Infrared Spectroscopy of the Recent Outburst in V1047 Cen (Nova Centauri 2005)

Abstract

Fourteen years after its eruption as a classical nova (CN), V1047 Cen (Nova Cen 2005) began an unusual re-brightening in 2019 April. The amplitude of the brightening suggests that this is a dwarf nova (DN) eruption in a CN system. Very few CNe have had DN eruptions within decades of the main CN outburst. The 14 years separating the CN and DN eruptions of V1047 Cen is the shortest of all instances recorded thus far. Explaining this rapid succession of CN and DN outbursts in V1047 Cen may be challenging within the framework of standard theories for DN outbursts. Following a CN eruption, the mass accretion rate is believed to remain high (Ṁ ∼ 10 −8 M ⊙ yr −1 ) for a few centuries, due to the irradiation of the secondary star by the still-hot surface of the white dwarf. Thus a DN eruption is not expected to occur during this high mass accretion phase as DN outbursts, which result from thermal instabilities in the accretion disk, and arise during a regime of low mass accretion rate (Ṁ ∼ 10 −10 M ⊙ yr −1 ). Here we present near-infrared spectroscopy to show that the present outburst is most likely a DN eruption, and discuss the possible reasons for its early occurrence. Even if the present re-brightening is later shown to be due to a cause other than a DN outburst, the present study provides invaluable documentation of this unusual event.

The 2019 outburst of the 2005 classical nova V1047 Cen: a record breaking dwarf nova outburst or a new phenomenon?

“…In order to derive the reddening towards the system, we use the equivalent widths of several absorption lines from diffuse interstellar bands, in combination with the empirical relations from Friedman et al (2011). We derive an average E(B −V ) ≈ 1.0±0.1 and A V = 3.0±0.1 for R V = 3.1, in good agreement with the results of Geballe et al (2019). We avoid using the interstellar Na i D absorption doublet due to saturation.…”

“…This is because, in systems characterized by long orbital periods, the accretion disk is large enough that the critical mass accretion rate, below which DN outbursts are possible, is also large. This critical mass accretion rate scales with the radius of the accretion disk as R 2.6 (Kim et al 1992;Cannizzo 1993;Warner 1995;Geballe et al 2019). Therefore, in the cases of GK Per and V1017 Sgr, with orbital periods around 2 and 5.7 days respectively, the fact that they show DN outbursts soon after nova eruptions is not surprising (Kim et al 1992).…”

“…The Gemini and SOFIA IR spectra are represented in Figures 14 and 15, respectively. A detailed description and analysis of the IR spectral evolution during the first 120 days of the outburst is presented in Geballe et al (2019). The Gemini JHK spectra obtained on day 322 show emission lines of H i (Paschen, Brackett, and Pfund series), He i, He ii, and O i.…”

“…Aydi et al (2019) reported optical spectroscopy, which showed DN outburst spectral features superimposed on spectral features of a classical nova nebula. Geballe et al (2019) reported infrared spectroscopy of the then ongoing outburst, during its first 160 days, concluding that the event was possibly a DN outburst. However, upon further follow-up, the 2019 outburst of V1047 Cen seems to be a more exotic phenomenon.…”

Galactic and Extragalactic Novae – A Multiwavelenght Review

“…The hibernation model predictions are in agreement with the observed decline rates of old novae [50] and the observation of shells around the dwarf novae Z Cam [160], AT Cnc [161] (that underwent a nova eruption about three centuries ago [165]), the dwarf nova in Te 11 (associated to the nova 483 CE in Orion) [94], the nova-like systems V1315 Aql [139] and IPHASX J210204.7+471015 [61]. Some novae have shown dwarf nova outbursts: V1213 Cen [99], V1047 Cen [57], Nova Sco 1437 AD [163].…”