arXiv subjects

Michael J. Stark

Publications and source records attributed to Michael J. Stark.

2 recordsLinked to original sources

arXiv2003

Doppler Modulation of X-ray lines in Cygnus X-3

We measured Doppler shifts of three bright spectral lines in the X-ray emission from Cygnus X-3 as recorded by the Chandra X-Ray Observatory. Doppler shifts of lines associated with Si XIV and S XVI exhibit orbital modulation. The magnitude and phasing of this modulation relative to the orbital ephemeris indicate the location of the source of this emission within the wind emanating from the compact object's companion. These observations enable us to make an indirect measurement of the separation of the two stars. Under certain assumptions our observation of a line associated with Fe XXV also limits the mass of the compact object M < 3.6 MSun.

astro-ph↗

arXiv1997

The Pulsar in GRO J1744-28 at Low Flux

The Bursting Pulsar, GRO J1744-28, has been observed with the Rossi X-ray Timing Explorer (RXTE) regularly since the launch of the satellite in December 1995. This accretion driven pulsar has undergone two outbursts which have been accompanied by significant spin-up of the pulsar. Between these two outbursts, the pulsar was detectable during each observation down to fluxes perhaps one thousandth of the persistent flux at the peak of the first outburst. We observe evidence of a change in the sign of the frequency derivative during the faintest period but the relationship between the observed luminosity and the frequency derivative is complex.

astro-ph↗