scholarly journals The evolution of Kerr discs and late-time tidal disruption event light curves

2018 ◽  
Vol 481 (3) ◽  
pp. 3348-3356 ◽  
Author(s):  
Steven A Balbus ◽  
Andrew Mummery
Keyword(s):  
Light Curves ◽  
Late Time ◽  
Tidal Disruption ◽  
Event Light ◽  
Disruption Event

scholarly journals Radio Monitoring of the Tidal Disruption Event Swift J164449.3+573451. III. Late-time Jet Energetics and a Deviation from Equipartition

2018 ◽  
Vol 854 (2) ◽  
pp. 86 ◽  
Author(s):  
T. Eftekhari ◽  
E. Berger ◽  
B. A. Zauderer ◽  
R. Margutti ◽  
K. D. Alexander
Keyword(s):  
Late Time ◽  
Tidal Disruption ◽  
Radio Monitoring ◽  
Disruption Event

scholarly journals Relativistic accretion disc in tidal disruption events

2020 ◽  
Vol 496 (2) ◽  
pp. 1784-1802
Author(s):  
T Mageshwaran ◽  
Sudip Bhattacharyya
Keyword(s):  
Surface Density ◽  
Accretion Disc ◽  
Time Parameter ◽  
Light Curves ◽  
Initial Time ◽  
Late Time ◽  
Tidal Disruption ◽  
Bolometric Luminosity ◽  
Spectral Bands ◽  
Accretion Model

ABSTRACT We construct a time-dependent relativistic accretion model for tidal disruption events (TDEs) with an α-viscosity and the pressure dominated by gas pressure. We also include the mass fallback rate $\dot{M}_\mathrm{ f}$ for both full and partial disruption TDEs, and assume that the infalling debris forms a seed disc in time tc, which evolves due to the mass addition from the infalling debris and the mass-loss via accretion on to the black hole. Besides, we derive an explicit form for the disc height that depends on the angular momentum parameter in the disc. We show that the surface density of the disc increases at an initial time due to mass addition, and then decreases as the mass fallback rate decreases, which results in a decrease in the disc mass Md with a late-time evolution of Md ∝ t−1.05 and t−1.38 for full and partial disruption TDEs, respectively, where t is the time parameter. The bolometric luminosity L shows a rise and decline that follows a power law at late times given by L ∝ t−1.8 and t−2.3 for full and partial disruption TDEs, respectively. Our obtained luminosity declines faster than the luminosity inferred using $L \propto \dot{M}_\mathrm{ f}$. We also compute the light curves in various spectral bands.

scholarly journals The unusual late-time evolution of the tidal disruption event ASASSN-15oi

2018 ◽  
Vol 480 (4) ◽  
pp. 5689-5703 ◽  
Author(s):  
T W-S Holoien ◽  
J S Brown ◽  
K Auchettl ◽  
C S Kochanek ◽  
J L Prieto ◽  
...  
Keyword(s):  
Time Evolution ◽  
Late Time ◽  
Tidal Disruption ◽  
Disruption Event

scholarly journals The tidal disruption event AT2017eqx: spectroscopic evolution from hydrogen rich to poor suggests an atmosphere and outflow

2019 ◽  
Vol 488 (2) ◽  
pp. 1878-1893 ◽  
Author(s):  
M Nicholl ◽  
P K Blanchard ◽  
E Berger ◽  
S Gomez ◽  
R Margutti ◽  
...  
Keyword(s):  
Host Galaxy ◽  
Mass Star ◽  
Late Time ◽  
Solar Mass ◽  
Tidal Disruption ◽  
Relativistic Jet ◽  
Proposed Model ◽  
Complete Disruption ◽  
Disruption Event ◽  
Rule Out

ABSTRACT We present and analyse a new tidal disruption event (TDE), AT2017eqx at redshift z = 0.1089, discovered by Pan-STARRS and ATLAS. The position of the transient is consistent with the nucleus of its host galaxy; the spectrum shows a persistent blackbody temperature T ≳ 20 000 K with broad H i and He ii emission; and it peaks at a blackbody luminosity of L ≈ 1044 erg s−1. The lines are initially centred at zero velocity, but by 100 d, the H i lines disappear while the He ii develops a blueshift of ≳ 5000 km s−1. Both the early- and late-time morphologies have been seen in other TDEs, but the complete transition between them is unprecedented. The evolution can be explained by combining an extended atmosphere, undergoing slow contraction, with a wind in the polar direction becoming visible at late times. Our observations confirm that a lack of hydrogen a TDE spectrum does not indicate a stripped star, while the proposed model implies that much of the diversity in TDEs may be due to the observer viewing angle. Modelling the light curve suggests AT2017eqx resulted from the complete disruption of a solar-mass star by a black hole of ∼106.3 M⊙. The host is another Balmer-strong absorption galaxy, though fainter and less centrally concentrated than most TDE hosts. Radio limits rule out a relativistic jet, while X-ray limits at 500 d are among the deepest for a TDE at this phase.

scholarly journals Workshop on Stellar Tidal Disruption

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.

scholarly journals ASASSN-15lh: a TDE about a maximally rotating 109 M⊙ black hole

2020 ◽  
Vol 497 (1) ◽  
pp. L13-L18 ◽  
Author(s):  
Andrew Mummery ◽  
Steven A Balbus
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Light Curves ◽  
The Novel ◽  
Black Hole Mass ◽  
Tidal Disruption ◽  
Scaling Relationships ◽  
Best Fitting ◽  
Infrared Frequencies ◽  
Disruption Event

ABSTRACT We model the light curves of the novel and extremely luminous transient ASASSN-15lh at nine different frequencies, from infrared to ultraviolet photon energies, as an evolving relativistic disc produced in the aftermath of a tidal disruption event (TDE). Good fits to all nine light curves are simultaneously obtained when Macc ≃ 0.07 M⊙ is accreted on to a black hole of mass M ≃ 109 M⊙ and near-maximal rotation a/rg = 0.99. The best-fitting black hole mass is consistent with a number of existing estimates from galactic scaling relationships. If confirmed, our results represent the detection of one of the most massive rapidly spinning black holes to date, and are strong evidence for a TDE origin for ASASSN-15lh. This would be the first TDE to be observed in the disc-dominated state at optical and infrared frequencies.

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

2020 ◽  
Vol 639 ◽  
pp. A100 ◽  
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.

scholarly journals Late time X-ray, IR and radio observations of the tidal disruption event galaxy NGC 5905

2015 ◽  
Vol 357 (1) ◽  
Author(s):  
H. Raichur ◽  
M. Das ◽  
A. Alonso Herrero ◽  
P. Shastri ◽  
N. G. Kantharia
Keyword(s):  
Late Time ◽  
Radio Observations ◽  
Tidal Disruption ◽  
X Ray ◽  
Disruption Event

scholarly journals Optical follow-up of the tidal disruption event iPTF16fnl: new insights from X-shooter observations

2019 ◽  
Vol 489 (1) ◽  
pp. 1463-1480 ◽  
Author(s):  
F Onori ◽  
G Cannizzaro ◽  
P G Jonker ◽  
M Fraser ◽  
Z Kostrzewa-Rutkowska ◽  
...  
Keyword(s):  
Exponential Decay ◽  
Emission Lines ◽  
Host Galaxy ◽  
Late Time ◽  
Tidal Disruption ◽  
Optical Telescope ◽  
Bolometric Luminosity ◽  
Luminosity Evolution ◽  
Disruption Event

ABSTRACT We present the results from Nordic Optical Telescope and X-shooter follow-up campaigns of the tidal disruption event (TDE) iPTF16fnl, covering the first ∼100 d after the transient discovery. We followed the source photometrically until the TDE emission was no longer detected above the host galaxy light. The bolometric luminosity evolution of the TDE is consistent with an exponential decay with e-folding constant t0 = 17.6 ± 0.2 d. The early-time spectra of the transient are dominated by broad He ii λ4686, H $\beta$, H $\alpha$, and N iii λ4100 emission lines. The latter is known to be produced together with the N iii λ4640 in the Bowen fluorescence mechanism. Due to the medium-resolution X-shooter spectra we have been able to separate the Bowen blend contribution from the broad He ii emission line. The detection of the Bowen fluorescence lines in iPTF16fnl place this transient among the N-rich TDE subset. In the late-time X-shooter spectra, narrow emission lines of [O iii] and [N ii] originating from the host galaxy are detected, suggesting that the host galaxy harbours a weak active galactic nucleus in its core. The properties of all broad emission lines evolve with time. The equivalent widths follow an exponential decay compatible with the bolometric luminosity evolution. The full width at half-maximum of the broad lines decline with time and the line profiles develop a narrow core at later epochs. Overall, the optical emission of iPTF16fnl can be explained by being produced in an optically thick region in which high densities favour the Bowen fluorescence mechanism and where multiple electron scatterings are responsible for the line broadening.

scholarly journals Constraints on the density distribution of type Ia supernovae ejecta inferred from late-time light-curve flattening

2020 ◽  
Vol 493 (4) ◽  
pp. 5617-5624
Author(s):  
Doron Kushnir ◽  
Eli Waxman
Keyword(s):  
Light Curve ◽  
Weighted Average ◽  
Far Infrared ◽  
Average Density ◽  
Light Curves ◽  
Type Ia Supernovae ◽  
Late Time ◽  
Simple Method ◽  
Type Ia ◽  
Ia Supernovae

ABSTRACT The finite time, τdep, over which positrons from β+ decays of 56Co deposit energy in type Ia supernovae ejecta lead, in case the positrons are trapped, to a slower decay of the bolometric luminosity compared to an exponential decline. Significant light-curve flattening is obtained when the ejecta density drops below the value for which τdep equals the 56Co lifetime. We provide a simple method to accurately describe this ‘delayed deposition’ effect, which is straightforward to use for analysis of observed light curves. We find that the ejecta heating is dominated by delayed deposition typically from 600 to 1200 d, and only later by longer lived isotopes 57Co and 55Fe decay (assuming solar abundance). For the relatively narrow 56Ni velocity distributions of commonly studied explosion models, the modification of the light curve depends mainly on the 56Ni mass-weighted average density, 〈ρ〉t3. Accurate late-time bolometric light curves, which may be obtained with JWST far-infrared (far-IR) measurements, will thus enable to discriminate between explosion models by determining 〈ρ〉t3 (and the 57Co and 55Fe abundances). The flattening of light curves inferred from recent observations, which is uncertain due to the lack of far-IR data, is readily explained by delayed deposition in models with $\langle \rho \rangle t^{3} \approx 0.2\, \mathrm{M}_{\odot }\, (10^{4}\, \textrm{km}\, \textrm{s}^{-1})^{-3}$, and does not imply supersolar 57Co and 55Fe abundances.

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