2022A&A...666A...6W


Query : 2022A&A...666A...6W

2022A&A...666A...6W - Astronomy and Astrophysics, volume 666A, 6 (2022/10-1)

An elliptical accretion disk following the tidal disruption event AT 2020zso.

WEVERS T., NICHOLL M., GUOLO M., CHARALAMPOPOULOS P., GROMADZKI M., REYNOLDS T.M., KANKARE E., LELOUDAS G., ANDERSON J.P., ARCAVI I., CANNIZZARO G., CHEN T.-W., IHANEC N., INSERRA C., GUTIERREZ C.P., JONKER P.G., LAWRENCE A., MAGEE M.R., MULLER-BRAVO T.E., ONORI F., RIDLEY E., SCHULZE S., SHORT P., HIRAMATSU D., NEWSOME M., TERWEL J.H., YANG S. and YOUNG D.

Abstract (from CDS):


Aims. The modelling of spectroscopic observations of tidal disruption events (TDEs) to date suggests that the newly formed accretion disks are mostly quasi-circular. In this work we study the transient event AT 2020zso, hosted by an active galactic nucleus (AGN; as inferred from narrow emission line diagnostics), with the aim of characterising the properties of its newly formed accretion flow.
Methods. We classify AT 2020zso as a TDE based on the blackbody evolution inferred from UV/optical photometric observations and spectral line content and evolution. We identify transient, double-peaked Bowen (N III), He I, He II, and Hα emission lines. We model medium-resolution optical spectroscopy of the He II (after careful de-blending of the N III contribution) and Hα lines during the rise, peak, and early decline of the light curve using relativistic, elliptical accretion disk models.
Results. We find that the spectral evolution before the peak can be explained by optical depth effects consistent with an outflowing, optically thick Eddington envelope. Around the peak, the envelope reaches its maximum extent (approximately 1015 cm, or ∼3000-6000 gravitational radii for an inferred black hole mass of 5-10 × 105M) and becomes optically thin. The Hα and He II emission lines at and after the peak can be reproduced with a highly inclined (i = 85 ± 5 degrees), highly elliptical (e = 0.97 ± 0.01), and relatively compact (Rin = several 100 Rg and Rout = several 1000 Rg) accretion disk.
Conclusions. Overall, the line profiles suggest a highly elliptical geometry for the new accretion flow, consistent with theoretical expectations of newly formed TDE disks. We quantitatively confirm, for the first time, the high inclination nature of a Bowen (and X-ray dim) TDE, consistent with the unification picture of TDEs, where the inclination largely determines the observational appearance. Rapid line profile variations rule out the binary supermassive black hole hypothesis as the origin of the eccentricity; these results thus provide a direct link between a TDE in an AGN and the eccentric accretion disk. We illustrate for the first time how optical spectroscopy can be used to constrain the black hole spin, through (the lack of) disk precession signatures (changes in inferred inclination). We constrain the disk alignment timescale to > 15 days in AT2020zso, which rules out high black hole spin values (a < 0.8) for MBH ∼ 106M and disk viscosity α ≳ 0.1.

Abstract Copyright: © T. Wevers et al. 2022

Journal keyword(s): accretion - accretion disks - galaxies: active - quasars: supermassive black holes

Simbad objects: 14

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Number of rows : 14
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
#notes
1 NGC 1097 LIN 02 46 19.059 -30 16 29.68 10.46 9.97 9.48 8.72 9.8 ~ 1344 3
2 AT 2019qiz ev 04 46 37.880 -10 13 34.92           ~ 59 0
3 AT 2019ahk ev 07 00 11.410 -66 02 25.16           ~ 35 0
4 ATLAS 18nej ev 07 56 54.537 +34 15 43.61           ~ 64 0
5 ASASSN -18zj SN* 10 06 50.875 +01 41 33.96           SNII 67 0
6 ASASSN -14ae SN* 11 08 40.11 +34 05 52.4           ~ 104 0
7 LEDA 43234 AG? 12 48 15.2253025968 +17 46 26.475426228   16.5       ~ 265 0
8 NGC 4958 Sy1 13 05 48.8957905464 -08 01 12.999361656   12.10   10.77   ~ 103 0
9 PTF 09djl SN* 16 33 55.94 +30 14 16.3           SNII 61 0
10 ICRF J171914.4+485849 Sy2 17 19 14.4925971408 +48 58 49.423205136   15.86 14.81 9.44   ~ 313 1
11 ASASSN -15lh ev 22 02 15.4 -61 39 34           ~ 168 1
12 AT 2020zso ev 22 22 17.130 -07 15 59.08           ~ 10 0
13 LEDA 1021821 G 22 22 17.13240 -07 15 59.0576           ~ 2 0
14 AT 2018fyk ev 22 50 16.10 -44 51 53.5           ~ 66 0

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