http://hdl.handle.net/2248/166 Wed, 15 Apr 2026 14:21:42 GMT 2026-04-15T14:21:42Z http://prints:80/jspui/retrieve/30601262-b84c-465c-abb8-1c7f9e3663da/iao_2.jpg http://hdl.handle.net/2248/166 http://hdl.handle.net/2248/6401 Title: Properties of Newly Formed Dust Grains in the Luminous Type IIn Supernova 2010jl Authors: Maeda, K; Nozawa, T; Sahu, D. K; Minowa, Y; Motohara, K; Ueno, I; Folatelli, G; Pyo, T. S; Kitagawa, Y; Kawabata, K. S; Anupama, G. C; Kozasa, T; Moriya, T. J; Yamanaka, M; Nomoto, K; Bersten, M; Quimby, R; Iye, M Abstract: Supernovae (SNe) have been proposed to be the main production sites of dust grains in the universe. However, our knowledge of their importance to dust production is limited by observationally poor constraints on the nature and amount of dust particles produced by individual SNe. In this paper, we present a spectrum covering optical through near-Infrared (NIR) light of the luminous Type IIn supernova 2010jl around one and a half years after the explosion. This unique data set reveals multiple signatures of newly formed dust particles. The NIR portion of the spectrum provides a rare example where thermal emission from newly formed hot dust grains is clearly detected. We determine the main population of the dust species to be carbon grains at a temperature of ~1350-1450 K at this epoch. The mass of the dust grains is derived to be ~(7.5-8.5) × 10–4 M ☉. Hydrogen emission lines show wavelength-dependent absorption, which provides a good estimate of the typical size of the newly formed dust grains (lsim 0.1 μm, and most likely lsim 0.01 μm). We believe the dust grains were formed in a dense cooling shell as a result of a strong SN-circumstellar media (CSM) interaction. The dust grains occupy ~10% of the emitting volume, suggesting an inhomogeneous, clumpy structure. The average CSM density must be gsim 3 × 107 cm–3, corresponding to a mass loss rate of gsim 0.02 M ☉ yr–1 (for a mass loss wind velocity of ~100 km s–1). This strongly supports a scenario in which SN 2010jl and probably other luminous SNe IIn are powered by strong interactions within very dense CSM, perhaps created by Luminous-Blue-Variable-like eruptions within the last century before the explosion. Description: Restricted Access Thu, 10 Oct 2013 00:00:00 GMT http://hdl.handle.net/2248/6401 2013-10-10T00:00:00Z http://hdl.handle.net/2248/6079 Title: One year of monitoring of the Type IIb supernova SN 2011dh Authors: Sahu, D. K; Anupama, G. C; Chakradhari, N. K Abstract: Optical UBVRI photometry and low-resolution spectroscopy of the Type IIb supernova SN 2011dh in M51 are presented, covering the first year after the explosion. The light curve and spectral evolution are discussed. The early phase light-curve evolution of SN 2011dh is very similar to SN 1993J and SN 2008ax. In the late phase, however, SN 2011dh declines faster than SN 1993J. The late phase decline in the B band is steeper than in the R and I bands, indicating the possibility of dust formation. With a peak V-band absolute magnitude of MV = −17.123 ± 0.18 mag, SN 2011dh is a marginally faint type IIb event. The reddening corrected colour curves of SN 2011dh are found to be redder than other well-studied Type IIb supernovae. The bolometric light curve indicates ∼0.09 M⊙ of 56Ni is synthesized during the explosion. The He i lines were detected in the spectra during the rise to maximum. The nebular spectra of SN 2011dh show a box-shaped emission in the red wing of the [O i] 6300−6363 Å feature, that is attributed to Hα emission from a shock-excited circumstellar material. The analysis of nebular spectra indicates that ∼0.2 M⊙ of oxygen was ejected during the explosion. Further, the [Ca ii]/[O i] line ratio in the nebular phase is ∼0.7, indicating a progenitor with a main-sequence mass of 10–15 M⊙. Description: Restricted Access Sun, 21 Jul 2013 00:00:00 GMT http://hdl.handle.net/2248/6079 2013-07-21T00:00:00Z http://hdl.handle.net/2248/6055 Title: Habitable Planets Eclipsing Brown Dwarfs: Strategies for Detection and Characterization Authors: Belu, A. R; Selsis, F; Raymond, S. N; Palle, E; Street, R; Sahu, D. K; Braun, K. V; Bolmont, E; Figueira, P; Anupama, G. C; Ribas, Ignasi Abstract: Given the very close proximity of their habitable zones, brown dwarfs (BDs) represent high-value targets in the search for nearby transiting habitable planets that may be suitable for follow-up occultation spectroscopy. In this paper, we develop search strategies to find habitable planets transiting BDs depending on their maximum habitable orbital period (P HZ out). Habitable planets with P HZ out shorter than the useful duration of a night (e.g., 8-10 hr) can be screened with 100% completeness from a single location and in a single night (near-IR). More luminous BDs require continuous monitoring for longer duration, e.g., from space or from a longitude-distributed network (one test scheduling achieved three telescopes, 13.5 contiguous hours). Using a simulated survey of the 21 closest known BDs (within 7 pc) we find that the probability of detecting at least one transiting habitable planet is between $4.5^{+5.6}_{-1.4}$% and $56^{+31}_{-13}$%, depending on our assumptions. We calculate that BDs within 5-10 pc are characterizable for potential biosignatures with a 6.5 m space telescope using ~1% of a five-year mission's lifetime spread over a contiguous segment only one-fifth to one-tenth of this duration. Fri, 10 May 2013 00:00:00 GMT http://hdl.handle.net/2248/6055 2013-05-10T00:00:00Z http://hdl.handle.net/2248/6045 Title: Photometric and spectroscopic evolution of supernova SN 2009an: another case of a transitional Type Ia event Authors: Sahu, D. K; Anupama, G. C; Anto, P Abstract: We present optical UBVRI photometry and medium-resolution spectroscopy of a transitional Type Ia supernova, SN 2009an, over the period −6 to +150 d from the B maximum. With a Δm15(B) = 1.514 ± 0.132, SN 2009an declines faster than normal Type Ia events, but slower than the fast-declining, low-luminosity 1991bg-like events. The B-band absolute magnitude at maximum is −19.02 ± 0.20. The peak bolometric luminosity indicates that 0.41 M⊙ of 56Ni was synthesized during the explosion. The pre-maximum and early post-maximum spectral evolution of SN 2009an is very similar to that in the transitional Type Ia SN 2004eo. High-velocity features in the Ca ii near-infrared triplet are seen during the early phases. Similar to the other few objects belonging to this class, SN 2009an exhibits a higher value (0.4) of the Si ii line ratio R(Si ii). The velocity gradient of the Si ii 6355 Å line in the post-maximum epoch (v˙=60 km s−1 d−1) is at the boundary between the low-velocity-gradient and high-velocity-gradient groups. Description: Restricted Access Mon, 01 Apr 2013 00:00:00 GMT http://hdl.handle.net/2248/6045 2013-04-01T00:00:00Z