455 research outputs found
Discovery of a ~23 Mjup Brown Dwarf Orbiting ~700 AU from the Massive Star HIP 78530 in Upper Scorpius
We present the discovery of a substellar companion on a wide orbit around the
~2.5 Msun star HIP 78530, which is a member of the 5 Myr-old Upper Scorpius
association. We have obtained follow-up imaging over two years and show that
the companion and primary share common proper motion. We have also obtained JHK
spectroscopy of the companion and confirm its low surface gravity, in
accordance with the young age of the system. A comparison with Drift-Phoenix
synthetic spectra indicates an effective temperature of 2800+/-200 K and a
comparison with template spectra of young and old dwarfs indicates a spectral
type of M8+/-1. The mass of the companion is estimated to be 19-26 Mjup based
on its bolometric luminosity and the predictions of evolutionary models. The
angular separation of the companion is 4.5", which at the distance of the
primary star, 156.7 pc, corresponds to a projected separation of ~710 AU. This
companion features one of the lowest mass ratios (~0.009) of any known
companion at separations greater than 100 AU.Comment: To appear in ApJ, 9 pages, 9 figure
"Es hat nämlich nicht die gleiche Kraft, wenn etwas in der eigenen Sprache auf Hebräisch gesagt wird und wenn es in eine andere Sprache übersetzt wird" (SirProl 21f.) : Anmerkungen zur Übersetzung der Aopkryphen in der Revision der Lutherbibel 2017
"Weisheit" in der alttestamentlichen Wissenschaft : ausgewählte literatur- und theologiegeschichtliche Fragestellungen und Entwicklungen
Characterization of Low-mass, Wide-separation Substellar Companions to Stars in Upper Scorpius: Near-infrared Photometry and Spectroscopy
We present new 0.9-2.45 m spectroscopy (), and , ,
, , photometry, obtained at Gemini North, of three low-mass
brown dwarf companions on wide orbits around young stars of the Upper Scorpius
OB association: HIP 78530 B, [PGZ2001] J161031.9-191305 B, and GSC 06214-00210
B. We use these data to assess the companions' spectral type, temperature,
surface gravity and mass, as well as the ability of the BT-Settl and
Drift-Phoenix atmosphere models to reproduce the spectral features of young
substellar objects. For completeness, we also analyze the archival spectroscopy
and photometry of the Upper Scorpius planetary mass companion 1RXS
J160929.1-210524 b. Based on a comparison with model spectra we find that the
companions, in the above order, have effective temperatures of 2700, 2500, 2300
and 1700 K. These temperatures are consistent with our inferred spectral types,
respectively M7 , M9 , M9 , and L4 . From
bolometric luminosities estimated from atmosphere model spectra adjusted to our
photometry, and using evolution models at 5-10 Myr, we estimate masses of
21-25, 28-70, 14-17 and 7-12 , respectively. J1610-1913 B appears
significantly over-luminous for its inferred temperature, which explains its
higher mass estimate. Synthetic spectra based on the BT-Settl and Drift-Phoenix
atmosphere models generally offer a good fit to our observed spectra, although
our analysis has highlighted a few problems. For example, the best fits in the
individual near-infrared bands occur at different model temperatures. Also,
temperature estimates based on a comparison of the broadband magnitudes and
colors of the companions to synthetic magnitudes from the models are
systematically lower than the temperature estimates based on a comparison with
synthetic spectra.Comment: 16 pages, 8 figures, published in the Astrophysical Journa
- …