45 research outputs found
K2-136: A Hyades Binary Star with a Neptune-sized Planet
We report the discovery of a Neptune-size planet (Rp = 3.0 Re) in the Hyades
Cluster. The host star is in a binary system, comprising a K5V star and M7/8V
star with a projected separation of 40 AU. The planet orbits the primary star
with an orbital period of 17.3 days and a transit duration of 3 hours. The host
star is bright (V=11.2, J=9.1) and so may be a good target for precise radial
velocity measurements. K2-136A c is the first Neptune-sized planet to be found
orbiting in a binary system within an open cluster. The Hyades is the nearest
star cluster to the Sun, has an age of 625-750 Myr, and forms one of the
fundamental rungs in the distance ladder; understanding the planet population
in such a well-studied cluster can help us understand and set constraints on
the formation and evolution of planetary systems.Comment: 13 pages, 8 figures, 2 tables. Accepted to AAS Journal
Discovery of a Transiting Adolescent Sub-Neptune Exoplanet with K2
The role of stellar age in the measured properties and occurrence rates of
exoplanets is not well understood. This is in part due to a paucity of known
young planets and the uncertainties in age-dating for most exoplanet host
stars. Exoplanets with well-constrained ages, particularly those which are
young, are useful as benchmarks for studies aiming to constrain the
evolutionary timescales relevant for planets. Such timescales may concern
orbital migration, gravitational contraction, or atmospheric photo-evaporation,
among other mechanisms. Here we report the discovery of an adolescent
transiting sub-Neptune from K2 photometry of the low-mass star K2-284. From
multiple age indicators we estimate the age of the star to be 120 Myr, with a
68% confidence interval of 100-760 Myr. The size of K2-284 b ( = 2.8
0.1 ) combined with its youth make it an intriguing case study for
photo-evaporation models, which predict enhanced atmospheric mass loss during
early evolutionary stages.Comment: Accepted to AJ, 36 pages, 17 figures, 5 table
A transient transit signature associated with the young star RIK-210
We find transient transit-like dimming events within the K2 time series photometry of the young star RIK-210 in the Upper Scorpius OB association. These dimming events are variable in depth, duration, and morphology. High spatial resolution imaging revealed that the star is single and radial velocity monitoring indicated that the dimming events cannot be due to an eclipsing stellar or brown dwarf companion. Archival and follow-up photometry suggest the dimming events are transient in nature. The variable morphology of the dimming events suggests they are not due to a single spherical body. The ingress of each dimming event is always shallower than egress, as one would expect for an orbiting body with a leading tail. The dimming events are periodic and synchronous with the stellar rotation. However, we argue it is unlikely the dimming events could be attributed to anything on the stellar surface based on the observed depths and durations. Variable obscuration by a protoplanetary disk is unlikely on the basis that the star is not actively accreting and lacks the infrared excess associated with an inner disk. Rather, we explore the possibilities that the dimming events are due to magnetospheric clouds, a transiting protoplanet surrounded by circumplanetary dust and debris, eccentric orbiting bodies undergoing periodic tidal disruption, or an extended field of dust or debris near the corotation radius.Publisher PDFPeer reviewe
A warm Jupiter-sized planet transiting the pre-main sequence star V1298 Tau
We report the detection of V1298 Tau b, a warm Jupiter-sized planet ( =
0.91 0.05~ , days) transiting a young solar
analog with an estimated age of 23 million years. The star and its planet
belong to Group 29, a young association in the foreground of the Taurus-Auriga
star-forming region. While hot Jupiters have been previously reported around
young stars, those planets are non-transiting and near-term atmospheric
characterization is not feasible. The V1298 Tau system is a compelling target
for follow-up study through transmission spectroscopy and Doppler tomography
owing to the transit depth (0.5\%), host star brightness ( = 8.1 mag), and
rapid stellar rotation ( = 23 \kms). Although the planet is
Jupiter-sized, its mass is presently unknown due to high-amplitude radial
velocity jitter. Nevertheless, V1298 Tau b may help constrain formation
scenarios for at least one class of close-in exoplanets, providing a window
into the nascent evolution of planetary interiors and atmospheres.Comment: Accepted to A
K2-136: A Binary System in the Hyades Cluster Hosting a Neptune-sized Planet
We report the discovery of a Neptune-size planet (R_p = 3.0 R⊕) in the Hyades Cluster. The host star is in a binary system, comprising a K5V star and M7/8V star with a projected separation of 40 au. The planet orbits the primary star with an orbital period of 17.3 days and a transit duration of 3 hrs. The host star is bright (V = 11.2, J = 9.1) and so may be a good target for precise radial velocity measurements. K2-136A c is the first Neptune-sized planet to be found orbiting in a binary system within an open cluster. The Hyades is the nearest star cluster to the Sun, has an age of 625–750 Myr, and forms one of the fundamental rungs in the distance ladder; understanding the planet population in such a well-studied cluster can help us understand and set constraints on the formation and evolution of planetary systems
Observations of Arp 220 using Herschel-SPIRE: An Unprecedented View of the Molecular Gas in an Extreme Star Formation Environment
We present Herschel SPIRE-FTS observations of Arp~220, a nearby ULIRG. The
FTS continuously covers 190 -- 670 microns, providing a good measurement of the
continuum and detection of several molecular and atomic species. We detect
luminous CO (J = 4-3 to 13-12) and water ladders with comparable total
luminosity; very high-J HCN absorption; OH+, H2O+, and HF in absorption; and CI
and NII. Modeling of the continuum yields warm dust, with T = 66 K, and an
unusually large optical depth of ~5 at 100 microns. Non-LTE modeling of the CO
shows two temperature components: cold molecular gas at T ~ 50 K and warm
molecular gas at T ~1350 K. The mass of the warm gas is 10% of the cold gas,
but dominates the luminosity of the CO ladder. The temperature of the warm gas
is in excellent agreement with H2 rotational lines. At 1350 K, H2 dominates the
cooling (~20 L_sun/M_sun) in the ISM compared to CO (~0.4 L_sun/M_sun). We
found that only a non-ionizing source such as the mechanical energy from
supernovae and stellar winds can excite the warm gas and satisfy the energy
budget of ~20 L_sun/M_sun. We detect a massive molecular outflow in Arp 220
from the analysis of strong P-Cygni line profiles observed in OH+, H2O+, and
H2O. The outflow has a mass > 10^{7} M_sun and is bound to the nuclei with
velocity < 250 km/s. The large column densities observed for these molecular
ions strongly favor the existence of an X-ray luminous AGN (10^{44} ergs/s) in
Arp 220.Comment: Accepted in ApJ on September 1, 201
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A 2 R_⊕ Planet Orbiting the Bright Nearby K Dwarf Wolf 503
Since its launch in 2009, the Kepler telescope has found thousands of planets with radii between that of Earth and Neptune. Recent studies of the distribution of these planets have revealed a gap in the population near 1.5–2.0 R⊕, informally dividing these planets into "super-Earths" and "sub-Neptunes." The origin of this division is difficult to investigate directly because the majority of planets found by Kepler orbit distant, dim stars and are not amenable to radial velocity follow-up or transit spectroscopy, making bulk density and atmospheric measurements difficult. Here, we present the discovery and validation of a newly found 2.03^(+0.08)_(-0.07) R⊕ planet in direct proximity to the radius gap, orbiting the bright (J = 8.32 mag), nearby (D = 44.5 pc) high proper motion K3.5V star Wolf 503 (EPIC 212779563). We determine the possibility of a companion star and false positive detection to be extremely low using both archival images and high-contrast adaptive optics images from the Palomar observatory. The brightness of the host star makes Wolf 503b a prime target for prompt radial velocity follow-up, and with the small stellar radius (0.690 ± 0.025R⊙), it is also an excellent target for HST transit spectroscopy and detailed atmospheric characterization with JWST. With its measured radius near the gap in the planet radius and occurrence rate distribution, Wolf 503b offers a key opportunity to better understand the origin of this radius gap as well as the nature of the intriguing populations of "super-Earths" and "sub-Neptunes" as a whole
A 2 Earth Radius Planet Orbiting the Bright Nearby K-Dwarf Wolf 503
Since its launch in 2009, the Kepler telescope has found thousands of planets
with radii between that of Earth and Neptune. Recent studies of the
distribution of these planets have revealed a rift in the population near
1.5-2.0, informally dividing these planets into "super-Earths"
and "sub-Neptunes". The origin of this division is not well understood, largely
because the majority of planets found by Kepler orbit distant, dim stars and
are not amenable to radial velocity follow-up or transit spectroscopy, making
bulk density and atmospheric measurements difficult. Here, we present the
discovery and validation of a newly found
planet in direct proximity to the radius gap, orbiting the bright
(~mag), nearby (~pc) high proper motion star Wolf 503 (EPIC
212779563). We classify Wolf 503 as a K3.5V star and member of the thick disc
population. We determine the possibility of a companion star and false positive
detection to be extremely low using both archival images and high-contrast
adaptive optics images from the Palomar observatory. The brightness of the host
star makes Wolf 503b a prime target for prompt radial velocity follow-up, HST
transit spectroscopy, as well as detailed atmospheric characterization with
JWST. With its measured radius near the gap in the planet radius and occurrence
rate distribution, Wolf 503b offers a key opportunity to better understand the
origin of this radius gap as well as the nature of the intriguing populations
of "super-Earths" and "sub-Neptunes" as a whole