Browsing by Subject "collapse"
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Item Molecular Line Observations Of The Small Protostellar Group L1251B(2007-12) Lee, Jeong-Eun; Di Francesco, James; Bourke, Tyler L.; Evans, Neal J.; Wu, Jingwen; Evans, Neal J.We present molecular line observations of L1251B, a small group of pre- and protostellar objects, and its immediate environment in the dense (CO)-O-18 core L1251E. These data are complementary to near-infrared, submillimeter, and millimeter continuum observations reported by Lee et al. The single-dish data of L1251B described here show very complex kinematics, including infall, rotation, and outflow motions, and the interferometer data reveal these in greater detail. Interferometer data of N2H+ 1-0 suggest a very rapidly rotating flattened envelope between two young stellar objects, IRS1 and IRS2. In addition, interferometer data of CO 2-1 resolve the outflow associated with L1251B seen in single-dish maps into a few narrow and compact components. Furthermore, the high-resolution data support recent theoretical studies of molecular depletions and enhancements that accompany the formation of protostars within dense cores. Beyond L1251B, single-dish data are also presented of a dense core located similar to 150 '' to the east that Lee et al. detected at 850 mu m, but that has no associated point sources at near- and mid-infrared wavelengths. The relative brightness between molecules, which have different chemical timescales, suggests that it is less chemically evolved than L1251B. This core may be a site for future star formation, however, since line profiles of HCO+, CS, and HCN show asymmetry with a stronger blue peak, which is interpreted as an infall signature.Item A Novel Paradigm For Short Gamma-Ray Bursts With Extended X-Ray Emission(2015-04) Rezzolla, Luciano; Kumar, Pawan; Kumar, PawanThe merger of a binary of neutron stars provides natural explanations for many of the features of short gamma-ray bursts (SGRBs), such as the generation of a hot torus orbiting a rapidly rotating black hole, which can then build a magnetic jet and provide the energy reservoir to launch a relativistic outflow. However, this scenario has problems explaining the recently discovered long-term and sustained X-ray emission associated with the afterglows of a subclass of SGRBs. We propose a new model that explains how an X-ray afterglow can be sustained by the product of the merger and how the X-ray emission is produced before the corresponding emission in the gamma-band, though it is observed to follow it. Overall, our paradigm combines in a novel manner a number of well-established features of the emission in SGRBs and results from simulations. Because it involves the propagation of an ultra-relativistic outflow and its interaction with a confining medium, the paradigm also highlights a unifying phenomenology between short and long GRBs.Item A Parameter Study Of The Dust And Gas Temperature In A Field Of Young Stars(2009-06) Urban, Andrea; Evans, Neal J.; Doty, Steven D.; Urban, Andrea; Evans, Neal J.We model the thermal effect of young stars on their surrounding environment in order to understand clustered star formation. We take radiative heating of dust, dust-gas collisional heating, cosmic-ray heating, and molecular cooling into account. Using DUSTY, a spherical continuum radiative transfer code, we model the dust temperature distribution around young stellar objects with various luminosities and surrounding gas and dust density distributions. We have created a grid of dust temperature models, based on our modeling with DUSTY, which we can use to calculate the dust temperature in a field of stars with various parameters. We then determine the gas temperature assuming energy balance. Our models can be used to make large-scale simulations of clustered star formation more realistic.Item A Semianalytical Light Curve Model And Its Application To Type IIp Supernovae Light(2014-11) Nagy, A. P.; Ordasi, A.; Vinko, J.; Wheeler, J. C.; Vinko, J.; Wheeler, J. C.The aim of this work is to present a semianalytical light curve model code that can be used for estimating physical properties of core collapse supernovae (SNe) in a quick and efficient way. To verify our code we fit light curves of Type II SNe and compare our best parameter estimates to those from hydrodynamical calculations. For this analysis, we use quasi-bolometric light curves of five different Type IIP SNe. In each case, we obtain appropriate results for initial pre-supernova parameters. We conclude that this semianalytical light curve model is useful to obtaining approximate physical properties of Type II SNe without using time-consuming numerical hydrodynamic simulations. lightItem A Semianalytical Light Curve Model And Its Application To Type IIp Supernovae Light(2014-11) Nagy, A. P.; Ordasi, A.; Vinko, J.; Wheeler, J. C.; Vinko, J.; Wheeler, J. C.The aim of this work is to present a semianalytical light curve model code that can be used for estimating physical properties of core collapse supernovae (SNe) in a quick and efficient way. To verify our code we fit light curves of Type II SNe and compare our best parameter estimates to those from hydrodynamical calculations. For this analysis, we use quasi-bolometric light curves of five different Type IIP SNe. In each case, we obtain appropriate results for initial pre-supernova parameters. We conclude that this semianalytical light curve model is useful to obtaining approximate physical properties of Type II SNe without using time-consuming numerical hydrodynamic simulations. light