1999/07/06 by M. Guainazzi, Guainazzi, M., A. N. Parmar +3
Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics (astro-ph) #FOS: Physical sciences #Gamma-ray bursts and supernovae #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/9907067
7 Latex pages, 6 figures, Accepted for publication in Astronomy & Astrophysics
arxiv created 1999/07/06 · openalex publication_date 1999/07/06 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
During a BeppoSAX observation of the X-ray burst source X1732-304 located in the globular cluster Terzan 1 in 1999 April, the source was detected in an anomalously low-state with an X-ray luminosity of 1.4 x 1033 erg/s, about 300 times fainter than the lowest previously reported measure of the persistent flux. The spectral shape and intensity of this low-state emission is similar to that of a number of neutron star soft X-ray transients in quiescence, being well fit by a ~0.34 keV blackbody together with a power-law with a photon index of ~1.0. These similarities suggest that the same mechanism, such as the inhibition of accretion due to the propeller effect, is also operating in X1732-304. Alternatively, the X1732-304 low-state may be due to obscuration of the line of sight to the central neutron star, with only scattered and/or reflected X-rays being detected. The possibility that the source detected by BeppoSAX is not X1732-304, but a nearby dim source of the cluster field (what would make the observed dimming of X1732-304 even more remarkable) is also discussed.