8 research outputs found
Supernova PTF12glz: a possible shock breakout driven through an aspherical wind
We present visible-light and ultraviolet (UV) observations of the supernova
PTF12glz. The SN was discovered and monitored in near-UV and R bands as part of
a joint GALEX and Palomar Transient Factory campaign. It is among the most
energetic Type IIn supernovae observed to date (~10^51erg). If the radiated
energy mainly came from the thermalization of the shock kinetic energy, we show
that PTF12glz was surrounded by ~1 solar mass of circumstellar material (CSM)
prior to its explosive death. PTF12glz shows a puzzling peculiarity: at early
times, while the freely expanding ejecta are presumably masked by the optically
thick CSM, the radius of the blackbody that best fits the observations grows at
~8000km/s. Such a velocity is characteristic of fast moving ejecta rather than
optically thick CSM. This phase of radial expansion takes place before any
spectroscopic signature of expanding ejecta appears in the spectrum and while
both the spectroscopic data and the bolometric luminosity seem to indicate that
the CSM is optically thick. We propose a geometrical solution to this puzzle,
involving an aspherical structure of the CSM around PTF12glz. By modeling
radiative diffusion through a slab of CSM, we show that an aspherical geometry
of the CSM can result in a growing effective radius. This simple model also
allows us to recover the decreasing blackbody temperature of PTF12glz.
SLAB-Diffusion, the code we wrote to model the radiative diffusion of photons
through a slab of CSM and evaluate the observed radius and temperature, is made
available on-line.Comment: Sumbitted to ApJ. Comments are welcom
The detection rate of early UV emission from supernovae: A dedicated GALEX/PTF survey and calibrated theoretical estimates
The radius and surface composition of an exploding massive star,as well as
the explosion energy per unit mass, can be measured using early UV observations
of core collapse supernovae (SNe). We present the first results from a
simultaneous GALEX/PTF search for early UV emission from SNe. Six Type II SNe
and one Type II superluminous SN (SLSN-II) are clearly detected in the GALEX
NUV data. We compare our detection rate with theoretical estimates based on
early, shock-cooling UV light curves calculated from models that fit existing
Swift and GALEX observations well, combined with volumetric SN rates. We find
that our observations are in good agreement with calculated rates assuming that
red supergiants (RSGs) explode with fiducial radii of 500 solar, explosion
energies of 10^51 erg, and ejecta masses of 10 solar masses. Exploding blue
supergiants and Wolf-Rayet stars are poorly constrained. We describe how such
observations can be used to derive the progenitor radius, surface composition
and explosion energy per unit mass of such SN events, and we demonstrate why UV
observations are critical for such measurements. We use the fiducial RSG
parameters to estimate the detection rate of SNe during the shock-cooling phase
(<1d after explosion) for several ground-based surveys (PTF, ZTF, and LSST). We
show that the proposed wide-field UV explorer ULTRASAT mission, is expected to
find >100 SNe per year (~0.5 SN per deg^2), independent of host galaxy
extinction, down to an NUV detection limit of 21.5 mag AB. Our pilot GALEX/PTF
project thus convincingly demonstrates that a dedicated, systematic SN survey
at the NUV band is a compelling method to study how massive stars end their
life.Comment: See additional information including animations on
http://www.weizmann.ac.il/astrophysics/ultrasa
Supernova PTF 12glz: A Possible Shock Breakout Driven through an Aspherical Wind
We present visible-light and ultraviolet (UV) observations of the supernova PTF 12glz. The SN was discovered and monitored in the near-UV and R bands as part of a joint GALEX and Palomar Transient Factory campaign. It is among the most energetic SNe IIn observed to date (≈10^(51) erg). If the radiated energy mainly came from the thermalization of the shock kinetic energy, we show that PTF 12glz was surrounded by ~1 M⊙ of circumstellar material (CSM) prior to its explosive death. PTF 12glz shows a puzzling peculiarity: at early times, while the freely expanding ejecta are presumably masked by the optically thick CSM, the radius of the blackbody that best fits the observations grows at ≈7000 km s^(−1). Such a velocity is characteristic of fast moving ejecta rather than optically thick CSM. This phase of radial expansion takes place before any spectroscopic signature of expanding ejecta appears in the spectrum and while both the spectroscopic data and the bolometric luminosity seem to indicate that the CSM is optically thick. We propose a geometrical solution to this puzzle, involving an aspherical structure of the CSM around PTF 12glz. By modeling radiative diffusion through a slab of CSM, we show that an aspherical geometry of the CSM can result in a growing effective radius. This simple model also allows us to recover the decreasing blackbody temperature of PTF 12glz. SLAB-Diffusion, the code we wrote to model the radiative diffusion of photons through a slab of CSM and evaluate the observed radius and temperature, is made available online
Portaria 078/CSE/2017 - Designa servidores para comporem Comissão Eleitoral
We present visible-light and ultraviolet (UV) observations of the supernova PTF12glz. The SN was discovered and monitored in near-UV and R bands as part of a joint GALEX and Palomar Transient Factory campaign. It is among the most energetic Type IIn supernovae observed to date (~10^51erg). If the radiated energy mainly came from the thermalization of the shock kinetic energy, we show that PTF12glz was surrounded by ~1 solar mass of circumstellar material (CSM) prior to its explosive death. PTF12glz shows a puzzling peculiarity: at early times, while the freely expanding ejecta are presumably masked by the optically thick CSM, the radius of the blackbody that best fits the observations grows at ~8000km/s. Such a velocity is characteristic of fast moving ejecta rather than optically thick CSM. This phase of radial expansion takes place before any spectroscopic signature of expanding ejecta appears in the spectrum and while both the spectroscopic data and the bolometric luminosity seem to indicate that the CSM is optically thick. We propose a geometrical solution to this puzzle, involving an aspherical structure of the CSM around PTF12glz. By modeling radiative diffusion through a slab of CSM, we show that an aspherical geometry of the CSM can result in a growing effective radius. This simple model also allows us to recover the decreasing blackbody temperature of PTF12glz. SLAB-Diffusion, the code we wrote to model the radiative diffusion of photons through a slab of CSM and evaluate the observed radius and temperature, is made available on-line