Search Publications
Overall properties of the Gaia DR1 reference frame
Liu, N.; Zhu, Z.; Liu, J. -C. +1 more
Aims: The first Gaia data release (Gaia DR1) provides 2191 ICRF2 sources with their positions in the auxiliary quasar solution and five astrometric parameters - positions, parallaxes, and proper motions - for stars in common between the Tycho-2 catalogue and Gaia in the joint Tycho-Gaia astrometric solution (TGAS). We aim to analyze the overa…
The globular cluster system of NGC 1316. IV. Nature of the star cluster complex SH2
Bresolin, F.; Hilker, M.; Gómez, M. +3 more
Context. The light of the merger remnant NGC 1316 (Fornax A) is dominated by old and intermediate-age stars. The only sign of current star formation in this big galaxy is the Hii region SH2, an isolated star cluster complex with a ring-like morphology and an estimated age of 0.1 Gyr at a galactocentric distance of about 35 kpc. A nearby intermedia…
Reanalysis of high-resolution XMM-Newton data of V2491 Cygni using models of collisionally ionized hot absorbers
Balman, Ş.; Gamsızkan, Ç.
Aims: We model spectral absorption features in data of the high-resolution XMM-Newton Reflection Grating Spectrometer.
Methods: We performed X-ray spectral analysis and modeling using the SRON software SPEX version 2.05.04.
Results: We present a reanalysis of data obtained with the XMM-Newton Reflection Grating Spectrometer of the c…
Structure and variability in the corona of the ultrafast rotator LO Pegasi
Schmitt, J. H. M. M.; Singh, K. P.; Lalitha, S.
Context. Low-mass ultrafast rotators show the typical signatures of magnetic activity and are known to produce flares, probably as a result of magnetic reconnection. As a consequence, the coronae of these stars exhibit very large X-ray luminosities and high plasma temperatures, as well as a pronounced inverse FIP effect.
Aims: To probe the re…
Young, active radio stars in the AB Doradus moving group
Ros, E.; Hormuth, F.; Ortiz, J. L. +5 more
Context. Precise determination of stellar masses is necessary to test the validity of pre-main-sequence (PMS) stellar evolutionary models, whose predictions are in disagreement with measurements for masses below 1.2 M⊙. To improve such a test, and based on our previous studies, we selected the AB Doradus moving group (AB Dor-MG) as the …
Gaia and VLT astrometry of faint stars: Precision of Gaia DR1 positions and updated VLT parallaxes of ultracool dwarfs
Sahlmann, J.; Lazorenko, P. F.
Aims: We compared positions of the Gaia first data release (DR1) secondary data set at its faint limit with CCD positions of stars in 20 fields observed with the Very Large Telescope (VLT) FORS2. We aim at an independent verification of the DR1 astrometric precision taking advantage of the FORS2 position uncertainties which are smaller than o…
Photometric and spectroscopic variability of the B5IIIe star HD 171219
Poretti, E.; Rainer, M.; Uytterhoeven, K. +11 more
We analyzed the star HD 171219, one of the relatively bright Be stars observed in the seismo field of the CoRoT satellite, in order to determine its physical and pulsation characteristics. Classical Be stars are main-sequence objects of mainly B-type, whose spectra show, or have shown at some epoch, Balmer lines in emission and an infrared excess.…
A deep staring campaign in the σ Orionis cluster. Variability in substellar members
Eislöffel, J.; Scholz, A.; Jayawardhana, R. +2 more
Context. The young star cluster near σ Orionis is one of the primary environments to study the properties of young brown dwarfs down to masses comparable to those of giant planets.
Aims: Deep optical imaging is used to study time-domain properties of young brown dwarfs over typical rotational timescales and to search for new substellar and pl…
XMM-Newton imaging of V1818 Orionis: a young stellar group on the eastern edge of the κ Ori ring
Megeath, S. T.; Pillitteri, I.; Wolk, S. J.
We present the results of a 40 ks XMM-Newton observation centered on the variable star V1818 Ori. Using a combination of the XMM-Newton and AllWISE catalog data, we identify a group of about 31 young stellar objects (YSOs) around V1818 Ori. This group is coincident with the eastern edge of the dust ring surrounding κ Ori. Previously, we concluded …
Medium-resolution échelle spectroscopy of the Red Square Nebula, MWC 922
Kaper, L.; Bally, J.; Tielens, A. G. G. M. +4 more
Context. Medium-resolution échelle spectra of the Red Square Nebula surrounding the star MWC 922 are presented. The spectra have been obtained in 2010 and 2012 using the X-shooter spectrograph mounted on the Very Large Telescope (VLT) in Paranal, Chile. The spectrum covers a wavelength range between 300 nm-2.5 µm and shows that the nebula is…