The Low-luminosity Type IIP Supernova 2016bkv with Early-phase Circumstellar Interaction (original) (raw)
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SN 2016esw: a luminous Type II supernova observed within the first day after the explosion
Monthly Notices of the Royal Astronomical Society, 2018
We present photometry, spectroscopy, and host-galaxy integral-field spectroscopy of the Type II supernova (SN II) 2016esw in CGCG 229-009 from the first day after the explosion up to 120 d. Its light-curve shape is similar to that of a typical SN II; however, SN 2016esw is near the high-luminosity end of the SN II distribution, with a peak of M max V = −18.36 mag. The V-band light curve exhibits a long recombination phase for a SN II (similar to the longlived plateau of SN 2004et). Considering the well-known relation between the luminosity and the plateau decline rate, SN 2016esw should have a V-band slope of ∼2.10 mag (100 d) −1 ; however, SN 2016esw has a substantially flatter plateau with a slope of 1.01 ± 0.26 mag (100 d) −1 , perhaps indicating that interacting Type II supernovae are not useful for cosmology. At 19.5 d post-explosion, the spectrum presents a boxy H α emission line with flat absorption profiles, suggesting interaction between the ejecta and circumstellar matter. Finally, based on the spectral properties, SN 2016esw shows similarities with the luminous and interacting SN 2007pk at early epochs, particularly in terms of observable line features and their evolution.
The Astrophysical Journal, 2008
SN 2006tf is the third most luminous supernova (SN) discovered so far, after SN 2005ap and SN 2006gy. SN 2006tf is valuable because it provides a link between two regimes: (1) luminous type IIn supernovae powered by emission directly from interaction with circumstellar material (CSM), and (2) the most extremely luminous SNe where the CSM interaction is so optically thick that energy must diffuse out from an opaque shocked shell. As SN 2006tf evolves, it slowly transitions from the second to the first regime as the clumpy shell becomes more porous. This link suggests that the range in properties of the most luminous SNe is largely determined by the density and speed of hydrogen-rich material ejected shortly before they explode. The total energy radiated by SN 2006tf was at least 7 × 10 50 ergs. If the bulk of this luminosity came from the thermalization of shock kinetic energy, then the star needs to have ejected ∼18 M ⊙ in the 4-8 yr before core collapse, and another 2-6 M ⊙ in the decades before that. A Type Ia explosion is therefore excluded. From the Hα emission-line profile, we derive a blast-wave speed of 2,000 km s −1 that does not decelerate, and from the narrow P Cygni absorption from pre-shock gas we deduce that the progenitor's wind speed was ∼190 km s −1. This is reminiscent of the wind speeds of luminous blue variables (LBVs), but not of red supergiants or Wolf-Rayet stars. We propose that like SN 2006gy, SN 2006tf marked the death of a very massive star that retained a hydrogen envelope until the end of its life, and suffered extreme LBV-like mass loss in the decades before it exploded.
SN 2008in—BRIDGING THE GAP BETWEEN NORMAL AND FAINT SUPERNOVAE OF TYPE IIP
The Astrophysical Journal, 2011
We present optical photometric and low-resolution spectroscopic observations of the Type II plateau supernova (SN) 2008in, which occurred in the outskirts of the nearly face-on spiral galaxy M 61. Photometric data in the X-rays, ultraviolet and near-infrared bands have been used to characterize this event. The SN field was imaged with the ROTSE-IIIb optical telescope about seven days before the explosion. This allowed us to constrain the epoch of the shock breakout to JD = 2454825.6. The duration of the plateau phase, as derived from the photometric monitoring, was ∼ 98 days. The spectra of SN 2008in show a striking resemblance to those of the archetypal low-luminosity IIP SNe 1997D and 1999br. A comparison of ejecta kinematics of SN 2008in with the hydrodynamical simulations of Type IIP SNe by indicates that it is a less energetic event (∼ 5 × 10 50 erg). However, the light curve indicates that the production of radioactive 56 Ni is significantly higher than that in the low-luminosity SNe. Adopting an interstellar absorption along the SN direction of A V ∼ 0.3 mag and a distance of 13.2 Mpc, we estimated a synthesized 56 Ni mass of ∼ 0.015M ⊙ . Employing semi-analytical formulae (Litvinova & Nadezhin 1985), we derived a pre-SN radius of ∼ 126R ⊙ , an explosion energy of ∼ 5.4 × 10 50 erg and a total ejected mass of ∼ 16.7M ⊙ . The latter indicates that the zero age main-sequence mass of the progenitor did not exceed 20M ⊙ . Considering the above properties of SN 2008in and its occurrence in a region of sub-solar metallicity ([O/H] ∼ 8.44 dex), it is unlikely that fall-back of the ejecta onto a newly formed black hole occurred in SN 2008in. We therefore favor a low-energy explosion scenario of a relatively compact, moderate-mass progenitor star that generates a neutron star.
SN 2015ba: a Type IIP supernova with a long plateau
Monthly Notices of the Royal Astronomical Society
We present optical photometry and spectroscopy from about a week after explosion to ∼272 d of an atypical Type IIP supernova, SN 2015ba, which exploded in the edge-on galaxy IC 1029. SN 2015ba is a luminous event with an absolute V-band magnitude of −17.1 ± 0.2 mag at 50 d since explosion and has a long plateau lasting for ∼123 d. The distance to the SN is estimated to be 34.8 ± 0.7 Mpc using the expanding photosphere and standard candle methods. High-velocity H Balmer components constant with time are observed in the late-plateau phase spectra of SN 2015ba, which suggests a possible role of circumstellar interaction at these phases. Both hydrodynamical and analytical modelling suggest a massive progenitor of SN 2015ba with a pre-explosion mass of 24-26 M. However, the nebular spectra of SN 2015ba exhibit insignificant levels of oxygen, which is otherwise expected from a massive progenitor. This might be suggestive of the non-monotonical link between O-core masses and the zero-age main sequence mass of pre-supernova stars and/or uncertainties in the mixing scenario in the ejecta of supernovae.
SN 2017dio: A Type-Ic Supernova Exploding in a Hydrogen-rich Circumstellar Medium
The Astrophysical Journal, 2018
SN 2017dio shows both spectral characteristics of a type-Ic supernova (SN) and signs of a hydrogen-rich circumstellar medium (CSM). Prominent, narrow emission lines of H and He are superposed on the continuum. Subsequent evolution revealed that the SN ejecta are interacting with the CSM. The initial SN Ic identification was confirmed by removing the CSM interaction component from the spectrum and comparing with known SNe Ic, and reversely, adding a CSM interaction component to the spectra of known SNe Ic and comparing them to SN 2017dio. Excellent agreement was obtained with both procedures, reinforcing the SN Ic classification. The light curve constrains the pre-interaction SN Ic peak absolute magnitude to be around M g = −17.6 mag. No evidence of significant extinction is found, ruling out a brighter luminosity required by a SN Ia classification. These pieces of evidence support the view that SN 2017dio is a SN Ic, and therefore the first firm case of a SN Ic with signatures of hydrogen-rich CSM in the early spectrum. The CSM is unlikely to have been shaped by steady-state stellar winds. The mass loss of the progenitor star must have been intense,Ṁ ∼ 0.02 (ǫ Hα /0.01) −1 (v wind /500 km s −1) (v shock /10000 km s −1) −3 M ⊙ yr −1 , peaking at a few decades before the SN. Such a high mass loss rate might have been experienced by the progenitor through eruptions or binary stripping.
The Astrophysical Journal
We present detailed observations of ZTF18abukavn (SN2018gep), discovered in high-cadence data from the Zwicky Transient Facility as a rapidly rising (1.4 ± 0.1 mag/hr) and luminous (M g,peak = −20 mag) transient. It is spectroscopically classified as a broad-lined stripped-envelope supernova (Ic-BL SN). The high peak luminosity (L bol 3×10 44 erg s −1), the short rise time (t rise = 3 day in g-band), and the blue colors at peak (g −r ∼ −0.4) all resemble the high-redshift Ic-BL iPTF16asu, as well as several other unclassified fast transients. The early discovery of SN2018gep (within an hour of shock breakout) enabled an intensive spectroscopic campaign, including the highest-temperature (T eff 40, 000K)
SN 2009ib: a Type II-P supernova with an unusually long plateau
Monthly Notices of the Royal Astronomical Society, 2015
We present optical and near-infrared photometry and spectroscopy of SN 2009ib, a Type II-P supernova in NGC 1559. This object has moderate brightness, similar to those of the intermediate-luminosity SNe 2008in and 2009N. Its plateau phase is unusually long, lasting for about 130 d after explosion. The spectra are similar to those of the subluminous SN 2002gd, with moderate expansion velocities. We estimate the 56 Ni mass produced as 0.046 ± 0.015 M. We determine the distance to SN 2009ib using both the expanding photosphere method (EPM) and the standard candle method. We also apply EPM to SN 1986L, a Type II-P SN that exploded in the same galaxy. Combining the results of different methods, we conclude the distance to NGC 1559 as D = 19.8 ± 3.0 Mpc. We examine archival, pre-explosion images of the field taken with the Hubble Space Telescope, and find a faint source at the position of the SN, which has a yellow colour [(V − I) 0 = 0.85 mag]. Assuming it is a single star, we estimate its initial mass as M ZAMS = 20 M. We also examine the possibility, that instead of the yellow source the progenitor of SN 2009ib is a red supergiant star too faint to be detected. In this case, we estimate the upper limit for the initial zero-age main sequence (ZAMS) mass of the progenitor to be ∼14-17 M. In addition, we infer the physical properties of the progenitor at the explosion via hydrodynamical modelling of the observables, and estimate the total energy as ∼0.55 × 10 51 erg, the pre-explosion radius as ∼400 R , and the ejected envelope mass as ∼15 M , which implies that the mass of the progenitor before explosion was ∼16.5-17 M .
SN 2017gmr: An Energetic Type II-P Supernova with Asymmetries
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We present high-cadence ultraviolet (UV), optical, and near-infrared (NIR) data on the luminous Type II-P supernova SN 2017gmr from hours after discovery through the first 180 days. SN 2017gmr does not show signs of narrow, high-ionization emission lines in the early optical spectra, yet the optical lightcurve evolution suggests that an extra energy source from circumstellar medium (CSM) interaction must be present for at least 2 days after explosion. Modeling of the early lightcurve indicates a ∼ 500R ⊙ progenitor radius, consistent with a rather compact red supergiant, and late-time luminosities indicate up to 0.130 ± 0.026 M ⊙ of 56 Ni are present, if the lightcurve is solely powered by radioactive decay, although the 56 Ni mass may be lower if CSM interaction contributes to the post-plateau luminosity. Prominent multi-peaked emission lines of Hα and [O I] emerge after day 154, as a result of either an asymmetric explosion or asymmetries in the CSM. The lack of narrow lines within the first two days of explosion in the likely presence of CSM interaction may be an example of close, dense, asymmetric CSM that is quickly enveloped by the spherical supernova ejecta.
Monthly Notices of the Royal Astronomical Society, 2016
Spectrophotometry of SN 1996al carried out throughout 15 yr is presented. The early photometry suggests that SN 1996al is a linear Type II supernova, with an absolute peak of M V ∼ −18.2 mag. Early spectra present broad asymmetric Balmer emissions, with superimposed narrow lines with P-Cygni profile, and He I features with asymmetric broad emission components. The analysis of the line profiles shows that the H and He broad components form in the same region of the ejecta. By day +142, the Hα profile dramatically changes: the narrow P-Cygni profile disappears, and the Hα is fitted by three emission components that will be detected over the remaining 15 yr of the supernova (SN) monitoring campaign. Instead, the He I emissions become progressively narrower and symmetric. A sudden increase in flux of all He I lines is observed between 300 and 600 d. Models show that the SN luminosity is sustained by the interaction of low-mass (∼1.15 M) ejecta, expelled in a low kinetic energy (∼1.6 × 10 50 erg) explosion, with highly asymmetric circumstellar medium. The detection of Hα emission in pre-explosion archive images suggests that the progenitor was most likely a massive star (∼25 M ZAMS) that had lost a large fraction of its hydrogen envelope before explosion, and was hence embedded in a H-rich cocoon. The low-mass ejecta and modest kinetic energy of the explosion are explained with massive fallback of material into the compact remnant, a 7-8-M black hole.