Search Publications
Abundance patterns of evolved stars with Hipparcos parallaxes and ages based on the APOGEE data base
Zhao, G.; Chen, Y. Q.; Zhao, J. K. +3 more
We investigate the abundance patterns for four groups of stars at evolutionary phases from sub-giant to red clump (RC) and trace the chemical evolution of the disc by taking 21 individual elemental abundances from APOGEE and ages from evolutionary models with the aid of Hipparcos distances. We find that the abundances of six elements (Si, S, K, Ca…
Dramatic X-ray spectral variability of a Compton-thick type-1 QSO at z ∼ 1
Buchner, J.; Nandra, K.; Merloni, A. +6 more
We report on the discovery of a dramatic X-ray spectral variability event observed in a z ∼ 1 broad line type-1 QSO. The XMM-Newton spectrum from the year 2000 is characterized by an unobscured power-law spectrum with photon index of Γ ∼ 2, a column density of NH∼ 5× 10^{20} cm^{-2}, and no prominent reflection component. Five years lat…
Spectral analysis of the He-enriched sdO-star HD 127493
Heber, Ulrich; Dorsch, Matti; Latour, Marilyn
The bright sdO star HD127493 is known to be of mixed H/He composition and excellent archival spectra covering both optical and ultraviolet ranges are available. UV spectra play a key role as they give access to many chemical species that do not show spectral lines in the optical, such as iron and nickel. This encouraged the quantitative spectral a…
Is 4C+29.48 a γ-ray source?
An, T.; Gabányi, K. É.; Frey, S.
Context. The Fermi Large Area Telescope revealed that the extragalactic γ-ray sky is dominated by blazars, active galactic nuclei (AGN) whose jet is seen at very small angle to the line of sight. To associate and then classify the γ-ray sources, data have been collected from lower frequency surveys and observations. Since those have superior angul…
Sesquinary reimpacts dominate surface characteristics on Phobos
Nayak, Michael
We use topographic data to show that impact craters with pitted floor deposits are among the deepest on Mars. This is consistent with the interpretation of pitted materials as primary crater-fill impactite deposits emplaced during crater formation. Our database consists of 224 pitted material craters ranging in size from ∼1 to 150 km in diameter. …
Spectral energy distribution variations of nearby Seyfert galaxies during AGN watch monitoring programs
Vestergaard, M.; Kilerci Eser, Ece
We present and analyse quasi-simultaneous multi-epoch spectral energy distributions (SEDs) of seven reverberation-mapped active galactic nuclei (AGNs) for which accurate black hole mass measurements and suitable archival data are available from the `AGN Watch' monitoring programs. We explore the potential of optical-UV and X-ray data, obtained wit…
Magnetic evolution linked to the interrelated activity complexes involving transequatorial coronal holes
Gutiérrez, Heidy; Taliashvili, Lela; Lazarian, Alexandre
We studied a magnetic evolution linked to a cadence of interrelated activities developed in a large solar region during Carrington rotations, CRs 2119-2121, based on multiwavelength and multispacecraft observations. Three coronal holes (CHs), two transequatorial and one isolated, eight filaments and some active regions were distributed closely in …
Searches for H2O masers toward narrow-line Seyfert 1 galaxies
Hagiwara, Yoshiaki; Doi, Akihiro; Hachisuka, Kazuya +1 more
We present searches for 22 GHz H2O masers toward 36 narrow-line Seyfert 1 galaxies (NLS1s), selected from known NLS1s with vsys ≲ 41000 km s-1. Out of the 36 NLS1s in our sample, 11 have been first surveyed in our observations, while the observations of other NLS1s were previously reported in literature. In our sur…
Variability and Jet Activity in the YSO MHO 3252 Y3 in Serpens South
Hodapp, Klaus W.; Chini, Rolf
The infrared young stellar outflow source MHO 3252 Y3 in the Serpens South star-forming region was found to be variable. The available photometric data can be fitted with a double-peaked light curve with a period of 904 days. Color variations are consistent with variable extinction with a flatter wavelength dependence than interstellar extinction,…
History of globulettes in the Milky Way
Grenman, Tiia; Elfgren, Erik; Weber, Hans
Globulettes are small (radii