Dust Formation in Common Envelope Binary Interaction -- I: 3D Simulations Using the Bowen Approximation

We carried out 3D smoothed particle hydrodynamics simulations of the common envelope binary interaction using the approximation of Bowen to calculate the dust opacity in order to investigate the resulting dust-driven accelerations. We have simulated two types of binary star: a 1.7 and a 3.7 $M_{\odot}$ thermally-pulsating, asymptotic giant branch stars with a 0.6 $M_{\odot}$ companion. We carried out simulations using both an ideal gas and a tabulated equations of state, with the latter considering the recombination energy of the envelope. We found that the dust-driven wind leads to a relatively small increase in the unbound gas, with the effect being smaller for the tabulated equation of state simulations and for the more massive primary. Dust acceleration does contribute to envelope expansion with only a slightly elongated morphology, if we believe the results from the tabulated equation of state as more reliable. The Bowen opacities in the outer envelopes of the two models, at late times, are large enough that the photosphere of the post-inspiral object is about ten times larger compared to the same without accounting for the dust opacities. As such, the prediction of the appearance of the transient would change substantially if dust is includedComment: 12 Pages, 9 Figure

Discovery of a New Classical Nova Shell Around a Nova-like Cataclysmic Variable

The morphology and optical spectrum of IPHASX J210204.7+471015, a nebula classified as a possible planetary nebula are, however, strikingly similar to those of AT Cnc, a classical nova shell around a dwarf nova. To investigate its true nature, we have obtained high-resolution narrowband [O iii] and [N ii] images and deep optical spectra. The nebula shows an arc of [N ii]-bright knots notably enriched in nitrogen, while an [O iii]-bright bow shock is progressing throughout the ISM. Diagnostic line ratios indicate that shocks are associated with the arc and bow shock. The central star of this nebula has been identified by its photometric variability. Time-resolved photometric and spectroscopic data of this source reveal a period of 4.26 hr, which is attributed to a binary system. The optical spectrum is notably similar to that of RW Sex, a cataclysmic variable star (CV) of the UX UMa nova-like (NL) type. Based on these results, we propose that IPHASX J210204.7 + 471015 is a classical nova shell observed around a CV-NL system in quiescence.© 2018. The American Astronomical Society. All rights reserved.M.A.G. acknowledges support of the grant AYA 2014-57280-P, cofunded with FEDER funds. L.S. acknowledges support from PAPIIT grant IA-101316 (Mexico). G.T. has been supported by grants PAPIIT IN108316 and CONACyT 166376. G. R.-L. acknowledges support from Universidad de Guadalajara, CONACyT, PRODEP, and SEP (Mexico). AA postdoctoral grant and some computational resources are from CONACyT 2015-CB/254132 and UNAM-DGAPA-PAPIIT-107215 projects. N.J.W. acknowledges an STFC Ernest Rutherford Fellowship. This article is partially based upon observations carried out at the Observatorio Astronomico Nacional on the Sierra San Pedro Martir (OAN SPM), Baja California, Mexico. We thank the daytime and night support staff at the OAN SPM for facilitating and helping obtain our observations. Some of the data presented here were obtained with ALFOSC, which is provided by the Instituto de Astrofisica de Andalucia (IAA) under a joint agreement with the University of Copenhagen and NOTSA. This article is based in part on observations made with the Gran Telescopio Canarias (GTC), installed in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias, in the island of La Palma. This paper also makes use of data obtained as part of the INT Photometric Ha Survey of the Northern Galactic Plane (IPHAS: http://www.iphas.org) carried out at the Isaac Newton Telescope (INT). The INT is operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias. All IPHAS data are processed by the Cambridge Astronomical Survey Unit at the Institute of Astronomy in Cambridge. The band-merged DR2 catalog was assembled at the Centre for Astrophysics Research, University of Hertfordshire, supported by STFC grant ST/J001333/1