Cerenkov radiation by neutrinos in a supernova core

Neutrinos with a magnetic dipole moment propagating in a medium with a velocity larger than the phase velocity of light emit photons by the Cerenkov process. The Cerenkov radiation is a helicity flip process via which a left-handed neutrino in a supernova core may change into a sterile right-handed one and freestream out of the core. Assuming that the luminosity of the sterile right-handed neutrinos is less than 10^{53} ergs/sec gives an upper bound on the neutrino magnetic dipole moment \mu_\nu < 0.5 \times 10^{-13} \mu_B. This is two orders of magnitude more stringent than the previously established bounds on \mu_\nu from considerations of supernova cooling rate by right-handed neutrinos

W40 region in the Gould Belt : An embedded cluster and H II region at the junction of filaments

We present a multiwavelength study of W40 star-forming region using IR observations in UKIRT JHK bands, Spitzer IRAC bands & Herschel PACS bands; 2.12 micron H2 narrow-band imaging; & radio observations from GMRT (610 & 1280 MHz), in a FoV of ~34'x40'. Spitzer observations along with NIR observations are used to identify 1162 Class II/III & 40 Class I sources in the FoV. The NN stellar surface density analysis shows that majority of these YSOs constitute the embedded cluster centered on the source IRS1A South. Some YSOs, predominantly younger population, are distributed along & trace the filamentary structures at lower stellar surface density. The cluster radius is obtained as 0.44pc - matching well with the extent of radio emission - with a peak density of 650pc^-2. The JHK data is used to map the extinction which is subsequently used to compute the cloud mass. It has resulted in 126 Msun & 71 Msun for the central cluster & the northern IRS5 region, respectively. H2 narrow-band imaging displays significant emission, which prominently resembles fluorescent emission arising at the borders of dense regions. Radio analysis shows this region as having blister morphology, with the radio peak coinciding with a protostellar source. Free-free emission SED analysis is used to obtain physical parameters of the overall region & the IRS5 sub-region. This multiwavelength scenario is suggestive of star formation having resulted from merging of multiple filaments to form a hub. Star formation seems to have taken place in two successive epochs, with the first epoch traced by the central cluster & the high-mass star(s) - followed by a second epoch which is spreading into the filaments as uncovered by the Class I sources & even younger protostellar sources along the filaments. The IRS5 HII region displays indications of swept-up material which has possibly led to the formation of protostars.Comment: 17 pages, 12 figures, 2 tables. Accepted for publication in The Astrophysical Journa

Exploring Foundations of Time-Independent Density Functional Theory for Excited-States

Based on the work of Gorling and that of Levy and Nagy, density-functional formalism for many Fermionic excited-states is explored through a careful and rigorous analysis of the excited-state density to external potential mapping. It is shown that the knowledge of the ground-state density is a must to fix the mapping from an excited-state density to the external potential. This is the excited-state counterpart of the Hohenberg-Kohn theorem, where instead of the ground-state density the density of the excited-state gives the true many-body wavefunctions of the system. Further, the excited-state Kohn-Sham system is defined by comparing it's non-interacting kinetic energy with the true kinetic energy. The theory is demonstrated by studying a large number of atomic systems.Comment: submitted to J. Chem. Phy