4 years ago

Fast, ultra-luminous X-ray bursts from tidal stripping of White Dwarfs by Intermediate-mass Black Holes.

Rong-feng Shen

Two X-ray sources were recently discovered by Irwin et al. in compact companions to elliptical galaxies to show ultra-luminous flares with fast rise (~ minute) and decay (~ hour), and with a peak luminosity ~10^{40-41} erg/s. Together with two other sources found earlier, they constitute a new type of fast transients which cannot be attributed to neutron stars but might be due to intermediate-mass black holes (IMBHs; 10^{2-4} M_sun). The flaring behavior is recurrent for at least two sources. If the flare represents a short period of accretion onto an IMBH during the periastron passage of a donor star on an eccentric (i.e., repeating) or parabolic (non-repeating) orbit, we argue that the flare's rise time corresponds to the duration during which the donor's tidally stripped mass joins a residual disk at the pericenter. This duration is in turn equal to three other time scales: the duration of stripping, the sound crossing time of the donor, and the circular orbit time at the pericenter radius. Only a white dwarf can have a sound crossing time as short as one minute. Therefore, the donor must be a white dwarf and it was stripped of ~10^{-10} M_sun upon each passage at several to tens of Schwarzschild radii from the IMBH. The flux decay corresponds to the viscous drainage of the supplied mass toward the hole. Aided with long-term X-ray monitoring, this type of fast transients would be an ideal target for next-generation gravitational wave detectors.

Publisher URL: http://arxiv.org/abs/1809.09359

DOI: arXiv:1809.09359v2

You might also like
Discover & Discuss Important Research

Keeping up-to-date with research can feel impossible, with papers being published faster than you'll ever be able to read them. That's where Researcher comes in: we're simplifying discovery and making important discussions happen. With over 19,000 sources, including peer-reviewed journals, preprints, blogs, universities, podcasts and Live events across 10 research areas, you'll never miss what's important to you. It's like social media, but better. Oh, and we should mention - it's free.

  • Download from Google Play
  • Download from App Store
  • Download from AppInChina

Researcher displays publicly available abstracts and doesn’t host any full article content. If the content is open access, we will direct clicks from the abstracts to the publisher website and display the PDF copy on our platform. Clicks to view the full text will be directed to the publisher website, where only users with subscriptions or access through their institution are able to view the full article.