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Confirmation of a Second Propeller: A High-inclination Twin of AE Aquarii

Garnavich, Peter and Littlefield, Colin and Wagner, R. M. and van Roestel, Jan and Jaodand, Amruta D. and Szkody, Paula and Thorstensen, John R. (2021) Confirmation of a Second Propeller: A High-inclination Twin of AE Aquarii. Astrophysical Journal, 917 (1). Art. No. 22. ISSN 0004-637X. doi:10.3847/1538-4357/ac0339.

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For decades, AE Aquarii (AE Aqr) has been the only cataclysmic variable star known to contain a magnetic propeller: a persistent outflow whose expulsion from the binary is powered by the spin-down of the rapidly rotating, magnetized white dwarf. In 2020, LAMOST J024048.51+195226.9 (J0240) was identified as a candidate eclipsing AE Aqr object, and we present three epochs of time-series spectroscopy that strongly support this hypothesis. We show that, during the photometric flares noted by Thorstensen, the Balmer and He i emission lines reach velocities of ~3000 km s⁻¹, well in excess of what is observed in normal cataclysmic variables. This is, however, consistent with the high-velocity emission seen in flares from AE Aqr. Additionally, we confirm beyond doubt that J0240 is a deeply eclipsing system. The flaring continuum, He i and much of the Balmer emission likely originate close to the WD because they disappear during the eclipse that is centered on inferior conjunction of the secondary star. The fraction of the Balmer emission remaining visible during eclipse is likely produced in the extended outflow. Most enticingly of all, this outflow produces a narrow P Cygni absorption component for nearly half of the orbit, and we demonstrate that this scenario closely matches the outflow kinematics predicted by Wynn et al. While an important piece of evidence for the magnetic-propeller hypothesis—a rapid WD spin period—remains elusive, our spectra provide compelling support for the existence of a propeller-driven outflow viewed nearly edge-on, enabling a new means of rigorously testing theories of the propeller phenomenon.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Garnavich, Peter0000-0003-4069-2817
Littlefield, Colin0000-0001-7746-5795
van Roestel, Jan0000-0002-2626-2872
Jaodand, Amruta D.0000-0002-3850-6651
Szkody, Paula0000-0003-4373-7777
Thorstensen, John R.0000-0002-4964-4144
Additional Information:© 2021. The American Astronomical Society. Received 2021 February 6; revised 2021 May 9; accepted 2021 May 18; published 2021 August 10. We thank R. Pogge and O. Kuhn for their help in obtaining the LBT observations. This work is partly based on observations obtained at the MDM Observatory, operated by Dartmouth College, Columbia University, The Ohio State University, Ohio University, and the University of Michigan.
Group:Space Radiation Laboratory
Funding AgencyGrant Number
Subject Keywords:Cataclysmic variable stars; Magnetic stars; White dwarf stars; DQ Herculis stars
Issue or Number:1
Classification Code:Unified Astronomy Thesaurus concepts: Cataclysmic variable stars (203); Magnetic stars (995); White dwarf stars (1799); DQ Herculis stars (407)
Record Number:CaltechAUTHORS:20210813-181203703
Persistent URL:
Official Citation:Peter Garnavich et al 2021 ApJ 917 22
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:110261
Deposited By: George Porter
Deposited On:13 Aug 2021 22:55
Last Modified:13 Aug 2021 22:55

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