Swift follow-up observations of the blazar PKS 1510-089 after a high optical flare
ATel #2047; F. D'Ammando (Univ. Tor Vergata, INAF-IASF Roma), H. Krimm (CRESST/GSFC/USRA), P. Romano, S. Vercellone (INAF-IASF Palermo)
on 15 May 2009; 21:37 UT
Credential Certification: Pat Romano (romano@ifc.inaf.it)
Subjects: X-ray, Gamma Ray, AGN
Following the extraordinary optical brightness level of the blazar PKS 1510-089 on May 08.9
(Larionov et al., ATel #2045), we report on the analysis of Swift data obtained immediately
after the optical flare.
The Swift/BAT hard X-ray transient monitor detected an outburst in PKS 1510-089
in the 15-50 keV energy band.
On 2009 May 10 (MJD 54961) the count rate was 0.009 +/- 0.005 cts/s/cm^2 (40 mCrab).
The source then declined to background on May 11, before rising again to 0.003 +/- 0.001 cts/s/cm^2 (14 mCrab) on May 13.
It has remained at nearly the same rate since then. This is roughly the same brightness as was reported
in March 2009 (Krimm et al, ATel #1963).
Target of Opportunity observations with Swift/XRT were obtained on May 11, 12, 13, and 14.
The first short (1.4 ks) Swift/XRT observation is strongly affected by the presence of a
hot column at the center of the PSF.
The spectra of the Swift/XRT following observations (4 to 5 ks each on-source time)
can be fit (0.3-10 keV energy range) with an absorbed power-law model
with a column density consistent with the Galactic one in the direction of the source
(n_H = 6.89E20 cm^-2, Kalberla et al. 2005) and a photon index of
1.34+/-0.09, 1.51+/-0.10 and 1.41+/-0.10, respectively.
The corresponding unabsorbed 0.3-10 keV fluxes are 1.3E-11, 1.0E-11, and 1.0E-11 erg cm^-2 s^-1.
The X-ray flux confirms the high activity of the source at the beginning of the Swift/XRT
observations.
We thank Neil Gehrels and the Swift Team for making these observations possible,
in particular the duty scientists and science planners.
