Flux Transition in Terzan 2
ATel #237; C. B. Markwardt (U. Maryland & GSFC), J. Swank (GSFC)
on 17 Feb 2004; 20:56 UT
Credential Certification: Craig B. Markwardt (craigm@lheamail.gsfc.nasa.gov)
Subjects: X-ray, Binary, Globular Cluster, Neutron Star, Transient
The bright X-ray source in Terzan 2 (possibly 4U 1724-307) has
undergone a flux transition. In PCA monitoring observations of the
galactic bulge, the flux of this source up to November 2003 had been a
relatively steady at 20 mCrab. Monitoring observations on Feb 7.6,
10.8 and 14.9 show the flux increasing to levels of 34, 44 and 66
mCrab respectively (2-10 keV). In the time between November and
February, pointing constraints prevented monitoring observations, but
the current trend suggests a rapid and ongoing flux increase.
A 2.3 ks pointed PCA observation starting on Feb 16.14 confirmed the
higher intensity. The X-ray spectrum is consistent with a cut-off
power law, photon index 0.5, and a cut-off energy of 4 keV. The 2-10
and 2-30 keV fluxes were 1.6 and 2.1 10^{-9} erg/s/cm^2, respectively.
The Fourier power density spectrum shows low frequency variability,
plus a broad noise feature peaked at ~30 Hz.
We cannot exlude the possibility that another X-ray source in the
Terzan 2 globular cluster has become active, however no other X-ray
sources have been detected with Chandra (Revnivtsev et al 2002,
Astron. Lett. 28, 237).
