scholarly journals First light from tidal disruption events

2021 ◽  
Author(s):  
Clément Bonnerot ◽  
Wenbin Lu ◽  
Philip F Hopkins
Keyword(s):  
Black Hole ◽  
The Self ◽  
Radiation Hydrodynamics ◽  
Significant Component ◽  
Tidal Disruption ◽  
Bolometric Luminosity ◽  
Tidal Forces ◽  
Initial Interaction ◽  
Insight Into ◽  
Injection Procedure

Abstract When a star comes too close to a supermassive black hole, it gets torn apart by strong tidal forces in a tidal disruption event, or TDE. Half of the elongated stream of debris comes back to the stellar pericenter where relativistic apsidal precession induces a self-crossing shock. As a result, the gas gets launched into an outflow that can experience additional interactions, leading to the formation of an accretion disc. We carry out the first radiation-hydrodynamics simulations of this process, making use of the same injection procedure to treat the self-crossing shock as in our previous adiabatic study. Two sets of realistic parameters of the problem are considered that correspond to different strengths of this initial interaction. In both cases, we find that the injected matter has its trajectories promptly circularized by secondary shocks taking place near the black hole. However, the generated internal energy efficiently diffuses away in the form of radiation, which results in a thin vertical profile of the formed disc. The diffusing photons promptly irradiate the surrounding debris until they emerge with a bolometric luminosity of $L\approx 10^{44} \, \rm erg\, s^{-1}$. Towards the self-crossing shock, diffusion is however slowed that results in a shallower luminosity increase, with a potentially significant component in the optical band. Matter launched to large distances continuously gains energy through radiation pressure, which can cause a significant fraction to become unbound. This work provides direct insight into the origin of the early emission from TDEs, which is accessed by a rapidly increasing number of observations.

scholarly journals Observational Progress in Identifying and Characterizing Tidal Disruption Flares

2016 ◽  
Vol 12 (S324) ◽  
pp. 93-98
Author(s):  
S. Bradley Cenko
Keyword(s):  
Black Hole ◽  
Optical Spectra ◽  
Starburst Galaxies ◽  
Electromagnetic Spectrum ◽  
Speed Of Light ◽  
Tidal Disruption ◽  
Massive Black Hole ◽  
X Ray ◽  
Tidal Forces

AbstractI present an overview of observational efforts across the electromagnetic spectrum to identify and study tidal disruption flares (TDFs), when a star wanders too close to a super-massive black hole and is torn apart by tidal forces. In particular I will focus on four unexpected surprises that challenge the most basic analytic picture of these events: 1) large inferred radii for the optical/UV-emitting material; 2) the ubiquity of outflows, detected at radio, X-ray, and UV wavelengths, ranging from speeds of 100 km/s to near the speed of light; 3) the peculiar atomic abundances observed in the UV and optical spectra of these objects; and, 4) the preference for these events to occur in post-starburst galaxies.

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 A loud quasi-periodic oscillation after a star is disrupted by a massive black hole

Science ◽  
2019 ◽  
Vol 363 (6426) ◽  
pp. 531-534 ◽  
Author(s):  
Dheeraj R. Pasham ◽  
Ronald A. Remillard ◽  
P. Chris Fragile ◽  
Alessia Franchini ◽  
Nicholas C. Stone ◽  
...  
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Periodic Oscillation ◽  
Host Galaxy ◽  
X Rays ◽  
Tidal Disruption ◽  
Massive Black Hole ◽  
Quasi Periodic Oscillation ◽  
Massive Black Holes ◽  
Tidal Forces

The tidal forces close to massive black holes can rip apart stars that come too close to them. As the resulting stellar debris spirals toward the black hole, the debris heats up and emits x-rays. We report observations of a stable 131-second x-ray quasi-periodic oscillation from the tidal disruption event ASASSN-14li. Assuming the black hole mass indicated by host galaxy scaling relations, these observations imply that the periodicity originates from close to the event horizon and that the black hole is rapidly spinning. Our findings demonstrate that tidal disruption events can generate quasi-periodic oscillations that encode information about the physical properties of their black holes.

scholarly journals What causes the fragmentation of debris streams in TDEs?

2020 ◽  
Vol 495 (1) ◽  
pp. 1227-1238
Author(s):  
Andrea Sacchi ◽  
Giuseppe Lodato ◽  
Claudia Toci ◽  
Valentina Motta
Keyword(s):  
Black Hole ◽  
Time Scales ◽  
Physical Processes ◽  
Tidal Disruption ◽  
Tidal Forces ◽  
Gaseous Stream ◽  
Gravitational Stability ◽  
Hydrodynamical Simulations ◽  
Self Gravity ◽  
Disruption Event

ABSTRACT A tidal disruption event (TDE) occurs when a star passes too close to a supermassive black hole and gets torn apart by its gravitational tidal field. After the disruption, the stellar debris form an expanding gaseous stream. The morphology and evolution of this stream are particularly interesting as it ultimately determines the observational properties of the event itself. In this work, we perform 3D hydrodynamical simulations of the TDE of a star modelled as a polytropic sphere of index γ = 5/3 and study the gravitational stability of the resulting gas stream. We provide an analytical solution for the evolution of the stream in the bound, unbound, and marginally bound cases, which allows us to describe the stream properties and analyse the time-scales of the physical processes involved, applying a formalism developed in star formation context. Our results are that, when fragmentation occurs, it is fuelled by the failure of pressure in supporting the gas against its self-gravity. We also show that a stability criterion that includes also the stream gas pressure proves to be far more accurate than one that only considers the black hole tidal forces, giving analytical predictions of the time evolution of the various forces associated with the stream. Our results point out that fragmentation occurs on time-scales longer compared with the observational windows of these events and is thus not expected to give rise to significant observational features.

scholarly journals Simulating disc formation in tidal disruption events

2020 ◽  
Vol 495 (1) ◽  
pp. 1374-1391 ◽  
Author(s):  
Clément Bonnerot ◽  
Wenbin Lu
Keyword(s):  
Black Hole ◽  
Initial Conditions ◽  
Large Fraction ◽  
Compact Object ◽  
Intersection Point ◽  
Tidal Disruption ◽  
Bolometric Luminosity ◽  
Supermassive Black Hole ◽  
Distribution Features ◽  
Early Radiation

ABSTRACT A star coming too close to a supermassive black hole gets disrupted by the tidal force of the compact object in a tidal disruption event, or TDE. Following this encounter, the debris evolves into an elongated stream, half of which coming back to pericentre. Relativistic apsidal precession then leads to a self-crossing shock that initiates the formation of an accretion disc. We perform the first simulation of this process considering a parabolic encounter with a supermassive black hole, which has so far eluded investigations for computational reasons. This numerical issue is alleviated by using as initial conditions the outflow launched by the self-crossing shock according the local simulation of Lu & Bonnerot (2020). We find that the gas leaving the intersection point experiences numerous secondary shocks that result in the rapid formation of a thick and marginally bound disc. The mass distribution features two overdensities identified as spiral shocks that drive slow gas inflow along the mid-plane. Inward motion primarily takes place along the funnels of the newly formed torus, from which a fraction of the matter can get accreted. Further out, the gas moves outward forming an extended envelope completely surrounding the accretion flow. Secondary shocks heat the debris at a rate of a few times $10^{44} \, \rm erg\, s^{-1}$ with a large fraction likely participating to the bolometric luminosity. These results pave the way towards a complete understanding of the early radiation from TDEs that progressively becomes accessible from observations.

The Relationship between Seeker and Spiritual Guide as portrayed in contemporary Western Sufi Autobiographies

2011 ◽  
Vol 5 (2) ◽  
pp. 297-332
Author(s):  
Kate Zebiri
Keyword(s):  
Life Writing ◽  
New Age ◽  
The Self ◽  
Individual Autonomy ◽  
Religious Authority ◽  
The Face ◽  
The Relationship ◽  
Insight Into ◽  
Continuity And Discontinuity

This article aims to explore the Shaykh-mur?d (disciple) or teacher-pupil relationship as portrayed in Western Sufi life writing in recent decades, observing elements of continuity and discontinuity with classical Sufism. Additionally, it traces the influence on the texts of certain developments in religiosity in contemporary Western societies, especially New Age understandings of religious authority. Studying these works will provide an insight into the diversity of expressions of contemporary Sufism, while shedding light on a phenomenon which seems to fly in the face of contemporary social and religious trends which deemphasize external authority and promote the authority of the self or individual autonomy.

Die Eigen-Werte der Literatur

2009 ◽  
Vol 54 (1) ◽  
pp. 103-119
Author(s):  
Matthias Bickenbach
Keyword(s):  
The Self ◽  
Literary Writing ◽  
Self Organisation ◽  
Insight Into

Eine der zentralen Fragen moderner Poetik ist, wie der Werkentstehungsprozeß von kreativer Materialfülle zur ästhetischen Bestimmtheit des Erzählten als autonomem Kunstwerk übergeht. Sten Nadolnys Poetikvorlesung gibt überraschende Einsichten in die Selbstorganisation von Steuerungsbewegungen, die noch unterhalb der Ebene des Schreibens liegen und die als Theorie der Eigenwerte in der Literatur herauszustellen ist. One of the central questions in modern poetics is, how literary writing proceeds from the creative richness of its material to an aesthetic determination as autonomous art. Sten Nadolnys lectures on his poetics enable an astonishing insight into the self-organisation of operations beyond writing, which can be considered as a theory of self-values in literature.

Speed vs. comfort: Testing the efficacy of a single question for predicting transit users’ route choices

2019 ◽  
Author(s):  
Joseph John Pyne Simons ◽  
Ilya Farber
Keyword(s):  
Data Collection ◽  
Efficient Method ◽  
Choice Task ◽  
The Self ◽  
Self Report ◽  
Model Parameters ◽  
Single Item ◽  
Alternative Approach ◽  
Single Question ◽  
Insight Into

Not all transit users have the same preferences when making route decisions. Understanding the factors driving this heterogeneity enables better tailoring of policies, interventions, and messaging. However, existing methods for assessing these factors require extensive data collection. Here we present an alternative approach - an easily-administered single item measure of overall preference for speed versus comfort. Scores on the self-report item predict decisions in a choice task and account for a proportion of the differences in model parameters between people (n=298). This single item can easily be included on existing travel surveys, and provides an efficient method to both anticipate the choices of users and gain more general insight into their preferences.

Women and Agency in Bankim’s Rajmohan’s Wife and Tagore’s The Home and The World

2020 ◽  
Vol 12 (5) ◽  
Author(s):  
Manju Dhariwal ◽  
Keyword(s):  
Nineteenth Century ◽  
The Self ◽  
Indian English ◽  
Colonial India ◽  
English Novel ◽  
The World ◽  
The Status ◽  
Insight Into ◽  
Status Of Women

Written almost half a century apart, Rajmohan’s Wife (1864) and The Home and the World (1916) can be read as women centric texts written in colonial India. The plot of both the texts is set in Bengal, the cultural and political centre of colonial India. Rajmohan’s Wife, arguably the first Indian English novel, is one of the first novels to realistically represent ‘Woman’ in the nineteenth century. Set in a newly emerging society of India, it provides an insight into the status of women, their susceptibility and dependence on men. The Home and the World, written at the height of Swadeshi movement in Bengal, presents its woman protagonist in a much progressive space. The paper closely examines these two texts and argues that women enact their agency in relational spaces which leads to the process of their ‘becoming’. The paper analyses this journey of the progress of the self, which starts with Matangini and culminates in Bimala. The paper concludes that women’s journey to emancipation is symbolic of the journey of the nation to independence.

scholarly journals Tidal forces near a black hole with scalar hairy

2020 ◽  
Vol 1690 ◽  
pp. 012181
Author(s):  
E L Andre ◽  
I M Potashov ◽  
Ju V Tchemarina ◽  
A N Tsirulev
Keyword(s):  
Black Hole ◽  
Tidal Forces
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