Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 461, Issue 4, Pages 3847-3853Publisher
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stw1576
Keywords
accretion, accretion discs; X-rays: binaries; X-rays: individual: Aql X-1
Categories
Funding
- Australian Research Council Future Fellowship [FT0991598]
- Australian Academy of Science
- Australian Research Council
Ask authors/readers for more resources
Periodic dips observed in approximate to 20 per cent of low-mass X-ray binaries (LMXBs) are thought to arise from obscuration of the neutron star by the outer edge of the accretion disc. We report the detection with the Rossi X-ray Timing Explorer of two dipping episodes in Aql X-1, not previously a known dipper. The X-ray spectrum during the dips exhibited an elevated neutral column density, by a factor between one and almost two orders of magnitude. Dips were not observed in every cycle of the 18.95-h orbit, so that the estimated frequency for these events is 0.10(0.05)(+0.07) cycle(-1). This is the first confirmed example of intermittent dipping in such a system. Assuming that the dips in Aql X-1 occur because the system inclination is intermediate between the non-dipping and dipping sources, implies a range of 72 degrees-79 degrees for the source. This result lends support for the presence of a massive (> 2M(circle dot)) neutron star in Aql X-1, and further implies that approximate to 30 additional LMXBs may have inclinations within this range, raising the possibility of intermittent dips in those systems also. Thus, we searched for dips from 24 other bursting systems, without success. For the system with the largest number of dip phases covered, 4U 1820-303, the non-detection implies a 95 per cent upper limit to the dip frequency of 1.4 x 10(-3) cycle(-1).
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available