The rebrightening of a ROSAT-selected tidal disruption event: repeated weak partial disruption flares from a quiescent galaxy?
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 $(1.0 \pm 0.1) \times 10^{-12}$ erg s$^{-1}$ cm$^{-2}$), ultra-soft ($kT=0.11 \pm 0.03$ keV) X-ray flare from a quiescent galaxy ($z=0.05189$). During its fift...
| Main Authors: | , , , , , , , , , , , , , |
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| Format: | Journal Article |
| Published: |
2023
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| Subjects: | |
| Online Access: | http://dx.doi.org/10.1093/mnras/stad022 http://hdl.handle.net/20.500.11937/97226 |
| Summary: | 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
$(1.0 \pm 0.1) \times 10^{-12}$ erg s$^{-1}$ cm$^{-2}$), ultra-soft ($kT=0.11
\pm 0.03$ keV) X-ray flare from a quiescent galaxy ($z=0.05189$). During its
fifth All-Sky survey (eRASS5) in 2022, SRG/eROSITA detected the repeated
flaring of J1331, where it had rebrightened to an observed 0.2-2 keV flux of
$(6.0 \pm 0.7) \times 10^{-13}$ erg s$^{-1}$ cm$^{-2}$, with spectral
properties ($kT=0.115 \pm 0.007$ keV) consistent with the ROSAT-observed flare
$\sim$30 years earlier. In this work, we report on X-ray, UV, optical, and
radio observations of this system. During a pointed XMM observation $\sim$17
days 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 $\gtrsim$40 over
this period. Given the extremely low probability ($\sim5\times 10^{-6}$) of
observing two independent full TDEs from the same galaxy over a 30 year period,
we consider the variability seen in J1331 to be likely caused by two partial
TDEs involving a star on an elliptical orbit around a black hole. J1331-like
flares show faster rise and decay timescales ($\mathcal{O}(\mathrm{days})$)
compared to standard TDE candidates, with neglible ongoing accretion at late
times post-disruption between outbursts. |
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