TY - JOUR
T1 - A Year-long Superoutburst from an Ultracompact White Dwarf Binary Reveals the Importance of Donor Star Irradiation
AU - Rivera Sandoval, L. E.
AU - MacCarone, T. J.
AU - Pichardo Marcano, M.
N1 - Publisher Copyright:
© 2020. The American Astronomical Society. All rights reserved.
PY - 2020/9/10
Y1 - 2020/9/10
N2 - SDSS J080710+485259 is the longest-period outbursting ultracompact white dwarf binary. Its first-ever detected superoutburst started in 2018 November and lasted for a year, the longest detected so far for any short orbital period accreting white dwarf. Here we show the superoutburst duration of SDSS J080710+485259 exceeds the ∼2 month viscous time of its accretion disk by a factor of about 5. Consequently it follows that neither the empirical relation nor the theoretical relation between the orbital period and the superoutburst duration for AM CVn systems. Six months after the end of the superoutburst the binary remained 0.4 mag brighter than its quiescent level before the superoutburst. We detect a variable X-ray behavior during the post-outburst cooling phase, demonstrating changes in the mass accretion rate. We discuss how irradiation of the donor star, a scenario poorly explored so far and that ultimately can have important consequences for AM CVns as gravitational-wave sources, might explain the unusual observed features of the superoutburst.
AB - SDSS J080710+485259 is the longest-period outbursting ultracompact white dwarf binary. Its first-ever detected superoutburst started in 2018 November and lasted for a year, the longest detected so far for any short orbital period accreting white dwarf. Here we show the superoutburst duration of SDSS J080710+485259 exceeds the ∼2 month viscous time of its accretion disk by a factor of about 5. Consequently it follows that neither the empirical relation nor the theoretical relation between the orbital period and the superoutburst duration for AM CVn systems. Six months after the end of the superoutburst the binary remained 0.4 mag brighter than its quiescent level before the superoutburst. We detect a variable X-ray behavior during the post-outburst cooling phase, demonstrating changes in the mass accretion rate. We discuss how irradiation of the donor star, a scenario poorly explored so far and that ultimately can have important consequences for AM CVns as gravitational-wave sources, might explain the unusual observed features of the superoutburst.
UR - http://www.scopus.com/inward/record.url?scp=85091706561&partnerID=8YFLogxK
U2 - 10.3847/2041-8213/abb130
DO - 10.3847/2041-8213/abb130
M3 - Article
AN - SCOPUS:85091706561
SN - 2041-8205
VL - 900
JO - Astrophysical Journal Letters
JF - Astrophysical Journal Letters
IS - 2
M1 - L37
ER -