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Register a new userLSQ14efd: observations of the cooling of a shock break-out event in a type Ic Supernova
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Cristina Barbarino Dr
Publication date
2017
fields
Physics
and research's language is
English
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We present the photometric and spectroscopic evolution of the type Ic supernova LSQ14efd, discovered by the La Silla QUEST survey and followed by PESSTO. LSQ14efd was discovered few days after explosion and the observations cover up to ~100 days. The early photometric points show the signature of the cooling of the shock break-out event experienced by the progenitor at the time of the supernova explosion, one of the first for a type Ic supernova. A comparison with type Ic supernova spectra shows that LSQ14efd is quite similar to the type Ic SN 2004aw. These two supernovae have kinetic energies that are intermediate between standard Ic explosions and those which are the most energetic explosions known (e.g. SN 1998bw). We computed an analytical model for the light-curve peak and estimated the mass of the ejecta 6.3 +/- 0.5 Msun, a synthesized nickel mass of 0.25 Msun and a kinetic energy of Ekin = 5.6 +/- 0.5 x 10^51 erg. No connection between LSQ14efd and a GRB event could be established. However we point out that the supernova shows some spectroscopic similarities with the peculiar SN-Ia 1999ac and the SN-Iax SN 2008A. A core-collapse origin is most probable considering the spectroscopic, photometric evolution and the detection of the cooling of the shock break-out.
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Type Ic supernovae (SNe Ic) arise from the core-collapse of H (and He) poor stars, which could be either single WR stars or lower-mass stars stripped of their envelope by a companion. Their light curves are radioactively powered and usually show a fast rise to peak ($sim$10-15 d), without any early (first few days) emission bumps (with the exception of broad-lined SNe Ic) as sometimes seen for other types of stripped-envelope SNe (e.g., Type IIb SN 1993J and Type Ib SN 2008D). We have studied iPTF15dtg, a spectroscopically normal SN Ic with an early excess in the optical light curves followed by a long ($sim$30 d) rise to the main peak. It is the first spectroscopically-normal double-peaked SN Ic observed. We aim to determine the properties of this explosion and of its progenitor star. Optical photometry and spectroscopy of iPTF15dtg was obtained with multiple telescopes. The resulting light curves and spectral sequence are analyzed and modelled with hydrodynamical and analytical models, with particular focus on the early emission. Results. iPTF15dtg is a slow rising SN Ic, similar to SN 2011bm. Hydrodynamical modelling of the bolometric properties reveals a large ejecta mass ($sim$10 $M_{odot}$) and strong $^{56}$Ni mixing. The luminous early emission can be reproduced if we account for the presence of an extended ($sim$500 R$_{odot}$), low-mass ($sim$0.045 M$_{odot}$) envelope around the progenitor star. Alternative scenarios for the early peak, such as the interaction with a companion, a shock-breakout (SBO) cooling tail from the progenitor surface, or a magnetar-driven SBO are not favored. The large ejecta mass and the presence of H and He free extended material around the star suggest that the progenitor of iPTF15dtg was a massive ($gtrsim$ 35 M$_{odot}$) WR star suffering strong mass loss.
We present early-time Swift and Chandra X-ray data along with late-time optical and near-infrared observations of SN 2013by, a Type IIL supernova (SN) that occurred in the nearby spiral galaxy ESO 138$-$G10 (D $sim 14.8$ Mpc). Optical and NIR photometry and spectroscopy follow the late-time evolution of the supernova from days +89 to +457 post-maximum brightness. The optical spectra and X-ray light curves are consistent with the picture of a SN having prolonged interaction with circumstellar material (CSM) that accelerates the transition from supernova to supernova remnant (SNR). Specifically, we find SN 2013bys H$alpha$ profile exhibits significant broadening ($sim$ 10,000 km s$^{-1}$) on day +457, the likely consequence of high-velocity, H-rich material being excited by a reverse shock. A relatively flat X-ray light curve is observed that cannot be modeled using inverse-Compton scattering processes alone but requires an additional energy source most likely originating from the SN-CSM interaction. In addition, we see the first overtone of CO emission near 2.3 $mu$m on day +152, signaling the formation of molecules and dust in the SN ejecta and is the first time CO has been detected in a Type IIL supernova. We compare SN 2013by to Type IIP supernovae whose spectra show the rarely observed SN-to-SNR transition in varying degrees and conclude that Type IIL SNe may enter the remnant phase at earlier epochs than their Type IIP counterparts.
During the first few days after explosion, Type II supernovae (SNe) are dominated by relatively simple physics. Theoretical predictions regarding early-time SN light curves in the ultraviolet (UV) and optical bands are thus quite robust. We present, for the first time, a sample of $57$ $R$-band Type II SN light curves that are well monitored during their rise, having $>5$ detections during the first 10 days after discovery, and a well-constrained time of explosion to within $1-3$ days. We show that the energy per unit mass ($E/M$) can be deduced to roughly a factor of five by comparing early-time optical data to the model of Rabinak & Waxman (2011), while the progenitor radius cannot be determined based on $R$-band data alone. We find that Type II SN explosion energies span a range of $E/M=(0.2-20)times 10^{51} ; rm{erg/(10 M}_odot$), and have a mean energy per unit mass of $leftlangle E/M rightrangle = 0.85times 10^{51} ; rm{erg/(10 M}_odot$), corrected for Malmquist bias. Assuming a small spread in progenitor masses, this indicates a large intrinsic diversity in explosion energy. Moreover, $E/M$ is positively correlated with the amount of $^{56}rm{Ni}$ produced in the explosion, as predicted by some recent models of core-collapse SNe. We further present several empirical correlations. The peak magnitude is correlated with the decline rate ($Delta m_{15}$), the decline rate is weakly correlated with the rise time, and the rise time is not significantly correlated with the peak magnitude. Faster declining SNe are more luminous and have longer rise times. This limits the possible power sources for such events.
Aims. We present and analyse late-time observations of the type-Ib supernova with possible pre-supernova progenitor detection, iPTF13bvn, taken at $sim$300 days after the explosion, and discuss these in the context of constraints on the supernovas progenitor. Previous studies have proposed two possible natures for the progenitor of the supernova, i.e. a massive Wolf-Rayet star or a lower-mass star in close binary system. Methods. Our observations show that the supernova has entered the nebular phase, with the spectrum dominated by Mg~I]$lambdalambda$4571, [O~I]$lambdalambda$6300, 6364, and [Ca~II]$lambdalambda$7291, 7324 emission lines. We measured the emission line fluxes to estimate the core oxygen mass and compare the [O~I]/[Ca~II] line ratio with other supernovae. Results. The core oxygen mass of the supernova progenitor was estimated to be $lesssim$0.7 M$_odot$, which implies initial progenitor mass not exceeding $sim$15 -- 17 M$_odot$. Since the derived mass is too small for a single star to become a Wolf-Rayet star, this result lends more support to the binary nature of the progenitor star of iPTF13bvn. The comparison of [O~I]/[Ca~II] line ratio with other supernovae also shows that iPTF13bvn appears to be in close association with the lower-mass progenitors of stripped-envelope and type-II supernovae.
We present extensive ultraviolet (UV) and optical photometry, as well as dense optical spectroscopy for type II Plateau (IIP) supernova SN 2016X that exploded in the nearby ($sim$ 15 Mpc) spiral galaxy UGC 08041. The observations span the period from 2 to 180 days after the explosion; in particular, the Swift UV data probably captured the signature of shock breakout associated with the explosion of SN 2016X. It shows very strong UV emission during the first week after explosion, with contribution of $sim$ 20 -- 30% to the bolometric luminosity (versus $lesssim$ 15% for normal SNe IIP). Moreover, we found that this supernova has an unusually long rise time of about 12.6 $pm$ 0.5 days in the $R$ band (versus $sim$ 7.0 days for typical SNe IIP). The optical light curves and spectral evolution are quite similar to the fast-declining type IIP object SN 2013ej, except that SN 2016X has a relatively brighter tail. Based on the evolution of photospheric temperature as inferred from the $Swift$ data in the early phase, we derive that the progenitor of SN 2016X has a radius of about 930 $pm$ 70 R$_{odot}$. This large-size star is expected to be a red supergiant star with an initial mass of $gtrsim$ 19 -- 20 M$_{odot}$ based on the mass $--$ radius relation of the Galactic red supergiants, and it represents one of the most largest and massive progenitors found for SNe IIP.
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