TY - JOUR
T1 - The Remarkable Spin-down and Ultrafast Outflows of the Highly Pulsed Supersoft Source of Nova Herculis 2021
AU - Drake, Jeremy J.
AU - Ness, Jan Uwe
AU - Page, Kim L.
AU - Luna, G. J.M.
AU - Beardmore, Andrew P.
AU - Orio, Marina
AU - Osborne, Julian P.
AU - Mróz, Przemek
AU - Starrfield, Sumner
AU - Banerjee, Dipankar P.K.
AU - Balman, Solen
AU - Darnley, M. J.
AU - Bhargava, Y.
AU - Dewangan, G. C.
AU - Singh, K. P.
N1 - Publisher Copyright:
© 2021. The Author(s). Published by the American Astronomical Society..
PY - 2021/12/1
Y1 - 2021/12/1
N2 - 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 o˙. 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.
AB - 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 o˙. 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.
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U2 - 10.3847/2041-8213/ac34fd
DO - 10.3847/2041-8213/ac34fd
M3 - Article
AN - SCOPUS:85120706970
SN - 2041-8205
VL - 922
JO - Astrophysical Journal Letters
JF - Astrophysical Journal Letters
IS - 2
M1 - L42
ER -