Further analysis of SAS 3 observations of the rapid burster (MXB 1730--335)

Journal Article · Mon Jan 15 04:00:00 EST 1979 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/156765· OSTI ID:6326429

Marshall, H L; Ulmer, M P; Hoffman, J A; Doty, J; Lewin, W H.G.

Results from further analysis of SAS 3 observations of MXB 1730--335 (the rapid burster) are presented. It was found that there were two stable patterns in the recurrence of the rapidly repetitive type II bursts; we designate them models I and II. The range of type II burst energies is a factor of about 100 for mode I and a factor of about 10 for mode II. The type II burst spectra (for bursts of 40 s duration) are best fitted by that of a blackbody of constant temperature (Tapprox.18 x 10/sup 6/ K) and constant column density (N/sub H/approx.3 x 10/sup 22/ cm/sup -2/), but of decreasing intensity, which implies that the physical or apparent size of the emission region is decreasing. Assuming spherical symmetry and a distance to the source of D kpc, the radii of the emitting regions are (16 +- 2) -(D/10) km, for the first 15 s, decreasing to (11 +- 2) x (D/10) km, about 20 s later.The type I bursts from the rapid burster are also best fitted by a blackbody spectrum, but one with decreasing temperature (Tapprox. =24 x 10/sup 6/ K during the first few seconds; Tapprox. =16 x 10/sup 6/ K about 10 s later). The size of the emitting regions of the type I bursts remains approximately constant throughout the bursts. Assuming spherical symmetry, the radii are (9 +- 2) x (D/10) km. The following model for the rapid burster is suggestive. It is probably a neutron star, which like other recurrent transient X-ray sources, occasionally becomes a source of X-rays as a result of increased accretion. The active periods of MXB 1730--335 occur about every 6 months and last about 2--6 weeks. An instability in the accretion flow produces the rapidly repetitive type II X-ray bursts. After several hours, when enough matter has accumulated upon the neutron star's surface, a thermonuclear flash may take place which accounts perhaps for the type I bursts such as those commonly observed from other X-ray burst sources.

• Research Organization: Department of Physics and Center for Space Research, Massachusetts Institute of Technology
• OSTI ID: 6326429
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 227:2; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640103* -- Astrophysics & Cosmology-- Quasi-Stellar
Radio
& X-Ray Sources-- (-1987)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
COSMIC RAY SOURCES
COSMIC X-RAY SOURCES
DATA
DATA FORMS
EXPERIMENTAL DATA
INFORMATION
ISOLATED VALUES
LUMINOSITY
NEUTRON STARS
NUMERICAL DATA
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
SPECTRA
STAR ACCRETION
STAR EVOLUTION
STARS
VARIABLE STARS
X-RAY SPECTRA