The recurrent symbiotic nova V745 Sco exploded on 2014 February 6 and was observed on February 22 and 23 by the Chandra X-ray Observatory Transmission Grating Spectrometers. By that time the supersoft source phase had already ended, and Chandra spectra are consistent with emission from a hot, shock-heated circumstellar medium with temperatures exceeding 107 K. X-ray line profiles are more sharply peaked than expected for a spherically symmetric blast wave, with a full width at zero intensity of approximately 2400 km s-1, an FWHM of 1200 ± 30 km s-1, and an average net blueshift of 165 ± 10 km s-1. The red wings of lines are increasingly absorbed toward longer wavelengths by material within the remnant. We conclude that the blast wave was sculpted by an aspherical circumstellar medium in which an equatorial density enhancement plays a role, as in earlier symbiotic nova explosions. Expansion of the dominant X-ray-emitting material is aligned close to the plane of the sky and is most consistent with an orbit seen close to face-on. Comparison of an analytical blast wave model with the X-ray spectra, Swift observations, and near-infrared line widths indicates that the explosion energy was approximately 1043 erg and confirms an ejected mass of approximately 10-7 M Ȯ. The total mass lost is an order of magnitude lower than the accreted mass required to have initiated the explosion, indicating that the white dwarf is gaining mass and is a Type Ia supernova progenitor candidate.
Bibliographical noteFunding Information:
We thank the Chandra X-ray Center (CXC) Mission Planning team for rapid and timely scheduling of the ToO observations reported on here. J.J.D. and V.K. were funded by NASA contract NAS8-03060 to the CXC and thank the director, B. Wilkes, and the CXC science team for advice and support. L.D. and M.H. acknowledge the support of the Spanish Ministry of Economy and Competitivity (MINECO) under the grant ESP2014-56003-R. J.M.L. was supported by basic research funds of the CNR. K.L.P. acknowledges funding from the UK Space Agency. S.S. acknowledges partial support from NASA, NSF, and Chandra grants to ASU. R.D.G. was supported by NASA and the United States Air Force. C.E.W. acknowledges support from Chandra award G04-15023A. Finally, we also thank H. Tananbaum for useful comments on the original manuscript.
- X-rays: binaries
- X-rays: stars
- novae, cataclysmic variables
- shock waves
- stars: individual (V745 Sco)