keV Light Curve Research Articles

An EXOSAT Observation of Spectral Variability From the RS CVn Binary AR LAC

AbstractThe eclipsing RS CVn system AR Lac (G2IV+K0IV) has been observed continuously for one 2 day binary cycle with the EXOSAT observatory. Below 1 keV a factor of two intensity modulation is seen with a flat bottomed minimum around the time of primary eclipse and a shallow dip preceeding primary eclipse. Above 1 keV, where only emission with temperatures > 107 K would be detected, no orbital modulation or eclipse is seen. This suggests that the > 20 million degree emission comes from a large region, comparable in size to the binary seperation. The modulation in the < 1 keV lightcurve has been modelled by x2 fitting to X-ray bright spots and by using maximum entropy deconvolution. The lower temperature emission is found to orginate in compact regions with a pressure and temperature similar to that of the flaring sun.

The discovery of 2.93 hour periodic intensity dips from X1323-619

view Abstract Citations (35) References (33) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Discovery of 2.93 Hour Periodic Intensity Dips from X1323-619 Parmar, A. N. ; Gottwald, M. ; van der Klis, M. ; van Paradijs, J. Abstract A 30 hr duration Exosat observation of the low-mass X-ray binary X1323-619 is reported. The 1-8 keV light curve obtained with the medium-energy (ME) instrument shows irregular intensity dips that recur every 2.93 hr as well as type 1 X-ray bursts. The intensity declines to about 50 percent of its unaffected value during the 50-minute duration dips. The dip and burst-free ME spectrum is similar to that of other X-ray burst sources, being fitted by a power-law model with energy index 0.5. Considerable low-energy absorption is also required. Spectral changes observed during dipping intervals are consistent with absorption by material with a wide range of abundances. From an analysis of the burst properties, the distance of X1323-619 is constrained to be between 10 and 20 kpc. Publication: The Astrophysical Journal Pub Date: March 1989 DOI: 10.1086/167255 Bibcode: 1989ApJ...338.1024P Keywords: Companion Stars; Gamma Ray Bursts; Light Curve; Stellar Mass; X Ray Binaries; Exosat Satellite; Heao 2; Stellar Spectra; X Ray Spectra; Astronomy; STARS: INDIVIDUAL ALPHANUMERIC: X1323-619; X-RAYS: BINARIES full text sources ADS | data products SIMBAD (13)

A multi-wavelength study of the long-period AM Her system E2003+225 - I. The soft X-ray light curve and overall energy spectrum

X-ray, UV and optical data are presented of the longest period AM Her object, E2003+225, from October 12, 1983, together with a new linear polarization ephemeris. The optical and X-ray data were obtained simultaneously and the UV observations were carried out on the same day. A 6-hr observation with the Exosat 500 line/mm objective grating restricts soft X-ray blackbody temperatures to the range 18-29 eV. The blackbody luminosity exceeds the hard X-ray luminosity by at least a factor of 4.5, but is of the same order as the optical/UV component. Soft (0.1-0.25 keV) and hard X-ray (1-6 keV) light curves covering almost two orbital periods are presented and discussed.

Long-term observations of Cygnus X-3 with VELA 5B

We present long-term (1969–1979) observations of Cygnus X-3, obtained by the Vela 5B satellite. The 3–12 keV light curve has 10 day time resolution. Cyg X-3 is a peculiar high-luminosity X-ray source, radiating from the radio region to hard gamma rays of more than 1016 eV. It has a 4.8 hour period, probably orbital, which is not resolved by our present analysis. Long term periodicities of ~17, 20, and 33–34 days have been reported by several authors, and explained as the effects of apsidal motion, precession, or an eccentric orbit. We do not observe the ~17 and 33–34 day variations, and set upper limits significantly lower than the reported amplitude of the 33–34 day variation. There is weak evidence for a 20 day flux variation. The light curve shows high and low states which alternate with a characteristic timescale of ~1 year. There is no counterpart, at this time resolution, of the giant radio outburst of 1972 September.

Long term observations of Cyg X-3 with Vela 5B

We present long-term (1969–1979) observations of Cygnus X-3, obtained by the Vela 5B satellite. The 3–12 keV light curve has 10 day time resolution. Cyg X-3 is a peculiar high-luminosity X-ray source, radiating from the radio region to hard gamma rays of more than 1016 eV. It has a 4.8 hour period, probably orbital, which is not resolved by our present analysis. Long term periodicities of ∼17, 20, and 33–34 days have been reported by several authors, and explained as the effects of apsidal motion, precession, or an eccentric orbit. We do not observe the ∼17 and 33–34 day variations, and set upper limits significantly lower than the reported amplitude of the 33–34 day variation. There is weak evidence for a 20 day flux variation. The light curve shows high and low states which alternate with a characteristic timescale of ∼1 year. There is no counterpart, at this time resolution, of the giant radio outburst of 1972 September.

High-energy X-ray observations of VELA X-1

view Abstract Citations (18) References (25) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS High-energy X-ray observations of VELA X-1. Bautz, M. ; Howe, S. ; Gorecki, A. ; Lang, F. ; Levine, A. ; Primini, F. ; Lewin, W. H. G. Abstract Results are presented of observations of Vela X-1 in the 13-180 keV spectral range made with the A-4 instrument on board the HEAO 1 satellite. It is shown that the pulse period, measured during May-December 1978, is consistent with the long-term trend observed between 1975 and 1979. No evidence is detected for gross changes in the shape of the Vela X-1 pulse shape between May 1978 and December 1978, although some details of the 13-20 keV pulse profile seem to have varied during this period. The shape of the pulse profile is found to vary with energy between 13 keV and 70 keV. Pulse-phase-resolved spectroscopy is presented for Vela X-1 in this energy range. In addition, it is found that high energy (13-80 keV) light curves, obtained during each of three 50 day periods in 1977 and 1978, are quite similar to long-term light curves observed at lower energies. Publication: The Astrophysical Journal Pub Date: March 1983 DOI: 10.1086/160827 Bibcode: 1983ApJ...266..794B Keywords: Binary Stars; Eclipsing Binary Stars; Pulsars; X Ray Sources; Energy Spectra; Heao 1; Light Curve; Orbital Elements; Astronomy full text sources ADS | data products SIMBAD (1)

33 second X-ray pulsations in AE Aquarii

view Abstract Citations (93) References (14) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS 33 second X-ray pulsations in AE Aquarii. Patterson, J. ; Branch, D. ; Chincarini, G. ; Robinson, E. L. Abstract The discovery of 33-s pulsations in the 0.1-4.0 keV light curve of the nova-like variable AE Aquarii is reported. These pulsations agree in period and phase with the optical pulsations. The periodicity probably originated from an accretion-induced hot spot on a rapidly rotating, magnetized white dwarf. It is possible that transient pulsations at nearby periods, similar to those seen in the optical light curve, are also present in the X-ray light curve. Publication: The Astrophysical Journal Pub Date: September 1980 DOI: 10.1086/183339 Bibcode: 1980ApJ...240L.133P Keywords: Binary Stars; Stellar Rotation; Variable Stars; White Dwarf Stars; X Ray Sources; Light Curve; Power Spectra; Stellar Oscillations; Astrophysics; Pulsations:X-Ray Binaries; X-Ray Binaries:Models full text sources ADS | data products SIMBAD (2)