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LISA pathfinder appreciably constrains collapse models
Slagmolen, B. J. J.; Helou, Bassam; McClelland, David E. +1 more
Spontaneous collapse models are phenomological theories formulated to address major difficulties in macroscopic quantum mechanics. We place significant bounds on the parameters of the leading collapse models, the continuous spontaneous localization (CSL) model, and the Diosi-Penrose (DP) model, by using LISA Pathfinder's measurement, at a record a…
On the progenitor of the Type IIb supernova 2016gkg
Treu, Tommaso; Kilpatrick, Charles D.; Foley, Ryan J. +7 more
We present a detection in pre-explosion Hubble Space Telescope (HST) imaging of a point source consistent with being the progenitor star of the Type IIb supernova (SN IIb) 2016gkg. Post-explosion imaging from the Keck adaptive optics system was used to perform relative astrometry between the Keck and HST imaging. We identify a single point source …
Evidence that the AGN dominates the radio emission in z ∼ 1 radio-quiet quasars
Jarvis, Matt J.; Kalfountzou, Eleni; White, Sarah V. +4 more
In order to understand the role of radio-quiet quasars (RQQs) in galaxy evolution, we must determine the relative levels of accretion and star-formation activity within these objects. Previous work at low radio flux densities has shown that accretion makes a significant contribution to the total radio emission, in contrast with other quasar studie…
Luminous and Variable Stars in M31 and M33. IV. Luminous Blue Variables, Candidate LBVs, B[e] Supergiants, and the Warm Hypergiants: How to Tell Them Apart
Humphreys, Roberta M.; Gordon, Michael S.; Martin, John C. +2 more
In this series of papers we have presented the results of a spectroscopic survey of luminous stars in the nearby spirals M31 and M33. Here, we present spectroscopy of 132 additional stars. Most have emission-line spectra, including luminous blue variables (LBVs) and candidate LBVs, Fe II emission line stars, the B[e] supergiants, and the warm hype…
Absolute Ages and Distances of 22 GCs Using Monte Carlo Main-sequence Fitting
Chaboyer, Brian; O'Malley, Erin M.; Gilligan, Christina
The recent Gaia Data Release 1 of stellar parallaxes provides ample opportunity to find metal-poor main-sequence stars with precise parallaxes. We select 21 such stars with parallax uncertainties better than σ π /π ≤ 0.10 and accurate abundance determinations suitable for testing metal-poor stellar evolution models and determining the …
Properties of the cosmological filament between two clusters: A possible detection of a large-scale accretion shock by Suzaku
Kaastra, J. S.; Mernier, F.; Ishisaki, Y. +7 more
We report on the results of a Suzaku observation of the plasma in the filament located between the two massive clusters of galaxies, Abell 399 and Abell 401. Abell 399 (z = 0.0724) and Abell 401 (z = 0.0737) are expected to be in the initial phase of a cluster merger. In the region between the two clusters, we find a clear enhancement in the tempe…
The Sirius System and Its Astrophysical Puzzles: Hubble Space Telescope and Ground-based Astrometry
Schaefer, Gail H.; Bond, Howard E.; Burleigh, Matthew R. +11 more
Sirius, the seventh-nearest stellar system, is a visual binary containing the metallic-line A1 V star Sirius A, the brightest star in the sky, orbited in a 50.13 year period by Sirius B, the brightest and nearest white dwarf (WD). Using images obtained over nearly two decades with the Hubble Space Telescope (HST), along with photographic observati…
Sulfur dioxide in the Venus atmosphere: I. Vertical distribution and variability
Vandaele, A. C.; Robert, S.; Montmessin, F. +18 more
Recent observations of sulfur containing species (SO2, SO, OCS, and H2SO4) in Venus' mesosphere have generated controversy and great interest in the scientific community. These observations revealed unexpected spatial patterns and spatial/temporal variability that have not been satisfactorily explained by models. S…
Diamagnetic region(s): structure of the unmagnetized plasma around Comet 67P/CG
Glassmeier, K. -H.; Nilsson, H.; Carr, C. +14 more
The ESA's comet chaser Rosetta has monitored the evolution of the ionized atmosphere of comet 67P/Churyumov-Gerasimenko (67P/CG) and its interaction with the solar wind, during more than 2 yr. Around perihelion, while the cometary outgassing rate was highest, Rosetta crossed hundreds of unmagnetized regions, but did not seem to have crossed a larg…
The PdBI Arcsecond Whirlpool Survey (PAWS): The Role of Spiral Arms in Cloud and Star Formation
Leroy, Adam K.; Meidt, Sharon E.; Hughes, Annie +9 more
The process that leads to the formation of the bright star-forming sites observed along prominent spiral arms remains elusive. We present results of a multi-wavelength study of a spiral arm segment in the nearby grand-design spiral galaxy M51 that belongs to a spiral density wave and exhibits nine gas spurs. The combined observations of the (ioniz…