Search Publications
Nonlinear Color-Metallicity Relations of Globular Clusters. II. A Test on the Nonlinearity Scenario for Color Bimodality Using the u-band Colors: The Case of M87 (NGC 4486)
Blakeslee, John P.; Sohn, Sangmo T.; Kim, Hak-Sub +4 more
The optical color distributions of globular clusters (GCs) in most large elliptical galaxies are bimodal. Based on the assumed linear relationship between GC colors and their metallicities, the bimodality has been taken as evidence of two GC subsystems with different metallicities in each galaxy and has led to a number of theories in the context o…
The influence of pickup protons, from interstellar neutral hydrogen, on the propagation of interplanetary shocks from the Halloween 2003 solar events to ACE and Ulysses: A 3-D MHD modeling study
Dryer, M.; Sun, W.; Intriligator, D. S. +3 more
We describe our 3-D, time-dependent, MHD solar wind model that we recently modified to include the physics of pickup protons from interstellar neutral hydrogen. The model has a time-dependent lower boundary condition, at 0.1 AU, that is driven by source surface map files through an empirical interface module. We describe the empirical interface an…
The stellar and hot gas content of low-mass galaxy clusters
Balogh, Michael L.; Theuns, Tom; Mazzotta, Pasquale +4 more
We analyse the stellar and hot gas content of 18 nearby, low-mass galaxy clusters, detected in redshift space and selected to have a dynamical mass 3 × 1014 < M/M⊙ < 6 × 1014 (h= 0.7), as measured from the 2dF Galaxy Redshift Survey. We combine X-ray measurements from both Chandra and XMM with ground-based ne…
Exploring Dust Extinction at the Edge of Reionization
Fynbo, Johan P. U.; Tanvir, Nial R.; Levan, Andrew J. +3 more
The brightness of gamma-ray burst (GRB) afterglows and their occurrence in young, blue galaxies make them excellent probes to study star-forming regions in the distant universe. We here elucidate dust extinction properties in the early universe through the analysis of the afterglows of all known z > 6 GRBs: GRB 090423, 080913, and 050904, at z …
Discovery of 59 ms pulsations from 1RXS J141256.0+792204 (Calvera)
Haberl, F.; Esposito, P.; Pellizzoni, A. +10 more
We report on the results of a multi-wavelength study of the compact object candidate 1RXS J141256.0+792204 (Calvera). Calvera was observed in the X-rays with XMM-Newton/EPIC twice for a total exposure time of ∼50 ks. The source spectrum is thermal and well reproduced by a two-component model composed of either two (absorbed) hydrogen atmosphere mo…
Anatomy of a Post-starburst Minor Merger: A Multi-wavelength WFC3 Study of NGC 4150
Mutchler, Max; McCarthy, Patrick J.; Calzetti, Daniela +22 more
We present a spatially resolved near-UV/optical study, using the Wide Field Camera 3 (WFC3) on board the Hubble Space Telescope, of NGC 4150, a sub-L *, early-type galaxy (ETG) of around 6 × 109 M sun, which has been observed as part of the WFC3 Early-Release Science Programme. Previous work indicates that this gal…
Twelve and a Half Years of Observations of Centaurus a with the Rossi X-Ray Timing Explorer
Wilms, J.; Pottschmidt, K.; Kadler, M. +5 more
The Rossi X-ray Timing Explorer (RXTE) has observed the nearest radio galaxy, Centaurus A (Cen A), in 13 intervals from 1996 August to 2009 February over the 3-200 keV band. Spectra accumulated over the 13 intervals were well described with an absorbed power law and an iron line. Cutoff power laws and Compton reflection from cold matter did not pr…
Very Long Baseline Array Astrometric Observations of the Cassini Spacecraft at Saturn
Jacobson, Robert A.; Jones, Dayton L.; Dhawan, Vivek +5 more
The planetary ephemeris is an essential tool for interplanetary spacecraft navigation, studies of solar system dynamics (including, for example, barycenter corrections for pulsar timing ephemerides), the prediction of occultations, and tests of general relativity. We are carrying out a series of astrometric very long baseline interferometry observ…
Discovery of an Energetic 38.5 ms Pulsar Powering the Gamma-ray Source IGR J18490-0000/HESS J1849-000
Gotthelf, E. V.; Terrier, R.; Halpern, J. P. +1 more
We report the discovery of a 38.5 ms X-ray pulsar in observations of the soft γ-ray source IGR J18490-0000 with the Rossi X-ray Timing Explorer (RXTE). PSR J1849-0001 is spinning down rapidly with period derivative 1.42 × 10-14 s s-1, yielding a spin-down luminosity \dot{E} = 9.8 × 1036 erg s-1, characte…
Observing Evolution in the Supergranular Network Length Scale During Periods of Low Solar Activity
McIntosh, Scott W.; Ulrich, Roger K.; Leamon, Robert J. +2 more
We present the initial results of an observational study into the variation of the dominant length scale of quiet solar emission: supergranulation. The distribution of magnetic elements in the lanes that from the network affects, and reflects, the radiative energy in the plasma of the upper solar chromosphere and transition region at the magnetic …