19 research outputs found
Light Curve and Spectral Evolution of Type IIb Supernovae
Stripped-Envelope Supernovae constitute the sub-class of core-collapse supernovae that strip off their outer hydrogen envelope due to high stellar winds or due to interaction with a binary companion where mass transfer occurs as a result of Roche lobe overflow. We present here the photometric and spectroscopic analysis of a member of this class : SN 2015as classified as a type IIb supernova. Light curve features are similar to those of SN 2011fu while spectroscopic features are quite similar to those of SN 2008ax and SN 2011dh. Early epoch spectra have been modelled with SYN++ which indicates a photospheric velocity of 8500 km sec-1 and temperature of 6500K. Spectroscopic lines show transitioning from H to He features confirming it to be a type IIb supernova. Prominent oxygen and calcium emission features are indicative of the asymmetry of the ejecta. We also estimate the signal to noise ratio of the 3.6m telescope data. This telescope is located at ARIES, Devasthal, Nainital at an altitude of 2450m. We also show the comparison plots of spectra taken with a 2m and 4m class telescopes to enlighten the importance of spectral features displayed by bigger diameter telescopes
SN 2015ba: A type IIP supernova with a long plateau
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 -17.10.2 mag at 50 d since explosion and has
a long plateau lasting for 123 d. The distance to the SN is estimated to
be 34.80.7 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.Comment: 42 pages, 7 pages Appendix, 20 figures, 10 tables, Accepted for
publication in MNRAS, 14-June-201
Evolution of A Peculiar Type Ibn Supernova SN 2019wep
We present a high-cadence short term photometric and spectroscopic monitoring
campaign of a type Ibn SN 2019wep, which is one of the rare SN Ibn after SNe
2010al and 2019uo to display signatures of flash ionization (\ion{He}{2},
\ion{C}{3}, \ion{N}{3}). We compare the decline rates and rise time of SN
2019wep with other SNe Ibn and fast transients. The post-peak decline in all
bands (0.1 mag d) are consistent with SNe Ibn but less than the fast
transients. On the other hand, the m values are slightly lower
than the average values for SNe Ibn but consistent with the fast transients.
The rise time is typically shorter than SNe Ibn but longer than fast
transients. SN 2019wep lies at the fainter end of SNe Ibn but possesses an
average luminosity amongst the fast transients sample. The peculiar color
evolution places it between SNe Ib and the most extreme SNe Ibn. The bolometric
light curve modelling shows resemblance with SN 2019uo with ejecta masses
consistent with SNe Ib. SN 2019wep belongs to the "P cygni" sub-class of SNe
Ibn and shows faster evolution in line velocities as compared to the "emission"
sub-class. The post-maximum spectra show close resemblance with ASASSN-15ed
hinting it to be of SN Ib nature. The low \ion{He}{1} CSM velocities and
residual H further justifies it and gives evidence of an intermittent
progenitor between WR and LBV star.Comment: 19 pages, 14 figures, 2 Tables, Accepted for publication in ApJ main
journa
SN 2015as: A low luminosity Type IIb supernova without an early light curve peak
We present results of the photometric (from 3 to 509 days past explosion) and
spectroscopic (up to 230 days past explosion) monitoring campaign of the
He-rich Type IIb supernova (SN) 2015as. The {\it (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 -band maximum about 22 days
after the explosion, at an absolute magnitude of -16.82 0.18 mag. At
75 days 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 days
after explosion, indicating that the progenitor of SN 2015as was partially
stripped. For SN~2015as, we estimate a Ni 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 mass (
0.1 M), a nearly-compact ( 0.0510 cm) H envelope
on top of a dense, compact ( 210 cm) and a more massive
( 1.2 M) He core. The analysis of the nebular phase spectra
indicates that 0.44 M of O is ejected in the explosion. The
intensity ratio of the [Ca II]/[O I] nebular lines favours either a main
sequence progenitor mass of 15 M or a Wolf Rayet star of 20
M.Comment: 23 pages, 18 figures, 10 tables, Accepted for publication in MNRAS,
16 February, 201
Photometric and spectroscopic evolution of the peculiar Type IIn SN 2012ab
We present an extensive ( 1200 d) photometric and spectroscopic
monitoring of the Type IIn supernova (SN) 2012ab. After a rapid initial rise
leading to a bright maximum (M = 19.39 mag), the light curves show a
plateau lasting about 2 months followed by a steep decline up to about 100 d.
Only in the band the decline is constant in the same interval. At later
phases, the light curves remain flatter than the Co decline suggesting
the increasing contribution of the interaction between SN ejecta with
circumstellar material (CSM). Although heavily contaminated by emission lines
of the host galaxy, the early spectral sequence (until 32 d) shows persistent
narrow emissions, indicative of slow unshocked CSM, and the emergence of broad
Balmer lines of hydrogen with P-Cygni profiles over a blue continuum, arising
from a fast expanding SN ejecta. From about 2 months to 1200 d, the
P-Cygni profiles are overcome by intermediate width emissions (FWHM
\kms), produced in the shocked region due to interaction. On the red wing a red
bump appears after 76 d, likely a signature of the onset of interaction of the
receding ejecta with the CSM. The presence of fast material both approaching
and then receding is suggestive that we are observing the SN along the axis of
a jet-like ejection in a cavity devoid of or uninterrupted by CSM in the
innermost regions.Comment: 8 Tables, 17 Figures. Accepted for publication in MNRA