Scholars 2009

2009 Past - Astrophysics, History of the Universe

Horesh Assaf

Tel Aviv University, Department of Astrophysics

“Gravitational Lensing Statistics in Galaxy Clusters”

Update December 2016

Personal webpage:

Progress report: 

After receiving his PhD from Tel-Aviv University, Dr. Horesh moved to the US as a postdoctoral researcher at the California Institute of Technology (Caltech).  At Caltech he shifted his focus to a new research field, broadening his field of research to study transients in detail.

To accomplish this goal he joined the Palomar Transient Factory (PTF), and began conducting numerous optical observations using large facilities such as the Palomar 5-m telescope and the Keck telescope, thus becoming an experienced observer. Subsequently he accepted the challenge to lead the radio-wave follow-up observing campaign within the PTF collaboration - a completely new skill.

Thought it required completely new skills, Dr. Horesh adapted and went through the training process required to become a radio astronomer.  Currently he leads the radio observing effort in the PTF collaboration (using multiple approved programs at various observatories: the Very Large Array, the Combined Array for Radio Astronomy in Millimeter wave, the Australia Telescope Compact Array, and the Arcminute Microkelvin Imager).

Since achieving his PhD, he's worked on a variety of projects, e.g.: work on SN2011dh constituted some of the earliest and systematic radio observations of a core collapse SN, and has had a large impact on the understanding of this type of SN. In these studies he concluded that the blast wave largely deviates from equipartition - a result that has an impact on the understanding of shockwave physics.

He's undertaken the earliest and most sensitive radio observations of a Type Ia supernova to date (SN 2011fe). His analysis showed that a large subset of single degenerate models can be ruled out. During his time at Caltech he initiated and led, together with Prof. Gregg Hallinan, a major novel effort to conduct a radio time-domain survey of “SDSS Stripe 82” with the VLA. As part of this work he mentored student Kunal Mooley. Mooley has completed his PhD, and the project, (initiated and lead by Dr. Horesh) that became a major part of Kunal’s thesis is now also published (this is the most advanced radio time-domain survey to date). Incidentally, the lessons learned through this work are used for planning the next generation VLA all sky survey (VLASS).

After three years at Caltech he returned to Israel to become a senior postdoctoral research at the Weizmann Institute of Science. Since going back to Israel for his second postdoc, he continued leading his own projects as well as continuing to lead radio observer for the PTF collaboration.

Among his recent discoveries, made under his personal programs, is the first and earliest detailed radio spectrum of the rare type of ultra-long GRBs. His research revealed that radio spectrum is uniquely different from regular long GRB population. Another first discovery from his research is that of a late (months after detection) radio flare turn-on from a tidal disruption event. This discovery has major consequences for the understanding of TDEs.

In addition to both his independent work and his PTF collaborative work, he was to join, the ThunderKAT team which is the time-domain key project for the new radio telescope, MeerKAT. He now leads the cosmic explosion work group (together with Ralph Wijers) in the ThuderKAT project.

Dr. Horesh initiated a radio program with the PESSTO collaboration. PESSTO (the Public ESO Spectroscopic Survey of Transient Objects) is a 5 year ESO project (now in its final year) that obtains multiple-epoch optical spectra of supernovae. As PESSTO had been lacking a radio follow-up program. He proposed such a program to the collaboration and his proposal was accepted by the PESSTO board.

In October 2016, he joined the faculty at The Hebrew University of Jerusalem (HUJI). A purely theoretical group to develop observational astronomy. It is Horesh's personal goal to develop the field of time domain radio astronomy in Israel - and to raise the future generation of Israel radio astronomers. He intends that his current work will pave the way for a collarboration with Israel to become official partners in the international Square Kilometer Array (SKA) project, the largest radio telescope array on earth. 

Horesh Assaf CV