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Swift detected a renewed X-ray activity in IGR J00291+5934

ATel #7836; A. Sanna (UNICA), F. Pintore (UNICA), A. Riggio (UNICA), L. Burderi (UNICA), T. Di Salvo (UNIPA), R. Iaria (UNIPA), F. Scarano (UNICA), A. Papitto (ICE CSIC-IEEC, Spain), E. Bozzo (ISDC, Switzerland)
on 24 Jul 2015; 21:54 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Andrea Sanna (andrea.sanna@dsf.unica.it)

Subjects: X-ray, Binary, Neutron Star, Transient, Pulsar

Referred to by ATel #: 7837, 7849, 7852, 7949

Triggered by the increased X-ray activity detected by Swift/BAT in the direction of IGR J00291+5934, we obtained a Swift/XRT pointed observation of the source on July, 24th 2015, starting at 13:24 UT for approximately 1000 seconds of exposure.

Using the method of Evans et al. (2009, MNRAS, 397, 1177), we found a UVOT-enhanced position of

RA = 7.26273 deg, Dec = 59.57237 deg

(J2000), with an associated uncertainty of 2.3 arcsec (90% c.l.). This location is consistent, within errors, with the radio position of IGR J00291+5934 reported by Rupen et al. (2004), suggesting that the accreting millisecond X-ray pulsar started a new outburst. This result is in line with the optical flare of IGR J00291+5934 reported in ATEL #7835.

The Swift/XRT PC-mode data (~400 seconds) are heavily piled-up due to the high count rate of the source (~3 cts/s). The Swift/XRT WT-mode data (~600 seconds) showed a count rate of 7 cts/s. On this data we performed a spectral analysis adopting an absorbed power-law. We found an absorption column density of (7+/-1)E21 cm^-2 and a power-law photon index of 1.4 +/- 0.1. The estimated 0.3-10 keV unabsorbed X-ray flux is 6E-10 erg/cm^2/s, about three times higher than the beginning of the 2008 outbursts (ATEL #1667, #1726).

We thank the Swift team for the prompt scheduling of the reported observation. Additional Swift/XRT observations have been requested. Multi-wavelength observations are encouraged.