Orbit Solution for the Millisecond Pulsar IGR J00291+5934
ATel #360; C. B. Markwardt (U. Maryland & GSFC), D. K. Galloway (MIT), D. Chakrabarty (MIT), E. H. Morgan (MIT), T. E. Strohmayer (GSFC)
on 7 Dec 2004; 03:07 UT
Credential Certification: Craig B. Markwardt (firstname.lastname@example.org)
Subjects: X-ray, Binary, Neutron Star, Transient, Pulsar
Referred to by ATel #: 1660
The INTEGRAL Transient IGR J00291+5934 (ATEL #352), now known to
be a 1.67 millisecond X-ray pulsar (ATEL #353), was observed by the
RXTE PCA on Dec 5 and 6. The source has decayed to approximately 27
mCrab (2-10 keV).
The data were barycentered using the Fox & Kulkarni optical
counterpart position (ATEL #354). Pulsations with a sinusoidal
frequency modulation are clearly detected in each observation. The
best fitting orbit has a period of 147.412 +/- 0.006 min and an a_x
sin(i) of 65.0 +/- 0.2 lt-ms. The mass function is 2.81e-5 +/-
0.02e-5 M_sun. Assuming a neutron star of mass 1.4 M_sun, the
companion mass must be larger than 0.038 M_sun.
The orbit and inferred companion of IGR J00291+5934 appear to be
very similar to that of SAX J1808.4-3658, the first known millisecond
There is presently no evidence of X-ray eclipses or X-ray bursts.
RXTE continues to observe the source.