Search Publications
Constraining the period of the ringed secondary companion to the young star J1407 with photographic plates
Reichart, D. E.; Grindlay, J. E.; Haislip, J. B. +16 more
Context. The 16 Myr old star 1SWASP J140747.93-394542.6 (V1400 Cen) underwent a series of complex eclipses in May 2007, interpreted as the transit of a giant Hill sphere filling debris ring system around a secondary companion, J1407b. No other eclipses have since been detected, although other measurements have constrained but not uniquely determin…
Reconstruction of asteroid spin states from Gaia DR2 photometry
Hanuš, J.; Ďurech, J.
Context. In addition to stellar data, Gaia Data Release 2 (DR2) also contains accurate astrometry and photometry of about 14 000 asteroids covering 22 months of observations.
Aims: We used Gaia asteroid photometry to reconstruct rotation periods, spin axis directions, and the coarse shapes of a subset of asteroids with enough observations. On…
Spatially resolved spectroscopy across stellar surfaces. III. Photospheric Fe I lines across HD 189733A (K1 V)
Ludwig, Hans-Günter; Dravins, Dainis; Gustavsson, Martin
Context. Spectroscopy across spatially resolved stellar surfaces reveals spectral line profiles free from rotational broadening, whose gradual changes from disk center toward the stellar limb reflect an atmospheric fine structure that is possible to model by 3D hydrodynamics.
Aims: Previous studies of photospheric spectral lines across stella…
When nature tries to trick us. An eclipsing eccentric close binary superposed on the central star of the planetary nebula M 3-2
Jones, David; Miszalski, Brent; Saviane, Ivo +7 more
Bipolar planetary nebulae (PNe) are thought to result from binary star interactions and, indeed, tens of binary central stars of PNe have been found, in particular using photometric time-series that allow for the detection of post-common envelope systems. Using photometry at the NTT in La Silla we have studied the bright object close to the centre…
Physics of a clumpy lensed galaxy at z = 1.6
Schaerer, D.; Dessauges-Zavadsky, M.; Cava, A. +3 more
Observations have shown that massive star-forming clumps are present in the internal structure of high-redshift galaxies. One way to study these clumps in detail with a higher spatial resolution is by exploiting the power of strong gravitational lensing which stretches images on the sky. In this work, we present an analysis of the clumpy galaxy A6…
Search for trans-iron elements in hot, helium-rich white dwarfs with the HST Cosmic Origins Spectrograph
Hoyer, D.; Rauch, T.; Werner, K. +1 more
The metal abundances in the atmospheres of hot white dwarfs (WDs) entering the cooling sequence are determined by the preceding Asymptotic Giant Branch (AGB) evolutionary phase and, subsequently, by the onset of gravitational settling and radiative levitation. In this paper, we investigate three hot He-rich WDs, which are believed to result from a…
Possible systematics in the VLBI catalogs as seen from Gaia
Liu, N.; Zhu, Z.; Liu, J. -C.
Aims: In order to investigate the systematic errors in the very long baseline interferometry (VLBI) positions of extragalactic sources (quasars) and the global differences between Gaia and VLBI catalogs, we use the first data release of Gaia (Gaia DR1) quasar positions as the reference and study the positional offsets of the second realizatio…
Role of environment and gas temperature in the formation of multiple protostellar systems: molecular tracers
van Dishoeck, E. F.; Karska, A.; Mottram, J. C. +2 more
Context. Simulations suggest that gas heating due to radiative feedback is a key factor in whether or not multiple protostellar systems will form. Chemistry is a good tracer of the physical structure of a protostellar system, since it depends on the temperature structure.
Aims: We aim to study the relationship between envelope gas temperature…
Planetary nebulae with UVIT: Far ultra-violet halo around the Bow Tie nebula (NGC 40)
Sutaria, F.; Murthy, J.; Ray, A. +3 more
Context. NGC 40 is a planetary nebula with diffuse X-ray emission, suggesting an interaction of the high-speed wind from WC8 central star (CS) with the nebula. It shows strong C IV 1550 Å emission that cannot be explained by thermal processes alone. We present here the first map of this nebula in C IV emission using broad band filters on the Ultra…
Line shapes of the magnesium resonance lines in cool DZ white dwarf atmospheres
Dufour, P.; Kielkopf, J. F.; Allard, N. F. +4 more
Context. Line shapes of the magnesium resonance lines in white dwarf spectra are determined by the properties of magnesium atoms and the structure of the white dwarf atmosphere. Through their blanketing effect, these lines have a dominant influence on the model structure and thus on the determination from the spectra of other physical parameters t…