Search Publications
Star Count Density Profiles and Structural Parameters of 26 Galactic Globular Clusters
Dalessandro, E.; Sanna, N.; Beccari, G. +6 more
We used an appropriate combination of high-resolution Hubble Space Telescope observations and wide-field, ground-based data to derive the radial stellar density profiles of 26 Galactic globular clusters from resolved star counts (which can be all freely downloaded on-line). With respect to surface brightness (SB) profiles (which can be biased by t…
Atmospheric escape from HD 189733b observed in H I Lyman-α: detailed analysis of HST/STIS September 2011 observations
Ehrenreich, D.; Lecavelier des Etangs, A.; Bourrier, V. +8 more
Observations of transits of the hot giant exoplanet
The rapid assembly of an elliptical galaxy of 400 billion solar masses at a redshift of 2.3
Altieri, B.; Aussel, H.; Pérez-Fournon, I. +41 more
Stellar archaeology shows that massive elliptical galaxies formed rapidly about ten billion years ago with star-formation rates of above several hundred solar masses per year. Their progenitors are probably the submillimetre bright galaxies at redshifts z greater than 2. Although the mean molecular gas mass (5 × 1010 solar masses) of th…
The Space Motion of Leo I: Hubble Space Telescope Proper Motion and Implied Orbit
van der Marel, Roeland P.; Majewski, Steven R.; Besla, Gurtina +3 more
We present the first absolute proper motion measurement of Leo I, based on two epochs of Hubble Space Telescope ACS/WFC images separated by ~5 years in time. The average shift of Leo I stars with respect to ~100 background galaxies implies a proper motion of (µ W , µ N ) = (0.1140 ± 0.0295, -0.1256 ± 0.0293) mas y…
Constraints on millicharged particles from Planck data
Dolgov, A. D.; Tkachev, I. I.; Rubtsov, G. I. +1 more
We revisit cosmic microwave background constraints on the abundance of millicharged particles based on the Planck data. The stringent limit Ωmcph2<0.001 (95% CL) may be set using the cosmic microwave background data alone if millicharged particles participate in the acoustic oscillations of baryon-photon plasma at the reco…
The Gemini NICI Planet-Finding Campaign: The Frequency of Giant Planets around Young B and A Stars
Nielsen, Eric L.; Lin, Douglas N. C.; Shkolnik, Evgenya L. +22 more
We have carried out high contrast imaging of 70 young, nearby B and A stars to search for brown dwarf and planetary companions as part of the Gemini NICI Planet-Finding Campaign. Our survey represents the largest, deepest survey for planets around high-mass stars (≈1.5-2.5 M ⊙) conducted to date and includes the planet hosts β Pic and F…
Interferometric radii of bright Kepler stars with the CHARA Array: θ Cygni and 16 Cygni A and B
Stello, D.; White, T. R.; Baron, F. +18 more
We present the results of long-baseline optical interferometry observations using the Precision Astronomical Visual Observations (PAVO) beam combiner at the Center for High Angular Resolution Astronomy (CHARA) Array to measure the angular sizes of three bright Kepler stars: θ Cygni, and both components of the binary system 16 Cygni. Supporting inf…
Discovery of high-frequency iron K lags in Ark 564 and Mrk 335
Fabian, A. C.; Uttley, P.; Cackett, E. M. +3 more
We use archival XMM-Newton observations of Ark 564 and Mrk 335 to calculate the frequency-dependent time lags for these two well-studied sources. We discover high-frequency Fe K lags in both sources, indicating that the red wing of the line precedes the rest-frame energy by roughly 100 and 150 s for Ark 564 and Mrk 335, respectively. Including the…
An age difference of two billion years between a metal-rich and a metal-poor globular cluster
Anderson, J.; Stetson, P. B.; Rich, R. M. +9 more
Globular clusters trace the formation history of the spheroidal components of our Galaxy and other galaxies, which represent the bulk of star formation over the history of the Universe. The clusters exhibit a range of metallicities (abundances of elements heavier than helium), with metal-poor clusters dominating the stellar halo of the Galaxy, and…
A new life for sterile neutrinos: resolving inconsistencies using hot dark matter
Hamann, Jan; Hasenkamp, Jasper
Within the standard ΛCDM model of cosmology, the recent Planck measurements have shown discrepancies with other observations, e.g., measurements of the current expansion rate H0, the galaxy shear power spectrum and counts of galaxy clusters. We show that if ΛCDM is extended by a hot dark matter component, which could be interpreted as a…