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  • Oxford University Press (OUP)  (10)
  • Gromadzki, M  (10)
  • Nicholl, M  (10)
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  • Oxford University Press (OUP)  (10)
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  • 1
    Online Resource
    Online Resource
    Photometric and spectroscopic evolution of the interacting transient AT 2016jbu(Gaia16cfr)
    Oxford University Press (OUP) ; 2022
    In:  Monthly Notices of the Royal Astronomical Society Vol. 513, No. 4 ( 2022-05-27), p. 5642-5665
    Details
    In: Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP), Vol. 513, No. 4 ( 2022-05-27), p. 5642-5665
    Abstract: We present the results from a high-cadence, multiwavelength observation campaign of AT 2016jbu (aka Gaia16cfr), an interacting transient. This data set complements the current literature by adding higher cadence as well as extended coverage of the light-curve evolution and late-time spectroscopic evolution. Photometric coverage reveals that AT 2016jbu underwent significant photometric variability followed by two luminous events, the latter of which reached an absolute magnitude of MV ∼ −18.5 mag. This is similar to the transient SN 2009ip whose nature is still debated. Spectra are dominated by narrow emission lines and show a blue continuum during the peak of the second event. AT 2016jbu shows signatures of a complex, non-homogeneous circumstellar material (CSM). We see slowly evolving asymmetric hydrogen line profiles, with velocities of 500 km s−1 seen in narrow emission features from a slow-moving CSM, and up to 10 000 km s−1 seen in broad absorption from some high-velocity material. Late-time spectra (∼+1 yr) show a lack of forbidden emission lines expected from a core-collapse supernova and are dominated by strong emission from H, He i, and Ca ii. Strong asymmetric emission features, a bumpy light curve, and continually evolving spectra suggest an inhibit nebular phase. We compare the evolution of H α among SN 2009ip-like transients and find possible evidence for orientation angle effects. The light-curve evolution of AT 2016jbu suggests similar, but not identical, circumstellar environments to other SN 2009ip-like transients.
    Type of Medium: Online Resource
    ISSN: 0035-8711 , 1365-2966
    URL: Article
    DOI: 10.1093/mnras/stac1243
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2022
    detail.hit.zdb_id: 2016084-7
    SSG: 16,12
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  • 2
    Online Resource
    Online Resource
    Progenitor, environment, and modelling of the interacting transient AT 2016jbu (Gaia16cfr)
    Oxford University Press (OUP) ; 2022
    In:  Monthly Notices of the Royal Astronomical Society Vol. 513, No. 4 ( 2022-05-27), p. 5666-5685
    Details
    In: Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP), Vol. 513, No. 4 ( 2022-05-27), p. 5666-5685
    Abstract: We present the bolometric light curve, identification and analysis of the progenitor candidate, and preliminary modelling of AT 2016jbu (Gaia16cfr). We find a progenitor consistent with a ∼ 22–25 M⊙ yellow hypergiant surrounded by a dusty circumstellar shell, in agreement with what has been previously reported. We see evidence for significant photometric variability in the progenitor, as well as strong Hα emission consistent with pre-existing circumstellar material. The age of the environment, as well as the resolved stellar population surrounding AT 2016jbu, supports a progenitor age of & gt;10 Myr, consistent with a progenitor mass of ∼22 M⊙. A joint analysis of the velocity evolution of AT 2016jbu and the photospheric radius inferred from the bolometric light curve shows the transient is consistent with two successive outbursts/explosions. The first outburst ejected material with velocity ∼650 km s−1, while the second, more energetic event ejected material at ∼4500 km s−1. Whether the latter is the core collapse of the progenitor remains uncertain. We place a limit on the ejected 56Ni mass of & lt;0.016 M⊙. Using the Binary Population And Spectral Synthesis (BPASS) code, we explore a wide range of possible progenitor systems and find that the majority of these are in binaries, some of which are undergoing mass transfer or common-envelope evolution immediately prior to explosion. Finally, we use the SuperNova Explosion Code (SNEC) to demonstrate that the low-energy explosions within some of these binary systems, together with sufficient circumstellar material, can reproduce the overall morphology of the light curve of AT 2016jbu.
    Type of Medium: Online Resource
    ISSN: 0035-8711 , 1365-2966
    URL: Article
    DOI: 10.1093/mnras/stac1228
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2022
    detail.hit.zdb_id: 2016084-7
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  • 3
    Online Resource
    Online Resource
    DES16C3cje: A low-luminosity, long-lived supernova
    Oxford University Press (OUP) ; 2020
    In:  Monthly Notices of the Royal Astronomical Society Vol. 496, No. 1 ( 2020-07-21), p. 95-110
    Details
    In: Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP), Vol. 496, No. 1 ( 2020-07-21), p. 95-110
    Abstract: We present DES16C3cje, a low-luminosity, long-lived type II supernova (SN II) at redshift 0.0618, detected by the Dark Energy Survey (DES). DES16C3cje is a unique SN. The spectra are characterized by extremely narrow photospheric lines corresponding to very low expansion velocities of ≲1500 km s−1, and the light curve shows an initial peak that fades after 50 d before slowly rebrightening over a further 100 d to reach an absolute brightness of Mr ∼ −15.5 mag. The decline rate of the late-time light curve is then slower than that expected from the powering by radioactive decay of 56Co, but is comparable to that expected from accretion power. Comparing the bolometric light curve with hydrodynamical models, we find that DES16C3cje can be explained by either (i) a low explosion energy (0.11 foe) and relatively large 56Ni production of 0.075 M⊙ from an ∼15 M⊙ red supergiant progenitor typical of other SNe II, or (ii) a relatively compact ∼40 M⊙ star, explosion energy of 1 foe, and 0.08 M⊙ of 56Ni. Both scenarios require additional energy input to explain the late-time light curve, which is consistent with fallback accretion at a rate of ∼0.5 × 10−8 M⊙ s−1.
    Type of Medium: Online Resource
    ISSN: 0035-8711 , 1365-2966
    URL: Article
    DOI: 10.1093/mnras/staa1452
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2020
    detail.hit.zdb_id: 2016084-7
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  • 4
    Online Resource
    Online Resource
    GRB 171010A/SN 2017htp: a GRB-SN at z = 0.33
    Oxford University Press (OUP) ; 2019
    In:  Monthly Notices of the Royal Astronomical Society Vol. 490, No. 4 ( 2019-12-21), p. 5366-5374
    Details
    In: Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP), Vol. 490, No. 4 ( 2019-12-21), p. 5366-5374
    Abstract: The number of supernovae known to be connected with long-duration gamma-ray bursts (GRBs) is increasing and the link between these events is no longer exclusively found at low redshift (z ≲ 0.3) but is well established also at larger distances. We present a new case of such a liaison at z = 0.33 between GRB 171010A and SN 2017htp. It is the second closest GRB with an associated supernova of only three events detected by Fermi-LAT. The supernova is one of the few higher redshift cases where spectroscopic observations were possible and shows spectral similarities with the well-studied SN 1998bw, having produced a similar Ni mass ($M_{\rm Ni}=0.33\pm 0.02 ~\rm {M_{\odot }}$) with slightly lower ejected mass ($M_{\rm ej}=4.1\pm 0.7~\rm {M_{\odot }}$) and kinetic energy ($E_{\rm K} = 8.1\pm 2.5 \times 10^{51} ~\rm {erg}$). The host-galaxy is bigger in size than typical GRB host galaxies, but the analysis of the region hosting the GRB revealed spectral properties typically observed in GRB hosts and showed that the progenitor of this event was located in a very bright H ii region of its face-on host galaxy, at a projected distance of ∼ 10 kpc from its galactic centre. The star-formation rate (SFRGRB ∼ 0.2 M⊙ yr−1) and metallicity (12  + log(O/H) ∼8.15 ± 0.10) of the GRB star-forming region are consistent with those of the host galaxies of previously studied GRB–SN systems.
    Type of Medium: Online Resource
    ISSN: 0035-8711 , 1365-2966
    URL: Article
    DOI: 10.1093/mnras/stz2900
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2019
    detail.hit.zdb_id: 2016084-7
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  • 5
    Online Resource
    Online Resource
    SN 2017ivv: two years of evolution of a transitional Type II supernova
    Oxford University Press (OUP) ; 2020
    In:  Monthly Notices of the Royal Astronomical Society Vol. 499, No. 1 ( 2020-10-13), p. 974-992
    Details
    In: Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP), Vol. 499, No. 1 ( 2020-10-13), p. 974-992
    Abstract: We present the photometric and spectroscopic evolution of the Type II supernova (SN II) SN 2017ivv (also known as ASASSN-17qp). Located in an extremely faint galaxy (Mr = −10.3 mag), SN 2017ivv shows an unprecedented evolution during the 2 yr of observations. At early times, the light curve shows a fast rise (∼6−8 d) to a peak of ${\it M}^{\rm max}_{g}= -17.84$ mag, followed by a very rapid decline of 7.94 ± 0.48 mag per 100 d in the V band. The extensive photometric coverage at late phases shows that the radioactive tail has two slopes, one steeper than that expected from the decay of 56Co (between 100 and 350 d), and another slower (after 450 d), probably produced by an additional energy source. From the bolometric light curve, we estimated that the amount of ejected 56Ni is ∼0.059 ± 0.003 M⊙. The nebular spectra of SN 2017ivv show a remarkable transformation that allows the evolution to be split into three phases: (1) Hα strong phase ( & lt;200 d); (2) Hα weak phase (between 200 and 350 d); and (3) Hα broad phase ( & gt;500 d). We find that the nebular analysis favours a binary progenitor and an asymmetric explosion. Finally, comparing the nebular spectra of SN 2017ivv to models suggests a progenitor with a zero-age main-sequence mass of 15–17 M⊙.
    Type of Medium: Online Resource
    ISSN: 0035-8711 , 1365-2966
    URL: Article
    DOI: 10.1093/mnras/staa2763
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2020
    detail.hit.zdb_id: 2016084-7
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  • 6
    Online Resource
    Online Resource
    Close, bright, and boxy: the superluminous SN 2018hti
    Oxford University Press (OUP) ; 2022
    In:  Monthly Notices of the Royal Astronomical Society Vol. 512, No. 3 ( 2022-04-07), p. 4484-4502
    Details
    In: Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP), Vol. 512, No. 3 ( 2022-04-07), p. 4484-4502
    Abstract: SN 2018hti was a very nearby (z = 0.0614) superluminous supernova with an exceedingly bright absolute magnitude of −21.7 mag in r band at maximum. The densely sampled pre-maximum light curves of SN 2018hti show a slow luminosity evolution and constrain the rise time to ∼50 rest-frame d. We fitted synthetic light curves to the photometry to infer the physical parameters of the explosion of SN 2018hti for both the magnetar and the CSM-interaction scenarios. We conclude that one of two mechanisms could be powering the luminosity of SN 2018hti; interaction with ∼10 M⊙ of circumstellar material or a magnetar with a magnetic field of Bp∼ 1.3 × 1013 G, and initial period of Pspin∼ 1.8 ms. From the nebular spectrum modelling we infer that SN 2018hti likely results from the explosion of a ${\sim}40\, \mathrm{M}_\odot$ progenitor star.
    Type of Medium: Online Resource
    ISSN: 0035-8711 , 1365-2966
    URL: Article
    DOI: 10.1093/mnras/stac744
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2022
    detail.hit.zdb_id: 2016084-7
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  • 7
    Online Resource
    Online Resource
    The tidal disruption event AT 2018hyz – I. Double-peaked emission lines and a flat Balmer decrement
    Oxford University Press (OUP) ; 2020
    In:  Monthly Notices of the Royal Astronomical Society Vol. 498, No. 3 ( 2020-09-24), p. 4119-4133
    Details
    In: Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP), Vol. 498, No. 3 ( 2020-09-24), p. 4119-4133
    Abstract: We present results from spectroscopic observations of AT 2018hyz, a transient discovered by the All-Sky Automated Survey for Supernova survey at an absolute magnitude of MV ∼ −20.2 mag, in the nucleus of a quiescent galaxy with strong Balmer absorption lines. AT 2018hyz shows a blue spectral continuum and broad emission lines, consistent with previous TDE candidates. High cadence follow-up spectra show broad Balmer lines and He i in early spectra, with He ii making an appearance after ∼70–100 d. The Balmer lines evolve from a smooth broad profile, through a boxy, asymmetric double-peaked phase consistent with accretion disc emission, and back to smooth at late times. The Balmer lines are unlike typical active galactic nucleus in that they show a flat Balmer decrement (Hα/Hβ ∼ 1.5), suggesting the lines are collisionally excited rather than being produced via photoionization. The flat Balmer decrement together with the complex profiles suggests that the emission lines originate in a disc chromosphere, analogous to those seen in cataclysmic variables. The low optical depth of material due to a possible partial disruption may be what allows us to observe these double-peaked, collisionally excited lines. The late appearance of He ii may be due to an expanding photosphere or outflow, or late-time shocks in debris collisions.
    Type of Medium: Online Resource
    ISSN: 0035-8711 , 1365-2966
    URL: Article
    DOI: 10.1093/mnras/staa2065
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2020
    detail.hit.zdb_id: 2016084-7
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  • 8
    Online Resource
    Online Resource
    Transitional events in the spectrophotometric regime between stripped envelope and superluminous supernovae
    Oxford University Press (OUP) ; 2021
    In:  Monthly Notices of the Royal Astronomical Society Vol. 508, No. 3 ( 2021-10-22), p. 4342-4358
    Details
    In: Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP), Vol. 508, No. 3 ( 2021-10-22), p. 4342-4358
    Abstract: The division between stripped-envelope supernovae (SE-SNe) and superluminous supernovae (SLSNe) is not well-defined in either photometric or spectroscopic space. While a sharp luminosity threshold has been suggested, there remains an increasing number of transitional objects that reach this threshold without the spectroscopic signatures common to SLSNe. In this work, we present data and analysis on four SNe transitional between SE-SNe and SLSNe; the He-poor SNe 2019dwa and 2019cri, and the He-rich SNe 2019hge and 2019unb. Each object displays long-lived and variable photometric evolution with luminosities around the SLSN threshold of Mr & lt; −19.8 mag. Spectroscopically however, these objects are similar to SE-SNe, with line velocities lower than either SE-SNe and SLSNe, and thus represent an interesting case of rare transitional events.
    Type of Medium: Online Resource
    ISSN: 0035-8711 , 1365-2966
    URL: Article
    DOI: 10.1093/mnras/stab2864
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2021
    detail.hit.zdb_id: 2016084-7
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  • 9
    Online Resource
    Online Resource
    PS15cey and PS17cke: prospective candidates from the Pan-STARRS Search for kilonovae
    Oxford University Press (OUP) ; 2020
    In:  Monthly Notices of the Royal Astronomical Society Vol. 500, No. 3 ( 2020-12-07), p. 4213-4228
    Details
    In: Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP), Vol. 500, No. 3 ( 2020-12-07), p. 4213-4228
    Abstract: Time domain astronomy was revolutionized with the discovery of the first kilonova, AT2017gfo, in August 2017, which was associated with the gravitational wave signal GW170817. Since this event, numerous wide-field surveys have been optimizing search strategies to maximize their efficiency of detecting these fast and faint transients. With the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS), we have been conducting a volume-limited survey for intrinsically faint and fast-fading events to a distance of D ≃ 200 Mpc. Two promising candidates have been identified from this archival search, with sparse data – PS15cey and PS17cke. Here, we present more detailed analysis and discussion of their nature. We observe that PS15cey was a luminous, fast-declining transient at 320 Mpc. Models of BH–NS mergers with a very stiff equation of state could possibly reproduce the luminosity and decline but the physical parameters are extreme. A more likely scenario is that this was an AT2018kzr-like merger event. PS17cke was a faint and fast-declining event at 15 Mpc. We explore several explosion scenarios of this transient including models of it as a NS–NS and BH–NS merger, the outburst of a massive luminous star, and compare it against other known fast-fading transients. Although there is uncertainty in the explosion scenario due to difficulty in measuring the explosion epoch, we find PS17cke to be a plausible kilonova candidate from the model comparisons.
    Type of Medium: Online Resource
    ISSN: 0035-8711 , 1365-2966
    URL: Article
    DOI: 10.1093/mnras/staa3361
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2020
    detail.hit.zdb_id: 2016084-7
    SSG: 16,12
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  • 10
    Online Resource
    Online Resource
    Evidence for rapid disc formation and reprocessing in the X-ray bright tidal disruption event candidate AT 2018fyk
    Oxford University Press (OUP) ; 2019
    In:  Monthly Notices of the Royal Astronomical Society Vol. 488, No. 4 ( 2019-10-01), p. 4816-4830
    Details
    In: Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP), Vol. 488, No. 4 ( 2019-10-01), p. 4816-4830
    Abstract: 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 a TDE, entering a plateau after ∼40 d of decline from peak. After 80 d the UV/optical light curve breaks again to decline further, while the X-ray emission becomes brighter and harder. In addition to broad H, He, and potentially O/Fe lines, narrow emission lines emerge in the optical spectra during the plateau phase. We identify both high-ionization (O iii) and low-ionization (Fe ii) lines, which are visible for ∼45 d. We similarly identify Fe ii lines in optical spectra of ASASSN–15oi 330 d after discovery, indicating that a class of Fe-rich TDEs exists. The spectral similarity between AT 2018fyk, narrow-line Seyfert 1 galaxies, and some extreme coronal line emitters suggests that TDEs are capable of creating similar physical conditions in the nuclei of galaxies. The Fe ii lines can be associated with the formation of a compact accretion disc, as the emergence of low-ionization emission lines requires optically thick, high-density gas. Taken together with the plateau in X-ray and UV/optical luminosity this indicates that emission from the central source is efficiently reprocessed into UV/optical wavelengths. Such a two-component light curve is very similar to that seen in the TDE candidate ASASSN–15lh, and is a natural consequence of a relativistic orbital pericentre.
    Type of Medium: Online Resource
    ISSN: 0035-8711 , 1365-2966
    URL: Article
    DOI: 10.1093/mnras/stz1976
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2019
    detail.hit.zdb_id: 2016084-7
    SSG: 16,12
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