The Supernova Gamma-Ray Burst Connection

The chief distinction between ordinary supernovae and long-soft gamma-ray bursts (GRBs) is the degree of differential rotation in the inner several solar masses when a massive star dies, and GRBs are rare mainly because of the difficulty achieving the necessary high rotation rate. Models that do provide the necessary angular momentum are discussed, with emphasis on a new single star model whose rapid rotation leads to complete mixing on the main sequence and avoids red giant formation. This channel of progenitor evolution also gives a broader range of masses than previous models, and allows the copious production of bursts outside of binaries and at high redshifts. However, even the production of a bare helium core rotating nearly at break up is not, by itself, a sufficient condition to make a gamma-ray burst. Wolf-Rayet mass loss must be low, and will be low in regions of low metallicity. This suggests that bursts at high redshift (low metallicity) will, on the average, be more energetic, have more time structure, and last longer than bursts nearby. Every burst consists of three components: a polar jet (~0.1 radian), high energy, subrelativistic mass ejection (~1 radian), and low velocity equatorial mass that can fall back after the initial explosion. The relative proportions of these three components can give a diverse assortment of supernovae and high energy transients whose properties may vary with redshift.Comment: 10 pages, to appear in AIP Conf. Proc. "Gamma Ray Bursts in the Swift Era", Eds. S. S. Holt, N. Gehrels, J. Nouse

Exceptionally Bright Type Ib Supernova 1991D

Photometric and spectroscopic observations of the peculiar Type Ib Supernova 1991D are presented. SN 1991D was exceptionally bright for a Type Ib supernova. The He I lines were rather weak and the velocity at the photosphere as a function of time was unusually low. Comparison of the observed and synthetic spectra indicates that either hydrogen was ejected with a minimum velocity of 12,000 km/s or the spectrum contained features caused by lines of Ne I. Light curve modelling suggests that the progenitor probably had a very large radius (~10^14 cm) and that a considerable amount of 56Ni was synthesized during the explosion (~0.7 Msolar). We suggest a progenitor model of SN 1991D that involves a binary system.Comment: 7 pages, 9 figures, MNRAS in pres

Use of Dried Capillary Blood Sampling for Islet Autoantibody Screening in Relatives:A Feasibility Study

Background: Islet autoantibody testing provides the basis for assessment of risk of progression to type 1 diabetes. We set out to determine the feasibility and acceptability of dried capillary blood spot–based screening to identify islet autoantibody–positive relatives potentially eligible for inclusion in prevention trials. Materials and Methods: Dried blood spot (DBS) and venous samples were collected from 229 relatives participating in the TrialNet Pathway to Prevention Study. Both samples were tested for glutamic acid decarboxylase, islet antigen 2, and zinc transporter 8 autoantibodies, and venous samples were additionally tested for insulin autoantibodies and islet cell antibodies. We defined multiple autoantibody positive as two or more autoantibodies in venous serum and DBS screen positive if one or more autoantibodies were detected. Participant questionnaires compared the sample collection methods. Results: Of 44 relatives who were multiple autoantibody positive in venous samples, 42 (95.5%) were DBS screen positive, and DBS accurately detected 145 of 147 autoantibody-negative relatives (98.6%). Capillary blood sampling was perceived as more painful than venous blood draw, but 60% of participants would prefer initial screening using home fingerstick with clinic visits only required if autoantibodies were found. Conclusions: Capillary blood sampling could facilitate screening for type 1 diabetes prevention studies.</p

A Black Hole in the X-Ray Nova Velorum 1993

We have obtained 17 moderate-resolution (~2.5 A) optical spectra of the Galactic X-ray Nova Velorum 1993 in quiescence with the Keck-II telescope. The orbital period (P) is 0.285206 +/- 0.0000014 d, and the semiamplitude (K_2) is 475.4 +/- 5.9 km/s. Our derived mass function, f(M_1) = PK_2^3 /2 pi G = 3.17 +/- 0.12 M_sun, is close to the conventional absolute limiting mass for a neutron star (~ 3.0-3.2 M_sun) -- but if the orbital inclination i is less than 80 degrees (given the absences of eclipses), then M_1 is greater than 4.2-4.4 M_sun for nominal secondary-star masses of 0.5 M_sun (M0) to 0.65 M_sun (K6). The primary star is therefore almost certainly a black hole rather than a neutron star. The velocity curve of the primary from H-alpha emission has a semiamplitude (K_1) of 65.3 +/- 7.0 km/s, but with a phase offset by 237 degrees (rather than 180 degrees) from that of the secondary star. The nominal mass ratio q = M_2/M_1 = K_1/K_2 = 0.137 +/- 0.015, and hence for M_2 = 0.5-0.65 M_sun we derive M_1 = 3.64-4.74 M_sun. An adopted mass M_1 ~ 4.4 M_sun is significantly below the typical value of ~ 7 M_sun found for black holes in other low-mass X-ray binaries. Keck observations of MXB 1659-29 (V2134 Oph) in quiescence reveal a probable optical counterpart at R = 23.6 +/- 0.4 mag.Comment: 16 pages, 9 figures, added references, revised per. referee's comments Accepted for publication in August 1999 issue of PAS

The Optical SN 2012bz Associated with the Long GRB 120422A

The association of Type Ic SNe with long-duration GRBs is well established. We endeavor, through accurate ground-based observational campaigns, to characterize these SNe at increasingly high redshifts. We obtained a series of optical photometric and spectroscopic observations of the Type Ic SN2012bz associated with the Swift long-duration GRB120422A (z=0.283) using the 3.6-m TNG and the 8.2-m VLT telescopes. The peak times of the light curves of SN2012bz in various optical filters differ, with the B-band and i'-band light curves reaching maximum at ~9 and ~23 rest-frame days, respectively. The bolometric light curve has been derived from individual bands photometric measurements, but no correction for the unknown contribution in the near-infrared (probably around 10-15%) has been applied. Therefore, the present light curve should be considered as a lower limit to the actual UV-optical-IR bolometric light curve. This pseudo-bolometric curve reaches its maximum (Mbol = -18.56 +/- 0.06) at 13 +/- 1 rest-frame days; it is similar in shape and luminosity to the bolometric light curves of the SNe associated with z<0.2 GRBs and more luminous than those of SNe associated with XRFs. A comparison with the model generated for the bolometric light curve of SN2003dh suggests that SN2012bz produced only about 15% less 56Ni than SN2003dh, about 0.35 Msol. Similarly the VLT spectra of SN2012bz, after correction for Galactic extinction and for the contribution of the host galaxy, suggest comparable explosion parameters with those observed in SN2003dh (EK~3.5 x 10^52 erg, Mej~7 Msol) and a similar progenitor mass (~25-40 Msol). GRB120422A is consistent with the Epeak-Eiso and the EX,iso-Egamma,iso-E_peak relations. GRB120422A/SN2012bz shows the GRB-SN connection at the highest redshift so far accurately monitored both photometrically and spectroscopically.Comment: 7 pages, 6 figures, 2 tables, accepted for publication in Astronomy & Astrophysic

SN 2006gy: was it really extra-ordinary?

We present an optical photometric and spectroscopic study of the very luminous type IIn SN 2006gy for a time period spanning more than one year. In photometry, a broad, bright (M_R~-21.7) peak characterizes all BVRI light curves. Afterwards, a rapid luminosity fading is followed by a phase of slow luminosity decline between day ~170 and ~237. At late phases (>237 days), because of the large luminosity drop (>3 mag), only upper visibility limits are obtained in the B, R and I bands. In the near-infrared, two K-band detections on days 411 and 510 open new issues about dust formation or IR echoes scenarios. At all epochs the spectra are characterized by the absence of broad P-Cygni profiles and a multicomponent Halpha profile, which are the typical signatures of type IIn SNe. After maximum, spectroscopic and photometric similarities are found between SN 2006gy and bright, interaction-dominated SNe (e.g. SN 1997cy, SN 1999E and SN 2002ic). This suggests that ejecta-CSM interaction plays a key role in SN 2006gy about 6 to 8 months after maximum, sustaining the late-time-light curve. Alternatively, the late luminosity may be related to the radioactive decay of ~3M_sun of 56Ni. Models of the light curve in the first 170 days suggest that the progenitor was a compact star (R~6-8 10^(12)cm, M_ej~5-14M_sun), and that the SN ejecta collided with massive (6-10M_sun), opaque clumps of previously ejected material. These clumps do not completely obscure the SN photosphere, so that at its peak the luminosity is due both to the decay of 56Ni and to interaction with CSM. A supermassive star is not required to explain the observational data, nor is an extra-ordinarily large explosion energy.Comment: 33 pages, 8 figures. Accepted by ApJ. Paper with high-resolution figures available at http://web.oapd.inaf.it/supern/sn2006gy_astroph/agnoletto_2006gy.pd

A low energy core-collapse supernova without a hydrogen envelope

The final fate of massive stars depends on many factors, including mass, rotation rate, magnetic fields and metallicity. Theory suggests that some massive stars (initially greater than 25-30 solar masses) end up as Wolf-Rayet stars which are deficient in hydrogen because of mass loss through strong stellar winds. The most massive of these stars have cores which may form a black hole and theory predicts that the resulting explosion produces ejecta of low kinetic energy, a faint optical display and a small mass fraction of radioactive nickel(1,2,3). An alternative origin for low energy supernovae is the collapse of the oxygen-neon core of a relatively lowmass star (7-9 solar masses) through electron capture(4,5). However no weak, hydrogen deficient, core-collapse supernovae are known. Here we report that such faint, low energy core-collapse supernovae do exist, and show that SN2008ha is the faintest hydrogen poor supernova ever observed. We propose that other similar events have been observed but they have been misclassified as peculiar thermonuclear supernovae (sometimes labelled SN2002cx-like events(6)). This discovery could link these faint supernovae to some long duration gamma-ray bursts. Extremely faint, hydrogen-stripped core-collapse supernovae have been proposed to produce those long gamma-ray bursts whose afterglows do not show evidence of association with supernovae (7,8,9).Comment: Submitted 12 January 2009 - Accepted 24 March 200

Nearby Supernova Rates from the Lick Observatory Supernova Search. II. The Observed Luminosity Functions and Fractions of Supernovae in a Complete Sample

This is the second paper of a series in which we present new measurements of the observed rates of supernovae (SNe) in the local Universe, determined from the Lick Observatory Supernova Search (LOSS). In this paper, a complete SN sample is constructed, and the observed (uncorrected for host-galaxy extinction) luminosity functions (LFs) of SNe are derived. These LFs solve two issues that have plagued previous rate calculations for nearby SNe: the luminosity distribution of SNe and the host-galaxy extinction. We select a volume-limited sample of 175 SNe, collect photometry for every object, and fit a family of light curves to constrain the peak magnitudes and light-curve shapes. The volume-limited LFs show that they are not well represented by a Gaussian distribution. There are notable differences in the LFs for galaxies of different Hubble types (especially for SNe Ia). We derive the observed fractions for the different subclasses in a complete SN sample, and find significant fractions of SNe II-L (10%), IIb (12%), and IIn (9%) in the SN II sample. Furthermore, we derive the LFs and the observed fractions of different SN subclasses in a magnitude-limited survey with different observation intervals, and find that the LFs are enhanced at the high-luminosity end and appear more "standard" with smaller scatter, and that the LFs and fractions of SNe do not change significantly when the observation interval is shorter than 10 days. We also discuss the LFs in different galaxy sizes and inclinations, and for different SN subclasses. Some notable results are ... (abridged).Comment: Minor revisions after the referee's report. MNRAS accepted (Paper II of a series). For high-res figures, latex source, landscape tables, and online data, please visit http://astro.berkeley.edu/~weidong/rate

The Emergence of the Infrared transient VVV-WIT-06

We report the discovery of an enigmatic large-amplitude (ΔKs> 10.5 mag) transient event in near-IR data obtained by the VISTA Variables in the Via Lactea (VVV) ESO Public Survey. The object (designated VVV-WIT-06) is located at R.A. = 17:07:18.917, decl. = -39:06:26.45 (J2000), corresponding to Galactic coordinates l = 347.14539, b = 0.88522. It exhibits a clear eruption, peaking at Ks = 9 mag during 2013 July and fading to Ks ~ 16.5 in 2017. Our late near-IR spectra show post-outburst emission lines, including some broad emission lines (upward of {FWHM} ~ 3000 k/s). We estimate a total extinction of A_V=10--15 mag in the surrounding field, and no progenitor was observed in ZYJHKs images obtained during 2010-2012 (down to Ks> 18.5 mag). Subsequent deep near-IR imaging and spectroscopy, in concert with the available multiband photometry, indicate that VVV-WIT-06 may be either: (I) the closest Type I SN observed in about 400 years, (II) an exotic high-amplitude nova that would extend the known realm of such objects, or (III) a stellar merger. In all of these cases, VVV-WIT-06 is a fascinating and curious astrophysical target under any of the scenarios considered.Peer reviewe

Type II Supernovae as Probes of Cosmology

- Constraining the cosmological parameters and understanding Dark Energy have tremendous implications for the nature of the Universe and its physical laws. - The pervasive limit of systematic uncertainties reached by cosmography based on Cepheids and Type Ia supernovae (SNe Ia) warrants a search for complementary approaches. - Type II SNe have been shown to offer such a path. Their distances can be well constrained by luminosity-based or geometric methods. Competing, complementary, and concerted efforts are underway, to explore and exploit those objects that are extremely well matched to next generation facilities. Spectroscopic follow-up will be enabled by space- based and 20-40 meter class telescopes. - Some systematic uncertainties of Type II SNe, such as reddening by dust and metallicity effects, are bound to be different from those of SNe Ia. Their stellar progenitors are known, promising better leverage on cosmic evolution. In addition, their rate - which closely tracks the ongoing star formation rate - is expected to rise significantly with look- back time, ensuring an adequate supply of distant examples. - These data will competitively constrain the dark energy equation of state, allow the determination of the Hubble constant to 5%, and promote our understanding of the processes involved in the last dramatic phases of massive stellar evolution.Comment: Science white paper, submitted to the Decadal committee Astro201