Search Publications
Nuclear Spirals as Feeding Channels to the Supermassive Black Hole: The Case of the Galaxy NGC 6951
Östlin, Göran; Robinson, Andrew; Marconi, Alessandro +5 more
We report the discovery of gas streaming motions along nuclear spiral arms toward the LINER nucleus of the galaxy NGC 6951. The observations, obtained using the GMOS integral field spectrograph on the Gemini North telescope, yielded maps of the flux distributions and gas kinematics in the Hα, [N II] λ6584, and [S II] λλ6717, 6731 emission lines of…
NGC 5548 in a Low-Luminosity State: Implications for the Broad-Line Region
Peterson, Bradley M.; Pogge, Richard W.; Vestergaard, Marianne +15 more
We describe results from a new ground-based monitoring campaign on NGC 5548, the best-studied reverberation-mapped AGN. We find that it was in the lowest luminosity state yet recorded during a monitoring program, namely L5100=4.7×1042 ergs s-1. We determine a rest-frame time lag between flux variations in the conti…
Prompt and Afterglow Emission Properties of Gamma-Ray Bursts with Spectroscopically Identified Supernovae
Ramirez-Ruiz, Enrico; Kouveliotou, Chryssa; Kaneko, Yuki +8 more
We present a detailed spectral analysis of the prompt and afterglow emission of four nearby long-soft gamma-ray bursts (GRBs 980425, 030329, 031203, and 060218) that were spectroscopically found to be associated with Type Ic supernovae and compare them to the general GRB population. For each event, we investigate the spectral and luminosity evolut…
Source of Nitrogen Isotope Anomaly in HCN in the Atmosphere of Titan
Liang, Mao-Chang; Yung, Yuk L.; Heays, Alan N. +2 more
The 14N/15N ratio for N2 in the atmosphere of Titan was recently measured to be a factor of 2 higher than the corresponding ratio for HCN. Using a one-dimensional photochemical model with transport, we incorporate new isotopic photoabsorption and photodissociation cross sections of N2, computed quantum-m…
Evidence of a Broad Relativistic Iron Line from the Neutron Star Low-Mass X-Ray Binary Serpens X-1
Strohmayer, Tod E.; Bhattacharyya, Sudip
We report on an analysis of XMM-Newton data from the neutron star low-mass X-ray binary (LMXB) Serpens X-1 (Ser X-1). Spectral analysis of EPIC PN data indicates that the previously known broad iron Kα emission line from this source has a significantly skewed structure with a moderately extended red wing. The asymmetric shape of the line is well d…
The Intrinsically X-Ray Weak Quasar PHL 1811. I. X-Ray Observations and Spectral Energy Distribution
Jenkins, Edward B.; Halpern, Jules P.; Leighly, Karen M. +3 more
This is the first of two papers reporting observations and analysis of the unusually bright (mb=14.4), luminous (MB=-25.5), nearby (z=0.192) narrow-line quasar PHL 1811, focusing on the X-ray properties and the spectral energy distribution. Two Chandra observations reveal a weak X-ray source with a steep spectrum. Variability…
Photolytically Generated Aerosols in the Mesosphere and Thermosphere of Titan
Shemansky, Donald E.; Liang, Mao-Chang; Yung, Yuk L.
Analysis of the Cassini Ultraviolet Imaging Spectrograph (UVIS) stellar and solar occultations at Titan to date include 12 species: N2 (nitrogen), CH4 (methane), C2H2 (acetylene), C2H4 (ethylene), C2H6 (ethane), C4H2 (diacetylene), C6…
The Metallicity Distribution of Intracluster Stars in Virgo
Ferguson, Henry C.; Williams, Benjamin F.; Gerhard, Ortwin +11 more
We have used the Hubble Space Telescope's Advanced Camera for Surveys (ACS) to detect and measure ~5300 stars in a single intracluster field in the Virgo Cluster. By performing F606W and F814W photometry on these stars, we have determined their metallicity distribution function and constrained the types of stars present in this portion of Virgo's …
The UDF05 Follow-up of the Hubble Ultra Deep Field. I. The Faint-End Slope of the Lyman Break Galaxy Population at z ~ 5
Panagia, N.; Gardner, Jonathan P.; Ferguson, H. C. +14 more
We present the UDF05 HST program, which consists of three disjoint fields-NICP12, NICP34, plus the HUDF-with deep ACS (F606W, F775W, and F850LP) and NICMOS (F110W and F160W) imaging. Here we use the ACS data for the NICP12 and HUDF fields to implement a (V-i)-(i-z) selection criterion that allows us to identify a sample of 101 (133) z~5 Lyman brea…
Multispacecraft Measurement of Anisotropic Correlation Functions in Solar Wind Turbulence
Horbury, T. S.; Osman, K. T.
Multispacecraft measurements in the solar wind are used to determine the field-aligned anisotropy of magnetohydrodynamic inertial range turbulence. The ratio of the parallel to perpendicular correlation lengths is measured by using time-lagged two-point correlations to construct a spatial autocorrelation function. The mean ratio obtained, 1.79+/-0…