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Swift/BAT reports increased activity from three galactic sources

ATel #1426; H. A. Krimm (CRESST/GSFC/USRA), S. D. Barthelmy (GSFC),W. Baumgartner (CRESST/GSFC/UMBC), J. Cummings (CRESST/GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), C. B. Markwardt (CRESST/GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (CRESTT/GSFC/UMBC), G. Sato (GSFC/ISAS), G. Skinner (CRESST/GSFC/UMBC)
on 16 Mar 2008; 23:39 UT
Credential Certification: Hans A. Krimm (Hans.Krimm@nasa.gov)

Subjects: X-ray, Request for Observations, Binary, Transient, Pulsar

Referred to by ATel #: 1427, 1431, 1472, 2095, 2099, 3408

In recent observations, the Swift/BAT Hard X-ray Transient Monitor has detected increased activity from three galactic sources. All reported observations are in the 15-50 keV energy band.

The binary X-ray pulsar 4U 0115+634 is detected at a level of 0.020 ± 0.004 counts/sec/cm2 (~100 mcrab) beginning on March 12, 2008 (MJD 54537). This source was last active in Sep. 2004 (ATel #326) and is normally below the 7-mcrab detection threshold for the BAT transient monitor on a one-day timescale.

The accretion powered pulsar 4U 1626-67 has been steadily increasing in flux since approximately January 15, 2008. The most recent observations (March 15, 2008) show a count rate of 0.010 ± 0.001 counts/sec/cm^2 (~45 mcrab) compared to its normal level of 0.004 ± 0.002 counts/sec/cm^2.

Swift/BAT confirms the recently reported outburst of the neutron star transient SAX J1750.8-2900 (ATel #1425) and shows that it is also active in the hard X-ray band. The daily average flux for March 15, 2008 was 0.010 ± 0.001 counts/sec/cm^2 (45 mcrab). A burst from this source also triggered Swift on-board at 19:27 UT March 15 as reported in a GCN/Swift Transient Notice.

Swift/BAT Hard X-ray Transient Monitor