Discovery of Eclipses from the Accreting Millisecond X-ray Pulsar SWIFT J1749.4-2807
Abstract
We report the discovery of X-ray eclipses in the recently discovered accreting millisecond X-ray pulsar SWIFT J1749.4-2807. This is the first detection of X-ray eclipses in a system of this type and should enable a precise neutron star mass measurement once the companion star is identified and studied. We present a combined pulse and eclipse timing solution that enables tight constraints on the orbital parameters and inclination and shows that the companion mass is in the range 0.6-0.8 M sun for a likely range of neutron star masses, and that it is larger than a main-sequence star of the same mass. We observed two individual eclipse egresses and a single ingress. Our timing model shows that the eclipse features are symmetric about the time of 90° longitude from the ascending node, as expected. Our eclipse timing solution gives an eclipse duration (from the mid-points of ingress to egress) of 2172 ± 13 s. This represents 6.85% of the 8.82 hr orbital period. This system also presents a potential measurement of "Shapiro" delay due to general relativity; through this technique alone, we set an upper limit to the companion mass of 2.2 M sun.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 2010
- DOI:
- 10.1088/2041-8205/717/2/L149
- arXiv:
- arXiv:1005.3479
- Bibcode:
- 2010ApJ...717L.149M
- Keywords:
-
- pulsars: general;
- pulsars: individual: SWIFT J1749.4-2807;
- stars: neutron;
- X-rays: binaries;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- Accepted to ApJ Letters