Astrophysics Seminar

"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 ∼

"Astrophysics Seminar: Detecting gravitational waves with small systems: future relativistic quantum technologies"

Location: 
Kaplun building, Room No. 200
Tue, 02/12/2014 - 12:30 to 13:30

Lecturer: Dr. David Edward Bruschi Affiliation: Racah Institute of Physics, Hebrew University of Jerusalem Abstract: The field of quantum information has reached the point where commercial applications are being developed. Although quantum mechanics has proven to be very successful as the core for quantum information, it is still unknown how relativity enters the game. Cutting edge experiments are now reaching regimes where effects at the overlap between quantum and relativistic theories can be investigated. Therefore, it seems natural to

Astrophysics Seminar: "Balmer-dominated shocks around supernova remnants SN1006 and Tycho"

Location: 
Kaplun building, Room No. 200
Tue, 09/02/2016 - 12:30 to 13:30

Lecturer: Dr. Sladjana Knezevic Affiliation: Weizmann Institute of Science Abstract: I will present high-resolution spectrophotometric imaging of Balmer- dominated shocks (BDSs) around two historical supernova remnants, SN1006 and Tycho. BDSs are characterized by strong hydrogen emission lines with a narrow (~10 km/s) and a broad (~ 1000 km/s) component. The emission originates very close to the shock front and provides several important diagnostics for the physical processes in fast collisionless shocks. The line shapes and their spatial profiles are used

"Astrophysics Seminar: Structure and Properties of the Intra-Cluster Medium and the Role of Gas Streams"

Location: 
Kaplun building, Room No. 200
Tue, 02/06/2015 - 12:30 to 13:30

Lecturer: Mr. Elad Zinger Affiliation: Racah Institute of Physics, The Hebrew University of Jerusalem Abstract: We discuss the structure and properties of galaxy clusters with an emphasis on the dynamical state of the clusters. We show that inflowing gas streams play an important role in determining the properties of the ICM and whether a cluster is dynamically relaxed or disturbed. In addition, collisions of inflowing streams are shown to be a viable mechanism for generating shocks and 'Cold Fronts' in the ICM. The hot ICM, found behind the virial

"Astrophysics Seminar: A Cabinet of Curiosities in Near-Field Cosmology"

Location: 
Kaplun building, Room No. 200
Tue, 06/01/2015 - 12:30 to 13:30

Lecturer: Prof. James Peebles Affiliation: Princeton University Abstract: The LCDM cosmology is well established but certainly not the final theory of what happened as the universe expanded and cooled. I will review phenomenology on the scale of galaxies that seem to me to challenge LCDM and perhaps offer clues to a still better cosmology. Additional details of the upcoming Astrophysics' seminars can be found on the following link.

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: Core-Collapse Supernovae: A Phase-Diagram Analysis of the Shock Revival Mechanism"

Location: 
Kaplun building, Room No. 200
Tue, 17/11/2015 - 12:30 to 13:30

Lecturer: Mr. Daniel Gabay Affiliation: Racah Institute of Physics The Hebrew University of Jerusalem Abstract: As massive stars end their life, the iron core collapses forming a hydrodynamic shock wave in the inner region. This shock stalls few hundred milliseconds later rather than propagating directly to the envelope. The "delayed neutrino mechanism" is believed to play a crucial role in re-energizing the shock until it reaches the star's envelope and causes a supernova explosion. We show that the propagation of the shock can be analyzed through a series of quasi-stationary

"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: "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: 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