arXiv subjects

A. Owens

Publications and source records attributed to A. Owens.

22 records · Page 2Linked to original sources

arXiv1997

Spectral Properties of the Prompt X-ray emission and Afterglow from the Gamma-Ray Burst of 28 February 1997

We report high-energy spectral data of the prompt emission of GRB970228 and its X-ray afterglow. We establish that the nature of the X-ray afterglow emission is non-thermal and similar to the later portion of GRB970228. Our data can be used to discriminate different emission models of GRB afterglows. While cooling of excited compact objects can be ruled out, fireball models are constrained in the physics of the radiation emission processes and their evolution.

astro-ph↗

arXiv1997

Discovery of the X-Ray Afterglow of the Gamma-Ray Burst of February 28 1997

Here we report the discovery in the X-ray band of the first afterglow of a gamma-ray burst. It was detected and quickly positioned by the Beppo-SAX satellite on 1997 February 28 (GRB970228). The X-ray afterglow source was detected with the X-ray telescopes aboard the same satellite about eight hours after the burst and faded away in a few days with a power law decay function. The energetic content of the X-ray afterglow results to be a significant fraction of gamma-ray burst energetics. The Beppo-SAX detection and fast imaging of GRB970228 started a multiwavelength campaign that lead to the identification of a fading optical source in a position consistent with the X-ray source.

astro-ph↗

arXiv1997

The complex X-ray spectrum of the low-mass X-ray binary 4U 1626-67

We report on observations of the X-ray pulsar 4U 1626-67 by the LECS instrument on-board Bepposax. We confirm the recent ASCA discovery of excess emission near 1 keV (Angelini et al. 1995). The pulse period of 7.66794 +/- 0.00004 s indicates that the source continues to spin-down. The phase averaged spectrum is well fit by an absorbed power-law of photon index 0.61 +/- 0.02 and a blackbody of temperature 0.33 +/- 0.02 keV, together with an emission feature at 1.05 +/- 0.02 keV. This spectral shape is similar to that observed by ASCA during the spin-down phase, but significantly different from measurements during spin-up. This suggests that the change in spectrum observed by ASCA may be a stable feature during spin-down intervals. The source intensity is a factor ~2 lower than observed by ASCA three years earlier, confirming that 4U 1626-67 continues to become fainter with time.

astro-ph↗

arXiv1997

Low-energy line emission from Cygnus X-2 observed with the BeppoSAX LECS

We present a 0.2-10 keV spectrum of the low-mass X-ray binary Cygnus X-2 obtained using the Low Energy Concentrator Spectrometer on-board Bepposax. The spectrum can be described by a cut-off power-law model with absorption of (2.28 +/- 0.07) 10^{21} atoms/cm^2, a power-law index of 0.78 +/- 0.02 and a cut-off energy of 4.30 +/- 0.08 keV (68% confidence errors), except at energies near ~1 keV where excess emission is present. This can be modeled by a broad Gaussian line feature with an energy of 1.02 +/- 0.04 keV, a full width half-maximum of 0.47 +/- 0.07 keV and an equivalent width of 74 +/-^{25}_{11} eV. This result confirms earlier reports of line emission near 1 keV and shows the intensity and structure of the feature to be variable.

astro-ph↗