Aims. The aim of this paper is to discuss the nature of two type Ic supernovae SN 2007bg and SN 2007bi and their host galaxies. Both supernovae were discovered in wide-field, non-targeted surveys and ...are found to be associated with sub-luminous blue dwarf galaxies identified in SDSS images. Methods. We present BVRI photometry and optical spectroscopy of SN 2007bg and SN 2007bi and their host galaxies. Their lightcurves and spectra are compared to those of other type Ic SNe and analysis of these data provides estimates of the energetics, total ejected masses and synthesised mass of 56Ni. Detection of the host galaxy emission lines allows for metallicity measurements. Results. Neither SNe 2007bg nor 2007bi were found in association with an observed GRB, but from estimates of the metallicities of their host-galaxies they are found to inhabit similar low-metallicity environments as GRB associated supernovae. The radio-bright SN 2007bg is hosted by an extremely sub-luminous galaxy of magnitude MB = -12.4 ± 0.6 mag and an estimated oxygen abundance of 12+log(O/H) = 8.18 ± 0.17 (on the Pettini & Pagel 2004 scale). The early lightcurve evolution of SN 2007bg matches the fast-pace decline of SN 1994I giving it one of the fastest post-maximum decline rates of all broad-lined type Ic supernovae known to date and, when combined with its high expansion velocities, a high kinetic energy to ejected mass ratio (EK/Mej~2.7). We also show that SN 2007bi is possibly the most luminous type Ic known, reaching a peak magnitude of $M_{\rm R} $~ -21.3 mag and displays a remarkably slow decline, following the radioactive decay rate of 56Co to 56Fe throughout the course of its observed lifetime. SN 2007bi also displays an extreme longevity in its spectral evolution and is still not fully nebular at approximately one year post-maximum brightness. From a simple model of the bolometric light curve of SN 2007bi we estimate a total ejected 56Ni mass of MNi = 3.5-4.5 $M_\odot$, the largest 56Ni mass measured in the ejecta of a supernova to date. There are two models that could explain the high luminosity and large ejected 56Ni mass. One is a pair-instability supernova (PISN) which has been predicted to occur for massive stars at low metallicities. We measure the host galaxy metallicity of SN 2007bi to be 12+log(O/H) = 8.15 ± 0.15 (on the McGaugh 1991 scale) which is somewhat high to be consistent with the PISN model. An alternative is the core-collapse of a C+O star of 20-40 $M_{\odot}$ which is the core of a star of originally 50-100 $M_{\odot}$.
We present basic statistics for all supernovae discovered by the All-Sky Automated Survey for SuperNovae (ASAS-SN) during its first year-and-a-half of operations, spanning 2013 and 2014. We also ...present the same information for all other bright (mV less than or equal to 17), spectroscopically confirmed supernovae discovered from 2014 May 1 through the end of 2014, providing a comparison to the ASAS-SN sample starting from the point where ASAS-SN became operational in both hemispheres. In addition, we present collected redshifts and near-UV through IR magnitudes, where available, for all host galaxies of the bright supernovae in both samples. This work represents a comprehensive catalogue of bright supernovae and their hosts from multiple professional and amateur sources, allowing for population studies that were not previously possible because the all-sky emphasis of ASAS-SN redresses many previously existing biases. In particular, ASAS-SN systematically finds bright supernovae closer to the centres of host galaxies than either other professional surveys or amateurs, a remarkable result given ASAS-SN's poorer angular resolution. This is the first of a series of yearly papers on bright supernovae and their hosts that will be released by the ASAS-SN team.
ABSTRACT On 2014 December 9.61, the All-sky Automated Survey for SuperNovae (ASAS-SN or "Assassin") discovered ASASSN-14lp just ∼2 days after first light using a global array of 14 cm diameter ...telescopes. ASASSN-14lp went on to become a bright supernova (V = 11.94 mag), second only to SN 2014J for the year. We present prediscovery photometry (with a detection less than a day after first light) and ultraviolet through near-infrared photometric and spectroscopic data covering the rise and fall of ASASSN-14lp for more than 100 days. We find that ASASSN-14lp had a broad light curve ( ), a B-band maximum at 2457015.82 0.03, a rise time of days, and moderate host-galaxy extinction ( ). Using ASASSN-14lp, we derive a distance modulus for NGC 4666 of , corresponding to a distance of 14.7 1.5 Mpc. However, adding ASASSN-14lp to the calibrating sample of Type Ia supernovae still requires an independent distance to the host galaxy. Finally, using our early-time photometric and spectroscopic observations, we rule out red giant secondaries and, assuming a favorable viewing angle and explosion time, any nondegenerate companion larger than 0.34 .
Context. At low redshift, a handful of gamma-ray bursts (GRBs) have been discovered with luminosities that are substantially lower (Liso ≲ 1048.5 erg s-1) than the average of more distant ones (Liso ...≳ 1049.5 erg s-1). It has been suggested that the properties of several low-luminosity (low-L) GRBs are due to shock break-out, as opposed to the emission from ultrarelativistic jets. This has led to much debate about how the populations are connected. Aims. The burst at redshift z = 0.283 from 2012 April 22 is one of the very few examples of intermediate-L GRBs with a γ-ray luminosity of Liso ~ 1049.6−49.9 erg s-1 that have been detected up to now. With the robust detection of its accompanying supernova SN 2012bz, it has the potential to answer important questions on the origin of low- and high-L GRBs and the GRB-SN connection. Methods. We carried out a spectroscopy campaign using medium- and low-resolution spectrographs with 6–10-m class telescopes, which covered a time span of 37.3 days, and a multi-wavelength imaging campaign, which ranged from radio to X-ray energies over a duration of ~270 days. Furthermore, we used a tuneable filter that is centred at Hα to map star-formation in the host and the surrounding galaxies. We used these data to extract and model the properties of different radiation components and fitted the spectral energy distribution to extract the properties of the host galaxy. Results. Modelling the light curve and spectral energy distribution from the radio to the X-rays revealed that the blast wave expanded with an initial Lorentz factor of Γ0 ~ 50, which is a low value in comparison to high-L GRBs, and that the afterglow had an exceptionally low peak luminosity density of ≲2 × 1030 erg s-1 Hz-1 in the sub-mm. Because of the weak afterglow component, we were able to recover the signature of a shock break-out in an event that was not a genuine low-L GRB for the first time. At 1.4 hr after the burst, the stellar envelope had a blackbody temperature of kBT ~ 16 eV and a radius of ~7 × 1013 cm (both in the observer frame). The accompanying SN 2012bz reached a peak luminosity of MV = −19.7 mag, which is 0.3 mag more luminous than SN 1998bw. The synthesised nickel mass of 0.58 M⊙, ejecta mass of 5.87 M⊙, and kinetic energy of 4.10 × 1052 erg were among the highest for GRB-SNe, which makes it the most luminous spectroscopically confirmed SN to date. Nebular emission lines at the GRB location were visible, which extend from the galaxy nucleus to the explosion site. The host and the explosion site had close-to-solar metallicity. The burst occurred in an isolated star-forming region with an SFR that is 1/10 of that in the galaxy’s nucleus. Conclusions. While the prompt γ-ray emission points to a high-L GRB, the weak afterglow and the low Γ0 were very atypical for such a burst. Moreover, the detection of the shock break-out signature is a new quality for high-L GRBs. So far, shock break-outs were exclusively detected for low-L GRBs, while GRB 120422A had an intermediate Liso of ~1049.6−49.9 erg s-1. Therefore, we conclude that GRB 120422A was a transition object between low- and high-L GRBs, which supports the failed-jet model that connects low-L GRBs that are driven by shock break-outs and high-L GRBs that are powered by ultra-relativistic jets.
ABSTRACT We present optical and near-infrared (NIR) light curves and optical spectra of SN 2013dx, associated with the nearby (redshift 0.145) gamma-ray burst GRB 130702A. The prompt isotropic ...gamma-ray energy released from GRB 130702A is measured to be erg (1 keV to 10 MeV in the rest frame), placing it intermediate between low-luminosity GRBs like GRB 980425/SN 1998bw and the broader cosmological population. We compare the observed light curves of SN 2013dx to a SN 1998bw template, finding that SN 2013dx evolves ∼20% faster (steeper rise time), with a comparable peak luminosity. Spectroscopically, SN 2013dx resembles other broad-lined SNe Ic, both associated with (SN 2006aj and SN 1998bw) and lacking (SN 1997ef, SN 2007I, and SN 2010ah) gamma-ray emission, with photospheric velocities around peak of ∼ 21,000 km s−1. We construct a quasi-bolometric ( ) light curve for SN 2013dx, only the fifth GRB-associated SN with extensive NIR coverage and the third with a bolometric light curve extending beyond . Together with the measured photospheric velocity, we derive basic explosion parameters using simple analytic models. We infer a 56Ni mass of , an ejecta mass of , and a kinetic energy of erg (statistical uncertainties only), consistent with previous GRB-associated supernovae. When considering the ensemble population of GRB-associated supernovae, we find no correlation between the mass of synthesized 56Ni and high-energy properties, despite clear predictions from numerical simulations that should correlate with the degree of asymmetry. On the other hand, clearly correlates with the kinetic energy of the supernova ejecta across a wide range of core-collapse events.
Spectroscopic and photometric observations of the nearby Type Ia Supernova (SN Ia) SN 2014J are presented. Spectroscopic observations were taken −8 to +10 d relative to B-band maximum, using ...FRODOSpec, a multipurpose integral-field unit spectrograph. The observations range from 3900 to 9000 Å. SN 2014J is located in M82 which makes it the closest SN Ia studied in at least the last 28 yr. It is a spectroscopically normal SN Ia with high-velocity features. We model the spectra of SN 2014J with a Monte Carlo radiative transfer code, using the abundance tomography technique. SN 2014J is highly reddened, with a host galaxy extinction of E(B − V) = 1.2 (R
V
= 1.38). It has a Δm
15(B) of 1.08 ± 0.03 when corrected for extinction. As SN 2014J is a normal SN Ia, the density structure of the classical W7 model was selected. The model and photometric luminosities are both consistent with B-band maximum occurring on JD 245 6690.4 ± 0.12. The abundance of the SN 2014J behaves like other normal SN Ia, with significant amounts of silicon (12 per cent by mass) and sulphur (9 per cent by mass) at high velocities (12 300 km s−1) and the low-velocity ejecta (v < 6500 km s−1) consists almost entirely of 56Ni.
We present the results from a multi–epoch survey of two regions of M33 using the 3.5–m Wisconsin–Indiana–Yale–NOAO (WIYN) telescope. The inner field is located close to the centre of the galaxy, with ...the outer region situated about 5.1 kpc away in the southern spiral arm, allowing us to sample a large metallicity range. We have data for 167 fundamental mode Cepheids in the two regions. The reddening–free Wesenheit magnitude Wvi period–luminosity (PL) relations were used to establish the distance modulus of each region, with μinner= 24.37 ± 0.02 mag and μouter= 24.54 ± 0.03 mag. The apparent discrepancy between these two results can be explained by the significant metallicity gradient of the galaxy. We determine a value for the metallicity parameter of the PL relation =−0.29 ± 0.11 mag dex−1, consistent with previous measurements. This leads to a metallicity corrected distance modulus to M33 of μγ= 24.53 ± 0.11 mag.
The first direct detection of gravitational waves was made in 2015 September with the Advanced LIGO detectors. By prior arrangement, a worldwide collaboration of electromagnetic follow-up observers ...were notified of candidate gravitational wave events during the first science run, and many facilities were engaged in the search for counterparts. Three alerts were issued to the electromagnetic collaboration over the course of the first science run, which lasted from 2015 September to 2016 January. Two of these alerts were associated with the gravitational wave events since named GW150914 and GW151226. In this paper we provide an overview of the Liverpool Telescope contribution to the follow-up campaign over this period. Given the hundreds of square degree uncertainty in the sky position of any gravitational wave event, efficient searching for candidate counterparts required survey telescopes with large (∼degrees) fields of view. The role of the Liverpool Telescope was to provide follow-up classification spectroscopy of any candidates. We followed candidates associated with all three alerts, observing 1, 9 and 17 candidates respectively. We classify the majority of the transients we observed as supernovae. No counterparts were identified, which is in line with expectations given that the events were classified as black hole–black hole mergers. However these searches laid the foundation for similar follow-up campaigns in future gravitational wave detector science runs, in which the detection of neutron star merger events with observable electromagnetic counterparts is much more likely.
Abstract
The CNIa0.02 project aims to collect a complete, nearby sample of Type Ia supernovae (SNe Ia) light curves, and the SNe are volume-limited with host-galaxy redshifts
z
host
< 0.02. The main ...scientific goal is to infer the distributions of key properties (e.g., the luminosity function) of local SNe Ia in a complete and unbiased fashion in order to study SN explosion physics. We spectroscopically classify any SN candidate detected by the All-Sky Automated Survey for Supernovae (ASAS-SN) that reaches a peak brightness <16.5 mag. Since ASAS-SN scans the full sky and does not target specific galaxies, our target selection is effectively unbiased by host-galaxy properties. We perform multiband photometric observations starting from the time of discovery. In the first data release (DR1), we present the optical light curves obtained for 247 SNe from our project (including 148 SNe in the complete sample), and we derive parameters such as the peak fluxes, Δ
m
15
, and
s
BV
.
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