Optical studies of two stripped-envelope supernovae – SN 2015ap (Type Ib) and SN 2016P (Type Ic) (original) (raw)
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SN 2015an: a normal luminosity type II supernova with low expansion velocity at early phases
Monthly Notices of the Royal Astronomical Society, 2019
We present the photometry and spectroscopy of SN 2015an, a type II Supernova (SN) in IC 2367. The recombination phase of the SN lasts up to 120 d, with a decline rate of 1.24 mag/100d, higher than the typical SNe IIP. The SN exhibits bluer colours than most SNe II, indicating higher ejecta temperatures. The absolute V-band magnitude of SN 2015an at 50 d is −16.83 ± 0.04 mag, pretty typical for SNe II. However, the 56 Ni mass yield, estimated from the tail V-band light curve to be 0.021 ± 0.010 M , is comparatively low. The spectral properties of SN 2015an are atypical, with low H α expansion velocity and presence of high-velocity component of H α at early phases. Moreover, the continuum exhibits excess blue flux up to 50 d, which is interpreted as a progenitor metallicity effect. The high-velocity feature indicates ejecta-circumstellar material interaction at early phases. The semi-analytical modelling of the bolometric light curve yields a total ejected mass of 12 M , a pre-SN radius of 388 R and explosion energy of 1.8 foe.
Optical Photometry and Spectroscopy of the SN 1998bw-like Type Ic Supernova 2002ap
Publications of The Astronomical Society of The Pacific, 2003
We present optical photometric and spectral data of the peculiar Type Ic SN 2002ap. Photometric coverage includes UBVRI bands from 2002 January 30, the day after discovery, through 2002 December 12. There are 5 early-time spectra and 8 in the nebular phase. We determine that SN 2002ap is similar to SN 1997ef and the GRB-associated SN 1998bw with respect to spectral and photometric characteristics. The nebular spectra of SN 2002ap present the largest Mg I] \lambda 4571 to [O I] \lambda \lambda 6300, 6364 ratio of any supernova spectra yet published, suggesting that the progenitor of SN 2002ap was a highly stripped star. Comparing the nebular spectra of SN 1985F and SN 2002ap, we notice several similar features, casting the classification of SN 1985F as a normal Type Ib supernova in doubt. We also present nebular modeling of SN 2002ap and find that the object ejected >~ 1.5 M_{sun} of material within the outer velocity shell of the nebula (~5500 km/s) and synthesized ~0.09 M_{sun} of 56Ni.
Exploring the optical behaviour of a Type Iax supernova SN 2014dt
Monthly Notices of the Royal Astronomical Society, 2017
We present optical photometric (up to ∼410 d since Bmax) and spectroscopic (up to ∼157 d since Bmax) observations of a Type Iax supernova (SN) 2014dt located in M61. SN 2014dt is one of the brightest and closest (D ∼ 20 Mpc) discovered Type Iax SN. It best matches the light-curve evolution of SN 2005hk and reaches a peak magnitude of MB ∼ −18.13 ± 0.04 mag with Δm15 ∼ 1.35 ± 0.06 mag. The early spectra of SN 2014dt are similar to other Type Iax SNe, whereas the nebular spectrum at 157 d is dominated by narrow emission features with less blending as compared to SNe 2008ge and 2012Z. The ejecta velocities are between 5000 and 1000 km s−1, which also confirms the low-energy budget of Type Iax SN 2014dt compared to normal Type Ia SNe. Using the peak bolometric luminosity of SN 2005hk, we estimate the 56Ni mass of ∼0.14 M⊙. The striking similarity between SN 2014dt and SN 2005hk implies that a comparable amount of 56Ni would have been synthesized in the explosion of SN 2014dt.
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 2015as: a low-luminosity Type IIb supernova without an early light-curve peak
Monthly Notices of the Royal Astronomical Society
We present results of the photometric (from 3 to 509 d post-explosion) and spectroscopic (up to 230 d post-explosion) monitoring campaign of the He-rich Type IIb supernova (SN) 2015as. The (B − V) colour evolution of SN 2015as closely resemble those of SN 2008ax, suggesting that SN 2015as belongs to the SN IIb subgroup that does not show the early, short-duration photometric peak. The light curve of SN 2015as reaches the B-band maximum about 22 d after the explosion, at an absolute magnitude of −16.82 ± 0.18 mag. At ∼75 d after the explosion, its spectrum transitions from that of a SN II to a SN Ib. P Cygni features due to He i lines appear at around 30 d after explosion, indicating that the progenitor of SN 2015as was partially stripped. For SN 2015as, we estimate a 56Ni mass of ∼0.08 M⊙ and ejecta mass of 1.1–2.2 M⊙, which are similar to the values inferred for SN 2008ax. The quasi-bolometric analytical light-curve modelling suggests that the progenitor of SN 2015as has a modest m...
The optical properties of three Type II supernovae: 2014cx, 2014cy, and 2015cz
Monthly Notices of the Royal Astronomical Society, 2021
We present the photometric and spectroscopic analysis of three Type II supernovae (SNe): 2014cx, 2014cy, and 2015cz. SN 2014cx is a conventional Type IIP with shallow slope (0.2 mag/50 d) and an atypical short plateau (∼86 d). SNe 2014cy and 2015cz show relatively large decline rates (0.88 and 1.64 mag/50 d, respectively) at early times before settling to the plateau phase, unlike the canonical Type IIP/L SN light curves. All of them are normal luminosity SN II with an absolute magnitude at mid-plateau of M$_{V,14\mathrm{ cx}}^{50}$=$-16.6\, \pm \, 0.4\, \rm {mag}$, M$_{V,14\mathrm{ cy}}^{50}$=$-16.5\, \pm \, 0.2\, \rm {mag}$, and M$_{V,15\mathrm{ cz}}^{50}$=$-17.4\, \pm \, 0.3\, \rm {mag}$. A relatively broad range of 56Ni masses is ejected in these explosions (0.027–0.070 M⊙). The spectra shows the classical evolution of SNe II, dominated by a blue continuum with broad H lines at early phases and narrower metal lines with P Cygni profiles during the plateau. High-velocity H i f...
SN 2014J at M82 – I. A middle-class Type Ia supernova by all spectroscopic metrics
Monthly Notices of the Royal Astronomical Society, 2016
We present the intensive spectroscopic follow up of the Type Ia supernova (SN Ia) 2014J in the starburst galaxy M82. Twenty-seven optical spectra have been acquired from 2014 January 22 to September 1 with the Isaac Newton and William Herschel Telescopes. After correcting the observations for the recession velocity of M82 and for Milky Way and host galaxy extinction, we measured expansion velocities from spectral line blueshifts and pseudo-equivalent width of the strongest features in the spectra, which gives an idea on how elements are distributed within the ejecta. We position SN 2014J in the Benetti, Branch et al. and Wang et al. diagrams. These diagrams are based on properties of the Si II features and provide dynamical and chemical information about the SN ejecta. The nearby SN 2011fe, which showed little evidence for reddening in its host galaxy, is shown as a reference for comparisons. SN 2014J is a borderline object between the Core-normal and Broad-line groups, which corresponds to an intermediate position between low-velocity gradient and high-velocity gradient objects. SN 2014J follows the R(Si II)-m 15 correlation, which confirms its classification as a relatively normal SN Ia. Our description of the SN Ia in terms of the evolution of the pseudo-equivalent width of various ions as well as the position in the various diagrams put this specific SN Ia into the overall sample of SN Ia.
Monthly Notices of the Royal Astronomical Society
Photometric and spectroscopic data for two Low Luminosity Type IIP Supernovae (LL SNe IIP) 2020cxd and 2021aai are presented. SN 2020cxd was discovered 2 d after explosion at an absolute magnitude of Mr = −14.02 ± 0.21 mag, subsequently settling on a plateau which lasts for ∼120 d. Through the luminosity of the late light curve tail, we infer a synthesized 56Ni mass of (1.8 ± 0.5) × 10−3 M⊙. During the early evolutionary phases, optical spectra show a blue continuum ($T\, \gt 8000K)withbroadBalmerlinesdisplayingaPCygniprofile,whileatlaterphases,Caii,Feii,Scii,andBaiilinesdominatethespectra.Hydrodynamicalmodellingoftheobservablesyields8000 K) with broad Balmer lines displaying a P Cygni profile, while at later phases, Ca ii, Fe ii, Sc ii, and Ba ii lines dominate the spectra. Hydrodynamical modelling of the observables yields 8000K)withbroadBalmerlinesdisplayingaPCygniprofile,whileatlaterphases,Caii,Feii,Scii,andBaiilinesdominatethespectra.HydrodynamicalmodellingoftheobservablesyieldsR\, \simeq$ 575 R⊙ for the progenitor star, with Mej = 7.5 M⊙ and E,simeqE\, \simeqE,simeq 0.097 foe emitted during the explosion. This low-energy event originating from a low-mass progenitor star is compatible with both the explosion of a red supergiant (RSG) star and with an Electron Capture Supernova arising from a super asy...
A Peculiar Subclass of Type Ia Supernovae a.k.a. Type Iax
Bulletin de la Société Royale des Sciences de Liège, 2018
We present optical photometric (upto 410 days since Bmax) and spectroscopic (upto 235 days since Bmax) observations of a type Iax supernova SN 2014dt located in M61. The broad band light curves follow a linear decline upto 100 days after which a significant flattening is seen in the late-time (beyond 150 days) light curves of SN 2014dt. SN 2014dt best matches the light curve evolution of SN 2005hk and reaches a peak magnitude of MB -18.12±0.04 with m15 1.35±0.06 mag. The earliest spectrum at 23 days is dominated by FeII and CoII lines with the absence of the Si II 6150 Å line. Using the peak bolometric luminosity we estimate a 56Ni mass of 0.14 M in the case of SN 2005hk and the striking similarity between SN 2014dt and SN 2005hk implies that a comparable amount of 56Ni would have been synthesized in the explosion of SN 2014dt. There are several explosion scenarios proposed for these peculiar events. Being one of the brightest and closest SN, SN 2014dt is an ideal candid...
Monthly Notices of the Royal Astronomical Society, 2012
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