IUCAA Preprints

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    Observing high-redshift Supernovae in lensed galaxies
    (2000-01-28) Saini, Tarun Deep; Raychaudhury, Somak; Shchekinov, Yuri A.
    Supernovae in distant galaxies that are grav- tationally lensed by foreground galaxy clusters make ex- cellent cosmological candles for measuring quantities like the density of the Universe in its various components and the Hubble constant. Distant supernovae will be more eas- ly detectable since foreground cluster lenses would mag- nify such supernovae by up to 3–4 magnitudes. We show that in the case of the lens cluster Abell 2218, the de- tectability of high-redshift supernovae is significantly en- hanced due to the lensing effects of the cluster. Since ensed supernovae will remain point images even when their host galaxies are stretched into arcs, the signal-to- noise ratio for their observation will be further enhanced, typically by an order of magnitude. We recommend moni- toring well-modelled clusters with several known arclets for the detection of cosmologically useful SNe around z = 1 and beyond.
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    Living with Lambda
    (2000-10-24) Sahni, Varun
    This talk presents a brief overview of recent results pertaining to the cosmological con- stant ‘ ’. I summarize the observational situation focussing on observations of high redshift Type Ia supernovae which suggest > 0. Observations of small angular anisotropies in the cosmic mi- crowave background complement Type Ia supernovae observations and both CMB and Sn can be combined to place strong constraints on the value of . The presence of a small -term increases the age of the universe and slows down the formation of large scale structure. I also review recent the- oretical attempts to generate a small -term at the current epoch and a model independent approach for determining the cosmic equation of state.
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    Photometric and Spectroscopic study of a highly reddened type Ia supernova SN 2003hx in NGC 2076
    (2008-01-28) Misra, Kuntal; Sahu, D. K.
    We present UBV RI CCD photometry and optical spectra of the type Ia supernova SN 2003hx which appeared in the galaxy NGC 2076, obtained till ∼ 146 days after the epoch of B band maximum. The supernova reached at maximum brightness in B band on JD 245 2893 ± 1.0 with an apparent magnitude of 14.92 ± 0.01 mag which was estimated by making template fits to the light curves. SN 2003hx is an example of a highly reddened supernova with E(B −V ) = 0.56 ± 0.23. We estimate Rv = 1.97 ± 0.54 which indicates the small size of dust particles as compared to their galactic counterparts. The luminosity decline rate is ∆m15(B) = 1.17 ± 0.12 mag and the absolute B band magnitude obtained from the luminosity versus decline rate relation (Phillips et al. 1999) is MB max = -19.20 ± 0.18 mag. The peak bolometric luminosity indicates that ∼ 0.66 M⊙ mass of 56 Ni was ejected by the supernova. The spectral evolution indicates the supernova to be a normal type Ia event.