Radio follow-up of the Fermi-LAT Galactic Plane Transient J0109+6134 with the Effelsberg 100-m telescope

ATel #2428; L. Fuhrmann, U. Bach, I. Nestoras, T. P. Krichbaum, E. Angelakis (MPIfR) on behalf of the F-GAMMA team
on 10 Feb 2010; 10:46 UT
Credential Certification: Uwe Bach (ubach@mpifr.de)

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Following the Fermi-LAT detection of the gamma-ray transient near the Galactic Plane, J0109+6134 (ATEL #2414) and subsequent detections by AGILE and Swift (ATELs #2416, #2420, see also the discussion in ATEL #2421), a quasi-simultaneous radio spectrum of VCS2 J0109+6133 was obtained on Feb. 4, 2010 with the Effelsberg 100-m telescope. We obtain flux densities of (346+/-3) mJy at 2.6 GHz, (392+/-3) mJy at 4.85 GHz, (519+/-6) mJy at 8.3 GHz, (545+/-9) mJy at 10.45 GHz, (534+/-22) mJy at 14.6 GHz, (488+/-46) mJy at 23 GHz and (459+/-46) mJy at 32 GHz. Thus, these new observations reveal the source to exhibit an inverted radio spectrum peaking at ~10-15 GHz.

Compared to historical data the new 5 GHz flux density of 392 mJy appears to be at intermediate levels (1977-1981: 234-551 mJy, Gregory & Taylor 1986, AJ 92, 371). At 8 and 22 GHz, however, the flux density is higher by ~20% and ~50%, respectively, compared to archival observations.

Consequently, the spectral shape as well as the flux density levels are indicative of flaring activity also at radio bands, in agreement with the activity observed by Fermi-GST. We will continue to observe the source with the Effelsberg 100-m and IRAM 30-m telescopes in the 2-230 GHz range over the next months. We encourage observers to observe this source in these and in other spectral bands.