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Swift/XRT Follow-up of the Fermi-LAT Galactic Plane Transient J0109+6134

ATEL # 2420; C.C. Cheung (NRC/NRL), D. Donato (NASA GSFC), M. Ajello, R. Buehler, J. Vandenbroucke (Stanford/KIPAC), on behalf of the Fermi-LAT collaboration
on 3 Feb 2010; 20:23 UT
Distributed as an Instant Email Notice (Transients)
Password Certification: Teddy Cheung (

Subjects: X-ray, Gamma Ray, Transients
Referred to by ATEL #: 2421, 2428, 2429, 2433

Following the Fermi-LAT detection of the Galactic Plane gamma-ray transient Fermi J0109+6134 (l, b = 125.121 deg, -1.226 deg) peaking on 1 Feb 2010 (ATEL #2414), we obtained a Swift observation on 3 Feb (from 05:30 -10:00 UTC). This gamma-ray source was confirmed by AGILE (ATEL #2416).

In the 5 ksec XRT exposure, a bright X-ray source is detected with count rate (0.3-10 keV) =1.1 (+/- 0.2) e-2 cts/sec. The X-ray source (RA= 01:09:46.86 Decl. = +61:33:29.3, J2000, 90% confidence radius = 4.4") is positionally coincident with the flat-spectrum radio source VCS2 J0109+6133 (GT 0106+613) reported in ATEL #2414 and is a possible counterpart to the gamma-ray source. Assuming a power-law and Galactic absorption = 5.46e21 cm-2 (P. Kalberla et al. 2005, A&A, 440, 775), the 0.3-10 keV absorbed (unabsorbed) flux = 1.3e-12 (2.0e-12) erg/cm2/s with a photon index = 1.8 (-0.6 / +0.5).

One other marginally detected (2.5 sigma) X-ray source is visible in the XRT field at RA = 01:10:18.64, Decl. = +61:39:53.8, but is outside of the 95% confidence error radius (r=0.088 deg) of the LAT source.

Further Swift observations are planned to quantify any variability. Other multi-frequency observations are encouraged.

We thank the Swift team for their rapid scheduling of the observations.

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R. E. Rutledge , Editor
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