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  • The rebrightening of a ROSA...
    Malyali, A; Liu, Z; Rau, A; Grotova, I; Merloni, A; Goodwin, A J; Anderson, G E; Miller-Jones, J C A; Kawka, A; Arcodia, R; Buchner, J; Nandra, K; Homan, D; Krumpe, M

    Monthly notices of the Royal Astronomical Society, 02/2023, Volume: 520, Issue: 3
    Journal Article

    ABSTRACT The ROSAT-selected tidal disruption event (TDE) candidate RX J133157.6−324319.7 (J1331) was detected in 1993 as a bright 0.2–2 keV flux of (1.0 ± 0.1) × 10−12 erg s−1 cm−2, ultra-soft (kT = 0.11 ± 0.03 keV) X-ray flare from a quiescent galaxy (z = 0.051 89). During its fifth all-sky survey (eRASS5) in 2022, Spectrum-Roentgen-Gamma (SRG)/ eROSITA detected the repeated flaring of J1331, where it had rebrightened to an observed 0.2–2 keV flux of (6.0 ± 0.7) × 10−13 erg s−1 cm−2, with spectral properties (kT = 0.115 ± 0.007 keV) consistent with the ROSAT-observed flare ∼30 yr earlier. In this work, we report on X-ray, ultraviolet, optical, and radio observations of this system. During a pointed XMM observation ∼17 d after the eRASS5 detection, J1331 was not detected in the 0.2–2 keV band, constraining the 0.2–2 keV flux to have decayed by a factor of ≳40 over this period. Given the extremely low probability (∼5 × 10−6) of observing two independent full TDEs from the same galaxy over a 30 yr period, we consider the variability seen in J1331 to be likely caused by two partial TDEs involving a star on an elliptical orbit around a black hole. J1331-like flares show faster rise and decay time-scales $\mathcal {O}(\mathrm{d})$ compared to standard TDE candidates, with negligible ongoing accretion at late times post-disruption between outbursts.