On the Rebrightenings of Classical Novae during the Early Phase

Abstract

We report on the spectral evolution of 6 classical novae (V1186 Sco, V2540 Oph, V4745 Sgr, V5113 Sgr, V458 Vul, and V378 Ser), based on low-resolution spectra obtained at the Fujii-Bisei Observatory and the Bisei Astronomical Observatory, Japan. In the light curves, these 6 novae show several rebrightenings during the early phase lasting $\sim\ $10 d after the first maximum in fast novae, and $\sim\ $100 d in slow novae. The early spectra of all of these novae had emission lines with a P-Cygni profile at the maximum brightness. The absorption component of the P-Cygni profiles then disappeared after the maximum, and reappeared when the novae brightened to the next maximum. We suggest that the re-appearance of the absorption component at the rebrightening can be attributable to a re-expansion of the photosphere after it once shifts sufficiently inside. From the light curves, we found that the time intervals of the rebrightenings of these 6 novae show a similar systematic trend, which is applicable to all types of novae; fast and slow, and Fe II type and hybrid type. Moreover, we note the difference between the spectra at the rebrightenings during the early phase and at the rebrightening in V2362 Cyg, and at the oscillation during the transition phase in V1494 Aql, which means a difference in the physical mechanism of the rebrightening during the early phase and the later oscillations.

Ogle Atlas of Classical Novae. I. Galactic Bulge Objects

“…Tanaka et al (2011) noticed a similar systematic trend for a few other objects with secondary maxima. However, in the case of V5585 Sgr, time intervals shortened from 30 to 20 days; during the late decline, jitters were erratic.…”

“…V2677 Oph (Nova Oph 2012b The nova was discovered by John Seach in six exposures obtained on 2012 May 19.484 UT (Seach 2012 (Rudy et al 2004). In the early light curve, up to two months after the eruption, several rebrightenings were observed (Tanaka et al 2011). Tanaka et al (2011 also noticed that P-Cygni profiles have disappeared between successive brightness maxima.…”

The hybrid, coronal lines nova V5588 Sgr (2011 N.2) and its six repeating secondary maxima

“…it was not an hybrid nova, and its emission lines were twice as wide as in V5588 Sgr. In addition, while the spectra of V5588 Sgr did not change during SdM other than for the appearance of the weak broad pedestal, the emission lines of V4745 Sgr during SdM switched back to strong P-Cyg absorption profiles as for the primary maximum (Csák et al 2005, Tanaka et al 2011.…”

Radioactive Heating Rate of r-process Elements and Macronova Light Curve

“…We present here an analytic modeling which is capable to account for the both effects. Comparing the observations and modelings of the macronova light curves, the total mass of r-process elements produced in GW170817 is estimated as ∼ 0.05M (Cowperthwaite et al 2017;Drout et al 2017;Kasliwal et al 2017;Perego et al 2017;Kasliwal et al 2019;Tanaka et al 2017;Rosswog et al 2018;Waxman et al 2018). However, this mass estimate involves many systematic uncertainties, mostly due to the uncertain opacity and to lesser extent due to the unknown heating rate and ejecta geometry (see, e.g., Kasliwal et al 2019;Kawaguchi et al 2018).…”

“…Deriving a macronova light curve of ejecta with known properties (mass, composition and velocity profiles) requires the calculation of two ingredients -the heating rate and the radiative transfer. The latter is highly uncertain since it is based on the poorly constrained frequency dependent opacity of r-process elements Tanaka et al 2017). The heating rate, however, can be calculated much more accurately, since it depends mostly on physical properties of r-process elements that are measured by experiments.…”