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We present detailed optical photometry for 25 Type Ibc supernovae (SNe Ibc) within d ≈ 150 Mpc obtained with the robotic Palomar 60-inch telescope in [2004][2005][2006][2007]. This study represents the first uniform, systematic, and statistical sample of multi-band SNe Ibc light curves available to date. We correct the light curves for host galaxy extinction using a new technique based on the photometric color evolution, namely, we show that the (V − R) color of extinction-corrected SNe Ibc at ∆t ≈ 10 d after V −band maximum is tightly distributed, (V − R) V 10 = 0.26 ± 0.06 mag. Using this technique, we find that SNe Ibc typically suffer from significant host galaxy extinction, E(B −V ) ≈ 0.4 mag. A comparison of the extinction-corrected light curves for helium-rich (Type Ib) and helium-poor (Type Ic) SNe reveals that they are statistically indistinguishable, both in luminosity and decline rate. We report peak absolute magnitudes of M R = −17.9 ± 0.9 mag and M R = −18.3 ± 0.6 mag for SNe Ib and Ic, respectively. Focusing on the broad-lined (BL) SNe Ic, we find that they are more luminous than the normal SNe Ibc sample, M R = −19.0 ± 1.1 mag, with a probability of only 1.6% that they are drawn from the same population of explosions. By comparing the peak absolute magnitudes of SNe Ic-BL with those inferred for local engine-driven explosions (GRB-SN 1998bw, XRF-SN 2006aj, and SN 2009bb) we find a 25% probability that relativistic SNe are drawn from the overall SNe Ic-BL population. Finally, we fit analytic models to the light curves to derive typical 56 Ni masses of M Ni ≈ 0.2 and 0.5 M ⊙ for SNe Ibc and SNe Ic-BL, respectively. With reasonable assumptions for the photospheric velocities, we further extract kinetic energy and ejecta mass values of M ej ≈ 2 M ⊙ and E K ≈ 10 51 erg for SNe Ibc, while for SNe Ic-BL we find higher values, M ej ≈ 5 M ⊙ and E K ≈ 10 52 erg. We discuss the implications for the progenitors of SNe Ibc and their relation to those of engine-driven explosions.

Prepared by the LSST Science Collaborations, with contributions from the LSST Project. PrefaceMajor advances in our understanding of the Universe over the history of astronomy have often arisen from dramatic improvements in our ability to observe the sky to greater depth, in previously unexplored wavebands, with higher precision, or with improved spatial, spectral, or temporal resolution. Aided by rapid progress in information technology, current sky surveys are again changing the way we view and study the Universe, and the next-generation instruments, and the surveys that will be made with them, will maintain this revolutionary progress. Substantial progress in the important scientific problems of the next decade (determining the nature of dark energy and dark matter, studying the evolution of galaxies and the structure of our own Milky Way, opening up the time domain to discover faint variable objects, and mapping both the inner and outer Solar System) all require wide-field repeated deep imaging of the sky in optical bands.The wide-fast-deep science requirement leads to a single wide-field telescope and camera which can repeatedly survey the sky with deep short exposures. The Large Synoptic Survey Telescope (LSST), a dedicated telecope with an effective aperture of 6.7 meters and a field of view of 9.6 deg 2 , will make major contributions to all these scientific areas and more. It will carry out a survey of 20,000 deg 2 of the sky in six broad photometric bands, imaging each region of sky roughly 2000 times (1000 pairs of back-to-back 15-sec exposures) over a ten-year survey lifetime.The LSST project will deliver fully calibrated survey data to the United States scientific community and the public with no proprietary period. Near real-time alerts for transients will also be provided worldwide. A goal is worldwide participation in all data products. The survey will enable comprehensive exploration of the Solar System beyond the Kuiper Belt, new understanding of the structure of our Galaxy and that of the Local Group, and vast opportunities in cosmology and galaxy evolution using data for billions of distant galaxies. Since many of these science programs will involve the use of the world's largest non-proprietary database, a key goal is maximizing the usability of the data. Experience with previous surveys is that often their most exciting scientific results were unanticipated at the time that the survey was designed; we fully expect this to be the case for the LSST as well.The purpose of this Science Book is to examine and document in detail science goals, opportunities, and capabilities that will be provided by the LSST. The book addresses key questions that will be confronted by the LSST survey, and it poses new questions to be addressed by future study. It contains previously available material (including a number of White Papers submitted to the ASTRO2010 Decadal Survey) as well as new results from a year-long campaign of study and evaluation. This book does not attempt to be complete; there are many ...

Spectral analysis of Swift/XRT dataWe use the xspec v11.3.2 X-ray spectral fitting package to fit both a power law and a blackbody model to the XRT outburst data. In both models we allow for excess neutral hydrogen absorption (N H ) above the Galactic value along the line of sight to NGC 2770, N H,Gal = 1.7 × 10 20 cm −2 . The best-fit power law model (χ 2 = 7.5 for 17 degrees of freedom; probability, P = 0.98) has a photon index, Γ = 2.3 ± 0.3 (or, F ν ∝ ν −1.3±0.3 ) and N H = 6.9 +1.8 −1.5 × 10 21 cm −2 . The best-fit blackbody model is described by kT = 0.71 ± 0.08 keV and N H = 1.3 +1.0 −0.9 × 10 21 cm −2 . However, this model provides a much poorer fit to the data (χ 2 = 26.0 for 17 degrees of freedom; probability, P = 0.074). We therefore adopt the power law model as the best description of the data. The resulting count rate to flux conversion is 1 counts s −1 = 5 × 10 −11 erg cm −2 s −1 . The outburst undergoes a significant hard-to-soft spectral evolution as indicated by the ratio of counts in the 0.3 − 2 keV band and 2 − 10 keV band. The hardness ratio decreases from 1.35 ± 0.15 during the peak of the flare to 0.25 ± 0.10 about 400 s later. In the context of the power law model this spectral softening corresponds to a change from Γ = 1.70 ± 0.25 to 3.20 ± 0.35 during the same time interval. High resolution optical spectroscopyWe obtained the spectrum with the High Resolution Echelle Spectrometer (HIRES) mounted on the Keck I 10-m telescope beginning at Jan 17.46 UT. A total of four 1800-s exposures were obtained with a spectral resolution, R = 48, 000, and a slit width of 0.86 arcsec. The data reach a signal-to-noise ratio of 18 per pixel. We reduced the data with the MAKEE reduction package. We are interested in the Na I D and K I absorption features since they are sensitive to the gas column density, and hence extinction, along the line of the sight to the SN. Rejecting a Relativistic Origin for XRO 080109We investigate the possibility that XRO 080109 is the result of a relativistic outflow similar to that in GRBs. In this context the emission is non-thermal synchrotron radiation. The outburst flux density is 7.5 × 10 2 µJy at 0.3 keV. Simultaneously, we find 3σ limits on the flux density in the UBV bands (∼ 3 eV) of F ν < 9.0 × 10 2 µJy, indicating that the peak of the synchrotron spectrum must be located between the UV and X-ray bands. In the standard synchrotron model this requires the frequencies corresponding to electrons with the minimum and cooling Lorentz factors to obey ν m ≈ ν c ≈ 3 × 10 16 Hz, while the peak of the spectrum is F ν,p ≈ 3 mJy.The inferred values of ν m and ν c allow us to constrain 47 the outflow parameters and thus to check for consistency with the hypothesis of relativistic expansion. The relevant parameters are the bulk Lorentz factor (γ), the magnetic field (B), and the shock radius (R sh ). From the value of ν c we find γB 3 ≈ 8.3 × 10 3 , and since γ > 1 we conclude that B < 20 G. In addition, using ν m we find ǫ 2 e γ 3 B ≈ 3 × 10 4 ; here ǫ e is the fraction of posts...

Previous detections of individual astrophysical sources of neutrinos are limited to the Sun and the supernova 1987A, whereas the origins of the diffuse flux of high-energy cosmic neutrinos remain unidentified. On 22 September 2017, we detected a high-energy neutrino, IceCube-170922A, with an energy of ~290 tera-electron volts. Its arrival direction was consistent with the location of a known γ-ray blazar, TXS 0506+056, observed to be in a flaring state. An extensive multiwavelength campaign followed, ranging from radio frequencies to γ-rays. These observations characterize the variability and energetics of the blazar and include the detection of TXS 0506+056 in very-high-energy γ-rays. This observation of a neutrino in spatial coincidence with a γ-ray-emitting blazar during an active phase suggests that blazars may be a source of high-energy neutrinos.

Gamma-ray burst (GRB) afterglows have provided important clues to the nature of these massive explosive events, providing direct information on the nearby environment and indirect information on the central engine that powers the burst. We report the discovery of two bright X-ray flares in GRB afterglows, including a giant flare comparable in total energy to the burst itself, each peaking minutes after the burst. These strong, rapid X-ray flares imply that the central engines of the bursts have long periods of activity, with strong internal shocks continuing for hundreds of seconds after the gamma-ray emission has ended.Comment: 12 pages, 1 table, 2 figures. Originally submitted to Nature on 6/6/05. Declined on 6/9/05. Revised and submitted to Science on 6/14/05. Accepted for publication in Science on 7/29/05 (this version

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