Nova Mon 2012 resolved as a double radio source
ATel #4408; T. J. O'Brien (Manchester), Jun Yang (JIVE), Zsolt Paragi (JIVE), Laura Chomiuk (Michigan State/NRAO), Teddy Cheung (NRC/NRL), Thomas Nelson (Minnesota), Michael Rupen (NRAO), Greg Taylor (UNM), Jennifer Sokoloski (Columbia), Koji Mukai (UMBC/GSFC), Jennifer Weston (Columbia), Nirupam Roy (NRAO), Amy Mioduszewski (NRAO), Michael Bode (Liverpool John Moores), Stewart Eyres (Central Lancashire)
on 21 Sep 2012; 13:03 UT
Credential Certification: Tim O'Brien (tim.obrien@manchester.ac.uk)
Nova Mon 2012 was first reported as a gamma-ray transient (ATEL #4224), subsequently associated with an optical nova (ATEL #4310, CBET #3202) and detected in the radio (ATEL #4352, #4376) and X-ray/UV (ATEL #4321). This nova is only the third suggested to be associated with gamma-ray emission as detected by the Fermi Large Area Telescope, the others being V407 Cyg (ATEL #2487) in 2010 and Nova Sco 2012 (ATEL #4284).
Following the dramatic brightening at high radio frequencies (ATEL #4352), on Sep 18 we obtained e-VLBI radio observations of Nova Mon 2012 at 5.0 GHz using eight telescopes of the European VLBI Network (EVN), providing resolution of 6x8 milli-arcseconds.
A preliminary analysis of these data shows the source resolved into two compact components aligned NW-SE and separated by about 35 mas. In addition, some extended emission is seen near the NW component. The SE component has a total flux density of about 1.7 mJy whilst the NW component is around 0.8 mJy. With a brightness temperature of order a million Kelvin this emission could be either optically thick thermal bremsstrahlung or synchrotron.
The total flux density measured with the Karl G. Jansky Very Large Array (VLA) on September 8.5 was 4.7 mJy at 4.6 GHz and 9.2 mJy at 7.4 GHz. Since we expect the source was continuing to brighten, it is likely that a significant fraction of the emission from Nova Mon 2012 is resolved out and hence not seen in the much higher-resolution e-EVN observations taken 10 days later.
The coordinates of the brighter component are RA (J2000) 06 39 38.6006 and DEC (J2000) +05 53 52.826 with estimated errors of 1 and 2 mas, respectively. The errors are dominated by the positional errors of the phase-reference source J0645+0541.
If the e-VLBI components are associated with material ejected in the explosion, and if the explosion took place at the time of the gamma-ray transient (June 22) then the separation suggests an expansion speed of 0.4 mas/day.
Observations with the VLA and e-MERLIN are continuing and further observations with EVN are planned. Continued observations at other wavelengths are encouraged.
e-VLBI research infrastructure in Europe is supported by the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement RI-261525 NEXPReS. The EVN is a joint facility of European, Chinese, South African and other radio astronomy institutes funded by their national research councils. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.
E-Nova project website
