Search Publications
Testing Metal-Poor Stellar Models and Isochrones with HST Parallaxes of Metal-Poor Stars
McArthur, B. E.; Benedict, G. F.; Sarajedini, A. +7 more
Hubble Space Telescope (HST) fine guidance sensor observations were used to obtain parallaxes of eight metal-poor ([Fe/H] < -1.4) stars. The parallaxes of these stars determined by the new Hipparcos reduction average 17% accuracy, in contrast to our new HST parallaxes, which average 1% accuracy and have errors on the individual parallaxes rangi…
DDO 216-A1: A Central Globular Cluster in a Low-luminosity Transition-type Galaxy
Dolphin, Andrew E.; Skillman, Evan D.; Williams, Benjamin F. +11 more
We confirm that the object DDO 216-A1 is a substantial globular cluster at the center of Local Group galaxy DDO 216 (the Pegasus dwarf irregular), using Hubble Space Telescope ACS imaging. By fitting isochrones, we find the cluster metallicity [M/H] = -1.6 ± 0.2, for reddening E(B-V) = 0.16 ± 0.02 the best-fit age is 12.3 ± 0.8 Gyr. There are ≈ 30…
Comets: looking ahead
A'Hearn, Michael F.
We outline the key questions about comets that must be answered in order to understand cometary formation in the context of the protoplanetary disc and the role of comets in the formation and evolution of the solar system. We then discuss the new understanding of comets from Rosetta and from other recent advances, including work presented by other…
Mechanical and electrostatic experiments with dust particles collected in the inner coma of comet 67P by COSIMA onboard Rosetta
Altobelli, Nicolas; Haerendel, Gerhard; Langevin, Yves +30 more
The in situ cometary dust particle instrument COSIMA (COmetary Secondary Ion Mass Analyser) onboard ESA's Rosetta mission has collected about 31 000 dust particles in the inner coma of comet 67P/Churyumov-Gerasimenko since August 2014. The particles are identified by optical microscope imaging and analysed by time-of-flight secondary ion mass spec…
Shocks and Tides Quantified in the “Sausage” Cluster, CIZA J2242.8+5301 Using N-body/Hydrodynamical Simulations
Broadhurst, T.; Molnar, S. M.
The colliding cluster, CIZA J2242.8+5301, displays a spectacular, almost 2 Mpc long shock front with a radio based Mach number M≃ 5, that is puzzlingly large compared to the X-ray estimate of M≃ 2.5. The extent to which the X-ray temperature jump is diluted by cooler unshocked gas projected through the cluster currently lacks quantification. Here …
Looking at A 0535+26 at low luminosities with NuSTAR
Hailey, Charles J.; Fürst, Felix; Kretschmar, Peter +12 more
We report on two NuSTAR observations of the high-mass X-ray binary
On the Origin of the Flare Emission in IRIS’ SJI 2832 Filter:Balmer Continuum or Spectral Lines?
Krucker, Säm; Heinzel, Petr; Kleint, Lucia
Continuum (“white-light,” WL) emission dominates the energetics of flares. Filter-based observations, such as the IRIS SJI 2832 filter, show WL-like brightenings during flares, but it is unclear whether the emission arises from real continuum emission or enhanced spectral lines, possibly turning into emission. The difficulty in filter-based observ…
Separating galaxies from the cluster dark matter halo in Abell 611
Zitrin, A.; Koekemoer, A.; Postman, M. +7 more
We investigate the mass content of galaxies in the core of the galaxy cluster Abell 611. We perform a strong lensing analysis of the cluster core and use velocity dispersion measurements for individual cluster members as additional constraints. Despite the small number of multiply-imaged systems and cluster members with central velocity dispersion…
No Sign of Strong Molecular Gas Outflow in an Infrared-bright Dust-obscured Galaxy with Strong Ionized-gas Outflow
Imanishi, Masatoshi; Toba, Yoshiki; Nagao, Tohru +4 more
We report the discovery of an infrared (IR)-bright dust-obscured galaxy (DOG) that shows a strong ionized-gas outflow but no significant molecular gas outflow. Based on detailed analysis of their optical spectra, we found some peculiar IR-bright DOGs that show strong ionized-gas outflow ([O III] λ5007) from the central active galactic nucleus (AGN…
Exploratory Spectroscopy of Magnetic Cataclysmic Variables Candidates and Other Variable Objects
Oliveira, A. S.; Rodrigues, C. V.; Palhares, M. S. +5 more
The increasing number of synoptic surveys made by small robotic telescopes, such as the photometric Catalina Real-Time Transient Survey (CRTS), provides a unique opportunity to discover variable sources and improves the statistical samples of such classes of objects. Our goal is the discovery of magnetic Cataclysmic Variables (mCVs). These are rar…