Thick inhomogeneous shell models for the radio emission from Nova Serpentis 1970

Metzger

et al. 2018

ApJ

It has recently been discovered that some, if not all, classical novae emit GeV gamma-rays during outburst, but the mechanisms involved in the production ofgamma-rays are still not well understood. We present here a comprehensive multiwavelength data set-from radio to X-rays-for the most gamma-ray-luminous classical nova to date, V1324 Sco. Using this data set, we show that V1324 Sco is a canonical dusty Fe II-type nova, with a maximum ejecta velocity of 2600 km s −1 and an ejecta mass of a few´-10 5  M . There is also evidence for complex shock interactions, including a double-peaked radio light curve which shows high brightness temperatures at early times. To explore why V1324Sco was so gamma-ray luminous, we present a model of the nova ejecta featuring strong internal shocks and find that higher gamma-ray luminosities result from higher ejecta velocities and/or mass-loss rates. Comparison of V1324Sco with other gamma-ray-detected novae does not show clear signatures of either, and we conclude that a larger sample of similarly well-observed novae is needed to understand the origin and variation of gamma-rays in novae.

Section: Second Radio Maximum and Determination Of Ejecta Masssupporting

confidence: 68%

Section: Radio Datamentioning

confidence: 99%

A Detailed Observational Analysis of V1324 Sco, the Most Gamma-Ray-luminous Classical Nova to Date

Finzell

Metzger

et al. 2018

ApJ

“…Thereafter, it remained roughly flat or falling with frequency for all subsequent observations (see Figure 5). A freely expanding isothermal remnant (as in the so-called Hubble-flow model) is expected to remain completely optically thick during the initial period of radio brightening, producing the characteristic steeply rising spectrum of a blackbody in the Rayleigh-Jeans limit (e.g., Seaquist & Palimaka 1977;Hjellming et al 1979;Bode & Evans 2008). Indeed, radio emission from novae during the early stages of expansion of the remnant often has a spectral index α > 1 (e.g., 1.5 at low frequencies for V705 Cas, 1.6 for V339 Del; Eyres et al 2000;Chomiuk et al 2013).…”

Section: Radio Emissionmentioning

confidence: 99%

Shock-powered radio emission from V5589 Sagittarii (Nova Sgr 2012 #1)

Weston

Sokoloski

Mon. Not. R. Astron. Soc.

et al. 2016

Since the Fermi discovery of γ-rays from novae, one of the biggest questions in the field has been how novae generate such high-energy emission. Shocks must be a fundamental ingredient. Six months of radio observations of the 2012 nova V5589 Sgr with the VLA and 15 weeks of X-ray observations with Swift/XRT show that the radio emission consisted of: 1) a shock-powered, non-thermal flare; and 2) weak thermal emission from 10 −5 M of freely expanding, photoionized ejecta. Absorption features in the optical spectrum and the peak optical brightness suggest that V5589 Sgr lies 4 kpc away (3.2-4.6 kpc). The shock-powered flare dominated the radio light curve at low frequencies before day 100. The spectral evolution of the radio flare, its high radio brightness temperature, the presence of unusually hard (kT x > 33 keV) X-rays, and the ratio of radio to X-ray flux near radio maximum all support the conclusions that the flare was shock-powered and non-thermal. Unlike most other novae with strong shock-powered radio emission, V5589 Sgr is not embedded in the wind of a redgiant companion. Based on the similar inclinations and optical line profiles of V5589 Sgr and V959 Mon, we propose that shocks in V5589 Sgr formed from collisions between a slow flow with an equatorial density enhancement and a subsequent faster flow. We speculate that the relatively high speed and low mass of the ejecta led to the unusual radio emission from V5589 Sgr, and perhaps also to the non-detection of γ-rays.

“…The radio emission from most novae is thermal emission from the ionized expanding ejecta expelled in the nova event itself (Seaquist & Palimaka 1977;Hjellming et al 1979;Seaquist et al 1980), although a few novae with unusually dense environments have shown synchrotron emission or thermal emission from the circumbinary medium (Kantharia et al 2007;Rupen et al 2008;Chomiuk et al 2012). In the classical picture of thermal emission from novae, a multi-frequency radio light curve measures the entire density profile of the ejecta by monitoring the recession of the radio photosphere.…”

Section: Introductionmentioning

confidence: 99%

The 2011 Outburst of Recurrent Nova T Pyx: Radio Observations Reveal the Ejecta Mass and Hint at Complex Mass Loss

Nelson

Roy

et al. 2014

ApJ

Despite being the prototype of its class, T Pyx is arguably the most unusual and poorly understood recurrent nova. Here, we use radio observations from the Karl G. Jansky Very Large Array to trace the evolution of the ejecta over the course of the 2011 outburst of T Pyx. The radio emission is broadly consistent with thermal emission from the nova ejecta. However, the radio flux began rising surprisingly late in the outburst, indicating that the bulk of the radio-emitting material was either very cold, or expanding very slowly, for the first ∼50 days of the outburst. Considering a plausible range of volume filling factors and geometries for the ejecta, we find that the high peak flux densities of the radio emission require a massive ejection of (1 − 30) × 10 −5 M ⊙ . This ejecta mass is much higher than the values normally associated with recurrent novae, and is more consistent with a nova on a white dwarf well below the Chandrasekhar limit.