e-EVN observations of V1674 Her
ATel #14758; Z. Paragi (JIVE), U. Munari (INAF Padova), J. Yang (OSO), P. Veres (UAH), B. Marcote (JIVE), M. Giroletti (INAF-IRA Bologna)
on 6 Jul 2021; 15:29 UT
Credential Certification: Zsolt Paragi (zparagi@jive.nl)
Subjects: Radio, Nova, Transient
Here we report on very long baseline interferometry (VLBI) observations on Nova Her 2021 (V1674 Her, TCP J185730.95+165339.6; CBAT 2021 06 12.537, ATel #14704 #14705 #14710) with the European VLBI Network in one of its real-time correlation sessions (e-EVN).
The initial spectrum of V1674 Her was consistent with that of a classical nova with slow ejecta, but within a day the spectrum showed very broad absorption lines, indicative of a fast outflow (ATel #14704, #14710, #14718). The early Fermi detection is also consistent with high-speed ejecta (ATel #14705) and may be indicative of an interaction between the slow and fast outflows (ATel #14710, #14718). Kuin et al. (ATel #14736) note that the flat-topped line profiles reported by Woodward et al. (ATel #14723) and the rapid variability suggest a cone or jet-like geometry. Radio detection with the VLA (ATel #14731) between 5.1 - 34.9 GHz showed brightness temperatures in excess of 10^4 K, indicative of non-thermal emission.
We carried out 10-hours of e-EVN observations starting at 18:00 UT on 22 June 2021 (10 days after discovery), to probe the non-thermal emission on milliarcsecond scales. The dual-circular polarization observations were carried out at a central frequency of 1.6 GHz, with a bandwidth of 128 MHz per polarization (1 Gbit/s data rate, 2-bit sampling). The participating stations were Jodrell Bank (Mk2), Westerbork (single dish), Effelsberg, Irbene, Medicina, Noto, Onsala85, Tianma65, Torun, Hartbeesthoek, and the e-MERLIN outstations (limited to 64 MHz bandwidth) Darnhall, Knockin, and Pickmere. We do not detect emission at 1.6 GHz at the nova position (RA 18:57:30.978 DEC +16:53:39.49 +/-0.01" J2000; Kirill Sokolovsky & Laura Chomiuk, priv. comm.). Our preliminary result is a 3-sigma upper limit of 36 microJy/beam.
On a different note, the phase-reference calibrator to Nova Her in this observation was J1751+0939 (or 1749+096). This is a blazar currently in optical outburst (ATel #14727). Our EVN data on this calibrator source is available on request.
The European VLBI Network is a joint facility of independent European, African, Asian, and North American radio astronomy institutes. Scientific results from data presented in this publication are derived from the following EVN project code: RP033.
