Updated: 18 April 2014

MIT Kavli Institute for Astrophysics and Space Research

2014 Postdoc Symposium

April 30, May 1, and May 2 11:45am−1:30pm in 37-252 (Marlar Lounge)

This annual event features the MKI-affiliated postdocs presenting 15 minute talks (with 5 minutes of questions) on their past, present, and/or future research to the MKI community. Lunch will be provided, and the talks will promptly begin at noon. There will be three speakers each day; the full schedule with abstracts is below.

Speaker Schedule

April 30, 2014

Moderator: Victoria Grinberg

Speaker: Meng Su
Title: Degree-Scale CMB Polarization Measurements from Three Years of BICEP1 Data
Abstract: BICEP1 is a millimeter-wavelength telescope designed specifically to measure the inflationary B-mode polarization of the Cosmic Microwave Background (CMB) at degree angular scales. I will present results from an analysis of the BICEP1 data acquired during all three seasons of observations at the South Pole (2006 to 2008). This analysis also introduces a comprehensive estimation of band-power window functions, improved likelihood estimation methods and a new technique for deprojecting monopole temperature-to-polarization leakage which reduces this class of systematic uncertainty to a negligible level. We measure the angular power spectra at 21 <= l <= 335 and find that the EE spectrum is consistent with Lambda Cold Dark Matter (LCDM) cosmology, with the first acoustic peak of the EE spectrum now detected at 15 sigma. From B-modes only, we constrain the tensor-to-scalar ratio to r = 0.03+0.27-0.23, or r < 0.70 at 95% confidence level from BICEP1 final analysis. The analysis pipeline, especially the way to deproject instrumental systematics has been used in the recent BICEP2 analysis, which claimed a >5 sigma detection of the primordial gravitational waves.

Speaker: Salvatore Vitale
Title: Measuring the Spin of Black Holes Using Gravitational Waves
Abstract: Compact binary coalescences are promising sources of gravitational waves for ground based detectors. Binary systems containing one or two spinning black holes are particularly interesting due to spin-orbit (and eventual spin-spin) interactions, and these systems present an opportunity to measure spins directly through gravitational wave observations.  In this talk we analyze simulated signals emitted by spinning binaries with several values of masses, spins, orientation, and signal-to-noise ratio. We find spins can be estimated with an accuracy which is comparable to what obtained from X-ray binaries.

Speaker: Steven Ehlert
Title: Very Deep Chandra Observation of the Galaxy Cluster Abell 1795
Abstract: Deep Chandra observations of galaxy clusters have provided a spectacular view into the astrophysics of the Intracluster Medium (ICM); a hot, diffuse, metal rich plasma in which the cluster galaxies are embedded. Studies of individual clusters have demonstrated a remarkable diversity in the astrophysical processes that operate in galaxy clusters including radiative cooling, merger induced sloshing, and shock heating. In this talk I will discuss the extent to which these processes and others operate in Abell 1795, one of Chandra's calibration sources. Because this cluster is nearby (z=0.06) and has such a deep exposure we are able to probe these processes at a nearly unprecedented level of detail. I will discuss some of the surprising ways in which hot ICM gas in this cluster appears to be coupling to its hosted galaxies and cooler gas phases.

May 1, 2014

Moderator: Victoria Grinberg

Speaker: Bryce Croll
Title: Multiwavelength Observations of the Candidate Disintegrating sub-Mercury KIC 12557548b
Abstract: I'll present follow-up observations of the intriguing, disintegrating mercury-mass planet candidate KIC 12557548b. This intriguing object, first found through an analysis of Kepler photometry by our very own Saul Rappaport & his collaborators, displays transit depths that vary from orbit to orbit, and an asymmetric transit profile with a short ingress and long egress. These effects have been interpreted as evidence that KIC 12557548 harbours a disintegrating planet with a long, cometary tail streaming behind the planet, that is composed of a variable amount of material each orbit, due to the fact that the planet is disintegrating in fits and starts. The follow-up observations that I will present allow us to rule out false-positive scenarios -- thereby likely confirming that the planet is real -- and tell us that the planet's mass is likely less than that of Mercury, and that the largest particles in the cometary tail are at least ~0.5 microns in size or larger.

Speaker: Robert Penna
Title: Black Hole Disks and Jets: General Relativistic MHD Simulations
Abstract: Spinning black holes reshape their accretion disks and drive powerful jets. Understanding these processes is essential for black hole spin measurements and the interpretation of astrophysical jets. I will present the results of general relativistic magnetohydrodynamic simulations designed to test standard models of black hole disks and jets. I will explain how magnetic fields drain black hole rotational energy using the membrane paradigm.

Speaker: John Miller
Title: A Quantum Filter Cavity for Advanced LIGO
Abstract: The sensitivity of interferometric gravitational-wave detectors is limited by quantum vacuum fluctuations which enter from their readout ports. Past experiments have shown that replacing these fluctuations with non-classical `squeezed' states of light can mitigate this problem. However, in order for the same approach to be useful in the current generation of interferometers, the squeezed light must be filtered by a high-Q optical resonator prior to injection into the instrument. This resonator is known as a filter cavity. I will give a general introduction to this topic before discussing work currently underway at MIT to prepare a filter cavity for Advanced LIGO.

May 2, 2013

Moderator: Robert Penna

Speaker: Ruslan Vaulin
Title: Late-Time Radio Afterglows from Compact Binary Coalescence
Abstract: Coalescence of binary neutron stars and neutron star - black holes, collectively referred to as compact binary coalescence (CBC), are the strongest candidates for the progenitor of short gamma-ray bursts (SGRBs). They are also one of the most promising sources of transient gravitational waves (GW) for the advanced LIGO and Virgo detectors, which will begin their scientific observations in 2015. Interaction of the SGRB jet with the circumburst medium produces the late-time radio afterglow which can be observed even off-axes of the jet. We investigate detectability of the afterglows with the current or planned widefield radio telescopes. We discuss the role such observations can play in the follow-ups of the GW candidates found by LIGO and Virgo.

Speaker: Victoria Grinberg
Title: Timing the Beast: A Spectro-Timing Approach to Understanding X-ray Binaries
Abstract: Neither spectral nor timing studies alone allow us to disentangle the complex interplay of accretion and ejection processes. In this talk, I will show how combining both methods allows for an (almost) model-independent description of X-ray binary behavior across different accretion and ejection regimes and gives clues as to the contributions of accretion disk, disk winds, jets and Comptonization corona to the X-ray spectrum. As an example, we use over 12 years of RXTE monitoring of the black hole Cygnus X-1 to build up a template of spectro-timing behavior which enables an easy comparison among accreting sources acting on different mass and time scales. Particularly important is the comparison with AGN, where many of the relevant variability time scales that shape the interaction of the supermassive black hole with their surroundings are not accessible during an astronomer's lifetime.

Speaker: Kevin C. Schlaufman
Title: Planet Formation in Close-In Systems of Multiple Planets
Abstract: I'll present a test of a provocative new theory for the formation of the closely-packed multiple exoplanet systems discovered by Kepler. I'll then describe how that analysis enables a new calculation of the frequency of Solar System-analogs in the Galaxy.