Past Seminars

MSI Faculty Jamboree

MSI Faculty

McGill Space Institute
Sep 12, 2017

MSI Seminar
Bell Room

Learn about the diversity of research that goes on at the McGill Space Institute.

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Observing the Dynamics of Accretion Disks Around Supermassive Black Holes in Quasars

Mike Eracleous

The Pennsylvania State University
Sep 20, 2017

Astrophysics Seminar
Board Room (ERP 105)

The broad emission lines found in the spectra of quasars are a hallmark and defining characteristic of this class of astronomical object. They are thought to originate in dense (by astrophysical standards) gas that is in close proximity to the central supermassive black hole. The profiles of these lines and their time variability are now used as tools for a variety of applications. Examples include estimating black holes masses, probing the dynamics of the accretion flow, and searching for binary supermassive black holes. The utility of the broad lines as tools depends on our understanding of the structure of the gaseous medium that emits them, the "broad-line region." In this talk I will begin by summarizing what we know about the broad-line region and introduce some of the physical models that have been devised to describe it. I will then talk about projects that my collaborators and I have been carrying out in which we make use of the long-term variability of the broad emission lines. In one of these projects we exploit the variability of the line profiles on time scales of several years to probe the dynamics of the accretion disk that feeds the supermassive black hole. Through these studies we are arriving at a picture in which the accretion disk is massive and self-gravitating.

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Fade to Black: The Origin and Utility of Changing-Look Quasars

John Ruan

McGill Space Institute
Sep 26, 2017

MSI Seminar
MSI Conference Room

The proliferation of wide-field multi-epoch imaging surveys has now opened a new window to the time-domain for discovery of new and rare time-variable phenomena. From these surveys, the recent discovery of ‘changing-look’ quasars poses potential challenges to our understanding of accretion onto supermassive black holes. In this phenomenon, luminous quasars suddenly fade into quiescent galaxies over timescales of just a few years, a factor of 10000 faster than expected. I will examine different explanations for the origin of changing-look quasars, and discuss their incredible usefulness in probing accretion physics, supermassive black hole feedback, and galaxy evolution over cosmic time.

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MSI and Trottier Fellows Research Showcase

MSI and Trottier Fellows Research Showcase

Sep 28, 2017

MSI Seminar
Bell Room

Short presentations by students & postdoctoral fellows doing space-related research, supported by the Trottier Family Foundation

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Using High-Mass X-ray Binaries to Probe Massive Binary Evolution

Kristen Garofali

University of Washington
Oct 3, 2017

Astrophysics Seminar
Bell Room

High-mass X-ray binaries (HMXBs) provide an exciting window into the underlying processes of both binary as well as massive star evolution. Because HMXBs are systems containing a compact object accreting from a high-mass star at close orbital separations they are also likely progenitors of gamma-ray bursts and gravitational wave sources. I will present work on the classification and age measurements of HMXBs in M33 using a combination of deep Chandra X-ray imaging, and archival Hubble Space Telescope data. I am able to constrain the ages of the HMXB candidates by fitting the color-magnitude diagrams of the surrounding stars, which yield the star formation histories of the surrounding region. Unlike the age distributions measured for HMXB populations in the Magellenic Clouds, the age distribution for the HMXB population in M33 contains a number of extremely young (<5 Myr) sources, including M33 X-7, an eclipsing binary composed of a ~15 Msun black hole accreting from a 70 Msun O star companion. I will discuss these new results for M33 in the context of the effect of host galaxy properties on the observed HMXB population.

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Pushing Down and Out: Characterizing hot Jupiters in detail and expanding into new regimes

Emily Rauscher

University of Michigan
Oct 10, 2017

MSI Seminar
MSI Conference Room

We can characterize exoplanets by measuring their global, orbital, and atmospheric properties, through a variety of different observational methods. The first exoplanet discovery, the first detection of an exoplanet's atmosphere, and the vast majority of characterization measurements have all been of hot Jupiters, gas giants that orbit with about 0.1 AU of their host star. These planets are the biggest and brightest of the transiting exoplanets, making them the best targets for characterization measurements, although much work is being done to push to smaller and farther out planets. I will show that, even though we have been studying them the longest, hot Jupiters still show us mysterious properties, such as the presence of some kind of aerosol(s) in the atmospheres of some planets (but not all). I will present three-dimensional models that include a treatment for clouds or hazes, as part of our work toward understanding aerosols in this extreme regime. I will demonstrate that we can make progress in better characterizing these worlds through cutting-edge methods such as high-resolution spectroscopy, which contains detailed information about a planet's multi-dimensional temperature and wind structure, and enables us to constrain wind speeds, rotation rates, and temperature gradients. Finally, I will also demonstrate that in the upcoming JWST era we will be able to make exquisite observations beyond the hot Jupiter population, for example using secondary eclipse mapping to resolve two-dimensional images of planets on longer orbital periods, and I will discuss some of the scientific implications of these future results.

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Sarah Burke-Spolaor

West Virginia University
Oct 17, 2017

Astrophysics Seminar
Bell Room

We are seeking both light and gravitational waves from binary supermassive black holes, the biggest, meanest discrete binary systems in the Universe. When two supermassive binary black holes pair up as a binary at the center of a merger remnant, they may ignite as active nuclei and send off unique electromagnetic signatures as they consume the ambient matter from the remnant's core. During their inspiral and coalescence phases, they will produce intense gravitational radiation, which we expect to detect with Pulsar Timing Arrays in the coming ~decade. If the inspiral of black holes is isolated and smooth, we should by now have already detected nanohertz-frequency gravitational waves with pulsar timing arrays... or so we thought. This talk will discuss what our latest, most stringent limits on gravitational waves mean for galaxy evolution and supermassive binary black holes. It will also show a few results from several ongoing searches for binary supermassive black holes, and will consider the prospects of Pulsar Timing Arrays to detect or place physically interesting gravitational wave limits on these targets.

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High-energy X-rays from the Galactic Center: "zombie stars" and particle physics

Kerstin Perez

Massachusetts Institute of Technology
Oct 24, 2017

Astrophysics Seminar
Bell Room

The inner parsecs of the Galaxy contain one of the highest concentrations of both high-energy sources and dark matter in the Milky Way. The supermassive black hole, pulsar wind nebulae, supernova remnants, X-ray binaries, and hot interstellar gas are copious emitters of X-rays and gamma-rays. In addition, this region contains a large density of dark matter, making it an important source of both dark matter interaction signatures and backgrounds to dark matter searches. NuSTAR provides a view of the hard X-ray (3-79 keV) band, a critical bridge between the soft X-ray and gamma-ray emission, with unprecedented angular resolution. I will present the first sub-parsec scale images of the Galactic Center in hard X-rays, obtained with NuSTAR, which offer leading constraints on the radiative decay of dark matter, in particular from sterile neutrinos, as well as new insight into the “zombie star” population that underlies this emission.

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Strong field tests of gravity with PSR J1141-6545

Vivek V. Krishnan

Swinburne University
Oct 25, 2017

Special Astrophysics Seminar
MSI Conference Room

Pulsars in relativistic binary systems provide the most stringent tests of gravity to date in the strong field regime. While pulsars such as the double neutron star system (B1913+16) and the double pulsar (J0737-3039A/B) provide significant tests for the predictions of the General Theory of Relativity (GR), their gravitational symmetry makes them less sensitive to testing the predictions of alternative theories of gravity such as scalar-tensor theories. Such theories are natural extensions of GR that deviate strongly from GR in the strong-field regime, especially in the predictions of multipolar contributions to the gravitational radiation losses in the system. Pulsars in gravitationally asymmetric binaries, such as pulsars with white dwarf or black hole companions, are better-suited systems for testing such theories. PSR J1141-6545 is one such pulsar in a 4.8-hour relativistic orbit around a white dwarf companion. In this talk, I will talk about the 17-year timing campaign of this pulsar and the test of GR and scalar-tensor theories with this pulsar.

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Autonomous and robotic observations of the Arctic sea ice and the associated ecosystem

Christian Katlein

Alfred Wegener Institute
Oct 31, 2017

MSI Seminar
MSI Conference Room

To better observe the ongoing changes in the polar climate- and ice-associated ecosystem, the Alfred-Wegener-Institute is developing new technologies for ice-tethered observations in the framework of the Helmholtz initiative “FRontiers in Arctic marine Monitoring (FRAM)”. This includes the development and regular deployment of a new versatile remotely operated vehicle (ROV) for interdisciplinary observations under sea ice as well as the development of autonomous drifting observatories enabling the continuous monitoring of various physical and biogeochemical parameters in the sea ice and upper ocean. These platforms allow us to assess current changes, such as increasing light transmission through sea-ice, changing primary production and the polar carbon pump.

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Doors left ajar in storms: Insights into atmospheric planetary science

John Moores

York University
Nov 7, 2017

MSI Seminar
MSI Conference Room

Our spacecraft have taken us to visit and explore many stark and ancient landscapes in the solar system. At first glance, very little appears to have changed for billions of years, but if we look to the atmosphere we see a dynamism that belies active processes in the present era and that hints at changes at and below the surface. In this talk, we will proceed through these open doors to explore the movement of dust, ice and methane in the hauntingly familiar environment of Mars. We will then travel further to more exotic planetary destinations including Titan, Pluto and Venus. Past results will be discussed along with future developments to explore the atmospheres of our solar system and beyond.

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Gravitational-Wave Discoveries Driving the Promise of Multi-Messenger Astronomy

Vassiliki Kalogera

Northwestern University
Nov 21, 2017

MSI Seminar
Bell Room

The LIGO detectors have opened for us a new way of studying compact objects in the time domain with direct detections of gravitational-wave bursts from binary mergers of compact objects. I will highlight what current results imply and what we can look forward to in terms of advancing our understanding of the densest objects in nature, their origins and the explosive phenomena they cause.

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Setting Stellar Chronometers: The PTF(+) Open Cluster Survey

Marcel Agueros

Columbia University
Nov 28, 2017

Astrophysics Seminar
Bell Room

While we have known for 40 years of the existence of a relation between a solar-mass star's age, rotation, and magnetic activity, observational limitations have hampered the assembly of uniform samples of rotation and activity measurements for stars spanning a wide range of ages and masses. We are still far from being able to describe fully the evolution of either rotation or activity for low-mass stars, or from being able to use rotation or activity measurements to estimate accurately the ages of isolated field stars. I will describe results from our efforts to assemble a complete sample of rotation and activity measurements for low-mass stars in six nearby open clusters ranging in age from ~100 Myr to ~3 Gyr. I will focus on our recent results for the benchmark clusters Praesepe and the Hyades, on new results for NGC 752, and on tests of models of rotational evolution that these data have enabled.

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