|2014, Fall||2014, Spring|
|2013, Fall||2013, Spring||2013, Summer|
|2012, Fall||2012, Spring|
|2011, Fall||2011, Spring|
|2010, Fall||2010, Spring|
|Sep 8||No Colloquium|
|Sep 15||Henry Ferguson (STScI) - CANDELS: Observing Galaxy Assembly|
|Sep 22||Yuri Cavecchi (Univ. Amsterdam) - Propagation of Thermonuclear Flames on the Surface of Accreting Neutron Stars|
|Sep 29||Naoko Neilson (Drexel University) - Detecting Cosmic Neutrinos with IceCube at the Earth's South Pole|
|Oct 6||Stan Hunter (GSFC) - AdEPT Medium-energy Gamma-ray Telescope: Technology and Science|
|Oct 9||Special Date and Time: 12:00-1:00, B34, W150
Eugene Churazov (MPA, Germany) - Gamma-rays from Type Ia Supernova SN2014J
|Oct 13||No Colloquium|
|Oct 15||Special Date and Place: B34, W305
Marta Volonteri (Inst. Astrophysique Paris, France) - The First Massive Black Holes
|Oct 20||Sam Finn (PSU) - Pulsar Timing and Gravitational Wave Detection (tentative title)|
|Oct 27||Andy Gould (OSU) - Microlensing Overview (tentative title)|
|Nov 3||Mike McDonald (MIT) - Cool Stuff in Galaxy Clusters (tentative title)|
|Nov 10||Jochem Baselmans (SRON, the Netherlands) - MKIDs and Other Calorimeters (tentative title)|
|Nov 17||Yoshiyuki Inoue (ISAS, Japan) - Fermi Gamma-ray Background Results (tentative title)|
|Nov 24||Bruce Allen (Max Planck Inst. for Grav. Physics) - LIGO (tentative title)|
|Dec 1||Manfred Cuntz (U. Texas at Arlington) - Habitability Around Single Stars and in Multiple Stellar Systems|
|Dec 8||Jamie Bock (Caltech) - BICEP/Planck (tentative title)|
|Dec 15||John Tomsick (Berkeley) - Recent Events at V404 Cyg, and Other Low-mass X-ray Binaries (tentative title)|
|Dec 22||Nico Cappelluti (Yale) - Cosmic Infrared and X-ray Backgrounds (tentative title)|
|Dec 29||No Colloqium|
CANDELS: Observing Galaxy Assembly
Tuesday, Sep 15, 2015
The Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey (CANDELS) is a multi-cycle observing program with the Hubble space telescope (and many other facilities) designed to document the first third of galactic evolution, from redshift z~8 to 1.5. It is also designed to find and measure Type Ia SNe beyond z > 1.5 and test their accuracy as standard candles for cosmology. The Hubble observations were completed in August 2013. The talk will discuss findings from ongoing analysis of the survey data , including observations of AGN hosts at high redshifts, and the evolution of structure of passive and star-forming galaxies.
Propagation of Thermonuclear Flames on the Surface of Accreting Neutron Stars
Tuesday, Sep 22, 2015
The Type I Bursts, thermonuclear explosions on the surface layers of accreting neutron stars, produce extremely bright X-ray flashes that outshine all the other emission for tens of seconds. Their light curves encode information about star parameters such as spin, mass and radius that are key to constraining the long sought for equation of state of the matter in the interior of the neutron stars. However, to be able to fully disentangle that information from the observations, we need a solid understanding of how the burning flame propagates across the surface. The mathematical complexity of the problem makes non-approximate analytical solutions impossible and we have to rely on numerical simulations. I will present the results of ab initio calculations of the flame spreading, describing the physical mechanisms behind the propagation and their dependence on the star parameters.
Detecting Cosmic Neutrinos with IceCube at the Earth's South Pole
Tuesday, Sep 29, 2015
The IceCube Neutrino Observatory has recently discovered a diffuse flux of astrophysical neutrinos, in other words, neutrinos from beyond the solar system. But how does one collect neutrinos at the South Pole? Why study neutrinos for astronomy? In this talk, I will try to answer such questions. I will discuss the multiple diffuse flux analyses in IceCube that observe the astrophysical flux, and what each can tell us. Spatial analyses that aim to identify the sources of such astrophysical neutrinos will also be discussed, followed by an attempt to reconcile all results, to draw a coherent picture that is the state of neutrino astronomy.
Gamma-rays from Type Ia Supernova SN2014J
Friday, Oct 9, 2015
SN2014J is the closest type Ia supernova in the era of space observatories and the first one from which gamma-ray lines have been detected with high significance. The flux of Co-56 lines at 847 and 1238 keV, observed with INTEGRAL, shows that about 0.6 Msun of radioactive Ni-56 has been synthesized during explosion. The line broadening suggests the characteristic expansion velocity of ~10000 km/s. Annihilation of positrons produced during decay of Co-56 makes significant contribution to the continuum below 511 keV. The total mass of the ejecta is consistent with 1.4 Msun progenitor, although the constraints are not very tight. Overall the gamma-ray data are broadly consistent with the expectations for canonical 1D models, such as delayed detonation or deflagration models for a near-Chandrasekhar mass White Dwarf. Pure detonation models or strongly sub-Chandrasekhar models are excluded by the gamma-ray data.
The First Massive Black Holes
Inst. Astrophysique Paris, France
Thursday, Oct 15, 2015
Massive black holes are the engines that power quasars and Active Galactic Nuclei (AGN) throughout cosmic time, and they dwell at the centers of nearby galaxies, including our own Milky Way. The discovery of quasars at z~6-7 demonstrates that massive black holes must form extremely early on and grow rapidly in order to grow to over a billion solar masses within less than 1 Gyr. In contrast to such monsters, today's black hole population extends down to small masses, and there are even galaxies bereft of central massive black holes. Therefore, studying black hole formation is needed to understand both the advent of the first luminous quasars, and the properties of black holes in today's galaxies, notably why some galaxies host a MBH, and some others do not, and what the minimum mass of a black hole is. I will critically discuss theoretical models of black hole formation in the first galaxies, the evolution of the black hole population, and possible observational diagnostics to probe how the first black holes formed.
Habitability Around Single Stars and in Multiple Stellar Systems
U. Texas at Arlington
Tuesday, Dec 1, 2015
Habitability, i.e., the planet’s potential to develop and sustain life, is a topic of intense research, encompassing both favorable conditions as, e.g., the size and stability of the stellar climatological habitable zones as well as adverse forcings. The latter encompass numerous factors including (but not limited to) intense UV, X-rays, and flares, including superflares, which have the potential of evaporating planetary atmospheres. These constituents apply to both planets around single stars and those hosted by multiple stellar systems. Regarding the latter, the analysis of planetary habitability is, however, more complex as, e.g., the presence of multiple stellar components affects both the extent and time-dependence of the climatological habitable zones and the domains of planetary orbital stability. Recent progress has been made in regard to binary systems, pertaining to both S-type and P-type planetary orbits. Detailed results have been obtained for a large variety of observed and theoretical systems, including systems detected by the Kepler mission. The purpose of my talk is to summarize recent results and to convey perspectives of future research.