PS1-10jh - a tidal disruption event with an extremely low disc temperature (original) (raw)
Related papers
Tidal Disruption Flares: The Accretion Disk Phase
The Astrophysical Journal, 2011
The evolution of an accretion disk, formed as a consequence of the disruption of a star by a black hole, is followed by solving numerically hydrodynamic equations. The present investigation aims to study the dependence of resulting light curves on dynamical and physical properties of such a transient disk during its existence. One of the main results derived from our simulations is that blackbody fits of X-ray data tend to overestimate the true mean disk temperature. In fact, the temperature derived from blackbody fits should be identified with the color X-ray temperature rather than the average value derived from the true temperature distribution along the disk. The time interval between the beginning of the circularization of the bound debris and the beginning of the accretion process by the black hole is determined by the viscous (or accretion) timescale, which also fixes the rising part of the resulting light curve. The luminosity peak coincides with the beginning of matter accretion by the black hole and the late evolution of the light curve depends on the evolution of the debris fallback rate. Peak bolometric luminosities are in the range 10 45 − 10 46 erg s −1 whereas peak luminosities in soft X-rays (0.2-2.0 keV) are typically one order of magnitude lower. The typical timescale derived from our preferred models for the flare luminosity to decay by two orders of magnitude is about 3-4 years. Predicted soft X-ray light curves reproduce quite well data on galaxies in which a variable X-ray emission, possibly related to a tidal event was detected. In the case of NGC 3599 and IC 3599, data are well reproduced by models defined by a black hole with mass ∼ 10 7 M ⊙ and a disrupted star of about one solar mass. The X-ray variation observed in XMMSL1 is consistent with a model defined by a black hole with mass ∼ 3 × 10 6 M ⊙ and a disrupted star of one solar mass, while that observed in the galaxy situated in the cluster A1689 is consistent with a model including a black hole of ∼ 10 7 M ⊙ and a disrupted star of ∼ 0.5 M ⊙ .
The Ultraviolet-bright, Slowly Declining Transient PS1-11af as a Partial Tidal Disruption Event
2013
We present the Pan-STARRS1 discovery of the long-lived and blue transient PS1-11af, which was also detected by GALEX with coordinated observations in the near-ultraviolet (NUV) band. PS1-11af is associated with the nucleus of an early-type galaxy at redshift z=0.4046 that exhibits no evidence for star formation or AGN activity. Four epochs of spectroscopy reveal a pair of transient broad absorption features in the UV on otherwise featureless spectra. Despite the superficial similarity of these features to P-Cygni absorptions of supernovae (SNe), we conclude that PS1-11af is not consistent with the properties of known types of SNe. Blackbody fits to the spectral energy distribution are inconsistent with the cooling, expanding ejecta of a SN, and the velocities of the absorption features are too high to represent material in homologous expansion near a SN photosphere. However, the constant blue colors and slow evolution of the luminosity are similar to previous optically-selected tidal disruption events (TDEs). The shape of the optical light curve is consistent with models for TDEs, but the minimum accreted mass necessary to power the observed luminosity is only ∼0.002 M ⊙ , which points to a partial disruption model. A full disruption model predicts higher bolometric luminosities, which would require most of the radiation to be emitted in a separate component at high energies where we lack observations. In addition, the observed temperature is lower than that predicted by pure accretion disk models for TDEs and requires reprocessing to a constant, lower temperature. Three deep non-detections in the radio with the VLA over the first two years after the event set strict limits on the production of any relativistic outflow comparable to Swift J1644+57, even if off-axis.
An ultraviolet–optical flare from the tidal disruption of a helium-rich stellar core
Nature, 2012
The flare of radiation from the tidal disruption and accretion of a star can be used as a marker for supermassive black holes that otherwise lie dormant and undetected in the centres of distant galaxies 1 . Previous candidate flares 2-6 have had declining light curves in good agreement with expectations, but with poor constraints on the time of disruption and the type of star disrupted, because the rising emission was not observed. Recently, two 'relativistic' candidate tidal disruption events were discovered, each of whose extreme X-ray luminosity and synchrotron radio emission were interpreted as the onset of emission from a relativistic jet 7-10 . Here we report the discovery of a luminous ultraviolet-optical flare from the nuclear region of an inactive galaxy at a redshift of 0.1696. The observed continuum is cooler than expected for a simple accreting debris disk, but the well-sampled rise and decline of its light curve follows the predicted mass accretion rate, and can be modelled to determine the time of disruption to an accuracy of two days. The black hole has a mass of about 2 million solar masses, modulo a factor dependent on the mass and radius of the star disrupted. On the basis of the spectroscopic signature of ionized helium from the unbound debris, we determine that the disrupted star was a helium-rich stellar core.
Tidal Disruption of a Main-sequence Star by an Intermediate-mass Black Hole: A Bright Decade
The Astrophysical Journal, 2018
There has been suggestive evidence of intermediate-mass black holes (IMBHs; 10 3−5 M e) existing in some globular clusters (GCs) and dwarf galaxies, but IMBHs as a population remain elusive. As a main-sequence star passes too close by an IMBH it might be tidally captured and disrupted. We study the long-term accretion and observational consequence of such tidal disruption events. The disruption radius is hundreds to thousands of the BH's Schwarzschild radius, so the circularization of the falling-back debris stream is very inefficient due to weak general relativity effects. Due to this and a high mass fallback rate, the bound debris initially goes through a ∼10 yr long super-Eddington accretion phase. The photospheric emission of the outflow ejected during this phase dominates the observable radiation and peaks in the UV/optical bands with a luminosity of 10 erg s 42 1-. After the accretion rate drops below the Eddington rate, the bolometric luminosity follows the conventional t −5/3 powerlaw decay, and X-rays from the inner accretion disk start to be seen. Modeling the newly reported IMBH tidal disruption event candidate 3XMM J2150-0551, we find a general consistency between the data and predictions. The search for these luminous, long-term events in GCs and nearby dwarf galaxies could unveil the IMBH population.
JETS FROM TIDAL DISRUPTIONS OF STARS BY BLACK HOLES
Tidal disruption of main-sequence stars by black holes has generally been thought to lead to a signal dominated by UV emission. If, however, the black hole spins rapidly and the poloidal magnetic field intensity on the black hole horizon is comparable to the inner accretion disk pressure, a powerful jet may form whose luminosity can easily exceed the thermal UV luminosity. When the jet beam points at Earth, its non-thermal luminosity can dominate the emitted spectrum. The thermal and non-thermal components decay differently with time. In particular, the thermal emission should remain roughly constant for a significant time after the period of maximum accretion, beginning to diminish only after a delay, whereas after the peak accretion rate, the non-thermal jet emission decays, but then reaches a plateau. Both transitions are tied to a characteristic timescale t Edd at which the accretion rate falls below Eddington. Making use of this timescale in a new parameter-inference formalism for tidal disruption events with significant emission from a jet, we analyze the recent flare source Swift J2058. It is consistent with an event in which a main-sequence solar-type star is disrupted by a black hole of mass ∼ 4 × 10 7 M. The beginning of the flat phase in the non-thermal emission from this source can possibly be seen in the late-time light curve. Optical photometry over the first 40 days of this flare is also consistent with this picture, but is only weakly constraining because the bolometric correction is very uncertain. We suggest that future searches for main-sequence tidal disruptions use methods sensitive to jet radiation as well as to thermal UV radiation.
Light Curves of Partial Tidal Disruption Events
The Astrophysical Journal, 2021
Tidal disruption events (TDEs) can uncover the quiescent black holes (BHs) at the center of galaxies and also offer a promising method to study them. In a partial TDE (PTDE), the BH's tidal force cannot fully disrupt the star, so the stellar core survives and only a varied portion of the stellar mass is bound to the BH and feeds it. We calculate the event rate of PTDEs and full TDEs (FTDEs). In general, the event rate of PTDEs is higher than that of FTDEs, especially for the larger BHs. And the detection rate of PTDEs is about dozens per year by Zwicky Transient Factory (ZTF). During the circularization process of the debris stream in PTDEs, no outflow can be launched due to the efficient radiative diffusion. The circularized debris ring then experiences viscous evolution and forms an accretion disk. We calculate the light curves of PTDEs contributed by these two processes, along with their radiation temperature evolution. The light curves have double peaks and the spectra peak in UV. Without obscuration or reprocessing of the radiation by an outflow, PTDEs provide a clean environment to study the circularization and transient disk formation in TDEs.
Astronomy & Astrophysics
A tidal disruption event (TDE) is an astronomical phenomenon in which a previously dormant black hole (BH) destroys a star passing too close to its central part. We analyzed the flaring episode detected from the TDE sources, Swift J164449.3+573451 and Swift J2058.4+0516 (hereafter Swift J1644+57 and Swift J2058+05, respectively) using RXTE, Swift and Suzaku data. The spectra are well fitted by the so called Bulk Motion Comptonization model for which the best-fit photon index Γ varies from 1.1 to 1.8. We have firmly established the saturation of the photon index versus mass accretion rate at Γ sat about 1.7-1.8. The saturation of Γ is usually identified as a signature of a BH now established in Swift J1644+57 and Swift J2058+05. In Swift J1644+57 we found the relatively low Γ sat values which indicate a high electron (plasma) temperature, kT e ∼ 30-40 keV. This is also consistent with high cutoff energies, E cut ∼ 60-80 keV found using best fits of the RXTE spectra. Swift J2058+05 shows a lower electron temperature, kT e ∼ 4-10 keV than that for Swift J1644+57. For the BH mass estimate we used the scaling technique taking the Galactic BHs, GRO J1655-40, GX 339-4, Cyg X-1 and 4U 1543-47 as reference sources and found that the BH mass in Swift J1644+57 is M BH ≥ 7 × 10 6 M assuming the distance to this source of 1.5 Gpc. For Swift J2058+05 we obtain M BH ≥ 2 × 10 7 M assuming the distance to this source of 3.7 Gpc. We have also found that the seed (disk) photon temperatures are quite low, of order of 100-400 eV, in both of the sources, which are consistent with the estimated BH masses.
The evolution of Kerr discs and late-time tidal disruption event light curves
Monthly Notices of the Royal Astronomical Society, 2018
An encounter between a passing star and a massive black hole at the centre of a galaxy, a socalled tidal disruption event or TDE, may leave a debris disc that subsequently accretes onto the hole. We solve for the time evolution of such a TDE disc, making use of an evolutionary equation valid for both the Newtonian and Kerr regimes. The late time luminosity emergent from such a disc is of interest as a model diagnostic, as it tends to follow a power law decline. The original simple ballistic fallback model, with equal mass in equal energy intervals, produces a −5/3 power law, while standard viscous disc descriptions yield a somewhat more shallow decline, with an index closer to −1.2. Of four recent, well-observed tidal disruption event candidates however, all had fall-off power law indices smaller than 1 in magnitude. In this work, we revisit the problem of thin disc evolution, solving this reduced problem in full general relativity. Our solutions produce power law indices that are in much better accord with observations. The late time observational data from many TDEs are generally supportive, not only of disc accretion models, but of finite stress persisting down to the innermost stable circular orbit.
An upper observable black hole mass scale for tidal destruction events with thermal X-ray spectra
Monthly Notices of the Royal Astronomical Society, 2021
We comprehensively model the X-ray luminosity emergent from time-dependent relativistic accretion discs, developing analytical models of the X-ray luminosity of thermal disc systems as a function of black hole mass M, disc mass Md, and disc α-parameter. The X-ray properties of these solutions will be directly relevant for understanding tidal disruption event (TDE) observations. We demonstrate an extremely strong suppression of thermal X-ray luminosity from large mass black holes, LX ∼ exp (− m7/6), where m is a dimensionless mass, roughly the black hole mass in unity of 106M⊙. This strong suppression results in upper observable black hole mass limits, which we demonstrate to be of order Mlim ≃ 3 × 107M⊙, above which thermal X-ray emission will not be observable. This upper observable black hole mass limit is a function of the remaining disc parameters, and the full dependence can be described analytically (equation 82). We demonstrate that the current population of observed X-ray TD...
Astronomy and Astrophysics, 2017
A tidal disruption event (TDE) is an astronomical phenomenon in which a previously dormant black hole (BH) destroys a star passing too close to its central part. We analyzed the flaring episode detected from the TDE sources, Swift J164449.3+573451 and Swift J2058.4+0516 (hereafter Swift J1644+57 and Swift J2058+05, respectively) using RXTE, Swift and Suzaku data. The spectra are well fitted by the so called Bulk Motion Comptonization model for which the best-fit photon index Γ varies from 1.1 to 1.8. We have firmly established the saturation of the photon index versus mass accretion rate at Γ sat about 1.7-1.8. The saturation of Γ is usually identified as a signature of a BH now established in Swift J1644+57 and Swift J2058+05. In Swift J1644+57 we found the relatively low Γ sat values which indicate a high electron (plasma) temperature, kT e ∼ 30-40 keV. This is also consistent with high cutoff energies, E cut ∼ 60-80 keV found using best fits of the RXTE spectra. Swift J2058+05 shows a lower electron temperature, kT e ∼ 4-10 keV than that for Swift J1644+57. For the BH mass estimate we used the scaling technique taking the Galactic BHs, GRO J1655-40, GX 339-4, Cyg X-1 and 4U 1543-47 as reference sources and found that the BH mass in Swift J1644+57 is M BH ≥ 7 × 10 6 M assuming the distance to this source of 1.5 Gpc. For Swift J2058+05 we obtain M BH ≥ 2 × 10 7 M assuming the distance to this source of 3.7 Gpc. We have also found that the seed (disk) photon temperatures are quite low, of order of 100-400 eV, in both of the sources, which are consistent with the estimated BH masses.