Search Publications
The Ca II infrared triplet's performance as an activity indicator compared to Ca II H and K. Empirical relations to convert Ca II infrared triplet measurements to common activity indices
Schmitt, J. H. M. M.; Schmidt, T. O. B.; Martin, J. +4 more
Aims: A large number of Calcium infrared triplet (IRT) spectra are expected from the Gaia and CARMENES missions. Conversion of these spectra into known activity indicators will allow analysis of their temporal evolution to a better degree. We set out to find such a conversion formula and to determine its robustness.
Methods: We have comp…
Very low-mass stellar content of the young supermassive Galactic star cluster Westerlund 1
Brandner, W.; Zinnecker, H.; de Marchi, G. +4 more
We present deep near-infrared HST/WFC3 observations of the young supermassive Galactic star cluster Westerlund 1 and an adjacent control field. The depth of the data is sufficient to derive the mass function for the cluster as a function of radius down to 0.15 M⊙ in the outer parts of the cluster. We identify for the first time a flatte…
3D shape of asteroid (6) Hebe from VLT/SPHERE imaging: Implications for the origin of ordinary H chondrites
Berthier, J.; Carry, B.; Delbo, M. +15 more
Context. The high-angular-resolution capability of the new-generation ground-based adaptive-optics camera SPHERE at ESO VLT allows us to assess, for the very first time, the cratering record of medium-sized (D 100-200 km) asteroids from the ground, opening the prospect of a new era of investigation of the asteroid belt's collisional history.
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New hard X-ray sources discovered in the ongoing INTEGRAL Galactic plane survey after 14 yr of observations
Sunyaev, Rashid A.; Tsygankov, Sergey S.; Lutovinov, Alexander A. +3 more
The International Gamma-Ray Astrophysics Laboratory (INTEGRAL) continues to successfully work in orbit after its launch in 2002. The mission provides the deepest ever survey of hard X-ray sources throughout the Galaxy at energies above 20 keV. We report on a catalogue of new hard X-ray source candidates based on the latest sky maps comprising 14 y…
Vertical structure of the near-surface expanding ionosphere of comet 67P probed by Rosetta
Altwegg, K.; Behar, E.; Nilsson, H. +14 more
The plasma environment has been measured for the first time near the surface of a comet. This unique data set has been acquired at 67P/Churyumov-Gerasimenko during ESA/Rosetta spacecraft's final descent on 2016 September 30. The heliocentric distance was 3.8 au and the comet was weakly outgassing. Electron density was continuously measured with Ro…
Are star formation rates of galaxies bimodal?
Feldmann, Robert
Star formation rate (SFR) distributions of galaxies are often assumed to be bimodal with modes corresponding to star-forming and quiescent galaxies, respectively. Both classes of galaxies are typically studied separately, and SFR distributions of star-forming galaxies are commonly modelled as lognormals. Using both observational data and results f…
Radio Follow-up on All Unassociated Gamma-Ray Sources from the Third Fermi Large Area Telescope Source Catalog
Edwards, Philip G.; Petrov, Leonid; Schinzel, Frank K. +1 more
The third Fermi Large Area Telescope γ-ray source catalog (3FGL) contains over 1000 objects for which there is no known counterpart at other wavelengths. The physical origin of the γ-ray emission from those objects is unknown. Such objects are commonly referred to as unassociated and mostly do not exhibit significant γ-ray flux variability. We per…
Constraints on the Distance Moduli, Helium, and Metal Abundances, and Ages of Globular Clusters from Their RR Lyrae and Non-variable Horizontal Branch Stars. II. Multiple Stellar Populations in 47 Tuc, M3, and M13
VandenBerg, Don A.; Denissenkov, Pavel A.; Kopacki, Grzegorz +1 more
We present a new set of horizontal branch (HB) models computed with the MESA stellar evolution code. The models adopt α-enhanced Asplund et al. metal mixtures and include the gravitational settling of He. They are used in our HB population synthesis tool to generate theoretical distributions of HB stars in order to describe the multiple stellar po…
Ultraviolet to optical diffuse sky emission as seen by the Hubble Space Telescope Faint Object Spectrograph
Oyabu, Shinki; Brandt, Timothy D.; Matsuoka, Yoshiki +5 more
We present an analysis of the blank-sky spectra observed with the Faint Object Spectrograph on board the Hubble Space Telescope. We study the diffuse sky emission from ultraviolet to optical wavelengths, which is composed of zodiacal light (ZL), diffuse Galactic light (DGL), and residual emission. The observations were performed towards 54 fields …
Multiwavelength Study of the Star Formation in the S237 H II Region
Dewangan, L. K.; Ojha, D. K.; Zinchenko, I. +2 more
We present a detailed multiwavelength study of observations from X-ray, near-infrared, and centimeter wavelengths to probe the star formation processes in the S237 region. Multiwavelength images trace an almost sphere-like shell morphology of the region, which is filled with the 0.5-2 keV X-ray emission. The region contains two distinct environmen…