26 research outputs found
Observational Properties of a Bright Type lax SN 2018cni and a Faint Type Iax SN 2020kyg
We present the optical photometric and spectroscopic analysis of two Type Iax supernovae (SNe), 2018cni and 2020kyg. SN 2018cni is a bright Type Iax SN (M V,peak = -17.81 ± 0.21 mag), whereas SN 2020kyg (M V,peak = -14.52 ± 0.21 mag) is a faint one. We derive 56Ni mass of 0.07 and 0.002 M ⊙ and ejecta mass of 0.48 and 0.14 M ⊙ for SNe 2018cni and 2020kyg, respectively. A combined study of the bright and faint Type Iax SNe in R/r-band reveals that the brighter objects tend to have a longer rise time. However, the correlation between the peak luminosity and decline rate shows that bright and faint Type Iax SNe exhibit distinct behavior. Comparison with standard deflagration models suggests that SN 2018cni is consistent with the deflagration of a CO white dwarf, whereas the properties of SN 2020kyg can be better explained by the deflagration of a hybrid CONe white dwarf. The spectral features of both the SNe point to the presence of similar chemical species but with different mass fractions. Our spectral modeling indicates stratification at the outer layers and mixed inner ejecta for both of the SNe
Multiband optical variability of 3C 279 on diverse time-scales
We have monitored the flat spectrum radio quasar, 3C 279, in the optical B, V, R, and I passbands from 2018 February to 2018 July for 24 nights, with a total of 716 frames, to study flux, colour, and spectral variability on diverse time-scales. 3C 279 was observed using seven different telescopes: two in India, two in Argentina, two in Bulgaria, and one in Turkey to understand the nature of the source in optical regime. The source was found to be active during the whole monitoring period and displayed significant flux variations in B, V, R, and I passbands. Variability amplitudes on intraday basis varied from 5.20 to 17.9 per cent. A close inspection of variability patterns during our observation cycle reveals simultaneity among optical emissions from all passbands. During the complete monitoring period, progressive increase in the amplitude of variability with frequency was detected for our target. The amplitudes of variability in B, V, R, and I passbands have been estimated to be 177 per cent, 172 per cent, 171 per cent, and 158 per cent, respectively. Using the structure function technique, we found intraday time-scales ranging from ∼23 min to about 115 min. We also studied colour–magnitude relationship and found indications of mild bluer-when-brighter trend on shorter time-scales. Spectral indices ranged from 2.3 to 3.0 with no clear trend on long-term basis. We have also generated spectral energy distributions for 3C 279 in optical B, V, R, and I passbands for 17 nights. Finally, possible emission mechanisms causing variability in blazars are discussed briefly.Fil: Agarwal, Aditi. Indian Institute of Astrophysics; IndiaFil: Cellone, Sergio Aldo. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - San Juan. Complejo Astronómico "El Leoncito". Universidad Nacional de Córdoba. Complejo Astronómico "El Leoncito". Universidad Nacional de la Plata. Complejo Astronómico "El Leoncito". Universidad Nacional de San Juan. Complejo Astronómico "El Leoncito"; ArgentinaFil: Andruchow, Ileana. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - La Plata. Instituto de AstrofÃsica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y GeofÃsicas. Instituto de AstrofÃsica La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y GeofÃsicas; ArgentinaFil: Mammana, Luis Antonio. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - San Juan. Complejo Astronómico "El Leoncito". Universidad Nacional de Córdoba. Complejo Astronómico "El Leoncito". Universidad Nacional de la Plata. Complejo Astronómico "El Leoncito". Universidad Nacional de San Juan. Complejo Astronómico "El Leoncito"; ArgentinaFil: Singh, Mridweeka. Aryabhatta Research Institute of Observational Sciences; IndiaFil: Anupama, G. C.. Indian Institute of Astrophysics; IndiaFil: Mihov, B.. Bulgarian Academy of Sciences; BulgariaFil: Raj, Ashish. Indian Institute of Astrophysics; IndiaFil: Slavcheva Mihova, L.. Bulgarian Academy of Sciences; BulgariaFil: Özdönmez, Aykut. Tübİtak National Observatory; TurquÃaFil: Ege, Ergün. Istanbul University; TurquÃ
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
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
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