SN 2007bg: The Complex Circumstellar Environment Around One of the Most Radio-Luminous Broad-Lined Type Ic Supernovae

In this paper we present the results of the radio light curve and X-ray observations of broad-lined Type Ic SN 2007bg. The light curve shows three distinct phases of spectral and temporal evolution, implying that the SNe shock likely encountered at least 3 different circumstellar medium regimes. We interpret this as the progenitor of SN 2007bg having at least two distinct mass-loss episodes (i.e., phases 1 and 3) during its final stages of evolution, yielding a highly-stratified circumstellar medium. Modelling the phase 1 light curve as a freely-expanding, synchrotron-emitting shell, self-absorbed by its own radiating electrons, requires a progenitor mass-loss rate of \dot{M}~1.9x10^{-6}(v_{w}/1000 km s^{-1}) Solar masses per year for the last t~20(v_{w}/1000 km s^{-1}) yr before explosion, and a total energy of the radio emitting ejecta of E\sim1x10^{48} erg after 10 days from explosion. This places SN 2007bg among the most energetic Type Ib/c events. We interpret the second phase as a sparser "gap" region between the two winds stages. Phase 3 shows a second absorption turn-on before rising to a peak luminosity 2.6 times higher than in phase 1. Assuming this luminosity jump is due to a circumstellar medium density enhancement from a faster previous mass-loss episode, we estimate that the phase 3 mass-loss rate could be as high as \dot{M}<~4.3x10^{-4}(v_{w}/1000 km s^{-1}) Solar masses per year. The phase 3 wind would have transitioned directly into the phase 1 wind for a wind speed difference of ~2. In summary, the radio light curve provides robust evidence for dramatic global changes in at least some Ic-BL progenitors just prior (~10-1000 yr) to explosion. The observed luminosity of this SN is the highest observed for a non-gamma-ray-burst broad-lined Type Ic SN, reaching L_{8.46 GHz}~1x10^{29} erg Hz^{-1} s^{-1}, ~567 days after explosion.Comment: 11 pages, 5 figures, accepted for publication in MNRA

Short-Baseline Electron Neutrino Disappearance, Tritium Beta Decay and Neutrinoless Double-Beta Decay

We consider the interpretation of the MiniBooNE low-energy anomaly and the Gallium radioactive source experiments anomaly in terms of short-baseline electron neutrino disappearance in the framework of 3+1 four-neutrino mixing schemes. The separate fits of MiniBooNE and Gallium data are highly compatible, with close best-fit values of the effective oscillation parameters Delta m^2 and sin^2 2 theta. The combined fit gives Delta m^2 >~ 0.1 eV^2 and 0.11 < sin^2 2 theta < 0.48 at 2 sigma. We consider also the data of the Bugey and Chooz reactor antineutrino oscillation experiments and the limits on the effective electron antineutrino mass in beta-decay obtained in the Mainz and Troitsk Tritium experiments. The fit of the data of these experiments limits the value of sin^2 2 theta below 0.10 at 2 sigma. Considering the tension between the neutrino MiniBooNE and Gallium data and the antineutrino reactor and Tritium data as a statistical fluctuation, we perform a combined fit which gives Delta m^2 \simeq 2 eV and 0.01 < sin^2 2 theta < 0.13 at 2 sigma. Assuming a hierarchy of masses m_1, m_2, m_3 << m_4, the predicted contributions of m_4 to the effective neutrino masses in beta-decay and neutrinoless double-beta-decay are, respectively, between about 0.06 and 0.49 and between about 0.003 and 0.07 eV at 2 sigma. We also consider the possibility of reconciling the tension between the neutrino MiniBooNE and Gallium data and the antineutrino reactor and Tritium data with different mixings in the neutrino and antineutrino sectors. We find a 2.6 sigma indication of a mixing angle asymmetry.Comment: 14 pages; final version published in Phys.Rev.D82:053005,201

Dust in the wind: the role of recent mass loss in long gamma-ray bursts

We study the late-time (t>0.5 days) X-ray afterglows of nearby (z<0.5) long Gamma-Ray Bursts (GRB) with Swift and identify a population of explosions with slowly decaying, super-soft (photon index Gamma_x>3) X-ray emission that is inconsistent with forward shock synchrotron radiation associated with the afterglow. These explosions also show larger-than-average intrinsic absorption (NH_x,i >6d21 cm-2) and prompt gamma-ray emission with extremely long duration (T_90>1000 s). Chance association of these three rare properties (i.e. large NH_x,i, super-soft Gamma_x and extreme duration) in the same class of explosions is statistically unlikely. We associate these properties with the turbulent mass-loss history of the progenitor star that enriched and shaped the circum-burst medium. We identify a natural connection between NH_x,i Gamma_x and T_90 in these sources by suggesting that the late-time super-soft X-rays originate from radiation reprocessed by material lost to the environment by the stellar progenitor before exploding, (either in the form of a dust echo or as reprocessed radiation from a long-lived GRB remnant), and that the interaction of the explosion's shock/jet with the complex medium is the source of the extremely long prompt emission. However, current observations do not allow us to exclude the possibility that super-soft X-ray emitters originate from peculiar stellar progenitors with large radii that only form in very dusty environments.Comment: 6 pages, Submitted to Ap

Preliminary Results from the Caltech Core-Collapse Project (CCCP)

We present preliminary results from the Caltech Core-Collapse Project (CCCP), a large observational program focused on the study of core-collapse SNe. Uniform, high-quality NIR and optical photometry and multi-epoch optical spectroscopy have been obtained using the 200'' Hale and robotic 60'' telescopes at Palomar, for a sample of 50 nearby core-collapse SNe. The combination of both well-sampled optical light curves and multi-epoch spectroscopy will enable spectroscopically and photometrically based subtype definitions to be disentangled from each other. Multi-epoch spectroscopy is crucial to identify transition events that evolve among subtypes with time. The CCCP SN sample includes every core-collapse SN discovered between July 2004 and September 2005 that was visible from Palomar, found shortly (< 30 days) after explosion (based on available pre-explosion photometry), and closer than ~120 Mpc. This complete sample allows, for the first time, a study of core-collapse SNe as a population, rather than as individual events. Here, we present the full CCCP SN sample and show exemplary data collected. We analyze available data for the first ~1/3 of the sample and determine the subtypes of 13 SNe II based on both light curve shapes and spectroscopy. We discuss the relative SN II subtype fractions in the context of associating SN subtypes with specific progenitor stars.Comment: To appear in the proceedings of the meeting "The Multicoloured Landscape of Compact Objects and their Explosive Origins", Cefalu, Italy, June 2006, to be published by AIP, Eds. L. Burderi et a

A Relativistic Type Ibc Supernova Without a Detected Gamma-ray Burst

Long duration gamma-ray bursts (GRBs) mark 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 by a central engine (an accreting black hole or neutron star). Observationally, this outflow is manifested 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 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, the recovery of undetected GRBs may be possible through radio searches 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 percent, measured independently from, but consistent with, the inferred 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 independently.Comment: To appear in Nature on Jan 28 2010. Embargoed for discussion in the press until 13:00 US Eastern Time on Jan 27 (Accepted version, 27 pages, Manuscript and Suppl. Info.

High Voltage in Noble Liquids for High Energy Physics

A workshop was held at Fermilab November 8-9, 2013 to discuss the challenges of using high voltage in noble liquids. The participants spanned the fields of neutrino, dark matter, and electric dipole moment physics. All presentations at the workshop were made in plenary sessions. This document summarizes the experiences and lessons learned from experiments in these fields at developing high voltage systems in noble liquids.Comment: 64 pages, 41 figures, 2 table

Relativistic supernovae have shorter-lived central engines or more extended progenitors: the case of SN\,2012ap

Deep late-time X-ray observations of the relativistic, engine-driven, type Ic SN2012ap allow us to probe the nearby environment of the explosion and reveal the unique properties of relativistic SNe. We find that on a local scale of ~0.01 pc the environment was shaped directly by the evolution of the progenitor star with a pre-explosion mass-loss rate <5x10^-6 Msun yr-1 in line with GRBs and the other relativistic SN2009bb. Like sub-energetic GRBs, SN2012ap is characterized by a bright radio emission and evidence for mildly relativistic ejecta. However, its late time (t~20 days) X-ray emission is ~100 times fainter than the faintest sub-energetic GRB at the same epoch, with no evidence for late-time central engine activity. These results support theoretical proposals that link relativistic SNe like 2009bb and 2012ap with the weakest observed engine-driven explosions, where the jet barely fails to breakout. Furthermore, our observations demonstrate that the difference between relativistic SNe and sub-energetic GRBs is intrinsic and not due to line-of-sight effects. This phenomenology can either be due to an intrinsically shorter-lived engine or to a more extended progenitor in relativistic SNe.Comment: Version accepted to ApJ. Significantly broadened discussio