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The Remarkable Spin-down and Ultrafast Outflows of the Highly Pulsed Supersoft Source of Nova Herculis 2021

Drake, Jeremy J. and Ness, Jan-Uwe and Page, Kim L. and Luna, G. J. M. and Beardmore, Andrew P. and Orio, Marina and Osborne, Julian P. and Mróz, Przemek and Starrfield, Sumner and Banerjee, Dipankar P. K. and Balman, Solen and Darnley, M. J. and Bhargava, Y. and Dewangan, G. C. and Singh, K. P. (2021) The Remarkable Spin-down and Ultrafast Outflows of the Highly Pulsed Supersoft Source of Nova Herculis 2021. Astrophysical Journal Letters, 922 (2). Art. No. L42. ISSN 2041-8205. doi:10.3847/2041-8213/ac34fd.

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Nova Her 2021 (V1674 Her), which erupted on 2021 June 12, reached naked-eye brightness and has been detected from radio to γ-rays. An extremely fast optical decline of 2 magnitudes in 1.2 days and strong Ne lines imply a high-mass white dwarf. The optical pre-outburst detection of a 501.42 s oscillation suggests a magnetic white dwarf. This is the first time that an oscillation of this magnitude has been detected in a classical nova prior to outburst. We report X-ray outburst observations from Swift and Chandra that uniquely show (1) a very strong modulation of supersoft X-rays at a different period from reported optical periods, (2) strong pulse profile variations and the possible presence of period variations of the order of 0.1–0.3 s, and (3) rich grating spectra that vary with modulation phase and show P Cygni–type emission lines with two dominant blueshifted absorption components at ∼3000 and 9000 km s⁻¹ indicating expansion velocities up to 11,000 km s⁻¹. X-ray oscillations most likely arise from inhomogeneous photospheric emission related to the magnetic field. Period differences between reported pre- and post-outburst optical observations, if not due to other period drift mechanisms, suggest a large ejected mass for such a fast nova, in the range 2 × 10⁻⁵ – 2 × 10⁻⁴ M_⊙. A difference between the period found in the Chandra data and a reported contemporaneous post-outburst optical period, as well as the presence of period drifts, could be due to weakly nonrigid photospheric rotation.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Drake, Jeremy J.0000-0002-0210-2276
Ness, Jan-Uwe0000-0003-0440-7193
Page, Kim L.0000-0001-5624-2613
Luna, G. J. M.0000-0002-2647-4373
Beardmore, Andrew P.0000-0001-5186-5950
Orio, Marina0000-0003-1563-9803
Osborne, Julian P.0000-0002-1041-7542
Mróz, Przemek0000-0001-7016-1692
Starrfield, Sumner0000-0002-1359-6312
Banerjee, Dipankar P. K.0000-0003-4896-2543
Balman, Solen0000-0001-6135-1144
Darnley, M. J.0000-0003-0156-3377
Bhargava, Y.0000-0002-5967-8399
Dewangan, G. C.0000-0003-1589-2075
Singh, K. P.0000-0001-6952-3887
Alternate Title:The Remarkable Spin-down and Ultra-fast Outflows of the Highly-Pulsed Supersoft Source of Nova Hercules 2021
Additional Information:© 2021. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2021 October 13; revised 2021 November 9; accepted 2021 November 10; published 2021 December 3. J.J.D. was supported by NASA contract NAS8-03060 to the Chandra X-ray Center and thanks the Director, Pat Slane, for continuing advice and support. We also thank the Chandra Mission Planning group for their work that enabled this DDT observation to be executed. G.J.M.L. is member of the CIC-CONICET (Argentina) and acknowledges support from grant ANPCYT-PICT 0901/2017. D.P.K.B. is supported by a CSIR Emeritus Scientist grant-in-aid which is being hosted by the Physical Research Laboratory, Ahmedabad. K.L.P. and A.P.B. acknowledge funding from the UK Space Agency.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)UNSPECIFIED
Agencia Nacional de Promoción Científica y Tecnológica (ANPCyT)0901/2017
Council of Scientific and Industrial Research (India)UNSPECIFIED
United Kingdom Space Agency (UKSA)UNSPECIFIED
Subject Keywords:Novae; Classical novae; Fast novae; X-ray novae; DQ Herculis stars; X-ray astronomy; X-ray transient sources; Cataclysmic variable stars; White dwarf stars; Stellar winds
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Novae (1127); Classical novae (251); Fast novae (530); X-ray novae (1818); DQ Herculis stars (407); X-ray astronomy (1810); X-ray transient sources (1852); Cataclysmic variable stars (203); White dwarf stars (1799)
Record Number:CaltechAUTHORS:20211207-393917000
Persistent URL:
Official Citation:Jeremy J. Drake et al 2021 ApJL 922 L42
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:112256
Deposited By: George Porter
Deposited On:07 Dec 2021 20:30
Last Modified:13 Dec 2021 22:33

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