Early VLA and AMI-LA Radio Detections of the Nova V392 Per

ATel #11647; J. D. Linford (George Washington University), J. Bright (University of Oxford), L. Chomiuk (Michigan State University), R. Fender (Univ. of Oxford), A. van der Horst (George Washington Univ.), A. Mioduszewski (NRAO), J. Sokoloski (Columbia), M. Rupen (NRC-HIA), T. Nelson (University of Pittsburgh), and K. Mukai (UMBC/NASA GSFC)
on 16 May 2018; 18:21 UT
Credential Certification: Justin Linford (jlinford@gwu.edu)

Tweet

We report radio observations of the young nova V392 Per (ATel #11588, ATel #11590, ATel #11601, ATel #11605, and ATel #11617) with the Karl G. Janksy Very Large Array (VLA) and the Arcminute Microkelvin Imager Large Array (AMI-LA).

We began monitoring V392 Per with the VLA on 2018 April 30, approximately one day after the nova was discovered. To date, we have 3 epochs with the VLA. We have observed with both L-band (1-2 GHz) and C-band (4-8 GHz). Our bandwidth at L-band is 1 GHz, and our bandwidth at C-band is 4 GHz. We split each band into 2 side-bands for better spectral coverage. The total time on source for each observation is about 10 minutes for L-band and 8 minutes for C-band.

We began monitoring the nova with the AMI-LA on 2018 May 11, about 12 days after it was discovered. Our AMI-LA observations are at 15.5 GHz with 5 GHz of total bandwidth. We have 2 AMI-LA epochs to date, both with total observing times of 4 hours.

The nova is clearly detected at 5.0, 7.0, and 15.5 GHz. There is a marginal detection at 1.74 GHz in our most recent VLA observation. Below are the tabulated results from our radio observations to date. The reported uncertainties include statistical uncertainties from fitting the source with an elliptical Gaussian in the image plane, and a 5% absolute flux calibration uncertainty. Upper limits are at 3-sigma levels based on image RMS.

 
Date [UT]    | Instrument | Freq. [GHz] | Flux Density [mJy] | 
============================================================== 
2018-04-30.9 | VLA        | 1.26        | <0.16              | 
             |            | 1.74        | <0.15              | 
             |            | 5.0         | <0.05              | 
             |            | 7.0         | <0.04              | 
============================================================== 
2018-05-08.7 | VLA        | 5.0         | 0.23 +/- 0.02      | 
             |            | 7.0         | 0.30 +/- 0.02      | 
============================================================== 
2018-05-11.5 | AMI-LA     | 15.5        | 1.13 +/- 0.07      | 
============================================================== 
2018-05-12.6 | VLA        | 1.26        | <0.26              | 
             |            | 1.74        | 0.15 +/- 0.04      | 
             |            | 5.0         | 0.50 +/- 0.03      | 
             |            | 7.0         | 0.75 +/- 0.04      | 
============================================================== 
2018-05-13.6 | AMI-LA     | 15.5        | 1.9 +/- 0.1        | 
============================================================== 

The nova is clearly increasing in flux density at all frequencies. Using our C-band observations, an ejecta expansion velocity of 4000 km/s (ATel #11605), and a distance of 3.9 kpc (Darnley & Starrfield 2018), we estimate a brightness temperature on the order of 10^5 K. The expected brightness temperature for nova ejecta emitting via thermal bremsstrahlung is 10^4 K. We therefore suspect there is significant contribution from synchrotron emission, most likely related to the shocks that produced the population of accelerated particles necessary for the detected gamma-ray emission (ATel #11590).

We will continue to monitor this source at radio frequencies, including upcoming observations with very long baseline interferometers. We encourage additional monitoring at all possible wavelengths.

We thank the NRAO and MRAO staff for carrying out these observations.