Astrophysics Seminar

"Astrophysics Seminar: The discovery of gamma-ray burst afterglows: a personal story"

Location: 
Kaplun building, Room No. 200
Tue, 24/03/2015 - 12:30 to 13:30

Lecturer: Dr. Titus J. Galama Affiliation: University of Southern California Abstract: Gamma-ray bursts (GRBs) are short lived, extremely bright gamma-ray sources. Since their accidental discovery in 1973 with the Vela satellites they were an astrophysical enigma for nearly a quarter of a century. In 1997 softer and longer-lived afterglow emission was discovered at X-ray, optical, millimeter, and radio wavelengths. These observations enabled accurate localization of their counterparts and revealed that GRBs come from cosmological distances, that they are by far the most

Astrophysics Seminar: "Could UHECRs originate from GRBs?"

Location: 
Kaplun building, Room No. 200
Tue, 29/03/2016 - 12:30 to 13:30

Lecturer: Dr.Noemie Globus Affiliation: Racah Institute of Physics, The Hebrew University of Jerusalem Abstract: Could UHECRs originate from gamma-ray bursts? To explore that very question, we performed numerical calculations of UHECRs accelerated at GRB internal shocks, taking into account all the relevant energy loss mechanisms. For various choices of the GRB parameters, we calculated the spectrum of cosmic rays escaping from the GRB environment as well as secondary particles produced either during the acceleration or extragalactic propagation. I will discuss the

"Astrophysics Seminar: How will the James Webb Space Telescope measure First Light Reionization, and Galaxy Assembly: The New Frontier after Hubble''

Location: 
Kaplun building, Room No. 200
Tue, 19/05/2015 - 12:30 to 13:30

Lecturer: Dr. Rogier Windhorst Affiliation: Arizona State University Abstract: I will review how the 6.5 meter James Webb Space Telescope (JWST) --- after its launch in 2018 --- can measure the epochs of First Light, Reionization, Galaxy Assembly, and Supermassive Black-Hole Growth, building on recent results from the Hubble Wide Field Camera 3. First, I'll briefly summarize the significant technical progress on the design and fabrication of JWST: more than 98% of its launch mass has been built, passed final design, or is being built as of spring 2015.

"Astrophysics Seminar: Science with orbital phase curves in the space age"

Location: 
Kaplun building, Room No. 200
Tue, 27/01/2015 - 12:30 to 13:30

Lecturer: Dr. Avi Shporer Affiliation: Caltech/JPL Abstract: Advancements in the field of observational astronomy are usually limited by technological capabilities. In the current era technology has allowed for space-based surveys delivering a growing sample of high quality time series photometry. This has finally enabled the detailed study of variability along the orbital motion, or orbital phase, of stellar binaries and star-planet systems. These orbital modulations are induced by a combination of gravitational and atmospheric processes. Gravitational

Astrophysics Seminar: "Asymptotic Steady State Solution to a Bow Shock with an Infinite Mach Number"

Location: 
Kaplun Bldg., Room No. 200
Tue, 19/01/2016 - 12:30 to 13:30

Lecturer: Mr. Almog Yalin Affiliation: Racah Institute of Physics The Hebrew University of Jerusalem Abstract: The problem of a cold gas flowing past a stationary object is considered. It is shown that at large distances from the obstacle the shock front forms a parabolic solid of revolution. The interior of the shock front is obtained by solution of the hydrodynamic equations in parabolic coordinates. The results are verified with a hydrodynamic simulation. The drag force and expected spectra are calculated for such shock, both in case of an optically thin

"Astrophysics Seminar: Fishing for Spectral Lines in the High-z Universe"

Location: 
Kaplun building, Room No. 200
Tue, 06/10/2015 - 12:30 to 13:30

Lecturer: Dr. Adi Zitrin Affiliation: Hubble Fellow, CALTECH Abstract: High-redshift science has been rapidly advancing in recent years on both theoretical and observational fronts. However, it is still vastly unclear whether galaxies could have reionized the universe, on what timescale, and what are the properties of these galaxies. I will review results from several recent projects we have been involved in, aimed to enhance our understanding of the first galaxies and the reionization process. In the first part of the talk I will review cluster lensing

"Astrophysics Seminar: The linear velocity field of SDSS DR7 galaxies: constraints on flow amplitudes and the growth rate"

Location: 
Kaplun building, Room No. 200
Tue, 10/03/2015 - 12:30 to 13:30

Lecturer: Dr. Martin Feix Affiliation: Israel Institute of Technology - Technion Abstract: Large-scale peculiar motion modulates the observed luminosity distribution of galaxies. Using galaxy redshift surveys, this can be harnessed to obtain bounds on peculiar velocity moments, the amplitude of the linear matter power spectrum, and the growth rate of density perturbations. In my talk, I will discuss this approach and its recent application to about half a million SDSS galaxies at z ~ 0.1. The obtained results agree well with the predictions of the LCDM model and are

Astrophysics Seminar: "Exocomets in the circumstellar gas disk of Beta Pictoris"

Location: 
Kaplun building, Room No. 200
Tue, 15/03/2016 - 12:30 to 13:30

Lecturer: Dr. Flavian Kiefer Affiliation: Tel-Aviv University Abstract: The young planetary system surrounding Beta Pictoris harbors active minor bodies. Spectroscopic observations of Beta Pictoris reveal a high rate of transits of small evaporating bodies, i.e. exo-comets (Kiefer et al. 2014). I will report the analysis of more than thousand spectra collected with HARPS between 2003 and 2011, providing a sample of about 6000 variable absorption signatures due to transiting exocomets. Statistical analysis of the observed properties of these exocomets reveals that

"Astrophysics Seminar: Magnetars and the Neutron Star Zoo"

Location: 
Kaplun building, Room No. 200
Tue, 28/04/2015 - 12:30 to 13:30

Lecturer: Prof. Victoria Kaspi Affiliation: McGill University Abstract: The last decade has shown us that the observational properties of neutron stars are remarkably diverse. From conventional radio pulsars like that in the Crab nebula to the powerful "magnetars" that emit sudden bursts of X-rays and gamma-rays, from the so-called Isolated Neutron Stars to Central Compact Objects, observational manifestations of neutron stars are surprisingly varied, with most properties totally unpredicted. The challenge is to establish an overarching physical theory of

"Astrophysics Seminar: Evolving Galaxies across Cosmic Time: The Individual and Ensemble Perspective"

Location: 
Kaplun building, Room No. 200
Tue, 09/12/2014 - 12:30 to 13:30

Lecturer: Mr. Sandro Tacchella Affiliation: ETH Zurich Abstract: We have gained many new insights in the formation of the first galaxies at very high redshifts (z~8-10) and the major buildup of the most massive ellipticals, bulges and disks at the peak of cosmic star formation rate (z~2) in the last century. I will show how we need to study individual galaxies as well as the whole population to understand how galaxies form and evolve with time. I start with a simple model that links the galaxy properties to the underlying dark matter population and

Astrophysics Seminar: "The Black Hole - Bulge mass relation in Megamaser host galaxies"

Location: 
Kaplub building, Room No. 200
Tue, 22/12/2015 - 12:30 to 13:30

Lecturer: Dr. Ronald Läsker Affiliation: University of Turku Abstract: In this talk, I will present revised scaling relations of masses (MBH) of Supermassive Black Holes (BHs) with galaxy and bulge properties, focusing on bulge masses (Mbul) in low-mass and late-type galaxies where the bulge is only a minor component. By means of HST/WFC3 optical and near-infrared data, we analyzed BH host galaxies with MBH precisely known by their nuclear Megamaser emission. Due to the superior image quality and detailed analysis techniques, we are able to decompose

"Astrophysics Seminar: Phenomenological model of radiatively efficient relativistic shocks"

Location: 
Kaplun building, Room No. 200
Tue, 07/07/2015 - 12:30 to 13:30

Lecturer: Prof. Evgeny Derishev Affiliation: Institute of Applied Physics, Nizhny Novgorod, Russia Abstract: We present a phenomenological model for emission from relativistic shocks. This model works best for those shocks, where dissipation of magnetic energy and radiative cooling of electrons take place on timescales shorter than the dynamical timescale. The model predicts that the ratio of synchrotron to inverse Compton emissivities is close to unity within the emitting region and that most of the IC radiation is absorbed in front of the shock and serves as a source of

"Astrophysics Seminar: Electromagnetic counterparts of compact binary mergers"

Location: 
Kaplun building, Room No. 200
Tue, 17/02/2015 - 12:30 to 13:45

Lecturer: Dr. Kenta Hotokezaka Affiliation: Racah Institute of Physics Hebrew University of Jerusalem Abstract: In this talk, I will focus on a compact binary merger, which is one of the most promising sources for the next generation gravitational- wave (GW) laser interferometers such as advanced LIGO, advanced Virgo, and KAGRA. The follow-up observation of electromagnetic (EM) counterparts will play an important role to confirm the event, to identify the host galaxy, and to study the nature of the GW sources. I will discuss mass ejection

Astrophysics Seminar: "Probing Core Magnetism in Stars via Asteroseismology"

Location: 
Kaplun building, Room No. 200
Tue, 01/03/2016 - 12:30 to 13:30

Lecturer: Prof. Lars Bildsten Affiliation: The Kavli Institute for Theoretical Physics, University of California, Santa Barbara Abstract: Additional details of the upcoming Astrophysics' seminars can be found on the following link. ‏האירוע הזה כולל שיחת וידאו ב-Google Hangouts.