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A likely high-frequency radio counterpart of the Fermi LAT transient J0910-5041

ATEL # 1843; E. Sadler (Univ. Sydney) on behalf of the AT20G team
on 13 Nov 2008; 11:40 UT
Password Certification: Elaine M. Sadler (ems@physics.usyd.edu.au)

Subjects: Radio, Gamma Ray, Transients

With reference to the Fermi LAT detection of the transient J0910-5041 located in the Galactic Plane (ATEL #1788) and the reported Swift/XRT detection of an associated X-ray source (ATEL #1822), we report that this object closely coincides in position with a high-frequency radio source detected in the Australia Telescope 20GHz (AT20G) Survey, AT20G J091058-504807.

The measured AT20G position for this source is (J2000) 09 10 58.08 -50 48 07.4, with an uncertainty of 0.7 arcsec in both RA and Dec. This potentially provides a more accurate localization for the Fermi LAT transient. The AT20G position is close to that of the low-frequency radio source MGPS J091057-504808 mentioned in ATEL #1822. We confirm that no optical or infrared counterpart is seen at this position down to the limits of the UK Schmidt Sky Survey.

The AT20G observations were made in October/November 2005, and at that time the measured flux density of the source was 127 +/- 6 mJy at 20 GHz, 82 +/- 4 mJy at 8.64 GHz and 81 +/- 4 mJy at 4.8 GHz. The fractional linear polarization at 20 GHz is <9%.

The AT20G survey is described by Massardi et al. (2008). AT20G J091058-504807 lies below the flux density limit of the catalogue presented by Massardi et al., but is in the full AT20G data catalogue due for public release early next year (Murphy et al. 2009). The radio spectrum of J091058-504807 is somewhat unusual, being roughly flat over the range 1 - 8 GHz but rising at 8 - 20GHz.


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