期刊
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
卷 476, 期 3, 页码 4272-4277出版社
OXFORD UNIV PRESS
DOI: 10.1093/mnras/sty501
关键词
accretion, accretion discs; stars: neutron; pulsars: general; X-rays: binaries; X-rays: general
资金
- Science and Technology Facilities Council [ST/K501979/1, ST/N50404X/1, ST/P000541/1]
- NASA [NNG08FD60C]
- NASA
- STFC [ST/P000541/1, ST/K501979/1, 1771048] Funding Source: UKRI
- Science and Technology Facilities Council [ST/K501979/1, ST/P000541/1, 1322596] Funding Source: researchfish
We search for transient sources in a sample of ultraluminous X-ray sources (ULXs) from the 3XMM-DR4 release of the XMM-Newton Serendipitous Source Catalogue in order to find candidate neutron star ULXs alternating between an accreting state and the propeller regime, in which the luminosity drops dramatically. By examining their fluxes and flux upper limits, we identify five ULXs that demonstrate long-term variability of over an order of magnitude. Using Chandra and Swift data to further characterize their light curves, we find that two of these sources are detected only once and could be X-ray binaries in outburst that only briefly reach ULX luminosities. Two others are consistent with being super-Eddington accreting sources with high levels of inter-observation variability. One source, M51 ULX-4, demonstrates apparent bimodal flux behaviour that could indicate the propeller regime. It has a hard X-ray spectrum, but no significant pulsations in its timing data, although with an upper limit of 10 per cent of the signal pulsed at similar to 1.5 Hz a pulsating ULX cannot be excluded, particularly if the pulsations are transient. By simulating XMM-Newton observations of a population of pulsating ULXs, we predict that there could be approximately 200 other bimodal ULXs that have not been observed sufficiently well by XMM-Newton to be identified as transient.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据