Photometric evolution, orbital modulation and progenitor of Nova Mon 2012

Journal article

Authors/Editors

Ribeiro, Valério

Research Areas

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Publication Details

Author list: Munari U, Dallaporta S, Castellani F, Valisa P, Frigo A, Chomiuk L, Ribeiro VARM

Publisher: Oxford University Press (OUP): Policy P - Oxford Open Option A

Place: OXFORD

Publication year: 2013

Journal: Monthly Notices of the Royal Astronomical Society (0035-8711)

Journal acronym: MON NOT R ASTRON SOC

Volume number: 435

Issue number: 1

Start page: 771

End page: 781

Number of pages: 11

ISSN: 0035-8711

eISSN: 1365-2966

Languages: English-Great Britain (EN-GB)

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Abstract

We present and discuss accurate and densely mapped BVRCIC light curves of the neon Nova Mon 2012, supplemented by the evolution in Stromgren b and y bands and in the integrated flux of relevant emission lines. Our monitoring started with the optical discovery of the nova (50 days past the first detection in gamma-rays by Fermi-LAT) and extend to day +270, well past the end of the super-soft phase in X-rays. The nova was discovered during the nebular decline, well past t(3) and the transition to optically thin ejecta. It displayed very smoothly evolving light curves. A bifurcation between y and V light curves took place at the start of the super-soft X-ray source (SSS) phase, and a knee developed towards the end of the SSS phase. The apparent magnitude of the nova at the unobserved optical maximum is constrained to +3 <= V <= 4.5. The appearance, grow in amplitude and then demise of a 0.29585 (+/- 0.00002) days orbital modulation of the optical brightness was followed along the nova evolution. The observed modulation, identical in phase and period with the analogue seen in the X-ray and satellite ultraviolet, has a near-sinusoidal shape and a weak secondary minimum at phase 0.5. We favour an interpretation in terms of super-imposed ellipsoidal distortion of the Roche lobe filling companion and irradiation of its side facing the WD. Similar light curves are typical of symbiotic stars where a Roche lobe filling giant is irradiated by a very hot WD. Given the high orbital inclination, mutual occultation between the donor star and the accretion disc could contribute to the observed modulation. The optical+infrared spectral energy distribution of Nova Mon 2012 during the quiescence preceding outburst is nicely fitted by an early K-type main-sequence star (similar to K3V) at 1.5 kpc distance, reddened by E(B - V) = 0.38, with a WD companion and an accretion disc contributing to the observed blue excess and moderate Ha emission. A typical early K-type main-sequence star with a mass of similar to 0.75 M-circle dot and a radius of similar to 0.8 R-circle dot would fill its Roche lobe for a P = 0.29585 d orbital period and a more massive WD companion (as implied by the large Ne overabundance of the ejecta).

Keywords

novae, cataclysmic variables

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