Dramatic Brightening of Nova Mon 2012 at High Radio Frequencies
ATel #4352; 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), Tim O'Brien (Manchester)
on 5 Sep 2012; 04:51 UT
Credential Certification: Laura Chomiuk (lchomiuk@cfa.harvard.edu)
Nova Mon 2012 was first identified as an astrophysical transient via its gamma
ray emission with the Fermi Large Area Telescope on 2012 June 22 (ATel #4224);
the associated optical nova was not discovered until 2012 Aug 9 (CBET #3202, ATel
#4310). Our Karl G. Jansky Very Large Array (VLA) monitoring program of Fermi
transients (PI Cheung) provided a radio detection of this source on 2012 June
30, significantly before its optical discovery. At first, its radio spectrum
appeared relatively flat; subsequently the source has brightened significantly
and shows a spectrum that rises steeply towards high frequencies. To date, the
measured VLA flux densities and observed frequencies (GHz) for this transient
are as follows (values are in mJy; upper limits are 3 σ).
| Date |
ν |
Sν |
ν |
Sν |
ν |
Sν |
ν |
Sν |
| June 30.7 2012 |
1.3 |
< 0.63 |
1.8 |
< 0.42 |
5.0 |
0.26 ± 0.03 |
6.0 |
0.16± 0.03 |
| July 4.7 2012 |
1.3 |
0.11 ± 0.20 |
1.8 |
0.42 ± 0.09 |
5.0 |
0.31 ± 0.05 |
6.0 |
0.42 ± 0.07 |
| July 28.6 2012 |
1.4 |
0.54 ± 0.14 |
1.8 |
0.37 ± 0.08 |
5.0 |
0.70 ± 0.04 |
6.0 |
0.84 ± 0.05 |
| Sept 1.4 2012 |
1.3 |
0.39 ± 0.07 |
1.8 |
0.65 ± 0.06 |
4.6 |
3.52 ± 0.03 |
7.4 |
7.16 ± 0.03 |
| |
13.3 |
20.20 ± 0.05 |
17.4 |
30.82 ± 0.10 |
27.5 |
73.59 ± 0.16 |
36.5 |
109.29 ± 0.36 |
The most recent epoch was observed as part of our newly approved program
for further multi-frequency monitoring of Nova Mon 2012 with the VLA. Further
observations with other instruments are strongly encouraged.
Assuming the emission is thermal with the surface brightness of a blackbody of
temperature 10
4 K, the most recent 4.6 GHz flux density implies a size of
order 150 mas. Combining this with a velocity of roughly 2000 km/s and an
explosion date corresponding to the first Fermi detection (22 June; ATel #
4224)
implies a distance of around 1.4 kpc. If the radio-emitting material was
ejected later the same argument would lead to a closer distance.
E-Nova Project Website
