Devendra Sahu

Indian Institute of Astrophysics | IIAP · Research Division Extragalactic Astronomy and Cosmology

We present an extensive, panchromatic photometric (UV, optical, and near-IR) and low-resolution optical spectroscopic coverage of a Type IIP supernova SN 2018gj that occurred on the outskirts of the host galaxy NGC 6217. From the V- band light curve, we estimate the plateau length to be ∼ 70 ± 2 days, placing it among the very few well-sampled shor...

We present early-phase panchromatic photometric and spectroscopic coverage spanning the far-ultraviolet to near-infrared regime of the nearest hydrogen-rich core-collapse supernova (SN) in the last 25 yr, SN 2023ixf. We observe early “flash” features in the optical spectra due to confined dense circumstellar material (CSM). We observe high-ionizati...

We present early-phase panchromatic photometric and spectroscopic coverage spanning far-ultraviolet (FUV) to the near-infrared (NIR) regime of the nearest hydrogen-rich core-collapse supernova in the last 25 years, SN~2023ixf. We observe early `flash' features in the optical spectra due to a confined dense circumstellar material (CSM). We observe h...

We present an extensive, panchromatic photometric (UV, Optical, and NIR) and low-resolution optical spectroscopic coverage of a Type IIP supernova SN 2018gj that occurred on the outskirts of the host galaxy NGC 6217. From the V-band light curve, we estimate the plateau length to be ~ 70 +- 2 d, placing it among the very few well-sampled short plate...

We present optical photometric and spectroscopic studies of three supernovae (SNe) SN 2013bz, PSN J0910+5003 and ASASSN-16ex (SN 2016ccj). UV-optical photometric data of ASASSN-16ex obtained with Swift-UVOT are also analyzed. These objects were initially classified as 09dc–like type Ia SNe. The decline rate parameters (Δm15(B)true) are derived as 0...

We present optical photometric and spectroscopic studies of three supernovae (SNe) SN 2013bz, PSN J0910+5003 and ASASSN-16ex. UV-optical photometric data of ASASSN-16ex obtained with Swift-UVOT are also analyzed. These objects were initially classified as 09dc-like type Ia SNe. The decline rate parameters ($\Delta m_{15}(B)_{true}$) are derived as...

We present optical observations and Monte Carlo radiative transfer modeling of the Type Ia supernova (SN Ia) SN 2011aa. With a Δ m 15 ( B ) of 0.59 ± 0.07 mag and a peak magnitude M B of −19.30 ± 0.27 mag, SN 2011aa has the slowest decline rate among SNe Ia. The secondary maximum in the I band is absent or as equally bright as the primary maximum....

We present and analyze 58 transit light curves of TrES-3b and 98 transit light curves of Qatar-1b, observed by the Transiting Exoplanet Survey Satellite, plus two transit light curves of Qatar-1b, observed by us, using a ground-based 1.23 m telescope. These light curves are combined with the best-quality light curves taken from the Exoplanet Transi...

We present and analyze 58 transit light curves of TrES-3b and 98 transit light curves of Qatar-1b observed by Transiting Exoplanet Survey Satellite (TESS), plus two transit light curves of Qatar-1b observed by us using a ground-based 1.23\,m telescope. These light curves are combined with the best-quality light curves taken from the Exoplanet Trans...

We present optical observations and Monte Carlo radiative transfer modeling of the Type Ia supernova SN 2011aa. With a $\Delta m_{15} (B)$ of $0.59 \pm 0.07$ mag and a peak magnitude $M_{\rm B}$ of $-19.30 \pm 0.27$ mag, SN 2011aa has the slowest decline rate among SNe Ia. The secondary maximum in the $I$-band is absent or equally bright as the pri...

In this Letter, we report the discovery of an ultraluminous fast-evolving transient in rest-frame UV wavelengths, MUSSES2020J, soon after its occurrence by using the Hyper Suprime-Cam (HSC) mounted on the 8.2 m Subaru telescope. The rise time of about 5 days with an extremely high UV peak luminosity shares similarities to a handful of fast blue opt...

In this letter we report a discovery of an ultra-luminous fast evolving transient in rest-frame UV wavelengths, MUSSES2020J, soon after its occurrence by using the Hyper Suprime-Cam (HSC) mounted on the 8.2m Subaru telescope. The rise time of about 5 days with an extremely high UV peak luminosity share similarities with a handful of fast blue optic...

We present spectroscopic and photometric observations of the Type IIP supernova, SN 2020jfo, in ultraviolet and optical wavelengths. SN 2020jfo occurred in the spiral galaxy M61 (NGC 4303), with eight observed supernovae in the past 100 yr. SN 2020jfo exhibited a short plateau lasting < 65 days, and achieved a maximum brightness in V band of M V =...

Comet 156P/Russell-LINEAR is a short period Jupiter family comet with an orbital period of 6.44 years. The results from spectroscopic, photometric, polarimetric observations and dust modelling studies are presented here. From the spectroscopic study, strong emissions from $CN (\Delta \nu = 0)$, $C_3 (\lambda 4050$ \AA), $C_2 (\Delta \nu = +1)$ and...

Comet 156P/Russell-LINEAR is a short period Jupiter family comet with an orbital period of 6.44 years. The results from spectroscopic, photometric, polarimetric observations and dust modelling studies are presented here. From the spectroscopic study, strong emissions from CN(Δν=0), C3 (λ4050Å), C2(Δν=+1) and C2(Δν=0) can be observed during both the...

We report results of optical imaging and low-resolution spectroscopic monitoring of supernova (SN) 2017iro that occurred in the nearby (∼31 Mpc) galaxy NGC 5480. The He i λ 5876 feature present in the earliest spectrum (−7 days) classified it as a Type Ib SN. The follow-up observations span from −7 to +266 days with respect to the B -band maximum....

We present spectroscopic and photometric observations of the Type IIP supernova, SN$~$2020jfo, in ultraviolet and optical wavelengths. SN$~$2020jfo occurred in the spiral galaxy M61 (NGC$\,$4303), with eight observed supernovae in the past 100 years. SN$~$2020jfo exhibited a short plateau lasting $58\pm2\,d$, and achieved a maximum brightness in $V...

We perform transit timing variation (TTV) and transmission spectroscopy analyses of the planet HAT-P-37b, which is a hot Jupiter orbiting a G-type star. Nine new transit light curves are obtained and analyzed together with 21 published light curves from the literature. The updated physical parameters of HAT-P-37b are presented. The TTV analyses sho...

We present optical UBVRI photometry and low-to-medium resolution spectroscopic observations of type Iax supernova SN 2020sck spanning −5.5 days to +67 days from maximum light in the B- band. From the photometric analysis we find Δ m B (15) = 2.03 ± 0.05 mag and M B = −17.81 ± 0.22 mag. Radiation diffusion model fit to the quasi-bolometric light cur...

We report results of optical imaging and low-resolution spectroscopic monitoring of supernova (SN) 2017iro that occurred in the nearby ($\sim$\,31 Mpc) galaxy NGC 5480. The \ion{He}{1} 5876 \AA\, feature present in the earliest spectrum (--\,7 d) classified it as a Type Ib SN. The follow-up observations span from --\,7 to +\,266 d with respect to t...

The transit timing variation (TTV) and transmission spectroscopy analyses of the planet HAT-P-37b, which is a hot Jupiter orbiting an G-type star, were performed. Nine new transit light curves are obtained and analysed together with 21 published light curves from the literature. The updated physical parameters of HAT-P-37b are presented. The TTV an...

We present optical UBVRI photometry and low-to-medium resolution spectroscopic observations of type Iax SN 2020sck spanning -5.5 d to +67 d from maximum light in the B-band. From the photometric analysis we find $\Delta m_{\rm{B}}$(15) = 2.03$\pm$0.05 mag and $M_{\rm{B}}$=-17.81$\pm$0.22 mag. Radiation diffusion model fit to the quasi-bolometric li...

We have investigated the possibility of transit timing variation (TTV) and its plausible cause in the hot-Jupiter systems TrES-3 and Qatar-1. In this study, total 160 transit light curves of TrES-3b and 197 transit light curves of Qatar-1b are considered. Using the mid-transit times determined from these light curves, we have improved the transit e...

We present comprehensive spectroscopic and photometric analyses of the intermediate luminosity Type Iax supernova (SN Iax) 2019muj based on multi-band datasets observed through the framework of the OISTER target-of-opportunity program. SN 2019muj exhibits almost identical characteristics with the subluminous SNe Iax 2008ha and 2010ae in terms of th...

Optical, near-infrared (NIR) photometric and spectroscopic studies along with the optical imaging polarimetric results for SN 2012au to constrain the nature of the progenitor and other properties are presented in this paper. Well-calibrated multi-band optical photometric data (from -0.2 to +413 d since B-band maximum) was used to compute the bolome...

Superluminous supernovae (SLSNe) are a new class of SNe (2–3 magnitudes brighter than classical SNe) that were recognized about a decade ago (Quimby et al. 2011). SLSNe comprising ∼0.01 per cent of normal core-collapse SNe (CCSNe), and nearly 150 objects have been spectroscopically confirmed so far. Like classical CCSNe, SLSNe are spectroscopically...

Considering the importance of investigating the transit timing variations (TTVs) of transiting exoplanets, we present a follow-up study of HAT-P-12b. We include six new light curves observed between 2011 and 2015 from three different observatories, in association with 25 light curves taken from the published literature. The sample of the data used...

We present the photometric and spectroscopic analysis of three Type II SNe: 2014cx, 2014cy and 2015cz. SN 2014cx is a conventional Type IIP with shallow slope (0.2 mag/50d) and an atypical short plateau (∼86 d). SNe 2014cy and 2015cz show relatively large decline rates (0.88 and 1.64 mag/50d, respectively) at early times before settling to the plat...

We present the photometric and spectroscopic analysis of three Type II SNe: 2014cx, 2014cy and 2015cz. SN 2014cx is a conventional Type IIP with a shallow slope (0.2 mag/50d) and an atypical short plateau ($\sim$86 d). SNe 2014cy and 2015cz show relatively large decline rates (0.88 and 1.64 mag/50d, respectively) at early times before settling to t...

We present the optical (UBVRI) and ultraviolet (Swift-UVOT) photometry, and optical spectroscopy of Type Ia supernova SN 2017hpa. We study broadband UV+optical light curves and low resolution spectroscopy spanning from −13.8 to +108 d from the maximum light in B-band. The photometric analysis indicates that SN 2017hpa is a normal type Ia with ΔmB(1...

We present the optical (UBVRI) and ultraviolet (Swift-UVOT) photometry, and optical spectroscopy of Type Ia supernova SN 2017hpa. We study broadband UV+optical light curves and low resolution spectroscopy spanning from −13.8 to +108 d from the maximum light in B-band. The photometric analysis indicates that SN 2017hpa is a normal type Ia with ∆m B...

Motivated by the unsettled conclusion on whether there are any transit timing variations (TTVs) for the exoplanet Qatar-1b, 10 new transit light curves are presented and the TTV analysis with a baseline of 1400 epochs are performed. Because the linear model provides a good fitting with reduced chi-square χ^{2}_{red] = 2.59 and the false-alarm proba...

Manx objects approach the inner solar system on long-period comet (LPC) orbits with the consequent high inbound velocities, but unlike comets, Manxes display very little to no activity even near perihelion. This suggests that they may have formed in circumstances different from typical LPCs; moreover, this lack of significant activity also renders...

We investigate the observational properties of a hydrogen-deficient superluminous supernova (SLSN) SN 2020ank (at z = 0.2485), with the help of early phase observations carried out between –21 and +52 d since g-band maximum. Photometrically, SN 2020ank is one of the brightest SLSN (Mg, peak ∼ –21.84 ± 0.10 mag), having fast pre-peak rising and post...

Comet 2I/Borisov is the first true interstellar comet discovered. Here we present results from observational programs at two Indian observatories, 2 m Himalayan Chandra Telescope at the Indian Astronomical Observatory, Hanle (HCT) and 1.2 m telescope at the Mount Abu Infrared Observatory (MIRO). Two epochs of imaging and spectroscopy were carried o...

Manx objects approach the inner solar system on long-period comet (LPC) orbits with the consequent high inbound velocities, but unlike comets, Manxes display very little to no activity even near perihelion. This suggests that they may have formed in circumstances different from typical LPCs; moreover, this lack of significant activity also renders...

Comet 2I/Borisov is the first true interstellar comet discovered. Here we present results from observational programs at two Indian observatories, 2 m Himalayan Chandra Telescope at the Indian Astronomical Observatory, Hanle (HCT) and 1.2 m telescope at the Mount Abu Infrared Observatory (MIRO). Two epochs of imaging and spectroscopy were carried o...

We investigate the observational properties of a hydrogen-deficient superluminous supernova (SLSN) SN 2020ank (at z = 0.2485), with the help of early phase observations carried out between $-$21 and +52 d since $g$-band maximum. Photometrically, SN 2020ank is one of the brightest SLSN ($M_{g,peak}$ $\sim$ $-$21.84 $\pm$ 0.10 mag), having fast pre-p...

Considering the importance of investigating the transit timing variations (TTVs) of transiting exoplanets, we present a follow-up study of HAT-P-12b. We include six new light curves observed between 2011 and 2015 from three different observatories, in association with 25 light curves taken from the published literature. The sample of the data used,...

Motivated by the unsettled conclusion on whether there are any transit timing variations (TTVs) for the exoplanet Qatar-1b, 10 new transit light curves are presented and the TTV analysis with a baseline of 1400 epochs are performed. Because the linear model provides a good fitting with reduced chi-square χ 2 red = 2.59 and the false-alarm probabili...

We present seven new transit light curves of the hot-Jupiter TrES-5b observed with the 2-m Himalayan Chandra Telescope, Hanle, India during 2016-2020 to look for the transit timing variation (TTV). For this study, total 59 transit light curves have been considered which include seven light curves from our new observations, 37 from the literature, a...

We present seven new transit light curves of the hot-Jupiter TrES-5b observed with the 2-m Himalayan Chandra Telescope, Hanle, India during 2016-2020 to look for the transit timing variation (TTV). For this study, total 59 transit light curves have been considered which include seven light curves from our new observations, 37 from the literature, a...

We present the photometric and spectroscopic studies of a Type Ib SN 2015ap and a Type Ic SN 2016P. SN 2015ap is one of the bright (MV = −18.04 mag) Type Ib while SN 2016P lies at an average value among the Type Ic SNe (MV = −17.53 mag). Bolometric light-curve modelling of SNe 2015ap and 2016P indicates that both the SNe are powered by 56Ni + magne...

We present the photometric and spectroscopic studies of a Type Ib SN 2015ap and a Type Ic SN 2016P. SN 2015ap is one of the bright (M$_{V}$ = $-$18.04 mag) Type Ib while SN 2016P lies at an average value among the Type Ic SNe (M$_{V}$ = $-$17.53 mag). Bolometric light curve modelling of SNe 2015ap and 2016P indicates that both the SNe are powered b...

We present twelve new transit light curves of the hot-Jupiter TrES-3b observed during $2012-2018$ to probe the transit timing variation (TTV). By combining the mid-transit times determined from these twelve transit data with those re-estimated through uniform procedure from seventy one transit data available in the literature, we derive new linear...

We present the discovery and high-cadence follow-up observations of SN 2018ivc, an unusual Type II supernova that exploded in NGC 1068 (D = 10.1 Mpc). The light curve of SN 2018ivc declines piecewise-linearly, changing slope frequently, with four clear slope changes in the first 40 days of evolution. This rapidly changing light curve indicates that...

We present photometric and spectroscopic observations of the type Ibn supernova (SN) 2019uo, the second ever SN Ibn with flash ionization (He II, C III, N III) features in its early spectra. SN 2019uo displays a rapid post-peak luminosity decline of 0.1 mag d$^{-1}$ similar to most of the SNe Ibn, but is fainter ($M^V_{max} = -18.30 \pm 0.24$ mag)...

Photometric and Spectroscopic Observations of Supernovae observed from the Himalayan Chandra Telescope

We present the discovery and high-cadence follow-up observations of SN 2018ivc, an unusual Type II supernova that exploded in NGC 1068 (D = 10.1 Mpc). The light curve of SN 2018ivc declines piecewise-linearly, changing slope frequently, with four clear slope changes in the first 40 days of evolution. This rapidly changing light curve indicates that...

High cadence ultraviolet, optical and near-infrared photometric and low-resolution spectroscopic observations of the peculiar Type II supernova (SN) 2018hna are presented. The early phase multiband light curves exhibit the adiabatic cooling envelope emission following the shock breakout up to ~14 days from the explosion. SN~2018hna has a rise time...

We present an extensive optical–ultraviolet photometry and analysis of a series of optical spectra of type Ia supernovae SN 2009ig and SN 2012cg. The observations range from −15 to +185 d for SN 2009ig and from −14 to 316 d for SN 2012cg, with respect to maximum light in B band. Both SN 2009ig and SN 2012cg exhibit similar properties. They have sim...

We report on the catastrophic disintegration of P/2016 G1 (PANSTARRS), an active asteroid, in April 2016. Deep images over three months show that the object is made up of a central concentration of fragments surrounded by an elongated coma, and presents previously unreported sharp arc-like and narrow linear features. The morphology and evolution of...

The optical and ultra-violet broadband photometric and spectroscopic observations of the Type II supernova (SN) 2016gfy are presented. The $V$-band light curve (LC) shows a distinct plateau phase with a slope, $s_2$ $\sim$ 0.12 mag / 100 d and a duration of 90 $\pm$ 5 d. Detailed analysis of SN 2016gfy provided a mean $\rm^{56}Ni$ mass of 0.033 $\p...

We present the results based on photometric ($Swift$ UVOT), broad-band polarimetric ($V$ and $R$-band) and optical spectroscopic observations of the Type IIn supernova (SN) 2017hcc. Our study is supplemented with spectropolarimetric data available in literature for this event. The post-peak light curve evolution is slow ($\sim$0.2 mag 100 d$^{-1}$...

We report on the catastrophic disintegration of P/2016 G1 (PANSTARRS), an active asteroid, in April 2016. Deep images o