### Weekly on Friday 11:30 am - 12:30 pm, at PRB M2005

COMING UP!

11:30 am, Friday, May 29th at PRB M2005 (Price Place)

Special talk (1) by Yoshiyuki Inoue (ISAS/JAXA)

Probing the nature of AGN coronae through future X-ray and sub-mm observations

Abstract:
 While the cosmic X-ray background is likely to originate from individual AGNs, the origin of the cosmic MeV gamma-ray background is not fully understood. We proposed that AGNs having non-thermal electrons in coronae may explain the MeV background. Such non-thermal electrons are expected to exist if a corona is heated by magnetic reconnections. However, the sensitivity of current MeV gamma-ray instrument is not sufficiently good to detect the expected power-law tail in the MeV band from individual AGNs. Furthermore, the heating mechanism of coronae in AGNs is still unknown, although magnetic reconnection heating is one possibility.  In this talk, I would like to introduce how we can probe the origin of the MeV background and the nature of AGN coronae such as magnetic field and non-thermal content through future observations by ASTRO-H and ALMA.

Special talk (2) by Irene Tamborra (GRAPPA)

High energy neutrinos from extra-galactic astrophysical sources

Abstract:
 The IceCube neutrino telescope recently discovered a flux of astrophysical neutrinos with energies up to few PeV.  In light of the new born high-energy neutrino astronomy era, I will discuss the expected high-energy neutrino emission from extra-galactic astrophysical sources as well as our chances to unveil the physics of the cosmic accelerators by employing neutrinos and their photon counterparts.

Summer 2015

11:30 am, Friday, May 22th at PRB M2005 (Price Place)

Special talk (1) by Scott Adams (OSU)

Not with a Bang, but a Whimper: Evidence for Low-energy Supernovae

Abstract:
 I will present new HST and Spitzer late-time imaging of SN 2008S and NGC 300-OT,the prototypes of a class of stellar transients whose true nature is debated. Bothobjects have faded below the luminosity of their progenitors and are now undetectedin both the near and mid-IR, providing strong evidence that these events wereterminal. This, combined with the mass constraints on the progenitors, indicates thatthis class of transients likely arise from electron-capture supernovae.

Special talk (2) by Kimberly Boddy (University of Hawaii)

Indirect Detection of Dark Matter Using MeV-Range Gamma-Ray Telescopes

Abstract:
 The astrophysics community is considering plans for a variety of gamma-ray telescopes in the energy range 1--100 MeV, which can fill in the so-called "MeV gap" in current sensitivity. We investigate the utility of such detectors for the study of low-mass dark matter annihilation or decay. For annihilating (decaying) dark matter with a mass below about 140 MeV (280 MeV) and couplings to first generation quarks, the final states will be dominated by photons or neutral pions, producing striking signals in gamma-ray telescopes. We determine the sensitivity of future detectors to the kinematically allowed final states. In particular, we find that planned detectors can improve on current sensitivity to this class of models by up to a few orders of magnitude.

11:30 am, Friday, May 15th at PRB M2005 (Price Place)

Special talk by Ilias Cholis (Fermilab)

The Fermi Galactic Center excess

Abstract:
 The possible gamma-ray excess in the inner Galaxy and the Galactic center suggested by Fermi-LAT observations has triggered great interest in the astro-particle physics community. Among its various interpretations have been WIMP dark matter annihilations, gamma-ray emission from a population of millisecond pulsars, or emission from cosmic rays injected in a sequence of burst-like events or continuously at the GC. Given that the galactic diffuse emission is the dominant (by an order of magnitude or more) at any direction greater than 2 degrees from the GC understanding the background systematics has been a vital missing piece in the discussion. I will present the first comprehensive study of model systematics coming from the Galactic diffuse emission in the inner part of our Galaxy and their impact on the inferred properties of the excess emission at Galactic latitudes between 2 and 20 degrees and energies 300 MeV to 500 GeV. I will show both theoretical and empirical model systematics, which are deduced from a large range of Galactic diffuse emission models and a principal component analysis of residuals in numerous test regions along the Galactic plane. The hypothesis of an extended spherical excess emission with a uniform energy spectrum is compatible with the Fermi-LAT data in the region of interest at 95% CL.  Assuming that this excess is the extended counterpart of the one seen in the inner few degrees of the Galaxy, a lower limit of 10 degrees (95% CL) can be derived on its extension away from the GC.  In light of the large correlated uncertainties that affect the subtraction of the Galactic diffuse emission in the relevant regions, the energy spectrum of the excess is equally compatible with both a simple broken power-law of break energy 2.1 $\pm$ 0.2 and with spectra predicted by the self-annihilation of dark matter, implying in the case of $\bar{b}b$ final states a dark matter mass of 49$^{+6.4}_{-5.4}$ GeV. I will also briefly discuss interpretations of this excess, based on annihilating DM, leptonic CR outburst and a population of millisecond pulsars.

Spring 2015

11:30 am, Friday, May 8th at PRB M2005 (Price Place)

11:30 am, Friday, May 1st at PRB M2005 (Price Place)
Special talk by Walter Winter (DESY Zeuthen, Germany)

Interpretation of IceCube results in the multi-messenger context

The discovery of high-energetic cosmic neutrinos is one of the recent
major breakthroughs in science. We discuss the concept of the neutrino
production, and interpret recent results taking into account the
information from other messengers (gamma-rays, cosmic rays). For
example, one question is if these neutrinos come from the most powerful
accelerators in the universe, i.e., the ones which can accelerate cosmic
rays to the highest observed energies. We also discuss future
perspectives for neutrino astronomy.

11:30 am, Friday, April 24th at PRB M2005 (Price Place)
Special talk(~30 mins) by Laura Lopez (CfA, Harvard)

Observational Tests of Cosmic-ray Diffusion in the Magellanic Clouds

Cosmic rays (CRs) play an important role in the interstellar medium: they ionize
dense molecular gas, they are responsible for the light elements in the periodic
table, and they account for 20% of the ISM energy budget. However, the means
by which CRs are first accelerated and then transported through external
galaxies are not well understood. I will present results from a recent study of the
Magellanic Clouds to constrain CR transport using Fermi gamma-ray
observations. I will show how we have characterized the spatial distribution of
gamma rays in the LMC and SMC and used the findings, in conjunction with
available multiwavelength data, to constrain CR transport based on how the
emission depends on physical parameters, such as gas density, massive star
formation, magnetic field structure, and turbulence properties.

AstroParticle lunch paper list:

12:30 pm, Friday, April 10th at PRB M2005 (Price Place)

Special talk!

Sam Stafford (OSU)
Analysis Interferometry of the Antarctic Impulse Transient Antenna (ANITA)

Ultra-high energy (UHE) neutrinos may facilitate observation of sources in the
remotest parts of the universe.  A flux of UHE (E > 10^18eV) neutrinos is expected
from interaction of UHE cosmic rays with the cosmic microwave background.
The Antarctic Impulse Transient Antenna (ANITA) campaign is a NASA Long-duration
balloon mission searching for coherent radio emission induced by ultra-high energy
neutrinos interacting in the Antarctic ice, as well as by UHE cosmic ray particle
cascades in the air.  The third ANITA flight began in December 2014 and lasted
for 22 days.  I give a general description of the ANITA-III payload and flight, and
present analysis methods to be used in identifying and localizing radio pulse events.