CfA Theory Seminars

[Kentaro Nagamine <knagamin cfa harvard edu>]

Tue, May 25, 12:30pm

Scott Gaudi (CfA)

Microlensing Searches for Extrasolar Planets

I review the theory of, results from, and future prospects for
microlensing searches for extrasolar planets.  Analyses of
well-sampled microlensing light curves by several collaborations have
demonstrated that current searches are quite sensitive to Jupiter-mass
planets at a few AU separations from M-dwarfs in the Galactic bulge.
To date, however, no clear planetary detections have been made.
Detailed analysis has shown that this null result implies that less
than 1/3 of typical stars (i.e. M-dwarfs) in the Galactic bulge have
Jupiter-mass (M ~ M_J) companions between 1.5 and 4 AU, and less than
45% have (M~3M_J) companions between 1 and 7 AU.  Recent upgrades by
the OGLE collaboration have resulted in a dramatic increase in the
number of alerted microlensing events per year.  This has allowed for
much more efficient searches for planets, and has led to the first
detection of a planet with microlensing.  Within a few years, it will
be possible to constrain the frequency of companions with mass as
small as ~15 Earth masses to ~10%.  Finally, I speculate on the future
of microlensing planet searches, focusing on the prospects for the
detection Earth-mass planets.  I argue that microlensing is likely to
be the only technique to supply reliable detections of Earth-mass
planets in the next decade.

The seminar will be held in Pratt Conference Room (G04) at 60
Garden St., CfA.

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Wed, May 26, 12:30pm

Eli Waxman (Weizmann Institute)

Gamma-Ray Bursts: Progress and open questions

The discovery during the past few years of X-ray to radio emission from
Gamma-Ray Bursts (GRBs) led to dramatic evolution in our understanding of
these explosions. We have strong evidence that GRBs are triggered by the
energy released during the formation of few solar mass black holes, most
likely following the collapse of a massive star. Many questions related to
the underlying physics of the model remain, however, open. Recent
developments in our understanding of GRBs will be described and the
prospects for resolving remaining open questions will be discussed.

The seminar will be held in Pratt Conference Room (G04) at 60 Garden St.,
CfA.

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