MIT Astrophysics Brown Bag Lunch Series: Spring 2018

Mondays at 12:05 PM in 37-187 (unless otherwise noted)
MIT Kavli Institute for Astrophysics and Space Research
70 Vassar Street, Cambridge, MA


The Brown Bag lunch is a forum for visiting astronomers/astrophysicists to speak about their research. Talks begin at 12:05 and speakers should plan 20 minutes of material, to leave room for questions during and after the presentation. If you are visiting MIT and would like to give a lunch talk, you may either contact the organizers directly or have your local colleagues arrange a time. The present organizers of the series are Rana Ezzeddine and Paul Torrey.


Monday January 22 -- Two Talks!

 


Supermassive Black Hole Binary Candidates from the Pan-STARRS1 Medium Deep Survey

Tingting Liu  
University of Maryland
 

We present a systematic search for periodically varying quasar and supermassive black hole binary (SMBHB) candidates in the Pan-STARRS1 Medium Deep Survey. From ~9,000 color-selected quasars in a ~50 deg^2 sky area, we identify 26 candidates with more than 1.5 cycles of variation. We extend the baseline of observations via our imaging campaign with the Discovery Channel Telescope and the Las Cumbres Observatory network and reevaluate the candidates using a more rigorous, maximum likelihood method; 3 candidates remained significant, if we assume the variability of all normal quasars are characterized by the Damped Random Walk process. The down-selected "gold" sample translates to an SMBHB rate of 0.3 per 10^3 quasars out to z~2, in tension with previous work by Graham et al. (2015) and Charisi et al. (2016). We also find that the binary residence times of the “gold" sample are best matched to the expected distribution if the mass ratio q = 0.3. Using our study with MDS as a benchmark, we estimate that ~10,000 periodic quasars with more than 3 cycles could be discovered by the Large Synoptic Survey Telescope, paving the way for the direct detection of individual gravitational wave sources by future pulsar timing array experiments.
 

Characterising exoplanet atmospheres as part of the LRG-BEASTS survey

James Kirk
University of Warwick

 
Abstract:
Studies of exoplanet atmospheres have revealed a startling diversity between systems, with many showing clouds and hazes which mask pressure-broadened absorption features. In the small sample of planets studied to date, no strong correlation has emerged between key planetary parameters and the presence, or absence, of clouds and hazes, although there is evidence that temperature might play a role. In order to characterise this diversity and unravel the underlying physical processes, it is essential that we expand the current sample of studied planets. This is the focus of the Low Resolution Ground-Based Exoplanet Atmosphere Survey using Transmission Spectroscopy (LRG-BEASTS, “large beasts”). I will present the latest results from LRG-BEASTS which is pioneering the use of 4-metre class telescopes for transmission spectroscopy.
 

Monday January 28

 

Knottiness of X-ray jets: testing the obstacle-in-jet model  

Sarka Wykes  
Harvard

Abstract:
Recently, it has become evident that X-ray jets are ubiquitous in low-power radio galaxies. In addition to diffuse X-ray emission, many of the jets feature compact X-ray brightness enhancements ('knots'). Their radio morphology is often similar, but not identical, to the X-ray morphology, and in some cases optical counterparts are observed as well. The issue of the knot origin(s) is yet undecided, although models exist suggesting that the knots with non-zero proper motion represent moving plasma packets while the knots without detected proper motions would originate from obstacles in the jet (stars and/or clouds) in interaction with the jet plasma flow. I will show some results from our 2D hydrodynamical simulations and analytical calculations of Centaurus A's jet interacting with winds of its internal, evolved stars, with a view to investigating the properties of shocks generated in these interactions and their match to the observed X-ray knots. The fate of the material released by the embedded stars, which is carried away by the jet at a rate of ~0.002 solar masses per year, will be also briefly addressed.


Monday February 5

 

TITLE

Speaker
Affiliation

 

 


Monday February 12

 

TITLE

Speaker
Affiliation

 


Monday February 19 -- MIT Holiday


 


Monday February 26

 

TITLE

Speaker
Affiliation

 


Monday March 5

 

TITLE

Speaker
Affiliation

 

 


Monday March 12

 

TITLE

Speaker
Affiliation

 

 


Monday March 19

 

TITLE

Speaker
Affiliation

 

 


Monday March 26 -- MIT Spring Vacation Week

 


Monday April 2

 

TITLE

Speaker
Affiliation

 

 


Monday April 9

 

TITLE

Speaker
Affiliation

 


Monday April 16 -- MIT Holiday

 


Monday April 23

 

TITLE

Speaker
Affiliation

 


Monday April 30

 


Monday May 7

 

TITLE

Speaker
Affiliation

 


Monday May 14

 

TITLE

Speaker
Affiliation

 


Monday May 21

 

TITLE

Speaker
Affiliation

 


Monday May 28 -- MIT Holiday