Dying pulse trains in Cygnus XR-1: Evidence for an event horizon?

Authors
Citation
Jf. Dolan, Dying pulse trains in Cygnus XR-1: Evidence for an event horizon?, PUB AST S P, 113(786), 2001, pp. 974-982
Citations number
23
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Space Sciences
Journal title
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC
ISSN journal
0004-6280 → ACNP
Volume
113
Issue
786
Year of publication
2001
Pages
974 - 982
Database
ISI
SICI code
0004-6280(200108)113:786<974:DPTICX>2.0.ZU;2-1
Abstract
The X-ray-emitting component in the Cyg XR-1/HDE 226868 system is a leading candidate for identification as a stellar-mass-sized black hole. The detec tion of an event horizon surrounding the point singularity in such a system would constitute a positive identification of a black hole as predicted by general relativity. One signature of such an event horizon would be the ex istence of dying pulse trains emitted by material spiraling into the event horizon from the last stable orbit around the black hole. We observed the C yg XR-1 system at three different epochs in a 1400-3000 Angstrom bandpass w ith 0.1 ms time resolution using the Hubble Space Telescope's High Speed Ph otometer. Repeated excursions of the detected flux by more than 3 sigma abo ve the mean are present in the UV flux with an FWHM of 1-10 ms. If any of t hese excursions are pulses of radiation produced in the system (and not jus t stochastic variability associated with the Poisson distribution of detect ed photon arrival times), then this short a timescale requires that the pul ses originate in the accretion disk around Cyg XR-1. Two series of pulses w ith characteristics similar to those expected from dying pulse trains were detected in 3 hr of observation.