Near-Ir Studies of Recurrent Nova V745 Scorpii During Its 2014 Outburst

Abstract

The recurrent nova (RN) V745 Scorpii underwent its third known outburst on 2014 February 6. Infrared monitoring of the eruption on an almost daily basis, starting from 1.3d after discovery, shows the emergence of a powerful blast wave generated by the high velocity nova ejecta exceeding 4000 kms −1 plowing into its surrounding environment. The temperature of the shocked gas is raised to a high value exceeding 10 8 K immediately after outburst commencement. The energetics of the outburst clearly surpass those of similar symbiotic systems like RS Oph and V407 Cyg which have giant secondaries. The shock does not show a free-expansion stage but rather shows a decelerative Sedov-Taylor phase from the beginning. Such strong shockfronts are known to be sites for γ ray generation. V745 Sco is the latest nova, apart from five other known novae, to show γ ray emission. It may be an important testbed to resolve the crucial question whether -2all novae are generically γ ray emitters by virtue of having a circumbinary reservoir of material that is shocked by the ejecta rather than γ ray generation being restricted to only symbiotic systems with a shocked red giant (RG) wind. The lack of a free-expansion stage favors V745 Sco to have a density enhancement around the white dwarf (WD), above that contributed by a RG wind. Our analysis also suggests that the WD in V745 Sco is very massive and a potential progenitor for a future SN Ia explosion.

M31N 2008-12a—THE REMARKABLE RECURRENT NOVA IN M31: PANCHROMATIC OBSERVATIONS OF THE 2015 ERUPTION

“…In agreement with NIR studies by Banerjee et al (2014), Drake et al (2016) interpreted the observational characteristics of the V745Sco eruption as a high-velocity blast wave interacting with an RG wind. This is consistent with early Fermi-LAT γ-ray detections (Cheung et al 2014).…”

“…Below we discuss that M31N 2008-12ahad a hotter SSS maximum than V745Sco, which would increase the contrast between the maximum count rate and the early hard emission for our nova by a factor of ∼3 based on temperature only. Additionally, the ejected mass of V745Sco was consistently estimated by Banerjee et al (2014), Page et al (2015), and Drake et al (2016) as ∼ -10 7   M , which is more than a factor of two higher than that for our object (HND15,DHS15).…”

“…This is consistent with early Fermi-LAT γ-ray detections (Cheung et al 2014). Banerjee et al (2014) showed the narrowing of the Pa β FWHM, suggesting that the shock was propagating into a wind that was not spherically symmetric. Drake et al (2016) inferred a collimation of the blast wave by an equatorial density enhancement.…”

A NuSTAR observation of the fast symbiotic nova V745 Sco in outburst

“…Dürbeck (1989) described the 1989 outbursts and classified the nova as a symbiotic system because of the TiO bands, clearly detected already in outburst, which are typical of an M6 III spectral type. In subsequent observations in quiescence the secondary was classified in the range M6±2 III, depending on indicators in the infrared and optical spectrum (see brief review by Banerjee et al 2014). V745 Sco was observed in X-rays in quiescence in 2010, and appeared as a faint, absorbed X-ray source (Luna et al 2014).…”

COLLIMATION AND ASYMMETRY OF THE HOT BLAST WAVE FROM THE RECURRENT NOVA V745 Sco

“…The explosion triggered observing campaigns over the entire electromagnetic spectrum, including radio (Rupen et al 2014;Kantharia et al 2016), infrared (Banerjee et al 2014), optical (Anupama et al 2014;Mróz et al 2014), X-ray Drake et al 2014;Mukai et al 2014;Page et al 2015), hard X-ray (Rana et al 2014;Orio et al 2015), and γ-ray (Cheung et al 2014(Cheung et al , 2015 wavelengths. Page et al (2015) present a detailed summary of the various observations.…”