Infrared spectroscopy of the recent outburst in V1047 Cen (Nova Centauri 2005) (1910.12786v1)

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 $(\dot{M}\sim10^{-8}$M$_\odot$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 $(\dot{M}\sim10^{-10}$M$_\odot$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 paper reveals that V1047 Cen’s 2019 outburst, occurring only 14 years after its classical nova eruption, challenges prevailing hibernation models.
• Utilizing Gemini South near-IR spectra, the study identifies high-velocity H I and He I emission lines with complex profiles indicative of intricate outflow dynamics.
• The extended brightness and signs of coronal activity suggest deeper insights into binary accretion processes, prompting revisions to current theoretical frameworks.

Infrared Spectroscopy of the Recent Outburst in V1047 Cen

The paper under review presents a detailed account of the infrared spectroscopic observations conducted on V1047 Cen, a cataclysmic variable system that exhibited an outburst in 2019. This event occurred fourteen years after its classical nova (CN) eruption in 2005, which is notably the shortest recorded gap between a CN outburst and a subsequent dwarf nova (DN) eruption. The paper aims to explore the characteristics of this rare event using near-infrared spectroscopy and light curve analysis, offering insights into the behavior of such systems.

Observational Insights and Key Findings

V1047 Cen, discovered in outburst again in April 2019, presented an uncommon astrophysical phenomenon. Traditionally, DN eruptions are not expected shortly after a CN event due to the prolonged high mass accretion phases theoretically predicted post-eruption. However, the 2019 event contradicts these expectations, providing a unique case paper.

The observational data encompassed two sets of near-infrared spectra captured by the Gemini South telescope. The spectra showcased significant emission lines, including #1{H}{i} and #1{He}{i}, with velocities up to 2000 km/s and peculiar line profiles hinting at a potentially intricate wind or outflow system. Notably absent were signatures typically recognized in recurrent novae, such as pronounced C, N, and O lines, except for a singular #1{O}{i} line detected in August observations.

The light curve notes a persistent brightness over several months, atypical for DN events, which generally last for shorter durations. This prolonged nature adds another dimension to the paper, as does the detection of potential coronal activity signified by the presence of #1{Si}{vi} in the spectra.

Theoretical Context and Challenges

The consistent gap between CN and DN outbursts in V1047 Cen poses a challenge to standard models, most notably the "hibernation" paradigm. Typically, post-CN systems exhibit high luminosity and mass accretion, deterring DN activity, which thrives under lower accretion conditions. The rapid recurrence of eruptions in V1047 Cen thus calls for a reconsideration or modification of existing theories to explain the conditions conducive to such phenomena.

Possible explanations could involve atypically high outer disk radii leading to higher accretion rates, as seen in systems like GK Per. The paper implies that the orbital characteristics and specifics of the accretion disk system may play a critical role in this unexpected DN activity.

Implications and Future Prospects

The observations and findings in this paper hold considerable implications for the field of cataclysmic variable research. The deviation from established behavior in V1047 Cen may guide future theoretical adjustments or alternative models for nova development and recurrence. Furthermore, the tracking and analysis of such systems could enhance understanding of accretion dynamics and mass transfer processes in binary systems.

Subsequent observational campaigns are recommended to monitor the evolution of V1047 Cen's outbursts and to determine if the peculiarities of this system are shared by other similar astrophysical objects. Follow-up studies integrating multi-wavelength approaches might also shed light on the broader applicability of the findings and contribute to refining the theoretical framework governing CV systems.