Breaking the AMSP mould: the increasingly strange case of HETE J1900.1-2455
Abstract
We present ongoing Rossi X-ray Timing Explorer (RXTE) monitoring observations of the 377.3 Hz accretion-powered pulsar, HETE J1900-2455. Activity continues in this system more than 3 yr after discovery, at a mean luminosity of 4.4×1036 erg s-1 (for d = 5 kpc), although pulsations were present only within the first 70 d. X-ray variability has increased each year, notably with a brief interval of non-detection in 2007, during which the luminosity dropped to below 10-3 of the mean level. A deep search of data from the intervals of non-detection in 2005 revealed evidence for extremely weak pulsations at an amplitude of 0.29% rms, a factor of ten less than the largest amplitude seen early in the outburst.
X-ray burst activity continued through 2008, with bursts typically featuring strong radius expansion. Spectral analysis of the most intense burst detected by RXTE early in the outburst revealed unusual variations in the inferred photospheric radius, as well as significant deviations from a black-body. We obtained much better fits instead with a Comptonization model.- Publication:
-
A Decade of Accreting MilliSecond X-ray Pulsars
- Pub Date:
- October 2008
- DOI:
- 10.1063/1.3031206
- arXiv:
- arXiv:0810.4382
- Bibcode:
- 2008AIPC.1068...55G
- Keywords:
-
- 78.70.En;
- 97.10.Gz;
- 97.60.Gb;
- 97.60.Jd;
- X-ray emission spectra and fluorescence;
- Accretion and accretion disks;
- Pulsars;
- Neutron stars;
- Astrophysics
- E-Print:
- 8 pages, 3 figures, one table