A candidate tidal disruption event in the Galaxy cluster Abell 3571

Cappelluti, N.; Ajello, M.; Rebusco, P.; Komossa, Stefanie; Bongiorno, A.; Clemens, C.; Salvato, M.; Esquej, P.; Aldcroft, Thomas L.; Greiner, J.; Quintana, H.

doi:10.1051/0004-6361/200811479

Cited by 73 publications

(90 citation statements)

References 33 publications

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“…Until now, about a dozen TDE candidates in non-AGN galaxies have been found from X-ray surveys (Komossa 2002;Komossa et al 2009;Esquej 2007Esquej , 2008Cappelluti et al 2009) and also in the UV/Optical (Renzini et al 1995;Gezari et al 2006Gezari et al , 2008. None of the events detected so far were found to be related to a high-luminosity AGN.…”

Section: A Stellar Tidal Disruption Event?mentioning

confidence: 99%

J004457+4123 (Sharov 21): not a remarkable nova in M 31 but a background quasar with a spectacular UV flare

Meusinger¹,

Henze

Birkle

et al. 2010

A&A

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Aims. We announce the discovery of a quasar behind the disk of M 31, which was previously classified as a remarkable nova in our neighbour galaxy. It is shown here to be a quasar with a single strong flare where the UV flux has increased by a factor of ∼20. The present paper is primarily aimed at the remarkable outburst of J004457+4123 (Sharov 21), with the first part focussed on the optical spectroscopy and the improvement in the photometric database. Methods. We exploited the archives of photographic plates and CCD observations from 15 wide-field telescopes and performed targetted new observations. In the second part, we try to fit the flare by models of (1) gravitational microlensing due to a star in M 31 and (2) a tidal disruption event (TDE) of a star close to the supermassive black hole of the quasar. Results. Both the optical spectrum and the broad band spectral energy distribution of Sharov 21 are shown to be very similar to that of normal, radio-quiet type 1 quasars. We present photometric data covering more than a century and resulting in a long-term light curve that is densely sampled over the past five decades. The variability of the quasar is characterized by a ground state with typical fluctuation amplitudes of ∼0.2 mag aroundB ∼ 20.5, superimposed by a singular flare of ∼2 yr duration (observer frame) with the maximum at 1992.81. The total energy in the flare is at least three orders of magnitudes higher than the radiated energy of the most luminous supernovae, provided that it comes from an intrinsic process and the energy is radiated isotropically. The profile of the flare light curve is asymmetric showing in particular a sudden increase before the maximum, whereas the decreasing part can be roughly approximated by a t −5/3 power law. Both properties appear to support the standard TDE scenario where a ∼10 M giant star was shredded in the tidal field of a ∼2 . . . 5 × 10 8 M black hole. The short fallback time derived from the observed light curve requires an ultra-close encounter where the pericentre of the stellar orbit is deep within the tidal disruption radius. This simple model neglects, however, the influence of the massive accretion disk, as well as general-relativistic effects on the orbit of the tidal debris. Gravitational microlensing probably provides an alternative explanation, although the probability of such a high amplification event is very low.

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Section: A Stellar Tidal Disruption Event?mentioning

confidence: 99%

J004457+4123 (Sharov 21): not a remarkable nova in M 31 but a background quasar with a spectacular UV flare

Meusinger¹,

Henze

Birkle

et al. 2010

A&A

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“…Spectra were produced for the three EPIC cameras from the 2010-06-22 XMM-Newton observation and fit with XSPEC (version 12.6.0). Fits were performed simultaneously on the ungrouped spectra, using the Cash statistic (Cash 1979), over the energy range 0.2−2 keV, using a constant to account for the small differences in normalisation between the instruments.…”

Section: X-ray Spectrummentioning

confidence: 99%

“…The accretion of tidally disrupted stellar debris may significantly contribute to the low-luminosity end of the AGN luminosity function (Milosavljevic et al 2006). To date, several candidate tidal disruption events (TDE) have been identified, based on a luminous flare seen at soft X-ray (e.g., Komossa & Bade 1999;Greiner et al 2000;Esquej et al 2007;Cappelluti et al 2009), UV (e.g., Gezari et al 2006;Gezari et al 2008) or optical (e.g., Cenko et al 2012;van Velzen et al 2011) wavelengths. The first X-ray tidal disruption flares were identified in the course of the ROSAT all-sky survey (Komossa & Bade 1999;Komossa & Greiner 1999;Grupe et al 1999;Greiner et al 2000).…”

Section: Introductionmentioning

confidence: 99%

A tidal disruption-like X-ray flare from the quiescent galaxy SDSS J120136.02+300305.5

Saxton

Read

Esquej

et al. 2012

A&A

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147

131

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Aims. The study of tidal disruption flares from galactic nuclei has historically been hampered by a lack of high quality spectral observations taken around the peak of the outburst. Here we introduce the first results from a program designed to identify tidal disruption events at their peak by making near-real-time comparisons of the flux seen in XMM-Newton slew sources with that seen in ROSAT. Methods. Flaring extragalactic sources, which do not appear to be AGN, are monitored with Swift and XMM-Newton to track their temporal and spectral evolution. Timely optical observations are made to monitor the reaction of circumnuclear material to the X-ray flare.Results. SDSS J120136.02+300305.5 was detected in an XMM-Newton slew from June 2010 with a flux 56 times higher than an upper limit from ROSAT, corresponding to L X ∼ 3 × 10 44 erg s −1 . It has the optical spectrum of a quiescent galaxy (z = 0.146). Overall the X-ray flux has evolved consistently with the canonical t −5/3 model, expected for returning stellar debris, fading by a factor ∼300 over 300 days. In detail the source is very variable and became invisible to Swift between 27 and 48 days after discovery, perhaps due to self-absorption. The X-ray spectrum is soft but is not the expected tail of optically thick thermal emission. It may be fit with a Bremsstrahlung or double-power-law model and is seen to soften with time and declining flux. Optical spectra taken 12 days and 11 months after discovery indicate a deficit of material in the broad line and coronal line regions of this galaxy, while a deep radio non-detection implies that a jet was not launched during this event.

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“…In recent years, flares from the nuclei of quiescent galaxies, detected either in X-rays [9][10][11] and in the UV [12][13][14] have been interpreted as arising from TDEs, essentially by a simple comparison of the light curve of the event to the expected t −5/3 law [4]. This has prompted several new theoretical investigations that aimed at clarifying the conditions under which one should really expect such a power-law decline in the luminosity of the event.…”

Section: Introductionmentioning

confidence: 99%

Challenges in the modeling of tidal disruption events lightcurves

Lodato

2012

EPJ Web of Conferences

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Abstract. In this contribution, I review the recent developments on the modeling of the lightcurve of tidal disruption events. Our understanding has evolved significantly from the earlier seminal results that imply a simple power-law decay of the bolometric light curve as t −5/3 . We now know that the details of the rise to the peak of the lightcurve is determined mainly by the internal structure of the disrupted star. We also have improved models for the disc thermal emission, showing that in this case the decline of the luminosity with time should be much flatter than the standard t −5/3 law, especially in optical and UV wavelengths, while the X-ray lightcurve is generally best suited to track the bolometric one. Finally, we are just starting to explore the interesting general relativistic effects that might arise for such events, for which the tidal radius lies very close to the black hole event horizon.

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A candidate tidal disruption event in the Galaxy cluster Abell 3571

Cited by 73 publications

References 33 publications

J004457+4123 (Sharov 21): not a remarkable nova in M 31 but a background quasar with a spectacular UV flare

J004457+4123 (Sharov 21): not a remarkable nova in M 31 but a background quasar with a spectacular UV flare

A tidal disruption-like X-ray flare from the quiescent galaxy SDSS J120136.02+300305.5

Challenges in the modeling of tidal disruption events lightcurves

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