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How primordial is the structure of comet 67P?. Combined collisional and dynamical models suggest a late formation
Benz, W.; Morbidelli, A.; Jutzi, M. +2 more
Context. There is an active debate about whether the properties of comets as observed today are primordial or, alternatively, if they are a result of collisional evolution or other processes.
Aims: We investigate the effects of collisions on a comet with a structure like 67P/Churyumov-Gerasimenko (67P). We develop scaling laws for the critica…
The scattering phase function of comet 67P/Churyumov-Gerasimenko coma as seen from the Rosetta/OSIRIS instrument
Jorda, L.; Lara, L. M.; Bertaux, J. -L. +52 more
The study of dust, the most abundant material in cometary nuclei, is pivotal in understanding the original materials forming the Solar system. Measuring the coma phase function provides a tool to investigate the nature of cometary dust. Rosetta/OSIRIS sampled the coma phase function of comet 67P/Churyumov-Gerasimenko, covering a large phase angle …
High energy polarimetry of prompt GRB emission
McConnell, Mark L.
[Evidence] of polarized γ-ray emission (> 50 keV) from Gamma-Ray Bursts (GRBs) has been accumulated in recent years. Measurements have been reported with levels in the range of 30-80%, typically with limited statistical significance. No clear picture has yet emerged with regards to the polarization properties of GRBs. Taken at face value, the d…
A Gaia-PS1-SDSS (GPS1) Proper Motion Catalog Covering 3/4 of the Sky
Goldman, Bertrand; Tian, Hai-Jun; Rix, Hans-Walter +7 more
We combine Gaia DR1, PS1, Sloan Digital Sky Survey (SDSS), and 2MASS astrometry to measure proper motions for 350 million sources across three-fourths of the sky down to a magnitude of {m}r∼ 20. Using positions of galaxies from PS1, we build a common reference frame for the multi-epoch PS1, single-epoch SDSS and 2MASS data, and calibrat…
Dust mass distribution around comet 67P/Churyumov-Gerasimenko determined via parallax measurements using Rosetta's OSIRIS cameras
Jorda, L.; Lara, L. M.; Bertaux, J. -L. +50 more
The OSIRIS (optical, spectroscopic and infrared remote imaging system) instrument on board the ESA Rosetta spacecraft collected data of 67P/Churyumov-Gerasimenko for over 2 yr. OSIRIS consists of two cameras, a Narrow Angle Camera and a Wide Angle Camera. For specific imaging sequences related to the observation of dust aggregates in 67P's coma, t…
Virgo Redux: The Masses and Stellar Content of Nuclei in Early-type Galaxies from Multiband Photometry and Spectroscopy
Cuillandre, Jean-Charles; Gwyn, Stephen; Côté, Patrick +14 more
We present an analysis of 39 nuclei and their early-type hosts in the Virgo Cluster using 10 broadband filters: F300W, F475W, F850LP, F160W, {u}* {\text{}}{griz}, and K s . We describe the Virgo Redux program, which provides high-resolution UV and NIR imaging. Combining this data with optical and NIR imaging from the ACS Vir…
Improved constraints on lepton asymmetry from the cosmic microwave background
Schwarz, Dominik J.; Oldengott, Isabel M.
A cosmic lepton asymmetry η\text{l}=(n\text{l}-n\bar{\text{l}})/nγ affects the primordial helium abundance and the expansion rate of the early Universe. Both of these effects have an impact on the anisotropies of the cosmic microwave background (CMB). We derive constraints on the neutrino chemical potent…
Probing the geometry and motion of AGN coronae through accretion disc emissivity profiles
Gallo, L. C.; Wilkins, D. R.; Gonzalez, A. G.
To gain a better understanding of the inner disc region that comprises active galactic nuclei, it is necessary to understand the pattern in which the disc is illuminated (the emissivity profile) by X-rays emitted from the continuum source above the black hole (corona). The differences in the emissivity profiles produced by various corona geometrie…
CME Dynamics Using STEREO and LASCO Observations: The Relative Importance of Lorentz Forces and Solar Wind Drag
Vourlidas, Angelos; Subramanian, Prasad; Bothmer, Volker +1 more
We seek to quantify the relative contributions of Lorentz forces and aerodynamic drag on the propagation of solar coronal mass ejections (CMEs). We use Graduated Cylindrical Shell (GCS) model fits to a representative set of 38 CMEs observed with the Solar and Heliospheric Observatory (SOHO) and the Solar and Terrestrial Relations Observatory (STER…
NGC 1980 Is Not a Foreground Population of Orion: Spectroscopic Survey of Young Stars with Low Extinction in Orion A
Fang, Min; Pascucci, Ilaria; Wang, Hongchi +6 more
We perform a spectroscopic survey of the foreground population in Orion A with MMT/Hectospec. We use these data, along with archival spectroscopic data and photometric data, to derive spectral types, extinction values, and masses for 691 stars. Using the Spitzer Space Telescope data, we characterize the disk properties of these sources. We identif…