Search Publications
Quenching of Carbon Monoxide and Methane in the Atmospheres of Cool Brown Dwarfs and Hot Jupiters
Moses, Julianne I.; Visscher, Channon
We explore CO\rightleftarrows CH_{4} quench kinetics in the atmospheres of substellar objects using updated timescale arguments, as suggested by a thermochemical kinetics and diffusion model that transitions from the thermochemical-equilibrium regime in the deep atmosphere to a quench-chemical regime at higher altitudes. More specifically, we exam…
Extended Schmidt Law: Role of Existing Stars in Current Star Formation
Papovich, Casey; Armus, Lee; Helou, George +4 more
We propose an "extended Schmidt law" with explicit dependence of the star formation efficiency (SFE = SFR/M gas) on the stellar mass surface density (Σstar). This relation has a power-law index of 0.48 ± 0.04 and a 1σ observed scatter on the SFE of 0.4 dex, which holds over five orders of magnitude in the stellar density for …
Establishing a Connection Between Active Region Outflows and the Solar Wind: Abundance Measurements with EIS/Hinode
Warren, Harry P.; Brooks, David H.
One of the most interesting discoveries from Hinode is the presence of persistent high-temperature high-speed outflows from the edges of active regions (ARs). EUV imaging spectrometer (EIS) measurements indicate that the outflows reach velocities of 50 km s-1 with spectral line asymmetries approaching 200 km s-1. It has been …
A Stochastic Model for the Luminosity Fluctuations of Accreting Black Holes
Siemiginowska, Aneta; Kelly, Brandon C.; Sobolewska, Małgorzata
In this work, we have developed a new stochastic model for the fluctuations in light curves of accreting black holes. The model is based on a linear combination of stochastic processes and is also the solution to the linear diffusion equation perturbed by a spatially correlated noise field. This allows flexible modeling of the power spectral densi…
Chandra Discovery of a Binary Active Galactic Nucleus in Mrk 739
Sanders, D. B.; Schawinski, Kevin; Koss, Michael +6 more
We have discovered a binary active galactic nucleus (AGN) in the galaxy Mrk 739 using Chandra and Swift BAT. We find two luminous (L 2-10 keV = 1.1 × 1043 and 1.0 × 1042 erg s-1), unresolved nuclei with a projected separation of 3.4 kpc (5farcs8 ± 0farcs1) coincident with two bulge components in the opti…
Magnetic Helicity Spectrum of Solar Wind Fluctuations as a Function of the Angle with Respect to the Local Mean Magnetic Field
Podesta, J. J.; Gary, S. P.
Magnetic field data acquired by the Ulysses spacecraft in high-speed streams over the poles of the Sun are used to investigate the normalized magnetic helicity spectrum σ m as a function of the angle θ between the local mean magnetic field and the flow direction of the solar wind. This spectrum provides important information about the …
Ice and Dust in the Quiescent Medium of Isolated Dense Cores
van Dishoeck, E. F.; Blake, G. A.; Decin, L. +6 more
The relation between ices in the envelopes and disks surrounding young stellar objects (YSOs) and those in the quiescent interstellar medium (ISM) is investigated. For a sample of 31 stars behind isolated dense cores, ground-based and Spitzer spectra and photometry in the 1-25 µm wavelength range are combined. The baseline for the broad and …
A Massive Progenitor of the Luminous Type IIn Supernova 2010jl
Van Dyk, Schuyler D.; Filippenko, Alexei V.; Smith, Nathan +6 more
The bright, nearby, recently discovered supernova (SN) 2010jl is a luminous Type IIn SN. Here, we report archival Hubble Space Telescope (HST) observations of its host galaxy UGC 5189A taken roughly 10 yr prior to explosion, as well as early-time optical spectra of the SN. The HST images reveal a luminous, blue point source at the position of the …
Cluster Mass Profiles from a Bayesian Analysis of Weak-lensing Distortion and Magnification Measurements: Applications to Subaru Data
Broadhurst, Tom; Zitrin, Adi; Umetsu, Keiichi +2 more
We directly construct model-independent mass profiles of galaxy clusters from combined weak-lensing distortion and magnification measurements within a Bayesian statistical framework, which allows for a full parameter-space extraction of the underlying signal. This method applies to the full range of radius outside the Einstein radius, and recovers…
The Progenitor of Supernova 2011dh/PTF11eon in Messier 51
Van Dyk, Schuyler D.; Filippenko, Alexei V.; Cenko, S. Bradley +12 more
We have identified a luminous star at the position of supernova (SN) 2011dh/PTF11eon, in pre-SN archival, multi-band images of the nearby, nearly face-on galaxy Messier 51 (M51) obtained by the Hubble Space Telescope with the Advanced Camera for Surveys. This identification has been confirmed, to the highest available astrometric precision, using …