A Mystery in Chamaeleon: Serendipitous Discovery of a Galactic Symbiotic Nova

Abstract

We present the serendipitous discovery of a low luminosity nova occurring in a symbiotic binary star system in the Milky Way. We lay out the extensive archival data alongside new follow-up observations related to the stellar object V${}^{\ast }$ CN Cha in the constellation of Chamaeleon. The object had long period ($\sim 250$day), high amplitude ($\sim 3$mag) optical variability in its recent past, preceding an increase in optical brightness by $\sim 8$magnitudes and a persistence at this luminosity for about 3 years, followed by a period of $\sim 1.4\mathrm{mag}{\mathrm{yr}}^{-1}$ dimming. The object's current optical luminosity seems to be dominated by H$\alpha$ emission, which also exhibits blue-shifted absorption (a P-Cygni-like profile). After consideration of a number of theories to explain these myriad observations, we determine that V${}^{\ast }$ CN Cha is most likely a symbiotic (an evolved star-white dwarf binary) system which has undergone a long-duration, low luminosity, nova. Interpreted in this way, the outburst in V${}^{\ast }$ CN Cha is among the lowest luminosity novae ever observed.

Submitted to AJ, 19 pages, 9 figure

References in corpus (14)

• The Gaia mission
• The Transiting Exoplanet Survey Satellite
• Theory of Star Formation
• galpy: A Python Library for Galactic Dynamics
• The All-Sky Automated Survey for Supernovae (ASAS-SN) Light Curve Server v1.0
• Initial Performance of the NEOWISE Reactivation Mission
• 4MOST: Project overview and information for the First Call for Proposals
• A Large Catalog of Accurate Distances to Local Molecular Clouds: The Gaia DR2 Edition
• A census of symbiotic stars in the 2MASS, WISE and Gaia surveys
• Gaia 17bpi: An FU Ori Type Outburst
• The Swift-UVOT ultraviolet and visible grism calibration
• Gaia 19ajj: A Young Star Brightening Due to Enhanced Accretion + Reduced Extinction
• Determination of pulsation periods and other parameters of 2875 stars classified as MIRA in the All Sky Automated Survey (ASAS)
• Multi-wavelength Observations of the 2015 Nova in the Local Group Irregular Dwarf Galaxy IC 1613

Cited by in corpus (3)

• Symbiotic stars in the era of modern ground- and space-based surveys
• The GALAH survey: Characterization of emission-line stars with spectral modelling using autoencoders
• Theoretical light curve models of the symbiotic nova CN Cha -- Optical flat peak for three years