Hae
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Optical follow-up of the tidal disruption event iPTF16fnl: new insights from X-shooter observations
We present the results from Nordic Optical Telescope and X-shooter follow-up campaigns of the tidal disruption event (TDE) iPTF16fnl, covering the first similar to 100 d after the transient discovery. We followed the source ...
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 ...
The lowest-metallicity type II supernova from the highest-mass red supergiant progenitor
Red supergiants have been confirmed as the progenitor stars of the majority of hydrogen-rich type II supernovae(1). However, while such stars are observed with masses > 25 M-circle dot (ref. (2)), detections of > 18 M-circle ...
Extreme variability in an active galactic nucleus: Gaia16aax
We present the results of a multiwavelength follow-up campaign for the luminous nuclear transient Gaia16aax, which was first identified in 2016 January. The transient is spatially consistent with the nucleus of an active ...
SN 2013ai: A Link between Hydrogen-rich and Hydrogen-poor Core-collapse Supernovae
We present a study of the optical and near-infrared (NIR) spectra of SN
2013ai along with its light curves. These data range from discovery
until 380 days after explosion. SN 2013ai is a fast declining Type II
supernova ...
Evidence for rapid disc formation and reprocessing in the X-ray bright tidal disruption event candidate AT 2018fyk
We present optical spectroscopic and Swift UVOT/XRT observations of the X-ray and UV/optical bright tidal disruption event (TDE) candidate AT 2018fyk/ASASSN-18ul discovered by ASAS-SN. The Swift light curve is atypical for ...
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 ...
Transient-optimized real-bogus classification with Bayesian convolutional neural networks - sifting the GOTO candidate stream
Large-scale sky surveys have played a transformative role in our understanding of astrophysical transients, only made possible by increasingly powerful machine learning-based filtering to accurately sift through the vast ...
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 ...