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Title: | The rise and fall of the king : the correlation between FO Aquarii's low states and the White Dwarf's Spindown |
Authors: | Littlefield, Colin Garnavich, Peter Kennedy, Mark R. Patterson, Joseph Kemp, Jonathan Stiller, Robert A. Hambsch, Franz-Josef Arranz Heras, Teofilo Myers, Gordon Stone, Geoffrey Sjoberg, George Dvorak, Shawn Nelson, Peter Popov, Velimir Bonnardeau, Michel Vanmunster, Tonny de Miguel, Enrique Alton, Kevin B. Harris, Barbara Cook, Lewis M. Graham, Keith A. Brincat, Stephen M. Lane, David J. Foster, James Pickard, Roger D. Sabo, Richard Vietje, Brad Lemay, Damien Briol, John Krumm, Nathan Dadighat, Michelle Goff, William Solomon, Rob Padovan, Stefano Bolt, Greg Kardasis, Emmanuel Debackere, Andre Thrush, Jeff Stein, William Walter, Bradley Coulter, Daniel Tsehmeystrenko, Valery Gout, Jean-Francois Lewin, Pablo Galdies, Charles Cejudo Fernandez, David Walker, Gary Boardman Jr., James Pellett, Emil |
Keywords: | Astrophysics Particles (Nuclear physics) Plasma dynamics |
Issue Date: | 2019 |
Publisher: | AAS Journals |
Citation: | Littlefield, C., Garnavich, P., Kennedy, M. R., Patterson, J., Kemp, J., Stiller, R. A., ... & Sjoberg, G. (2019). The rise and fall of the king : the correlation between FO Aquarii's low states and the White Dwarf's Spindown. arXiv preprint arXiv:1904.11505. |
Abstract: | The intermediate polar FO Aquarii experienced its first-reported low-accretion states in 2016, 2017, and 2018. We establish that these low states occurred shortly after the system's white dwarf (WD) began spinning down, after having spent a quarter-century spinning up. FO Aquarii is the only intermediate polar whose period derivative has undergone a sign change, and it has now done so twice. By combining our spin-pulse timings with previous data, we determine that the WD's spin period has varied quasi-sinusoidally since the system's discovery, and an extrapolation predicts that the white dwarf was spinning down during newly discovered low states in photographic plates from 1964, 1965, and 1974. Thus, FO Aquarii's low states appear to occur exclusively during epochs of spindown. Additionally, our time-series photometry of the 2016-18 low states reveals that the mode of accretion is extremely sensitive to the accretion rate; when the system is fainter than V~14.0, the accretion onto the WD is largely stream-fed, but when it is brighter, it is almost exclusively disk-fed. The system's grazing eclipse remained detectable throughout all observations, confirming the uninterrupted presence of a disk-like structure, regardless of the accretion state. Our observations are consistent with theoretical predictions that during the low states, the accretion disk dissipates into a ring of diamagnetic blobs. Finally, a new XMM-Newton observation from 2017 indicates that the system's anomalously soft X-ray spectrum and diminished X-ray luminosity in the wake of the 2016 low state appear to be long-lasting changes compared to pre-2016 observations. |
URI: | https://www.um.edu.mt/library/oar/handle/123456789/44926 |
Appears in Collections: | Scholarly Works - InsESEMP |
Files in This Item:
File | Description | Size | Format | |
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Littlefield et al (2019) FO Aquarii.pdf | 2.37 MB | Adobe PDF | View/Open |
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