LATE-TIME RADIO EMISSION FROM X-RAY-SELECTED TIDAL DISRUPTION EVENTS

AbstractXMM-Newton performs a survey of the sky in the 0.2-12 keV X-ray band while slewing between observation targets. The sensitivity in the soft X-ray band is comparable with that of the ROSAT all-sky survey, allowing bright transients to be identified in near real-time by a comparison of the flux in both surveys. Several of the soft X-ray flares are coincident with galaxy nuclei and five of these have been interpreted as candidate tidal disruption events (TDE). The first three discovered had a soft X-ray spectrum, consistent with the classical model of TDE, where radiation is released during the accretion phase by thermal processes. The remaining two have an additional hard, power-law component, which in only one case was accompanied by radio emission. Overall the flares decay with the classical index of t−5/3 but vary greatly in the early phase.

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Discovery and follow-up of ASASSN-19dj: an X-ray and UV luminous TDE in an extreme post-starburst galaxy

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3170 ◽

2020 ◽

Vol 500 (2) ◽

pp. 1673-1696 ◽

Cited By ~ 3

Author(s):

Jason T Hinkle ◽

T W-S Holoien ◽

K Auchettl ◽

B J Shappee ◽

J M M Neustadt ◽

...

Keyword(s):

Optical Emission ◽

Starburst Galaxy ◽

Late Time ◽

X Rays ◽

Tidal Disruption ◽

X Ray ◽

Bolometric Luminosity ◽

Order Of Magnitude ◽

High Cadence

ABSTRACT We present observations of ASASSN-19dj, a nearby tidal disruption event (TDE) discovered in the post-starburst galaxy KUG 0810+227 by the All-Sky Automated Survey for Supernovae (ASAS-SN) at a distance of d ≃ 98 Mpc. We observed ASASSN-19dj from −21 to 392 d relative to peak ultraviolet (UV)/optical emission using high-cadence, multiwavelength spectroscopy and photometry. From the ASAS-SN g-band data, we determine that the TDE began to brighten on 2019 February 6.8 and for the first 16 d the rise was consistent with a flux ∝t2 power law. ASASSN-19dj peaked in the UV/optical on 2019 March 6.5 (MJD = 58548.5) at a bolometric luminosity of L = (6.2 ± 0.2) × 1044 erg s−1. Initially remaining roughly constant in X-rays and slowly fading in the UV/optical, the X-ray flux increased by over an order of magnitude ∼225 d after peak, resulting from the expansion of the X-ray emitting region. The late-time X-ray emission is well fitted by a blackbody with an effective radius of ∼1 × 1012 cm and a temperature of ∼6 × 105 K. The X-ray hardness ratio becomes softer after brightening and then returns to a harder state as the X-rays fade. Analysis of Catalina Real-Time Transient Survey images reveals a nuclear outburst roughly 14.5 yr earlier with a smooth decline and a luminosity of LV ≥ 1.4 × 1043 erg s−1, although the nature of the flare is unknown. ASASSN-19dj occurred in the most extreme post-starburst galaxy yet to host a TDE, with Lick HδA = 7.67 ± 0.17 Å.

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RADIO MONITORING OF THE TIDAL DISRUPTION EVENT SWIFT J164449.3+573451. II. THE RELATIVISTIC JET SHUTS OFF AND A TRANSITION TO FORWARD SHOCK X-RAY/RADIO EMISSION

The Astrophysical Journal ◽

10.1088/0004-637x/767/2/152 ◽

2013 ◽

Vol 767 (2) ◽

pp. 152 ◽

Cited By ~ 78

Author(s):

B. A. Zauderer ◽

E. Berger ◽

R. Margutti ◽

G. G. Pooley ◽

R. Sari ◽

...

Keyword(s):

Radio Emission ◽

Tidal Disruption ◽

X Ray ◽

Radio Monitoring ◽

Relativistic Jet ◽

Forward Shock ◽

Disruption Event

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Workshop on Stellar Tidal Disruption

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312000701 ◽

2011 ◽

Vol 7 (S285) ◽

pp. 261-268

Author(s):

Glennys R. Farrar

Keyword(s):

Accretion Disks ◽

Main Sequence ◽

Light Curves ◽

Late Time ◽

Tidal Disruption ◽

X Ray ◽

Spectral Signatures ◽

The Past ◽

Observational Status

AbstractThe past year has seen major advances in the observational status of Stellar Tidal Disruption, with the discovery of two strong optical candidates in archived SDSS data and the real-time X-ray detection of Swift J1644+57, plus rapid radio and optical follow-up establishing it as a probable Tidal Disruption Flare (TDF) in “blazar mode”. These observations motivated a workshop devoted to discussion of such events and of the theory of their emission and flare rate. Observational contributions included a presentation of Swift J2058+05 (a possible second example of a TDF in blazar mode), reports on the late-time evolution and X-ray variability of the two Swift events, and a proposal that additional candidates may be evidenced by spectral signatures in SDSS. Theory presentations included models of radio emission, theory of light curves and the proposal that GRB101225A may be the Galactic tidal disruption of a neutron star, an interpretation of Swift J1644+57 as due to the disruption of a white dwarf instead of main-sequence star, calculation of the dependence of the TDF rate on the spin of the black hole, and analysis of the SDSS events, fitting their SEDs to profiles of thoretical emission from accretion disks and showing that their luminosity and rate are consistent with the proposal that TDEs can be responsible for UHECR acceleration.

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Swift J1644+5734: the EVN view

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317001107 ◽

2016 ◽

Vol 12 (S324) ◽

pp. 119-122

Author(s):

Z. Paragi ◽

J. Yang ◽

S. Komossa ◽

A. van der Horst ◽

L. I. Gurvits ◽

...

Keyword(s):

Radio Emission ◽

Viewing Angle ◽

Relativistic Jets ◽

Tidal Disruption ◽

X Ray ◽

Imaging Results ◽

Resolution Imaging ◽

Jet Velocity

AbstractA small fraction of Tidal Disruption Events (TDE) produce relativistic jets, evidenced by their non-thermal X-ray spectra and transient radio emission. Here we present milliarcsecond-resolution imaging results on TDE J1644+5734 with the European VLBI Network (EVN). These provide a strong astrometric constraint on the average apparent jet velocity βapp< 0.27, that constrains the intrinsic jet velocity for a given viewing angle.

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Implications from Late-time X-Ray Detections of Optically Selected Tidal Disruption Events: State Changes, Unification, and Detection Rates

The Astrophysical Journal ◽

10.3847/1538-4357/ab659c ◽

2020 ◽

Vol 889 (2) ◽

pp. 166 ◽

Cited By ~ 5

Author(s):

P. G. Jonker ◽

N. C. Stone ◽

A. Generozov ◽

S. van Velzen ◽

B. Metzger

Keyword(s):

Late Time ◽

Tidal Disruption ◽

Detection Rates ◽

X Ray ◽

State Changes

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Rapid late-time X-ray brightening of the tidal disruption event OGLE16aaa

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038165 ◽

2020 ◽

Vol 639 ◽

pp. A100 ◽

Cited By ~ 2

Author(s):

Jari J. E. Kajava ◽

Margherita Giustini ◽

Richard D. Saxton ◽

Giovanni Miniutti

Keyword(s):

Black Hole ◽

Host Galaxy ◽

Late Time ◽

Tidal Disruption ◽

Massive Black Hole ◽

X Ray ◽

Tidal Forces ◽

Upper Limits ◽

Optical Light Curve ◽

Disruption Event

Stars that pass too close to a super-massive black hole may be disrupted by strong tidal forces. OGLE16aaa is one such tidal disruption event (TDE) which rapidly brightened and peaked in the optical/UV bands in early 2016 and subsequently decayed over the rest of the year. OGLE16aaa was detected in an XMM-Newton X-ray observation on June 9, 2016 with a flux slightly below the Swift/XRT upper limits obtained during the optical light curve peak. Between June 16–21, 2016, Swift/XRT also detected OGLE16aaa and based on the stacked spectrum, we could infer that the X-ray luminosity had jumped up by more than a factor of ten in just one week. No brightening signal was seen in the simultaneous optical/UV data to cause the X-ray luminosity to exceed the optical/UV one. A further XMM-Newton observation on November 30, 2016 showed that almost a year after the optical/UV peak, the X-ray emission was still at an elevated level, while the optical/UV flux decay had already leveled off to values comparable to those of the host galaxy. In all X-ray observations, the spectra were nicely modeled with a 50–70 eV thermal component with no intrinsic absorption, with a weak X-ray tail seen only in the November 30 XMM-Newton observation. The late-time X-ray behavior of OGLE16aaa strongly resembles the tidal disruption events ASASSN-15oi and AT2019azh. We were able to pinpoint the time delay between the initial optical TDE onset and the X-ray brightening to 182 ± 5 days, which may possibly represent the timescale between the initial circularization of the disrupted star around the super-massive black hole and the subsequent delayed accretion. Alternatively, the delayed X-ray brightening could be related to a rapid clearing of a thick envelope that covers the central X-ray engine during the first six months.

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