EDP Sciences
Free access
Volume 434, Number 3, May II 2005
Page(s) L9 - L12
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:200500103

A&A 434, L9-L12 (2005)
DOI: 10.1051/0004-6361:200500103


XMM-Newton observations of two transient millisecond X-ray pulsars in quiescence

S. Campana1, N. Ferrari1, 2, L. Stella3 and G. L. Israel3

1  INAF - Osservatorio Astronomico di Brera, via Bianchi 46, 23807 Merate (Lc), Italy
    e-mail: campana@merate.mi.astro.it
2  Università degli Studi di Milano, via Celoria 16, 20133 Milano, Italy
3  INAF - Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monteporzio Catone (Roma), Italy

(Received 28 December 2004 / Accepted 22 March 2005 )

We report on XMM-Newton observations of two X-ray transient millisecond pulsars (XRTMSPs). We detected XTE J0929-314 with an unabsorbed luminosity of ${\sim} 7\times 10^{31}\rm\ erg \; s^{-1}$ (0.5-10 keV) at a fiducial distance of 10 kpc. The quiescent spectrum is consistent with a simple power law spectrum. The upper limit on the flux from a cooling neutron star atmosphere is about $20\%$ of the total flux. XTE J1807-294 instead was not detected. We can put an upper limit on the source quiescent 0.5-10 keV unabsorbed luminosity ${\la} 4\times10^{31}\rm\ erg \; s^{-1}$ at 8 kpc. These observations strenghten the idea that XRTMSPs have quiescent luminosities significantly lower than classical neutron star transients.

Key words: accretion, accretion disks -- binaries: close -- stars: individual: XTE J0929-314, XTE J1807-294 -- stars: neutron

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