HST FUV spectroscopy of the short orbital period recurrent nova CI Aql: Implications for white dwarf mass evolution

Abstract

An HST COS Far UV spectrum (1170 A to 1800 A) was obtained for the short orbital period recurrent novae (T Pyxidis subclass), CI Aquilae. CI Aql is the only classical CV known to have two eclipses of sensible depth per orbit cycle and also have pre- and post-outburst light curves that are steady enough to allow estimates of mass and orbital period changes. Our FUV spectral analysis with model accretion disks and NLTE high gravity photospheres, together with the Gaia parallax, reveal CI Aql's FUV light is dominated by an optically thick accretion disk with an accretion rate of the order of $4\times 10^{-8}$ $M_{\odot }/yr$. Its database of light curves, radial velocity curves, and eclipse timings is among the best for any CV. Its orbit period ($P$), $dP/dt$, and reference time are re-derived via simultaneous analysis of the three data types, giving a dimensionless post-outburst $dP/dt$ of $-2.49\pm 0.95\times 10^{-10}$. Lack of information on loss of orbital to rotational angular momentum leads to some uncertainty in the translation of $dP/dt$ to white dwarf mass change rate, $d{M}_1/dt$, but within the modest range of $+4.8\times 10^{-8}$ to $+7.8\times 10^{-8}$ $M_{\odot }/yr$. The estimated white dwarf mass change through outburst for CI Aql, based on simple differencing of its pre- and post outburst orbit period, is unchanged from the previously published $+5.3\times 10^{-6}{M}_{\odot }$. At the WD's estimated mass increase rate, it will terminate as a Type Ia supernova within 10 million years.

arXiv commentApJ, in press

References in corpus (17)

• Gaia Data Release 2: using Gaia parallaxes
• An Extended Grid of Nova Models: II. The Parameter Space of Nova Outbursts
• Comprehensive Photometric Histories of All Known Galactic Recurrent Novae
• Detailed Mid- and Far-Ultraviolet Model Spectra for Accretion Disks in Cataclysmic Binaries
• The Distances to Novae As Seen By Gaia
• On the Progenitors of Galactic Novae
• The Masses and Accretion Rates of White Dwarfs in Classical and Recurrent Novae
• Identifying and Quantifying Recurrent Novae Masquerading as Classical Novae
• The Change of the Orbital Periods Across Eruptions and the Ejected Mass For Recurrent Novae CI Aquilae and U Scorpii
• Modifying the Standard Disk Model for the Ultraviolet Spectral Analysis of Disk-dominated Cataclysmic Variables. I. The Novalikes MV Lyrae, BZ Camelopardalis, and V592 Cassiopeiae
• Modelling the Recurrent Nova CI Aql in Quiescence
• Distances of CVs and related objects derived from Gaia Data Release 1
• CI Aql: a Type Ia supernova progenitor?
• Chandra observations of the recurrent nova CI Aql after its April 2000 outburst
• The Long-Term Secular Mass Accretion Rate of the Recurrent Nova T Pyxidis
• On the Effect of Explosive Thermonuclear Burning on the Accreted Envelopes of White Dwarfs in Cataclysmic Variables
• The slow decline of the Galactic recurrent novae T Pyxidis, IM Normae, and CI Aquilae

Cited by in corpus (2)

• Carbon-Oxygen Classical Novae are Galactic ${}^7$Li Producers as well as Potential Supernova Ia Progenitors
• Connecting the m-dots: accretion rates and thermonuclear burst recurrence times on neutron stars and white dwarfs