Long duration gamma-ray bursts (GRBs) mark 1 the explosive death of some massive stars and are a rare sub-class of Type Ibc supernovae (SNe Ibc). They are distinguished by the production of an energetic and collimated relativistic outflow powered 2 by a central engine (an accreting black hole or neutron star).Observationally, this outflow is manifested 3 in the pulse of gamma-rays and a long-lived radio afterglow. To date, central engine-driven SNe have been discovered exclusively through their gamma-ray emission, yet it is expected 4 that a larger population goes undetected due to limited satellite sensitivity or beaming of the collimated emission away from our line-of-sight. In this framework, 2 Soderberg et al.the recovery of undetected GRBs may be possible through radio searches 5,6 for SNe Ibc with relativistic outflows. Here we report the discovery of luminous radio emission from the seemingly ordinary Type Ibc SN 2009bb, which requires a substantial relativistic outflow powered by a central engine. The lack of a coincident GRB makes SN 2009bb the first engine-driven SN discovered without a detected gamma-ray signal. A comparison with our extensive radio survey of SNe Ibc reveals that the fraction harboring central engines is low, ∼ 1%, measured independently from, but consistent with, the inferred 46 rate of nearby GRBs. Our study demonstrates that upcoming optical and radio surveys will soon rival gamma-ray satellites in pinpointing the nearest engine-driven SNe.A similar result for a different supernova is reported 8 independently. A Relativistic SN 3Unlike the optical emission from SNe which traces only the slowest explosion debris, radio observations uniquely probe 35 the fastest ejecta as the expanding blastwave (velocity, v) shocks and accelerates electrons in amplified magnetic fields. The resulting synchrotron emission is suppressed by self-absorption (SSA) producing a low frequency radio turnover that defines the spectral peak frequency, ν p . Combining our observations from the VLA and the Giant Meterwave Radio Telescope (GMRT), the radio spectra of SN 2009bbare well described by an SSA model across multiple epochs ( Figure 2). From our earliest spectrum on Apr 8 UT (∆t ≈ 20 days), we infer ν p ≈ 6 GHz and a spectral peak luminosity,Making the conservative assumption that the energy of the radio emitting material is partitioned equally into accelerating electrons and amplifying magnetic fields (equipartition), the properties of the SSA radio spectrum enable 13,35 a robust estimate of the blastwave radius, R ≈ 2.9 × 10 16 (L ν,p /10 28 erg ssynchrotron sources with a low spectral peak frequency thus require larger sizes (Figure 3).For SN 2009bb, we infer R ≈ 4.4 × 10 16 cm at ∆t ≈ 20 days and thus the mean expansion velocity is R/∆t = 0.85 ± 0.02c, where c is the speed of light. The transverse expansion speed, Γβc = R/∆t indicates that the blastwave is relativistic, Γ 1.3, at this time [bulk Lorentz factor Γ = (1 − β 2 ) −1/2 with β = v/c]. This is a lower limit on the initial velocity since th...

We report the discovery and detailed monitoring of X-ray emission associated with the Type IIb SN 2011dh using data from the Swift and Chandra satellites,

We investigate the environment of the nearby (d ≈ 40 Mpc) broad-lined Type Ic supernova SN 2009bb. This event was observed to produce a relativistic outflow likely powered by a central accreting compact object. While such a phenomenon was previously observed only in long-duration gamma-ray bursts (LGRBs), no LGRB was detected in association with SN 2009bb. Using an optical spectrum of the SN 2009bb explosion site, we determine a variety of ISM properties for the host environment, including metallicity, young stellar population age, and star formation rate. We compare the SN explosion site properties to observations of LGRB and broad-lined SN Ic host environments on optical emission line ratio diagnostic diagrams. Based on these analyses, we find that the SN 2009bb explosion site has a metallicity between 1.7Z ⊙ and 3.5Z ⊙ , in agreement with other broad-lined SN Ic host environments and at odds with the low-redshift LGRB host environments and recently proposed maximum metallicity limits for relativistic explosions. We consider the implications of these findings and the impact that SN 2009bb's unusual explosive properties and environment have on our understanding of the key physical ingredient that enables some SNe to produce a relativistic outflow. Subject headings: supernovae: individual (SN 2009bb) -galaxies: ISM -gamma rays: bursts emsque@ifa.hawaii.edu 1 This paper is based on data gathered with the 6.5 m Magellan telescopes located at Las Campanas, Chile.

The spectral response of several crystals grown by the Traveling Heater Method (THM) were investigated. An energy resolution of 0.98% for a Pseudo Frisch-Grid of 4 4 9 mm 3 and 2.1% FWHM for a coplanar-grid of size 11 11 5 mm 3 were measured using 137 Cs-662 keV. In addition a 4% FWHM at 122 keV has also been measured on 20 20 5 mm 3 monolithic pixellated devices. The material shows great potential toward producing large-volume detectors with spectral performance that meets the requirement for high-resolution gamma-ray spectroscopy.

We report progress on an experiment to measure the neutron lifetime using magnetically trapped neutrons. Neutrons are loaded into a 1.1 T deep superconducting Ioffe-type trap by scattering 0.89 nm neutrons in isotopically pure superfluid 4He. Neutron decays are detected in real time using the scintillation light produced in the helium by the beta-decay electrons. The measured trap lifetime at a helium temperature of 300 mK and with no ameliorative magnetic ramping is substantially shorter than the free neutron lifetime. This is attributed to the presence of neutrons with energies higher than the magnetic potential of the trap. Magnetic field ramping is implemented to eliminate these neutrons, resulting in an 833−63+74s trap lifetime, consistent with the currently accepted value of the free neutron lifetime.