First Radio Detections of the Two 2015 Novae in Sagittarius
ATel #7744; J. Linford (Michigan State), L. Chomiuk (Michigan State), T. Nelson (Minnesota), J. Sokoloski (Columbia), K. Mukai (UMBC/NASA GSFC), T. Finzell (Michigan State), J. Weston (Columbia), M. Rupen (NRC-HIA) and A. Mioduszewski (NRAO)
on 1 Jul 2015; 20:55 UT
Credential Certification: Justin Linford (jlinford@msu.edu)
We report detections of Nova Sgr 2015 No. 1 (PNV J18142514-2554343; CBET 4079) and Nova Sgr 2015 No. 2 (PNV J18365700-2855420; CBET 4080) with the Karl G. Janksy Very Large Array (VLA). We have been monitoring No. 1 since 2015 February 19 and No. 2 since 2015 March 17. We have observed the novae with the VLA at L-band (1-2 GHz), C-band (4-8 GHz), Ku-band (12-18 GHz), and Ka-band (27-40 GHz). Both novae were detected for the first time in the 2015 April 21.4 observation. Here, we present results from observations on 2015 April 21.4, 2015 May 16.3, and 2015 June 14.2.
Below are the tabulated results from the three epochs. All non-detections are 3-sigma upper limits. '***' indicates no observation at that frequency. 'xxx' indicates an observation was made but the data were unreliable.
Nova Sgr 2015 No. 1
2015-04-21.4 | | 2015-05-16.3 | | 2015-06-14.2 |
Freq. | Flux density | | Freq. | Flux density | | Freq. | Flux density |
[GHz] | [mJy] | | [GHz] | [mJy] | | [GHz] | [mJy] |
1.26 | <0.34 | | 1.26 | *** | | 1.26 | *** |
1.77 | <0.14 | | 1.77 | *** | | 1.77 | *** |
5.0 | <0.03 | | 4.5 | <0.06 | | 5.0 | <0.05 |
7.0 | <0.03 | | 7.4 | <0.05 | | 7.0 | <0.06 |
13.5 | *** | | 13.5 | <0.04 | | 13.5 | 0.11 ± 0.02 |
16.5 | *** | | 16.5 | <0.05 | | 16.5 | 0.19 ± 0.02 |
29.5 | 0.13 ± 0.02 | | 29.5 | xxx | | 29.5 | 0.36 ± 0.04 |
35.0 | 0.11 ± 0.03 | | 35.0 | xxx | | 35.0 | 0.40 ± 0.06 |
Nova Sgr 2015 No. 2
2015-04-21.4 | | 2015-05-16.3 | | 2015-06-14.2 |
Freq. | Flux density | | Freq. | Flux density | | Freq. | Flux density |
[GHz] | [mJy] | | [GHz] | [mJy] | | [GHz] | [mJy] |
1.26 | <0.75 | | 1.26 | *** | | 1.26 | <0.60 |
1.77 | <0.22 | | 1.77 | *** | | 1.77 | <0.25 |
5.0 | <0.04 | | 4.5 | 0.22 ± 0.02 | | 5.0 | 0.58 ± 0.02 |
7.0 | 0.06 ± 0.01 | | 7.4 | 0.40 ± 0.02 | | 7.0 | 0.84 ± 0.02 |
13.5 | *** | | 13.5 | 0.61 ± 0.02 | | 13.5 | 2.24 ± 0.02 |
16.5 | *** | | 16.5 | 0.70 ± 0.02 | | 16.5 | 3.05 ± 0.03 |
29.5 | 0.52 ± 0.03 | | 29.5 | xxx | | 29.5 | 2.99 ± 0.10 |
35.0 | 0.57 ± 0.03 | | 35.0 | xxx | | 35.0 | 2.87 ± 0.15 |
There is no evidence for strong synchrotron emission associated with forward shocks against a giant companion wind, as observed in embedded novae such as RS Oph, V745 Sco. Neither of the novae is likely to have post-sequence companion stars. The gamma-rays detected from Nova Sgr 2105 No. 2 by the Fermi Gamma Ray Space Telescope (ATEL #7283, #7315) are therefore likely to be the result of a population of accelerated particles created by internal shocks, similar to V959 Mon (ATEL #4224, #4321), V339 Del (ATEL #5302), and V1369 Cen (ATEL #5649, #5685).
We will continue to monitor both of these novae with the VLA, and we are especially looking forward to obtaining high-resolution images during the current A-configuration campaign. We strongly encourage others to monitor them at other wavelengths.
