Search Publications
The global history of reionization
Mesinger, Andrei; Greig, Bradley
Using a Bayesian framework, we quantify what current observations imply about the history of the epoch of reionization (EoR). We use a popular, three-parameter EoR model, flexible enough to accommodate a wide range of physically plausible reionization histories. We study the impact of various EoR observations: (I) the optical depth to the CMB meas…
Reconstruction of Galaxy Star Formation Histories through SED Fitting:The Dense Basis Approach
Gawiser, Eric; Iyer, Kartheik
We introduce the dense basis method for Spectral Energy Distribution (SED) fitting. It accurately recovers traditional SED parameters, including M *, SFR, and dust attenuation, and reveals previously inaccessible information about the number and duration of star formation episodes and the timing of stellar mass assembly, as well as unce…
The Atmospheric Dynamics of Venus
Sánchez-Lavega, Agustín; Imamura, Takeshi; Lebonnois, Sebastien +2 more
We review our current knowledge of the atmospheric dynamics of Venus prior to the Akatsuki mission, in the altitude range from the surface to approximately the cloud tops located at about 100 km altitude. The three-dimensional structure of the wind field in this region has been determined with a variety of techniques over a broad range of spatial …
Lessons from the Onset of a Common Envelope Episode: the Remarkable M31 2015 Luminous Red Nova Outburst
Ramirez-Ruiz, Enrico; MacLeod, Morgan; Grindlay, Jonathan +3 more
This paper investigates the recent stellar-merger transient M31LRN 2015 in the Andromeda galaxy. We analyze published optical photometry and spectroscopy along with a Hubble Space Telescope detection of the color and magnitude of the pre-outburst source. The transient outburst is consistent with dynamically driven ejecta at the onset of a common e…
Coronal Magnetic Field Models
Riley, Pete; Wiegelmann, Thomas; Petrie, Gordon J. D.
Coronal magnetic field models use photospheric field measurements as boundary condition to model the solar corona. We review in this paper the most common model assumptions, starting from MHD-models, magnetohydrostatics, force-free and finally potential field models. Each model in this list is somewhat less complex than the previous one and makes …
ULX spectra revisited: Accreting, highly magnetized neutron stars as the engines of ultraluminous X-ray sources
Vasilopoulos, Georgios; Bachetti, Matteo; Godet, Olivier +3 more
Aims: In light of recent discoveries of pulsating ultraluminous X-ray sources (ULXs) and recently introduced theoretical schemes that propose neutron stars (NSs) as the central engines of ULXs, we revisit the spectra of eighteen well known ULXs, in search of indications that favour this newly emerging hypothesis.
Methods: We examine the …
Seasonal variability of the hydrogen exosphere of Mars
Halekas, J. S.
The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission measures both the upstream solar wind and collisional products from energetic neutral hydrogen atoms that precipitate into the upper atmosphere after their initial formation by charge exchange with exospheric hydrogen. By computing the ratio between the densities of these populations, we d…
BAT AGN Spectroscopic Survey (BASS) - VI. The ΓX-L/LEdd relation
Lamperti, Isabella; Schawinski, Kevin; Veilleux, Sylvain +11 more
We study the relation between accretion rate (in terms of L/LEdd) and shape of the hard X-ray spectral energy distribution (namely the photon index Γx) for a large sample of 228 hard X-ray-selected, low-redshift active galactic nuclei (AGNs), drawn from the Swift/BAT AGN Spectroscopic Survey (BASS). This includes 30 AGNs for …
The Fraction of Cool-core Clusters in X-Ray versus SZ Samples Using Chandra Observations
Lovisari, Lorenzo; Andrade-Santos, Felipe; Jones, Christine +21 more
We derive and compare the fractions of cool-core clusters in the Planck Early Sunyaev-Zel’dovich sample of 164 clusters with z≤slant 0.35 and in a flux-limited X-ray sample of 100 clusters with z≤slant 0.30, using Chandra observations. We use four metrics to identify cool-core clusters: (1) the concentration parameter, which is the ratio of the in…
The host galaxies and explosion sites of long-duration gamma ray bursts: Hubble Space Telescope near-infrared imaging
Lyman, J. D.; Bloom, J. S.; Angus, C. R. +10 more
We present the results of a Hubble Space Telescope WFC3/F160W Snapshot survey of the host galaxies of 39 long-duration gamma-ray bursts (LGRBs) at z < 3. We have non-detections of hosts at the locations of four bursts. Sufficient accuracy to astrometrically align optical afterglow images and determine the location of the LGRB within its host wa…