Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userSN 2017czd: A Rapidly Evolving Supernova from a Weak Explosion of a Type IIb Supernova Progenitor
107
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We present optical and near-infrared observations of the rapidly evolving supernova (SN) 2017czd that shows hydrogen features. The optical light curves exhibit a short plateau phase ($sim 13$ days in the $R$-band) followed by a rapid decline by $4.5$ mag in $sim 20 mathrm{days}$ after the plateau. The decline rate is larger than those of any standard SNe, and close to those of rapidly evolving transients. The peak absolute magnitude is $-16.8$ mag in the $V$-band, which is within the observed range for SNe IIP and rapidly evolving transients. The spectra of SN 2017czd clearly show the hydrogen features and resemble those of SNe IIP at first. The H$alpha$ line, however, does not evolve much with time and it becomes similar to those in SNe IIb at decline phase. We calculate the synthetic light curves using a SN IIb progenitor which has 16 M$_{odot}$ at the zero-age main sequence and evolves in a binary system. The model with a low explosion energy ($5times 10^{50}$ erg) and a low ${}^{56}$Ni mass ($0.003 mathrm{M}_{odot}$) can reproduce the short plateau phase as well as the sudden drop of the light curve as observed in SN 2017czd. We conclude that SN 2017czd might be the first identified weak explosion from a SN IIb progenitor. We suggest that some rapidly evolving transients can be explained by such a weak explosion of the progenitors with little hydrogen-rich envelope.
rate research
Read More
ASASSN-18am/SN 2018gk is a newly discovered member of the rare group of luminous, hydrogen-rich supernovae (SNe) with a peak absolute magnitude of $M_V approx -20$ mag that is in between normal core-collapse SNe and superluminous SNe. These SNe show no prominent spectroscopic signatures of ejecta interacting with circumstellar material (CSM), and their powering mechanism is debated. ASASSN-18am declines extremely rapidly for a Type II SN, with a photospheric-phase decline rate of $sim6.0~rm mag~(100 d)^{-1}$. Owing to the weakening of HI and the appearance of HeI in its later phases, ASASSN-18am is spectroscopically a Type IIb SN with a partially stripped envelope. However, its photometric and spectroscopic evolution show significant differences from typical SNe IIb. Using a radiative diffusion model, we find that the light curve requires a high synthesised $rm ^{56}Ni$ mass $M_{rm Ni} sim0.4~M_odot$ and ejecta with high kinetic energy $E_{rm kin} = (7-10) times10^{51} $ erg. Introducing a magnetar central engine still requires $M_{rm Ni} sim0.3~M_odot$ and $E_{rm kin}= 3times10^{51} $ erg. The high $rm ^{56}Ni$ mass is consistent with strong iron-group nebular lines in its spectra, which are also similar to several SNe Ic-BL with high $rm ^{56}Ni$ yields. The earliest spectrum shows flash ionisation features, from which we estimate a mass-loss rate of $ dot{M}approx 2times10^{-4}~rm M_odot~yr^{-1} $. This wind density is too low to power the luminous light curve by ejecta-CSM interaction. We measure expansion velocities as high as $ 17,000 $ km/s for $H_alpha$, which is remarkably high compared to other SNe II. We estimate an oxygen core mass of $1.8-3.4$ $M_odot$ using the [OI] luminosity measured from a nebular-phase spectrum, implying a progenitor with a zero-age main sequence mass of $19-26$ $M_odot$.
We present seven epochs of spectropolarimetry of the Type IIb supernova (SN) 2011dh in M51, spanning 86 days of its evolution. The first epoch was obtained 9 days after the explosion, when the photosphere was still in the depleted hydrogen layer of the stripped-envelope progenitor. Continuum polarization is securely detected at the level of P~0.5% through day 14 and appears to diminish by day 30, which is different from the prevailing trends suggested by studies of other core-collapse SNe. Time-variable modulations in P and position angle are detected across P-Cygni line features. H-alpha and HeI polarization peak after 30 days and exhibit position angles roughly aligned with the earlier continuum, while OI and CaII appear to be geometrically distinct. We discuss several possibilities to explain the evolution of the continuum and line polarization, including the potential effects of a tidally deformed progenitor star, aspherical radioactive heating by fast-rising plumes of Ni-56 from the core, oblique shock breakout, or scattering by circumstellar material. While these possibilities are plausible and guided by theoretical expectations, they are not unique solutions to the data. The construction of more detailed hydrodynamic and radiative-transfer models that incorporate complex aspherical geometries will be required to further elucidate the nature of the polarized radiation from SN 2011dh and other Type IIb supernovae.
We investigate ZTF18aalrxas, a double-peaked Type IIb core-collapse supernova (SN) discovered during science validation of the Zwicky Transient Facility (ZTF). ZTF18aalrxas was discovered while the optical emission was still rising towards the initial cooling peak (0.7 mag over 2 days). Our observations consist of multi-band (UV, optical) light-curves, and optical spectra spanning from $approx0.7$ d to $approx180$ d past the explosion. We use a Monte-Carlo based non-local thermodynamic equilibrium (NLTE) model, that simultanously reproduces both the $rm ^{56}Ni$ powered bolometric light curve and our nebular spectrum. This model is used to constrain the synthesized radioactive nickel mass (0.17 $mathrm{M}_{odot}$) and the total ejecta mass (1.7 $mathrm{M}_{odot}$) of the SN. The cooling emission is modeled using semi-analytical extended envelope models to constrain the progenitor radius ($790-1050$ $mathrm{R}_{odot}$) at the time of explosion. Our nebular spectrum shows signs of interaction with a dense circumstellar medium (CSM), and this spetrum is modeled and analysed to constrain the amount of ejected oxygen ($0.3-0.5$ $mathrm{M}_{odot}$) and the total hydrogen mass ($approx0.15$ $mathrm{M}_{odot}$) in the envelope of the progenitor. The oxygen mass of ZTF18aalrxas is consistent with a low ($12-13$ $mathrm{M}_{odot}$) Zero Age Main Sequence mass progenitor. The light curves and spectra of ZTF18aalrxas are not consistent with massive single star SN Type IIb progenitor models. The presence of an extended hydrogen envelope of low mass, the presence of a dense CSM, the derived ejecta mass, and the late-time oxygen emission can all be explained in a binary model scenario.
We report, for the first time, the detection of the Mn-K$alpha$ line in the Type IIb supernova (SN IIb) remnant, Cassiopeia A. Manganese ($^{55}$Mn after decay of $^{55}$Co), a neutron-rich element, together with chromium ($^{52}$Cr after decay of $^{52}$Fe), is mainly synthesized at the explosive incomplete Si burning regime. Therefore, the Mn/Cr mass ratio with its neutron excess reflects the neutronization at the relevant burning layer during the explosion. Chandras archival X-ray data of Cassiopeia A indicate a low Mn/Cr mass ratio with values in the range 0.10--0.66, which, when compared to one-dimensional SN explosion models, requires that the electron fraction be 0.4990 $lesssim Y_{rm e} lesssim$ 0.5 at the incomplete Si burning layer. An explosion model assuming a solar-metallicity progenitor with a typical explosion energy ($1 times 10^{51}$ erg) fails to reproduce such a high electron fraction. In such models, the explosive Si-burning regime extends only to the Si/O layer established during the progenitors hydrostatic evolution; the $Y_e$ in the Si/O layer is lower than the value required by our observational constraints. We can satisfy the observed Mn/Cr mass ratio if the explosive Si-burning regime were to extend into the O/Ne hydrostatic layer, which has a higher $Y_{rm e}$. This would require an energetic ($> 2 times 10^{51}$ erg) and/or asymmetric explosion of a sub-solar metallicity progenitor ($Z lesssim 0.5Z_{odot}$) for Cassiopeia A. The low initial metallicity can be used to rule out a single-star progenitor, leaving the possibility of a binary progenitor with a compact companion (white dwarf, neutron star or black hole). We discuss the detectability of X-rays from Bondi accretion onto such a compact companion around the explosion site. We also discuss other possible mass-loss scenarios for the progenitor system of Cassiopeia A.
We present the discovery, photometric and spectroscopic follow-up observations of SN 2010X (PTF 10bhp). This supernova decays exponentially with tau_d=5 days, and rivals the current recordholder in speed, SN 2002bj. SN 2010X peaks at M_r=-17mag and has mean velocities of 10,000 km/s. Our light curve modeling suggests a radioactivity powered event and an ejecta mass of 0.16 Msun. If powered by Nickel, we show that the Nickel mass must be very small (0.02 Msun) and that the supernova quickly becomes optically thin to gamma-rays. Our spectral modeling suggests that SN 2010X and SN 2002bj have similar chemical compositions and that one of Aluminum or Helium is present. If Aluminum is present, we speculate that this may be an accretion induced collapse of an O-Ne-Mg white dwarf. If Helium is present, all observables of SN 2010X are consistent with being a thermonuclear Helium shell detonation on a white dwarf, a .Ia explosion. With the 1-day dynamic-cadence experiment on the Palomar Transient Factory, we expect to annually discover a few such events.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
