97 research outputs found
De mens in het heelal
Oratie uitgesproken bij de aanvaarding van het ambt van hoogleraar in de
Observationele Astrofysica aan de Universiteit LeidenStars and planetary system
Mapping weather on WASP-76b with high-resolution transmission spectroscopy
Stars and planetary system
Resolving chemical gradients in exoplanet atmospheres with high-resolution spectroscopy
Laboratory astrophysics and astrochemistryStars and planetary system
The 12CO/13CO isotopologue ratio of a young, isolated brown dwarf: possibly distinct formation pathways of super-Jupiters and brown dwarfs
Stars and planetary system
A chemical survey of exoplanets with ARIEL
Stars and planetary system
VLT/CRIRES science verification observations: A hint of C18O in the young brown dwarf 2M0355
Stars and planetary system
A weak spectral signature of water vapour in the atmosphere of HD 179949 b at high spectral resolution in the L band
High-resolution spectroscopy (R⩾20000) is currently the only known method to constrain the orbital solution and atmospheric properties of non-transiting hot Jupiters. It does so by resolving the spectral features of the planet into a forest of spectral lines and directly observing its Doppler shift while orbiting the host star. In this study, we analyse VLT/CRIRES (R=100000) L-band observations of the non-transiting giant planet HD 179949 b centred around 3.5 μm. We observe a weak (3.0σ, or S/N = 4.8) spectral signature of H2O in absorption contained within the radial velocity of the planet at superior-conjunction, with a mild dependence on the choice of line list used for the modelling. Combining this data with previous observations in the K band, we measure a detection significance of 8.4 σ for an atmosphere that is most consistent with a shallow lapse-rate, solar C/O ratio, and with CO and H2O being the only major sources of opacity in this wavelength range. As the two sets of data were taken 3 yr apart, this points to the absence of strong radial-velocity anomalies due, e.g. to variability in atmospheric circulation. We measure a projected orbital velocity for the planet of KP = (145.2 ± 2.0) km s−1 (1σ) and improve the error bars on this parameter by ∼70 per cent. However, we only marginally tighten constraints on orbital inclination (66.2+3.7−3.1 deg) and planet mass (0.963+0.036−0.031 Jupiter masses), due to the dominant uncertainties of stellar mass and semimajor axis. Follow ups of radial-velocity planets are thus crucial to fully enable their accurate characterization via high-resolution spectroscopy
Distant FR I radio galaxies in the Hubble Deep Field: implications for the cosmological evolution of radio-loud AGN
Deep and high resolution radio observations of the Hubble Deep Field and
flanking fields have shown the presence of two distant edge-darkened FR I radio
galaxies, allowing for the first time an estimate of their high redshift space
density. If it is assumed that the space density of FR I radio galaxies at z>1
is similar to that found in the local universe, then the chance of finding two
FR I radio galaxies at these high radio powers in such a small area of sky is
1
than at present, effectively ruling out the possibility that FR I radio sources
undergo no cosmological evolution. We suggest that FR I and FR II radio
galaxies should not be treated as intrinsically distinct classes of objects,
but that the cosmological evolution is simply a function of radio power with FR
I and FR II radio galaxies of similar radio powers undergoing similar
cosmological evolutions. Since low power radio galaxies have mainly FR I
morphologies and high power radio galaxies have mainly FR II morphologies, this
results in a generally stronger cosmological evolution for the FR IIs than the
FR Is. We believe that additional support from the V/Vmax test for evolving and
non-evolving populations of FR IIs and FR Is respectively is irrelevant, since
this test is sensitive over very different redshift ranges for the two classes.Comment: LaTeX, 6 pages, 3 figs. To appear in MNRA
Fast synthetic spectral fitting for large stellar samples: a critical test with 25 bright stars of known rotation
Stars and planetary system
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