Search Publications
Analysis of Supergranule Sizes and Velocities Using Solar Dynamics Observatory (SDO)/ Helioseismic Magnetic Imager (HMI) and Solar and Heliospheric Observatory (SOHO)/ Michelson Doppler Imager (MDI) Dopplergrams
Williams, Peter E.; Pesnell, W. Dean; Beck, John G. +1 more
Co-temporal Doppler images from Solar and Heliospheric Observatory (SOHO)/Michelson Doppler Imager (MDI) and Solar Dynamics Observatory (SDO)/Helioseismic Magnetic Imager (HMI) have been analyzed to extract quantitative information about global properties of the spatial and temporal characteristics of solar supergranulation. Preliminary comparison…
Dusty shells surrounding the carbon variables S Scuti and RT Capricorni
Blommaert, J. A. D. L.; Ottensamer, R.; Decin, L. +8 more
For the Mass-loss of Evolved StarS (MESS) programme, the unprecedented spatial resolution of the PACS photometer on board the Herschel Space Observatory was employed to map the dusty environments of asymptotic giant branch (AGB) and red supergiant (RSG) stars. Among the morphologically heterogeneous sample, a small fraction of targets is enclosed …
Ionization toward the high-mass star-forming region NGC 6334 I
Ceccarelli, Cecilia; Lis, Dariusz C.; Olmi, Luca +3 more
Context. Ionization plays a central role in the gas-phase chemistry of molecular clouds. Since ions are coupled with magnetic fields, which can in turn counteract gravitational collapse, it is of paramount importance to measure their abundance in star-forming regions.
Aims: We use spectral line observations of the high-mass star-forming regio…
Anomalous flows in a sunspot penumbra
Venkatakrishnan, P.; Mathew, Shibu K.; Louis, Rohan E. +1 more
Context. The photospheric Evershed flow is a distinct characteristic of penumbrae that is closely associated with the photometric and magnetic structure of sunspots.
Aims: We analyse the properties of an anomalous flow in the photosphere in a sunspot penumbra and compare it with those of the regular Evershed flow.
Methods: High-resolutio…
Cosmic-Ray Modulation: an Ab Initio Approach
Burger, R. A.; Engelbrecht, N. E.
A better understanding of cosmic-ray modulation in the heliosphere can only be gained through a proper understanding of the effects of turbulence on the diffusion and drift of cosmic rays. We present an ab initio model for cosmic-ray modulation, incorporating for the first time the results yielded by a two-component turbulence transport model. Thi…
XMM-Newton Observations of Young and Energetic Pulsar J2022+3842
Pavlov, G. G.; Kargaltsev, O.; Arumugasamy, P.
We report on XMM-Newton EPIC observations of the young pulsar J2022+3842, with a characteristic age of 8.9 kyr. We detected X-ray pulsations and found the pulsation period P ≈ 48.6 ms, and its derivative \dot{P}\approx 8.6\times 10^{-14}, which is two times larger than previously reported values. The pulsar exhibits two very narrow (FWHM ~1.2 ms) …
SCoPE: an efficient method of Cosmological Parameter Estimation
Das, Santanu; Souradeep, Tarun
Markov Chain Monte Carlo (MCMC) sampler is widely used for cosmological parameter estimation from CMB and other data. However, due to the intrinsic serial nature of the MCMC sampler, convergence is often very slow. Here we present a fast and independently written Monte Carlo method for cosmological parameter estimation named as Slick Cosmological …
Star Formation Rate and Extinction in Faint z ~ 4 Lyman Break Galaxies
Owen, Frazer N.; Wang, Wei-Hao; To, Chun-Hao
We present a statistical detection of 1.5 GHz radio continuum emission from a sample of faint z ~ 4 Lyman break galaxies (LBGs). To constrain their extinction and intrinsic star formation rate (SFR), we combine the latest ultradeep Very Large Array 1.5 GHz radio image and the Hubble Space Telescope Advanced Camera for Surveys (ACS) optical images …
Dust formation by failed supernovae
Kochanek, C. S.
We consider dust formation during the ejection of the hydrogen envelope of a red supergiant during a failed supernova (SN) creating a black hole. While the dense, slow moving ejecta are very efficient at forming dust, only the very last phases of the predicted visual transient will be obscured. The net grain production consists of Md ∼ …
Binary white dwarfs in the halo of the Milky Way
Toonen, Silvia; Brown, Anthony G. A.; Helmi, Amina +4 more
Aims: We study single and binary white dwarfs in the inner halo of the Milky Way in order to learn more about the conditions under which the population of halo stars was born, such as the initial mass function (IMF), the star formation history, or the binary fraction.
Methods: We simulate the evolution of low-metallicity halo stars at di…