Five-year optical and near-infrared observations of the extremely slow nova V1280 Scorpii

Abstract

We present optical (B, V, R c , I c and y) and near-infrared (J, H, and K s ) photometric and spectroscopic observations of a classical nova V1280 Scorpii for five years from 2007 to 2011. Our photometric observations show a declining event in optical bands shortly after the maximum light, which took about 250 days to recover. This event was most probably caused by dust formation. The event was accompanied by a short (∼30 days) re-brightening episode (∼2.5 mag in V), which suggests that there had been some re-ignition of the surface nuclear burning. After 2008, the y band observations show a very long plateau at around y = 10.5 for more than 1000 days until April 2011 (∼1500 days after the maximum light). The nova had taken a very long time (∼50 months) to enter the nebular phase, according to a clear detection of both [O iii] 4959 and 5007 and is still continuing to generate the wind caused by H-burning.This finding suggests that historically V1280 Sco is evolving at its slowest ever measured rate. The interval from the maximum light (2007 February 16) to the beginning of the nebular phase is longer than any previously known slow novae: V723 Cas (18 months), RR Pic (10 months), or HR Del (8 months). It suggests that the mass of a white dwarf in the V1280 Sco system might be 0.6 M or lower. The distance, based on our measurements of the expansion velocity combined with the directly measured size of the dust shell, is estimated to be 1.1 ± 0.5 kpc.

The expanding dusty bipolar nebula around the nova V1280 Scorpi

“…Based on an estimate of the total dust mass formed during the 250 days after outburst, Chesneau et al (2008) suggested that a mass as large as 10 −4 M was ejected. Naito et al (2012) provided an independent estimate from neutral oxygen lines that confirmed the high mass ejected, an additional argument for a low-mass WD progenitor, known to statistically eject more mass that fast, massive ones. The interferometric observations also provided a consistent picture of the expansion rate in the plane of the sky estimated at 0.35 mas/d.…”

“…The classical nova V1280 Sco was discovered in outburst by Yamaoka et al (2007) on 2007 February 04.86 (JD = 2 454 136.85), about 12 days before reaching its maximum in visual light (m V ∼ 4) and formed dust only two weeks after reaching maximum in visible (Das et al 2008). This nova experienced one of the slowest evolutions historically reported and the nebular phase was entered about 50 months (t ∼ 1600 d) after outburst (Naito et al 2012). This is a clear indication that the mass of the erupting WD is low (i.e.…”

“…The V flux has reached a roughly stable plateau at a magnitude of about 10.5 over a long period (Naito et al 2012) and the central source radiates efficiently in the K band. As shown by , the nova is still powering a strong wind, and extensive nuclear burning is thus thought to have continued.…”

“…This much smaller distance estimate demands that the VLTI-derived distance be scrutinized. Using the spatial expansion rate from the VLTI but a revised velocity range of the dust-forming ejecta of 350 ± 160 km s −1 based on the mean velocity measured from blue-shifted absorption lines of OI and SiII, Naito et al (2012) derived a revised distance of 1.1 ± 0.5 kpc.…”

A search and modeling of peculiar narrow transient line components in novae spectra

“…The majority of the selected novae are classified as fast or very fast novae, with one exception: Nova Sco 2007 (V1280 Sco). The actual decay time of this nova is uncertain due to the massive dust formation in the early phase of the outburst (Naito et al 2012), but it is considered a slow nova. Therefore it is possible that the presence of the transient narrow emission line component was related to the speed class.…”