Conveners
14 - Disks and jets
- Thierry Courvoisier (University of Geneva)
14 - Disks and jets
- Thierry Courvoisier (University of Geneva)
14 - Disks and jets
- Thierry Courvoisier (University of Geneva)
14 - Disks and jets
- Thierry Courvoisier (University of Geneva)
Massimo Cappi
(National Institute for Astrophysics - INAF)
12/16/15, 2:00โฏPM
Talk
I will briefly review the evidence for high-velocity (mildly relativistic) and massive winds in Active Galactic Nuclei. I will then highlight some new recent results obtained in X-rays (mostly using deep XMM and Chandra observations) and at multi-frequencies for both low-z AGNs and high-z QSOs. Among other things, these studies indicate that massive, high-velocity, outflows may be more common...
Luigi Pacciani
(IAPS/INAF)
12/16/15, 2:22โฏPM
Talk
High-Energy gamma-ray flares (E$>$10 GeV) of Flat Spectrum Radio Quasars (FSRQ) give us strong constraints of jet-physics, and of the surrounding-medium.
We performed the first study of these flares, examining FERMI-LAT archival-data, and triggering $\sim$40 ToO-observations from near-ir to TeV (e.g., for PKS 1441+25),
at the occurrence of new flares.
We identified $\sim$260 gamma-ray...
Robert Laing
(ESO)
12/16/15, 2:42โฏPM
Talk
We present new, deep, high-resolution images of the iconic jets in the nearby radio galaxy NGC 6251 made with the Karl G. Jansky VLA, resolving the faint counter-jet in width for the first time. We model the jet velocity field using the method of Laing & Bridle (2002, 2014). We assume that the jets are intrinsically symmetrical, axisymmetric, stationary flows and fit to images of linear...
Dr
Thomas Russell
(ICRAR/Curtin University)
12/16/15, 3:02โฏPM
Talk
There is a universal connection between the accretion and ejection phenomena that are observed in black holes across the mass scale. Quantifying this relationship is the first step in understanding how jets are launched, accelerated and collimated. X-ray binaries are ideal systems to study this relationship, as they evolve on human timescales. In outburst, their luminosities increase by...
Dr
Marek Nikolajuk
(University of Bialystok)
12/16/15, 3:22โฏPM
Talk
The microquasar GRS 1915+105 features well known spectral states that were never extensively studied up to the MeV range, where key spectral diagnostics are expected. We present hard X-ray observations obtained in 15 Msec with Swift/BAT and INTEGRAL and spectra collected during different states up to 400 keV. These spectra can be successfully fitted by the EQPAIR model revealing continuous...
Jรถrg Paul Rachen
(IMAPP / Radboud University Nijmegen)
12/16/15, 3:42โฏPM
Poster
We present time-resolved broad-band spectra of a complete
sample of blazars, selected by showing flat radio spectra up to 143
GHz, taken from observations with Planck, the Effelsberg 100m
telescope, and the IRAM 30m telescope. Dedicated Effelsberg
observations have been focused on times within two months around
Planck single survey scans of each source, with a cadence of 2-4 weeks
during...
Dr
Kyle Parfrey
(Lawrence Berkeley National Laboratory)
12/16/15, 4:15โฏPM
Talk
We propose a scenario for launching relativistic jets from rotating black holes, in which small-scale magnetic flux loops, sustained by disc turbulence, are forced to inflate and open by differential rotation between the black hole and the accretion flow. This mechanism does not require a large-scale net magnetic flux in the accreting plasma, whose presence in the environment of the central...
Karri Koljonen
(New York University Abu Dhabi)
12/16/15, 4:36โฏPM
Talk
Accreting black holes are responsible for producing the fastest, most powerful outflows of matter in the Universe. The formation process of powerful jets close to black holes is poorly understood, and the conditions leading to jet formation are currently hotly debated. In this talk I will present recent results that show empirical correlation between the properties of the plasma close to the...
Dr
Roberto Soria
(ICRAR-Curtin University)
12/16/15, 4:56โฏPM
Talk
Determining the power output and efficiency of accreting black holes is a fundamental astrophysical problem:
we want to know the relation between mass accretion rate, radiative output (photons) and mechanical output
(kinetic energy of jets and winds). We focus in particular on off-nuclear black holes that are accreting
from a donor star at a rate near or above the critical Eddington...
Dr
Pedro Luis Luque-Escamilla
(Universidad de Jaรฉn)
12/16/15, 5:17โฏPM
Talk
Jets appear in Astrophysics in very different environments and scales across the Universe, and they seem to share common features in all cases. Their study can then help us to understand a widespread outflow mechanism. However, their large-scale dynamics remain hidden to observation along human time scales because they usually develop too slowly, either because of their large sizes (in active...
Mr
Dimitrios Millas
(KU LEUVEN)
12/16/15, 5:59โฏPM
Talk
Several observations of astrophysical jets show evidence of a structure in the direction perpendicular to the jet axis, leading to the development of โspine & sheathโ models of jets.
Two-component jets have been already examined (e.g. Meliani & Keppens 2007, Meliani & Keppens 2009) for relativistic hydrodynamic jets and relativistic magnetized jets with poloidal magnetic field. These...
Dr
Luigi Foschini
(National Institute for Astrophysics - INAF)
12/16/15, 6:19โฏPM
Poster
How powerful relativistic jets are generated is still one of the most important topics of the modern astrophysics. One of the most interesting and adopted theories was developed by Blandford and Znajek in 1977 with reference to jets from black holes. In the present work, I would like to draw the attention on some relatively unexplored features of the theory, with particular reference to the...
Dr
Alla Miroshnichenko
(Institute of Radio Astronomy, NAS of Ukraine)
12/16/15, 6:22โฏPM
Poster
We consider four samples of steep-spectrum radio sources from our catalogue UTR-2 at the decameter band. These contain galaxies and quasars of both spectral types - with linear steep spectrum and break steep spectrum. To obtain the relation of low-frequency luminosity, at the frequency 25 MHz, L_25 and linear size R of sample objects we determine one at the different redshift ranges at the...
Emilia Jรคrvelรค
(Aalto University Metsรคhovi Radio Observatory)
12/17/15, 2:00โฏPM
Talk
The presence of powerful relativistic jets in narrow-line Seyfert 1 galaxies (NLS1) was confirmed when Fermi detected gamma-rays from a handful of them. In the current active galactic nuclei (AGN) paradigm powerful relativistic jets are produced only in massive elliptical galaxies with supermassive black holes, but NLS1 galaxies challenge this scenario since they have lower black hole masses,...
Marco Berton
(University of Padova - Department of Physics and Astronomy "G. Galilei")
12/17/15, 2:20โฏPM
Talk
Narrow-line Seyfert 1 galaxies (NLS1s) are active galactic nuclei (AGN) recently identified as a new class of $\gamma$-ray sources. The high energy emission is explained with the presence of a relativistic jet observed at small angles, just like in the two classes of blazars. When the latters are observed at larger angles they appear as radio-galaxies, but an analogue parent population for...
Dr
Luigi Foschini
(National Institute for Astrophysics - INAF)
12/17/15, 2:40โฏPM
Talk
We studied a sample of 42 radio loud narrow-1ine Seyfert 1 galaxies (RLNLS1s) by using all the available multiwavelength observations and the information in literature. The masses of the central black holes are in the range $\sim 10^{6-8}M_{\odot}$, smaller than blazars, while the accretion luminosities span from $\sim 0.01$ to $\sim 0.49L_{{\rm Edd}}$, with an outlier at $0.003$, similarly to...
Antonis Manousakis,
Bhupendra Mishra
(Nicolaus Copernicus Astronomical Center Warsaw Poland),
Frederic Vincent
(Observatoire de Paris)
12/17/15, 3:00โฏPM
Poster
We simulate a purely hydrodynamical torus with constant specific angular momentum around a Schwarzschild black hole. The goal is to search for quasi-periodic oscillations (QPOs) of the torus. Initial torus setup is subjected to radial, vertical and a diagonal (combination of radial and vertical) velocity perturbations. The hydrodynamical simulations are performed using the general relativistic...
Frederic Vincent
(Observatoire de Paris)
12/17/15, 3:03โฏPM
Poster
Quasi-periodic oscillations (QPO) are an important probe of the timing properties of black-hole binaries and a ubiquitous feature of their PDS. For that reason, many attempts to explain their origin have also reduced them to their frequencies. In order to explore their behavior beyond this, we consider three simple classes of models: elongated hot spots, tori and spirals. We perturb the...
Rebecca Nealon
(Monash University)
12/17/15, 3:06โฏPM
Poster
Observations of QPOs from neutron stars and black holes suggest they must be a feature of the accretion disc surrounding these objects. Their measured frequencies indicate they are from the inner disc, where effects from the Lense-Thirring precession are significant. However, because the properties of the high and low frequency QPOs are so different, it is thought that separate physical...
Matteo Bugli
(Max Planck Institute for Astrophysics)
12/17/15, 4:15โฏPM
Talk
Accretion on compact objects is commonly considered the most plausible mechanism to power up a list of astrophysical systems (such as AGNs, GRBs, X-Ray Binaries, etc. . . ) and in particular magnetic fields are believed to play a major role in enabling the accretion process through the development of magnetic instabilities. We investigated the effects of a finite resistivity in a magnetized...
Bhupendra Mishra
(Nicolaus Copernicus Astronomical Center Warsaw Poland)
12/17/15, 4:36โฏPM
Talk
The stability of geometrically thin radiation pressure dominated accretion disks around black holes remained under debate. Analytical work concludes that such disks should be thermally unstable. Newtonian shearing box simulations in the past show that these disks may be thermally stable. In last few years other pseudo-Newtonian shearing box simulations showed that the disks are thermally...
Anna Chashkina
(Tuorla Observatory, University of Turku)
12/17/15, 4:57โฏPM
Talk
One of the ultraluminous X-ray sources M82 X-2 was recently identified as a neutron star accreting at a rate significantly larger that ordinary X-ray pulsars. The accretion disc outside the magnetosphere probably still remains below the local Eddington limit but its structure may be affected by the radiation of the central source (accretion column) that together with magnetic torques shifts...
Pavel Abolmasov
(University of Turku)
12/17/15, 5:18โฏPM
Talk
Using general relativistic analytical treatment in Kerr metric and numerical simulations with the public HARM2D code, we consider the vertical structure and velocity field in the inner parts of a black hole accretion disk, both outside and inside the last stable orbit.
Chaotic magnetic fields frozen into the accreting matter easily become the dominant pressure source inside the sonic point...
Zakaria Meliani
(LUTH, Observatoire de Paris)
12/17/15, 5:38โฏPM
Talk
Accretion disks play an important role in the evolution of their relativistic inner compact objects. The emergence of a new generation of interferometers will allow resolving these accretion disks and providing more information about the properties of the central gravitating object. Due to this instrumental leap forward it is crucial to investigate the accretion disk physics near various types...
Viacheslav Zhuravlev
12/17/15, 5:59โฏPM
Talk
This work is related to one of the major unsolved problems in the theory of accretion disks:
the problem of pure hydrodynamical origin of effective viscosity in their interiors.
If it were solved, we would have a general alternative to the well-known conception of
supercritical turbulence excited by magneto-rotational instability. As has been widely discussed by fluid physicists since...
Mikhail Belyaev
(UC Berkeley/TAC)
12/17/15, 6:19โฏPM
Talk
Accretion is a ubiquitous process in astrophysics. In cases when the magnetic field is not too strong and a disk is formed, accretion can proceed through the mid plane all the way to the surface of the central compact object. Unless that compact object is a black hole, a boundary layer will be formed where the accretion disk touches its surfaces. The boundary layer is both dynamically and...
Dr
Antonio Stamerra
(INAF-Osservatorio Astrofisico di Torino, Italy)
12/17/15, 6:39โฏPM
Poster
We report on the results of a multifrequency campaign on the BL Lac object PG 1553+113 that was organized by the Whole Earth Blazar Telescope (WEBT) Collaboration in 2013 April-August. Nineteen optical, two near-IR, and three radio telescopes monitored the source to follow its behaviour at low energies during and around the high-energy observations by the MAGIC telescopes in April-July. A...
Ms
Lis Sulistiyowati
(Institut Teknologi Bandung)
12/17/15, 6:42โฏPM
Poster
In this study, we report the examinations of the spectra of ULXs in two nearby (< 10 Mpc) pairs of interacting galaxies M51 and NGC 4485/90 collected by Swift-XRT observations from 2005 to 2014 and 2008 to 2015 for each target, respectively. We consider 9 ULXs in M51 and 5 ULXs in NGC 4485/90. We obtain 116 ObsIDs of M51 and 37 ObsIDs of NGC 4485/90. For each pair of interacting galaxy, there...
