 1991), GX 1+4 (outburst Sept. 1993) and EXO2030+375 (periastron passsage, June 1993). ©1994 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.45926

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

Several AM Her objects show low amplitude, 1 Hz quasi‐periodic oscillations in power spectra of their optical emission. Wolff, Wood, and Imamura, in a recent series of papers, show that accretion noise driven radiative shocks are a plausible model for this phenomenon. Here, we discuss how two‐temperature effects can play an important role in regulating the frequency of the shock oscillations within the formalism outlined by Wolffetal. We argue that two‐temperature effects can be important in accretion flows onto white dwarfs with masses as low as 0.6M⊙if cyclotron radiation is an important energy loss process in the shocked gas. The planned USA x‐ray timing experiment on the ARGOS satellite should be able to detect the quasi‐periodic x‐ray oscillations predicted by our shock oscillation model. ©1994 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.45927

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

Resonant enhancements in the magnetic Compton cross section can produce regions of limited extent in an x‐ray pulsar magnetosphere where the radiation force on electrons balances the gravitational force on protons. Infalling material outside the pulsar accretion column can collect in this region to form a radiation‐supported scattering atmosphere. We propose that these scattering atmospheres can explain energy‐dependent features in the observed pulse profiles of 4U 1626‐67 and 4U 1538‐52. Less complex pulse profiles will be observed at higher photon energies because the scattering atmospheres, which are supported by resonant Compton radiation pressure, become transparent to photons with energies greater than the cyclotron energy at the pulsar surface. ©1994 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.45928

出版商:AIP    

年代:1994

数据来源: AIP