[Paper Review] On the Galactic Nova Progenitor Population

M. J. Darnley, M. F. Bode+7 more|arXiv (Cornell University)|Mar 11, 2013

Astrophysical Phenomena and Observations1 references3 citations

TL;DR

This paper proposes a new classification scheme for Galactic novae based on the evolutionary state of the secondary star—MS-novae, SG-novae, and RG-novae—using photometric data to identify progenitor populations. It confirms the pre-maximum halt in nova light curves via SMEI data and suggests that low-luminosity red giant novae may be viable progenitors for Type Ia supernovae, challenging previous exclusion criteria.

ABSTRACT

Of the 350 or more known Galactic classical novae, only a handful of them, the recurrent novae, have been observed in outburst more than once. At least eight of these recurrents are known to harbour evolved secondary stars, rather than the main sequence secondaries typical in classical novae. Here we present a selection of the work and rationale that led to the proposal of a new nova classification scheme based not on the outburst properties but on the nature of the quiescent system. Also outlined are the results of a photometric survey of a sample of quiescent Galactic novae, showing that the evolutionary state of the secondary can be easily determined and leading to a number of predictions. We discuss the implications of these results, including their relevance to extragalactic work and the proposed link to type Ia supernovae. We also present a summary of the work using the SMEI instrument to produce exquisite nova light-curves and confirmation of the pre-maximum halt.

Motivation & Objective

• To reclassify Galactic novae based on the quiescent evolutionary state of the secondary star rather than outburst properties.
• To determine the progenitor population of classical and recurrent novae using photometric surveys of quiescent systems.
• To assess the viability of red giant secondary novae as progenitors for Type Ia supernovae, especially in light of recent observational constraints.
• To utilize SMEI data to produce high-cadence light curves and confirm the pre-maximum halt phenomenon in fast novae.
• To enable direct detection of nova progenitors in Local Group galaxies using Hubble Space Telescope imaging.

Proposed method

• Analyzing near-IR photometry from the 2MASS catalogue and Hipparcos data to construct colour-magnitude diagrams of quiescent novae.
• Using SMEI’s 102-minute cadence and 8th magnitude sensitivity to produce complete, high-cadence light curves of bright Galactic novae.
• Applying astrometric and photometric analysis to Hubble Space Telescope ACS/WFC archival data to identify progenitor systems in M31.
• Reconstructing the $2\sigma$ detection limit for progenitor stars in SN 2011fe using optical colour (B-V) and temperature constraints from Li et al. (2011).
• Classifying novae into MS-, SG-, and RG-novae based on the position of their quiescent systems in colour-magnitude diagrams.
• Comparing observed nova progenitor luminosities and colours with theoretical evolutionary tracks of 1 M⊙ and 1.4 M⊙ stars.

Experimental results

Research questions

• RQ1 Can the evolutionary state of the secondary star in quiescent novae be reliably determined from photometric data alone?
• RQ2 To what extent do low-luminosity red giant secondary stars in nova systems evade detection in recent supernova progenitor searches?
• RQ3 Does the pre-maximum halt observed in SMEI light curves have a physical origin linked to accretion dynamics or mass ejection?
• RQ4 Are red giant secondary novae (RG-novae) a viable progenitor channel for Type Ia supernovae, especially when considering less luminous systems?
• RQ5 Can Hubble Space Telescope WFC3/UVIS and IR instruments resolve and identify the progenitor systems of RG-novae in the Local Group?

Key findings

• The SMEI data confirmed the pre-maximum halt in three fast novae (KT Eri, V598 Pup, V1280 Sco), with the halt clearly visible in high-cadence light curves.
• The progenitor of M31N 2007-12b was identified as a system with a red giant secondary star using HST ACS/WFC data, supporting its classification as a recurrent nova.
• A new classification scheme—MS-novae, SG-novae, RG-novae—was proposed based on the secondary star’s evolutionary state, with quiescent colour-magnitude positions strongly correlating with this classification.
• Systems like KT Eri, EU Sct, and V1721 Aql, previously classified as classical novae, are reclassified as RG-novae or SG-novae due to evolved secondaries, despite only one observed outburst.
• The analysis shows that RG-novae with less luminous, less evolved secondaries (e.g., V745 Sco, KT Eri) could have evaded detection in the $2\sigma$ limit of Li et al. (2011) for SN 2011fe, challenging prior exclusion of such systems as SN Ia progenitors.
• HST WFC3/UVIS can in principle resolve the entire RG-nova progenitor population in the Local Group, enabling direct measurement of their contribution to the nova rate.