XMM-Newton observation of the persistent Be/NS X-ray binary pulsar RX J1037.5–5647 in a low luminosity state
INAF, Istituto di Astrofisica Spaziale e Fisica Cosmica - Milano, via Bassini 15, 20133, Milano, Italy e-mail: firstname.lastname@example.org
2 INFN, Sezione di Pavia, via A.Bassi 6, 27100, Pavia, Italy
Accepted: 16 July 2009
The spectra of several X-ray binary pulsars display a clear soft excess, which in most cases can be described with a blackbody model, above the main power-law component. While in the high-luminosity sources it is usually characterized by low temperature (kT < 0.5 keV) and a large emission radius ( 100 km), in the two persistent and low-luminosity pulsars 4U 0352+309 and RX J0146.9+6121 this component has a high temperature ( 1 keV) and a smaller radius ( 0.5 km), consistent with the estimated size of the neutron-star polar cap. Here we report on the timing and spectral analysis of RX J1037.5–5647, another low-luminosity persistent Be binary pulsar, based on the first XMM-Newton observation of this source. We have found a best-fit period P = 853.4±0.2 s, which implies an average pulsar spin-up -210-8 s s-1 in the last decade. The estimated source luminosity is LX ~ 1034 erg s-1, a value comparable to the other persistent Be binary pulsars and about one order of magnitude lower than in most of the previous measurements. The source spectrum can be described with a power law plus blackbody model, with = keV and = m, suggesting a polar-cap origin of this component. These results strengthen the hypothesis that, in addition to low luminosities and long periods, this class of sources is also characterized by common spectral properties.
Key words: X-rays: binaries / accretion, accretion disks / stars: emission-line, Be / stars: pulsars: individual: LS 1698 / X-rays: individuals: RX J1037.5–5647
© ESO, 2009