Astrophysics Seminar

Astrophysics Seminar: "Signals and Interlopers: Exhausting Cosmological Information from the Depths of the Observable Universe"

Location: 
Kaplun buildilng, Room No. 200
Tue, 12/01/2016 - 12:30 to 13:30

Lecturer: Dr. Ely Kovetz Affiliation: Johns Hopkins University Abstract: The standard model of cosmology, encapsulated by a handful of parameters to describe the energy content of the universe, its rate of expansion, and the amplitude and scale- dependence of primordial perturbations, has been immensely successful when confronted with cosmological observations hitherto. However, this simple picture masks the extent of our ignorance regarding several fundamental questions in cosmology, such as what are the properties of inflation, what is the nature of

"Astrophysics Seminar: High-energy emission from Gamma-Ray Bursts: advancing our knowledge on GRBs and relativistic shocks through modeling of afterglow radiation"

Location: 
Kaplun building, Room No. 200
Tue, 05/05/2015 - 12:30 to 13:30

Lecturer: Dr. Lara Nava Affiliation: Racah Institute of Physics, The Hebrew University of Jerusalem Abstract: The physical origin of the temporally extended (~10^2 sec) high-energy emission (0.1-100 GeV) detected from Gamma-Ray Bursts by the Fermi/LAT instrument has not yet been completely understood. I present the evidences in favor of the external shock scenario, where the LAT emission is interpreted as radiation from electrons accelerated at the relativistic shock developed in interactions with the external medium. I show that the modelling of LAT

"Special Astrophysics Seminar: Probing general relativity, alternative theories of gravity, and relativistic geodesy with atomic clocks"

Location: 
Kaplun building, Room No. 200
Sun, 28/12/2014 - 14:15 to 15:15

Lecturer: Dr. Ruxandra Bondarescu Affiliation: University of Zurich Abstract: I will discuss the applicability of atomic clocks to test general relativity and alternative theories of gravity for planned missions such as the Gravitational Redshift Explorer (GRESE). We assume that the spacecraft that orbits the Earth is tracked using the observed tick rate of its clock, which is then compared to the tick rate of a local clock on the ground. The spacecraft's reconstructed 4-D trajectory can reveal the nature of gravitational perturbations

Astrophysics Seminar: "Long-Term Evolution of Binaries Toward SNIa"

Location: 
Kaplun building, Room No. 200
Tue, 08/03/2016 - 12:30 to 13:30

Lecturer: Mrs. Yael Hillman Affiliation: Tel-Aviv University Abstract: Can a white dwarf (WD) in a semi-detached binary system, accreting mass from its secondary, secularly grow, eventually reaching the Chandrasekhar mass and explode as a Type Ia supernovae (SNIa)? Via simulations of long term evolution over tens of thousands of nova cycles, we have determined the parameter space, defined by the WD mass, central temperature, and accretion rate, that may allow such growth. We have accounted for limits on the secondary mass as well as the time frame.

"Astrophysics Seminar: Exposing cohesion forces in asteroids using fast rotating bodies"

Location: 
Kaplun building, Room No. 200
Tue, 20/10/2015 - 12:30 to 13:30

Lecturer: Dr. David Polishook, Affiliation: Massachusetts Institute of Technology Abstract: Asteroids are considered to be collections of rocks separated by voids with no tensile strength to hold their components. When an asteroid is spinning-up, its gravity supposed to be the only force resisting the centrifugal acceleration before the body breaks apart. This notion is argumented by the observation that asteroids larger than ~300 m do not rotate faster than 2.2 hours per cycle. Smaller asteroids (<300 m) that reach faster rotations are therefore strong monolithic bodies

"Astrophysics Seminar: Upper limits on the Epoch of Reionization from LOFAR"

Location: 
Kaplun building, Room No. 200
Tue, 03/03/2015 - 12:30 to 13:30

Lecturer: Prof. Saleem Zaroubi Affiliation: University of Groningen Abstract: The Epoch of Reionization marks one of the last major phase transitions in the Universe. Our understanding of this period is very limited with most of the details of the process are still unknown. The redshifted 21 cm radiation from neutral hydrogen provides one of the most promising probes of the EoR. Currently, there are a number of telescopes in the world targeting this radiation. In this seminar I will talk about recent results from The LOw Frequency ARray, LOFAR,

Astrophysics Seminar: "The growth and death of galaxies: MAD Science"

Location: 
Kaplun building, Room No. 200
Tue, 08/12/2015 - 12:30 to 13:30

Lecturer: Prof. Marcella Carollo Affiliation: ETH, Zurich Abstract: I will summarize a number of results on the growth of mass and size of galaxies with time, and discuss a perspective that provides a unified answer to three major open questions in galaxy evolution, namely: (1) How do massive galaxies quench their star formation activity? (2) How do quenched galaxies grow their dense bulges? (3) What causes the observed growth with time of the average size of the quenched galaxy population? I will conclude with a look ahead on the MUSE Atlas of Disks (MAD), a just-

"Astrophysics Seminar: A New Look at AGN Accretion Discs and Black Hole Spin"

Location: 
Kaplun building, Room No. 200
Tue, 21/04/2015 - 12:30 to 13:30

Lecturer: Dr. Daniel Capellupo Affiliation: Tel-Aviv University Abstract: At the center of every active galactic nucleus (AGN) is a supermassive accreting black hole (BH). The physics of active BHs is governed by three key parameters: their mass, spin, and accretion rate. We therefore observe a sample of z ~ 1.5 AGN, selected to cover a wide range in BH mass and accretion rate, with X-shooter on the VLT. Using this unique dataset, we test models of AGN accretion discs and find that most of the observed spectral energy distributions (SEDs) can be

"Astrophysics Seminar: A critical phase in galaxy formation"

Location: 
Kaplun building, Room No. 200
Tue, 24/02/2015 - 12:30 to 13:30

Lecturer: Dr. Greg Stinson Affiliation: MPIA Heidelberg Abstract: As galaxies grow and evolve, they go through a violent phase of their evolution where intense star formation drives outflows. I will examine this phase using cosmological galaxy formation simulations. The simulations show that starbursts and outflows have implications for many observed properties of galaxies including their gaseous halos, morphology, potential, and star formation history. Additional details of the upcoming Astrophysics'

Astrophysics Seminar: "Unraveling GRB 060218"

Location: 
Kaplun building' Room No. 200
Tue, 16/02/2016 - 12:30 to 13:30

Lecturer: Dr. Christopher Irwin Affiliation: The University of Virginia Abstract: We consider a model for the long-duration, low- luminosity gamma-ray burst GRB 060218 that plausibly accounts for multiwavelength observations to day 20. The components of our model are: (1) a long-lived (t ~ 3000 s) central engine and accompanying low-luminosity (L ~ 1e47 erg/s), mildly relativistic jet; (2) a low- mass (~ 1e-2 Msun ) envelope surrounding the progenitor star; and (3) a modest amount of dust (A_V ~ 0.1) in the circumstellar or interstellar environment. Blackbody emission

"Astrophysics Seminar: Electromagnetic Counterparts to Gravitational Waves"

Location: 
Kaplun building, Room No. 200
Tue, 30/06/2015 - 12:30 to 13:30

Lecturer: Prof. K. Ioka Affiliation: The High Energy Accelerator Research Organization, KEK Abstract: Direct detection of gravitational waves (GWs) is on the horizon, with the most promising sources being the mergers of two neutron stars (NS-NS) or a black hole and a neutron star (BH-NS). Maximizing the scientific return of this new window into the universe requires identifying a coincident electromagnetic (EM) counterpart. One probable EM counterpart is a short gamma-ray burst (GRB) but the emission is highly collimated. Isotropic EM emissions are also suggested by the general

"Astrophysics Seminar: Pair-instability supernova progenitors with large mass loss"

Location: 
Kaplun building, Room No. 200
Thu, 22/01/2015 - 14:00 to 15:00

Lecturer: Dr. Takashi Moriya Affiliation: University of Bonn Abstract: Pair-instability supernovae (PISNe) are thermonuclear explosions of very massive stars. The stellar core needs to be heavier than about 60 Msun for stars to be PISNe. Mass loss prevents massive stars from making large enough cores to be PISNe, and PISNe are presumed to exist in metal-free or metal-poor environment where radiation-driven mass loss is small. Stellar evolution models show that such PISN progenitors evolve to red supergiants (RSGs) shortly before their explosions. However, RSGs are suggested to be

Astrophysics Seminar: "Dynamics and evolution of planetesimals in gaseous protoplanetary disks - the role of gas dynamical friction"

Location: 
Kaplun building, Room No. 200
Tue, 12/04/2016 - 12:30 to 13:30

Lecturer: Mr. Evgeni Grishin Affiliation: Technion - Israel Institute of Technology Abstract: The growth of small planetesimals into large planetary embryos occurs much before the dispersal of the gas from the protoplanetary disk. The planetesimal - disk interactions cause migration and orbital evolution of the planetesimals/planets. Small planetesimals are dominated by aerodynamic gas drag. Large protoplanets, >1000km in size, are dominated by type I migration torque. There is an additional size range, 200- 1000 km, of intermediate mass

"Astrophysics Seminar: Astrometric mock observations for determining the local dark matter density"

Location: 
Kaplun building, Room No. 200
Tue, 24/11/2015 - 12:30 to 13:30

Lecturer: Dr. Shigeki Inoue Affiliation: Racah Institute of Physics, The Hebrew University of Jerusalem Abstract: It is a classical problem in astronomy to determine the local dark matter density (LDMD) of the solar system. The DM density at the solar radius can be estimated from the Galactic rotation curve using a spherical assumption for the dark matter halo. However, dark matter haloes are generally aspherical, therefore the DM density deduced from the rotation curve can differ from the LDMD around the solar system. In other words, the difference between

"Astrophysics Seminar: Investigating the links between galaxy structure and environment in the high redshift Universe"

Location: 
Kaplun building, Room No. 200
Tue, 14/04/2015 - 12:30 to 13:30

Lecturer: Dr. Caterina Lani Affiliation: Tel-Aviv University Abstract: It has been long known that, in the local Universe, galaxy morphology is strongly related to environment. Furthermore, massive passive galaxies were observed to be 2 - 4 times more compact at z ~ 2 compared to the present day. Environment, in the form of mergers, halo mass and interactions, could explain the observed size increase as well as morphological transitions. I will present compelling evidence for a strong correlation between galaxy size and environment to z ∼