Hae
Aineistot 1-10 / 11
A kilonova as the electromagnetic counterpart to a gravitational-wave source
Gravitational waves were discovered with the detection of binary black-hole mergers(1) and they should also be detectable from lower-mass neutron-star mergers. These are predicted to eject material rich in heavy radioactive ...
Gaia17biu/SN 2017egm in NGC 3191: The Closest Hydrogen-poor Superluminous Supernova to Date Is in a "Normal," Massive, Metal-rich Spiral Galaxy
Hydrogen-poor superluminous supernovae (SLSNe-I) have been predominantly found in low-metallicity, star-forming dwarf galaxies. Here we identify Gaia17biu/SN 2017egm as an SLSN-I occurring in a "normal" spiral galaxy (NGC ...
ASASSN-18am/SN 2018gk: an overluminous Type IIb supernova from a massive progenitor
<p>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<sub>V</sub> ≈ -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 ∼6.0 mag (100 d)<sup>-1</sup>. Owing to the weakening of H I and the appearance of He I in its later phases, ASASSN-18am is spectroscopically a Type IIb SN with a partially stripped envelope. However, its photometric and spectroscopic evolution shows significant differences from typical SNe IIb. Using a radiative diffusion model, we find that the light curve requires a high synthesized <sup>56</sup>Ni mass M<sub>Ni</sub> ∼0.4 M<sub>⊙</sub> and ejecta with high kinetic energy E<sub>kin</sub> = (7-10) x 10<sup>51</sup> erg. Introducing a magnetar central engine still requires M<sub>Ni</sub> ∼0.3 M<sub>⊙</sub> and E-kin = 3 x 10<sup>51</sup> erg. The high <sup>56</sup>Ni mass is consistent with strong iron-group nebular lines in its spectra, which are also similar to several SNe Ic-BL with high <sup>56</sup>Ni yields. The earliest spectrum shows 'flash ionization' features, from which we estimate a mass-loss rate of Ṁ ≈ 2 x 10<sup>-4</sup> M<sub>⊙</sub> yr<sup>-1</sup>. 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<sup>-1</sup> for Hα, which is remarkably high compared to other SNe II. We estimate an oxygen core mass of 1.8-3.4 M<sub>⊙</sub> using the [O I] luminosity measured from a nebular-phase spectrum, implying a progenitor with a zero-age main-sequence mass of 19-26 M<sub>⊙</sub>.</p>...
SN 2016gsd: an unusually luminous and linear Type II supernova with high velocities
We present observations of the unusually luminous Type II supernova (SN) 2016gsd. With a peak absolute magnitude of V = -19.95 +/- 0.08, this object is one of the brightest Type II SNe, and lies in the gap of magnitudes ...
SN 2020wnt: a slow-evolving carbon-rich superluminous supernova with no O II lines and a bumpy light curve
We present the analysis of SN 2020wnt, an unusual hydrogen-poor superluminous supernova (SLSN-I), at a redshift of 0.032. The light curves of SN 2020wnt are characterized by an early bump lasting similar to 5 d, followed ...
Low-luminosity Type II supernovae - III. SN 2018hwm, a faint event with an unusually long plateau
<p>In this work, we present photometric and spectroscopic data of the low-luminosity (LL) Type IIP supernova (SN) 2018hwm. The object shows a faint (M<sub>r</sub> = -15 mag) and very long (~ 130 d) plateau, followed by a 2.7 mag drop in the r band to the radioactive tail. The first spectrum shows a blue continuum with narrow Balmer lines, while during the plateau the spectra show numerous metal lines, all with strong and narrow P-Cygni profiles. The expansion velocities are low, in the 1000-1400 km s<sup>-1</sup> range. The nebular spectrum, dominated by H α in emission, reveals weak emission from [O I] and [Ca II] doublets. The absolute light curve and spectra at different phases are similar to those of LL SNe IIP. We estimate that 0.002 M<sub>⊙</sub> of <sup>56</sup>Ni mass were ejected, through hydrodynamical simulations. The best fit of the model to the observed data is found for an extremely low explosion energy of 0.055 foe, a progenitor radius of 215 R<sub>⊙</sub>, and a final progenitor mass of 9-10 M<sub>⊙</sub>. Finally, we performed a modelling of the nebular spectrum, to establish the amount of oxygen and calcium ejected. We found a low M(<sup>16</sup>O)≈ 0.02M<sub>⊙</sub>, but a high M(<sup>40</sup>Ca) of 0.3 M<sub>⊙</sub>. The inferred low explosion energy, the low ejected <sup>56</sup>Ni mass, and the progenitor parameters, along with peculiar features observed in the nebular spectrum, are consistent with both an electron-capture SN explosion of a superasymptotic giant branch star and with a low-energy, Ni-poor iron core-collapse SN from a 10-12 M<sub>⊙</sub> red supergiant.</p>...
The First Data Release of CNIa0.02-A Complete Nearby (Redshift <0.02) Sample of Type Ia Supernova Light Curves*
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 double-peaked Type Ic supernova 2019cad: another SN 2005bf-like object
We present the photometric and spectroscopic evolution of supernova (SN) 2019cad during the first similar to 100 d from explosion. Based on the light-curve morphology, we find that SN 2019cad resembles the double-peaked ...
AT 2017be-a new member of the class of intermediate-luminosity red transients
We report the results of our spectrophotometric monitoring campaign for AT 2017be in NGC 2537. Its light curve reveals a fast rise to an optical maximum, followed by a plateau lasting about 30 d, and finally a fast decline. ...
COMMON ENVELOPE EJECTION FOR A LUMINOUS RED NOVA IN M101
We present the results of optical, near-infrared, and mid-infrared observations of M101 OT2015-1 (PSN J14021678+ 5426205), a luminous red transient in the Pinwheel galaxy (M101), spanning a total of 16 years. The light ...