222 research outputs found
On the Rates of Type Ia Supernovae in Dwarf and Giant Hosts with ROTSE-IIIb
We present a sample of 23 spectroscopically confirmed Type Ia supernovae that
were discovered in the background of galaxy clusters targeted by ROTSE-IIIb and
use up to 18 of these to determine the local (z = 0.05) volumetric rate. Since
our survey is flux limited and thus biased against fainter objects, the
pseudo-absolute magnitude distribution (pAMD) of SNeIa in a given volume is an
important concern, especially the relative frequency of high to low-luminosity
SNeIa. We find that the pAMD derived from the volume limited Lick Observatory
Supernova Search (LOSS) sample is incompatible with the distribution of SNeIa
in a volume limited (z<0.12) sub sample of the SDSS-II. The LOSS sample
requires far more low-luminosity SNeIa than the SDSS-II can accommodate. Even
though LOSS and SDSS-II have sampled different SNeIa populations, their
volumetric rates are surprisingly similar. Using the same model pAMD adopted in
the SDSS-II SNeIa rate calculation and excluding two high-luminosity SNeIa from
our sample, we derive a rate that is marginally higher than previous
low-redshift determinations. With our full sample and the LOSS pAMD our rate is
more than double the canonical value. We also find that 5 of our 18 SNeIa are
hosted by very low-luminosity (M_B > -16) galaxies, whereas only 1 out 79
nearby SDSS-II SNeIa have such faint hosts. It is possible that previous works
have under-counted either low luminosity SNeIa, SNeIa in low luminosity hosts,
or peculiar SNeIa (sometimes explicitly), and the total SNeIa rate may be
higher than the canonical value.Comment: 18 pages; accepted for publication in The Astronomical Journa
Calcium-rich gap transients in the remote outskirts of galaxies
From the first two seasons of the Palomar Transient Factory, we identify three peculiar transients (PTF09dav, PTF10iuv, PTF11bij) with five distinguishing characteristics: peak luminosity in the gap between novae and supernovae (M_R ≈ - 15.5 to -16.5), rapid photometric evolution (t_(rise) ≈12-15 days), large photospheric velocities (≈6000 to 11000 km s^(-1)), early spectroscopic evolution into nebular phase (≈1 to 3 months) and peculiar nebular spectra dominated by Calcium. We also culled the extensive decade-long Lick Observatory Supernova Search database and identified an additional member of this group, SN 2007ke. Our choice of photometric and spectroscopic properties was motivated by SN 2005E (Perets et al. 2010). To our surprise, as in the case of SN 2005E, all four members of this group are also clearly offset from the bulk of their host galaxy. Given the well-sampled early and late-time light curves, we derive ejecta masses in the range of 0.4--0.7 M_⊙. Spectroscopically, we find that there may be a diversity in the photospheric phase, but the commonality is in the unusual nebular spectra. Our extensive follow-up observations rule out standard thermonuclear and standard core-collapse explosions for this class of "Calcium-rich gap" transients. If the progenitor is a white dwarf, we are likely seeing a detonation of the white dwarf core and perhaps, even shock-front interaction with a previously ejected nova shell. In the less likely scenario of a massive star progenitor, a very non-standard channel specific to a low-metallicity environment needs to be invoked (e.g., ejecta fallback leading to black hole formation). Detection (or lack thereof) of a faint underlying host (dwarf galaxy, cluster) will provide a crucial and decisive diagnostic to choose between these alternatives
Using visual analytics to develop situation awareness in astrophysics
We present a novel collaborative visual analytics application for cognitively overloaded users in the astrophysics domain. The system was developed for scientists who need to analyze heterogeneous, complex data under time pressure, and make predictions and time-critical decisions rapidly and correctly under a constant influx of changing data. The Sunfall Data Taking system utilizes several novel visualization and analysis techniques to enable a team of geographically distributed domain specialists to effectively and remotely maneuver a custom-built instrument under challenging operational conditions. Sunfall Data Taking has been in production use for 2 years by a major international astrophysics collaboration (the largest data volume supernova search currently in operation), and has substantially improved the operational efficiency of its users. We describe the system design process by an interdisciplinary team, the system architecture and the results of an informal usability evaluation of the production system by domain experts in the context of Endsley's three levels of situation awareness
Real-time Detection and Rapid Multiwavelength Follow-up Observations of a Highly Subluminous Type II-P Supernova from the Palomar Transient Factory Survey
The Palomar Transient Factory (PTF) is an optical wide-field variability survey carried out using a camera with a 7.8 deg^2 field of view mounted on the 48 inch Oschin Schmidt telescope at Palomar Observatory. One of the key goals of this survey is to conduct high-cadence monitoring of the sky in order to detect optical transient sources shortly after they occur. Here, we describe the real-time capabilities of the PTF and our related rapid multiwavelength follow-up programs, extending from the radio to the γ-ray bands. We present as a case study observations of the optical transient PTF10vdl (SN 2010id), revealed to be a very young core-collapse (Type II-P) supernova having a remarkably low luminosity. Our results demonstrate that the PTF now provides for optical transients the real-time discovery and rapid-response follow-up capabilities previously reserved only for high-energy transients like gamma-ray bursts
iPTF13bvn: The First Evidence of a Binary Progenitor for a Type Ib Supernova
The recent detection in archival HST images of an object at the the location
of supernova (SN) iPTF13bvn may represent the first direct evidence of the
progenitor of a Type Ib SN. The object's photometry was found to be compatible
with a Wolf-Rayet pre-SN star mass of ~11 Msun. However, based on
hydrodynamical models we show that the progenitor had a pre-SN mass of ~3.5
Msun and that it could not be larger than ~8 Msun. We propose an interacting
binary system as the SN progenitor and perform evolutionary calculations that
are able to self-consistently explain the light-curve shape, the absence of
hydrogen, and the pre-SN photometry. We further discuss the range of allowed
binary systems and predict that the remaining companion is a luminous O-type
star of significantly lower flux in the optical than the pre-SN object. A
future detection of such star may be possible and would provide the first
robust identification of a progenitor system for a Type Ib SN.Comment: Accepted to AJ on July 26. Slight changes from original, however
delayed by slow refereeing proces
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