6,084 research outputs found
Speckle Interferometry of Metal-Poor Stars in the Solar Neighborhood. I
We report the results of speckle-interferometric observations of 109 high
proper-motion metal-poor stars made with the 6-m telescope of the Special
Astrophysical Observatory of the Russian Academy of Sciences. We resolve eight
objects -- G102-20, G191-55, BD+19~1185A, G89-14, G87-45, G87-47,
G111-38, and G114-25 -- into individual components and we are the first to
astrometrically resolve seven of these stars. New resolved systems included two
triple (G111-38, G87-47) and one quadruple (G89-14) star. The ratio of
single-to-binary-to-triple-to-quadruple systems among the stars of our sample
is equal to 71:28:6:1.Comment: 8 pages, 4 figures, accepted to Astrophysical Bulleti
HAT-P-16b: A 4 Mj Planet Transiting A Bright Star On An Eccentric Orbit
We report the discovery of HAT-P-16b, a transiting extrasolar planet orbiting
the V = 10.8 mag F8 dwarf GSC 2792-01700, with a period P = 2.775960 +-
0.000003 d, transit epoch Tc = 2455027.59293 +- 0.00031 (BJD), and transit
duration 0.1276 +- 0.0013 d. The host star has a mass of 1.22 +- 0.04 Msun,
radius of 1.24 +- 0.05 Rsun, effective temperature 6158 +-80 K, and metallicity
[Fe/H] = +0.17 +- 0.08. The planetary companion has a mass of 4.193 +- 0.094
MJ, and radius of 1.289 +- 0.066 RJ yielding a mean density of 2.42 +- 0.35
g/cm3. Comparing these observed characteristics with recent theoretical models,
we find that HAT-P-16b is consistent with a 1 Gyr H/He-dominated gas giant
planet. HAT-P-16b resides in a sparsely populated region of the mass{radius
diagram and has a non-zero eccentricity of e = 0.036 with a significance of 10
sigma.Comment: Submitted to Ap
The compact multiple system HIP 41431
The nearby (50 pc) K7V dwarf HIP 41431 (EPIC 212096658) is a compact three-tier hierarchy. Three K7V stars with similar masses, from 0.61 to 0.63 solar, make a triple-lined spectroscopic system where the inner binary with a period of 2.9 d is eclipsing, and the outer companion on a 59-d orbit exerts strong dynamical influence revealed by the eclipse time variation in the Kepler photometry. Moreover, the centre of mass of the triple system moves on a 3.9-yr orbit, modulating the proper motion. The mass of the fourth star is 0.35 solar. The Kepler and ground-based photometry and radial velocities from four different spectrographs are used to adjust the spectro-photodynamical model that accounts for dynamical interaction. The mutual inclination between the two inner orbits is 2{^{circ}.}16 ± 0{^{circ}.}11, while the outer orbit is inclined to their common plane by 21°±16°. The inner orbit precesses under the influence of both outer orbits, causing observable variation of the eclipse depth. Moreover, the phase of the inner binary is strongly modulated with a 59-d period and its line of apsides precesses. The middle orbit with eccentricity e = 0.28 also precesses, causing the observed variation of its radial velocity curve. Masses and other parameters of stars in this unique hierarchy are determined. This system is dynamically stable and likely old
HAT-P-55b: A Hot Jupiter Transiting a Sun-like Star
We report the discovery of a new transiting extrasolar planet, HAT-P-55b. The
planet orbits a V = 13.207 +/- 0.039 sun-like star with a mass of 1.013 +/-
0.037 solar masses, a radius of 1.011 +/- 0.036 solar radii and a metallicity
of -0.03 +/- 0.08. The planet itself is a typical hot Jupiter with a period of
3.5852467 +/- 0.0000064 days, a mass of 0.582 +/- 0.056 Jupiter masses and a
radius of 1.182 +/- 0.055 Jupiter radii. This discovery adds to the increasing
sample of transiting planets with measured bulk densities, which is needed to
put constraints on models of planetary structure and formation theories.Comment: 7 pages, 4 figures, accepted for publication in PAS
Bodies, technologies and action possibilities: when is an affordance?
Borrowed from ecological psychology, the concept of affordances is often said to offer the social study of technology a means of re-framing the question of what is, and what is not, âsocialâ about technological artefacts. The concept, many argue, enables us to chart a safe course between the perils of technological determinism and social constructivism. This article questions the sociological adequacy of the concept as conventionally deployed. Drawing on ethnographic work on the ways technological artefacts engage, and are engaged by, disabled bodies, we propose that the âaffordancesâ of technological objects are not reducible to their material constitution but are inextricably bound up with specific, historically situated modes of engagement and ways of life
HAT-P-15b: A 10.9-day Extrasolar Planet Transiting a Solar-type Star
We report the discovery of HAT-P-15b, a transiting extrasolar planet in the
`period valley', a relatively sparsely-populated period regime of the known
extrasolar planets. The host star, GSC 2883-01687, is a G5 dwarf with V=12.16.
It has a mass of 1.01+/-0.04 M(Sun), radius of 1.08+/-0.04 R(Sun), effective
temperature 5568+/-90 K, and metallicity [Fe/H] = +0.22+/-0.08. The planetary
companion orbits the star with a period 10.863502+/-0.000027 days, transit
epoch Tc = 2454638.56019+/-0.00048 (BJD), and transit duration 0.2285+/-0.0015
days. It has a mass of 1.946+/-0.066 M(Jup), and radius of 1.072+/-0.043 R(Jup)
yielding a mean density of 1.96+/-0.22 g/cm3. At an age of 6.8+/-2.1 Gyr, the
planet is H/He-dominated and theoretical models require about 2% (10 M(Earth))
worth of heavy elements to reproduce its measured radius. With an estimated
equilibrium temperature of 820 K during transit, and 1000 K at occultation,
HAT-P-15b is a potential candidate to study moderately cool planetary
atmospheres by transmission and occultation spectroscopy.Comment: 12 pages with 10 figures and 6 tables in emulateapj format. Submitted
to The Astrophysical Journa
Dynamical Masses for Pre-Main Sequence Stars: A Preliminary Physical Orbit for V773 Tau A
We report on interferometric and radial-velocity observations of the
double-lined 51-d period binary (A) component of the quadruple pre-main
sequence (PMS) system V773 Tau. With these observations we have estimated
preliminary visual and physical orbits of the V773 Tau A subsystem. Among other
parameters, our orbit model includes an inclination of 66.0 2.4 deg, and
allows us to infer the component dynamical masses and system distance. In
particular we find component masses of 1.54 0.14 and 1.332 0.097
M_{\sun} for the Aa (primary) and Ab (secondary) components respectively.
Our modeling of the subsystem component spectral energy distributions finds
temperatures and luminosities consistent with previous studies, and coupled
with the component mass estimates allows for comparison with PMS stellar models
in the intermediate-mass range. We compare V773 Tau A component properties with
several popular solar-composition models for intermediate-mass PMS stars. All
models predict masses consistent to within 2-sigma of the dynamically
determined values, though some models predict values that are more consistent
than others.Comment: ApJ in press; 25 pages, 6 figures; data tables available in journal
versio
HAT-P-49b: A 1.7 M_J Planet Transiting a Bright 1.5 M_S F-Star
We report the discovery of the transiting extrasolar planet HAT-P-49b. The
planet transits the bright (V = 10.3) slightly evolved F-star HD 340099 with a
mass of 1.54M_S and a radius of 1.83 R_S. HAT-P-49b is orbiting one of the 25
brightest stars to host a transiting planet which makes this a favorable
candidate for detailed follow-up. This system is an especially strong target
for Rossiter- McLaughlin follow-up due to the fast rotation of the host star,
16 km/s. The planetary companion has a period of 2.6915 d, mass of 1.73 M_J and
radius of 1.41 R_J. The planetary characteristics are consistent with that of a
classical hot Jupiter but we note that this is the fourth most massive star to
host a transiting planet with both M_p and R_p well determined.Comment: Accepted to the Astronomical Journa
HAT-P-39b--HAT-P-41b: Three Highly Inflated Transiting Hot Jupiters
We report the discovery of three new transiting extrasolar planets orbiting
moderately bright (V=11.1 to 12.4) F stars. The planets have periods of P =
2.6940 d to 4.4572 d, masses of 0.60 M_J to 0.80 M_J, and radii of 1.57 R_J to
1.73 R_J. They orbit stars with masses between 1.40 M_sun and 1.51 M_sun. The
three planets are members of an emerging population of highly inflated Jupiters
with 0.4 M_J 1.5 R_J.Comment: Submitted to AJ. 16 pages, 11 figures, 12 table
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