627 research outputs found
Pre-Discovery 2007 Image of the HR 8799 Planetary System
We present a pre-discovery H-band image of the HR 8799 planetary system that
reveals all three planets in August 2007. The data were obtained with the Keck
adaptive optics system, using angular differential imaging and a coronagraph.
We confirm the physical association of all three planets, including HR 8799d,
which had only been detected in 2008 images taken two months apart, and whose
association with HR 8799 was least secure until now. We confirm that the
planets are 2-3 mag fainter than field brown dwarfs of comparable near-infrared
colors. We note that similar under-luminosity is characteristic of young
substellar objects at the L/T spectral type transition, and is likely due to
enhanced dust content and non-equilibrium CO/CH_4 chemistry in their
atmospheres. Finally, we place an upper limit of 18 mag per square arc second
on the >120 AU H-band dust-scattered light from the HR 8799 debris disk. The
upper limit on the integrated scattered light flux is 1e-4 times the
photospheric level, 24 times fainter than the debris ring around HR 4796A.Comment: ApJ Letters, in press; 13 pages, 3 figures, 1 tabl
A Substellar Common Proper Motion Companion to the Pleiad HII 1348
We announce the identification of a proper motion companion to the star HII
1348, a K5V member of the Pleiades open cluster. The existence of a faint point
source 1.1arcsec away from HII 1348 was previously known from adaptive optics
imaging by Bouvier et al. However, because of a high likelihood of background
star contamination and in the absence of follow-up astrometry, Bouvier et al.
tentatively concluded that the candidate companion was not physically
associated with HII 1348. We establish the proper motion association of the
pair from adaptive optics imaging with the Palomar 5m telescope. Adaptive
optics spectroscopy with the integral field spectrograph OSIRIS on the Keck 10m
telescope reveals that the companion has a spectral type of M8\pm1. According
to substellar evolution models, the M8 spectral type resides within the
substellar mass regime at the age of the Pleiades. The primary itself is a
known double-lined spectroscopic binary, which makes the resolved companion,
HII 1348B, the least massive and widest component of this hierarchical triple
system and the first substellar companion to a stellar primary in the Pleiades.Comment: accepted by Ap
The Nearest Isolated Member of the TW Hydrae Association is a Giant Planet Analog
In a recent search for unusually red L and T dwarfs, we identified 2MASS
J11193254-1137466 as a likely young L7 dwarf and potential member of the TW
Hydrae association. We present spectra that confirm the youth of this object.
We also measure a radial velocity of 8.5 +/- 3.3 km/s that, together with the
sky position, proper motion and photometric distance, results in a 92%
probability of membership in the TW Hydrae association, with a calibrated field
contamination probability of 0.0005% using the BANYAN II tool. Using the age of
TW Hydrae and the luminosity of 2MASS J11193254-1137466, we estimate its mass
to be 4.3--7.6 MJup. It is the lowest-mass and nearest isolated member of TW
Hydrae at a kinematic distance of 28.9 +/- 3.6 pc, and the second-brightest
isolated <10 MJup object discovered to date.Comment: 6 pages, 3 figures, Accepted for publication in ApJ Letter
- …