19 research outputs found
No further evidence for a transiting inner companion to the hot Jupiter HATS-50b
Most hot Jupiter exoplanets do not have a nearby planetary companion in their
planetary system. One remarkable exception is the system of WASP-47 with an
inner and outer nearby companion to a hot Jupiter, providing detailed
constrains on its formation history. In this work, we follow-up on a tentative
photometric signal of a transiting inner companion to the hot Jupiter HATS-50b.
If confirmed, it would be the third case of a hot Jupiter with an inner
companion. 63 hours of new ground-based photometry were employed to rule out
this signal to about 96% confidence. The injection of artificial transit
signals showed the data to be of sufficient quality to reveal the potential
photometric feature at high significance. However, no transit signal was found.
The discrete pattern of observing blocks leaves a slight chance that the
transit was missed.Comment: 6 pages, 2 figures, accepted for publication in Astronomical Notes
(AN
Detection of Helium in the Atmosphere of the Exo-Neptune HAT-P-11b
The helium absorption triplet at a wavelength of 10,833 \AA\ has been
proposed as a way to probe the escaping atmospheres of exoplanets. Recently
this feature was detected for the first time using Hubble Space Telescope (HST)
WFC3 observations of the hot Jupiter WASP-107b. We use similar HST/WFC3
observations to detect helium in the atmosphere of the hot Neptune HAT-P-11b at
the confidence level. We compare our observations to a grid of 1D
models of hydrodynamic escape to constrain the thermospheric temperatures and
mass loss rate. We find that our data are best fit by models with high mass
loss rates of - g s. Although we do
not detect the planetary wind directly, our data are consistent with the
prediction that HAT-P-11b is experiencing hydrodynamic atmospheric escape.
Nevertheless, the mass loss rate is low enough that the planet has only lost up
to a few percent of its mass over its history, leaving its bulk composition
largely unaffected. This matches the expectation from population statistics,
which indicate that close-in planets with radii greater than 2 R
form and retain H/He-dominated atmospheres. We also confirm the independent
detection of helium in HAT-P-11b obtained with the CARMENES instrument, making
this the first exoplanet with the detection of the same signature of
photoevaporation from both ground- and space-based facilities.Comment: 12 pages, 9 figures, accepted for publication in ApJ
ExoClock project: an open platform for monitoring the ephemerides of Ariel targets with contributions from the public
The Ariel mission will observe spectroscopically around 1000 exoplanets to further characterise their atmospheres. For the mission to be as efficient as possible, a good knowledge of the planetsâ ephemerides is needed before its launch in 2028. While ephemerides for some planets are being refined on a per-case basis, an organised effort to collectively verify or update them when necessary does not exist. In this study, we introduce the ExoClock project, an open, integrated and interactive platform with the purpose of producing a confirmed list of ephemerides for the planets that will be observed by Ariel. The project has been developed in a manner to make the best use of all available resources: observations reported in the literature, observations from space instruments and, mainly, observations from ground-based telescopes, including both professional and amateur observatories. To facilitate inexperienced observers and at the same time achieve homogeneity in the results, we created data collection and validation protocols, educational material and easy to use interfaces, open to everyone. ExoClock was launched in September 2019 and now counts over 140 participants from more than 15 countries around the world. In this release, we report the results of observations obtained until the 15h of April 2020 for 120 Ariel candidate targets. In total, 632 observations were used to either verify or update the ephemerides of 84 planets. Additionally, we developed the Exoplanet Characterisation Catalogue (ECC), a catalogue built in a consistent way to assist the ephemeris refinement process. So far, the collaborative open framework of the ExoClock project has proven to be highly efficient in coordinating scientific efforts involving diverse audiences. Therefore, we believe that it is a paradigm that can be applied in the future for other research purposes, too
A Framework for Prioritizing the TESS Planetary Candidates Most Amenable to Atmospheric Characterization
A key legacy of the recently launched TESS mission will be to provide the
astronomical community with many of the best transiting exoplanet targets for
atmospheric characterization. However, time is of the essence to take full
advantage of this opportunity. JWST, although delayed, will still complete its
nominal five year mission on a timeline that motivates rapid identification,
confirmation, and mass measurement of the top atmospheric characterization
targets from TESS. Beyond JWST, future dedicated missions for atmospheric
studies such as ARIEL require the discovery and confirmation of several hundred
additional sub-Jovian size planets (R_p < 10 R_Earth) orbiting bright stars,
beyond those known today, to ensure a successful statistical census of
exoplanet atmospheres. Ground-based ELTs will also contribute to surveying the
atmospheres of the transiting planets discovered by TESS. Here we present a set
of two straightforward analytic metrics, quantifying the expected
signal-to-noise in transmission and thermal emission spectroscopy for a given
planet, that will allow the top atmospheric characterization targets to be
readily identified among the TESS planet candidates. Targets that meet our
proposed threshold values for these metrics would be encouraged for rapid
follow-up and confirmation via radial velocity mass measurements. Based on the
catalog of simulated TESS detections by Sullivan et al. (2015), we determine
appropriate cutoff values of the metrics, such that the TESS mission will
ultimately yield a sample of high-quality atmospheric
characterization targets across a range of planet size bins, extending down to
Earth-size, potentially habitable worlds.Comment: accepted to PAS
An Aligned Orbit for the Young Planet V1298 Tau b
The alignment of planetary orbits with respect to the stellar rotation preserves information on their dynamical histories. Measuring this angle for young planets helps illuminate the mechanisms that create misaligned orbits for older planets, as different processes could operate over timescales ranging from a few megayears to a gigayear. We present spectroscopic transit observations of the young exoplanet V1298 Tau b; we update the age of V1298 Tau to be 28 ± 4 Myr based on Gaia EDR3 measurements. We observed a partial transit with Keck/HIRES and LBT/PEPSI, and detected the radial velocity anomaly due to the Rossiter-McLaughlin effect. V1298 Tau b has a prograde, well-aligned orbit, with λ=4-10+7 deg. By combining the spectroscopically measured v sin iâ and the photometrically measured rotation period of the host star we also find that the orbit is aligned in 3D, Ï=8-7+4 deg. Finally, we combine our obliquity constraints with a previous measurement for the interior planet V1298 Tau c to constrain the mutual inclination between the two planets to be i mut = 0° ± 19°. This measurements adds to the growing number of well-aligned planets at young ages, hinting that misalignments may be generated over timescales of longer than tens of megayears. The number of measurements, however, is still small, and this population may not be representative of the older planets that have been observed to date. We also present the derivation of the relationship between i mut, λ, and i for the two planets
The PEPSI Exoplanet Transit Survey (PETS) I: Investigating the presence of a silicate atmosphere on the super-Earth 55 Cnc e
The study of exoplanets and especially their atmospheres can reveal key
insights on their evolution by identifying specific atmospheric species. For
such atmospheric investigations, high-resolution transmission spectroscopy has
shown great success, especially for Jupiter-type planets. Towards the
atmospheric characterization of smaller planets, the super-Earth exoplanet 55
Cnc e is one of the most promising terrestrial exoplanets studied to date.
Here, we present a high-resolution spectroscopic transit observation of this
planet, acquired with the PEPSI instrument at the Large Binocular Telescope.
Assuming the presence of Earth-like crust species on the surface of 55 Cnc e,
from which a possible silicate-vapor atmosphere could have originated, we
search in its transmission spectrum for absorption of various atomic and
ionized species such as Fe , Fe+, Ca , Ca+, Mg and K , among others. Not
finding absorption for any of the investigated species, we are able to set
absorption limits with a median value of 1.9 x RP. In conclusion, we do not
find evidence of a widely extended silicate envelope on this super-Earth
reaching several planetary radii.Comment: MNRAS, in pres
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The effect of stellar contamination on low-resolution transmission spectroscopy: needs identified by NASAâs Exoplanet Exploration Program Study Analysis Group 21
Study Analysis Group 21 (SAG21) of NASAâs Exoplanet Exploration Program Analysis Group was organized to study the effect of stellar contamination on space-based transmission spectroscopy, a method for studying exoplanetary atmospheres by measuring the wavelength-dependent radius of a planet as it transits its star. Transmission spectroscopy relies on a precise understanding of the spectrum of the star being occulted. However, stars are not homogeneous, constant light sources but have temporally evolving photospheres and chromospheres with inhomogeneities like spots, faculae, plages, granules, and flares. This SAG brought together an interdisciplinary team of more than 100 scientists, with observers and theorists from the heliophysics, stellar astrophysics, planetary science, and exoplanetary atmosphere research communities, to study the current research needs that can be addressed in this context to make the most of transit studies from current NASA facilities like Hubble Space Telescope and JWST. The analysis produced 14 findings, which fall into three science themes encompassing (i) how the Sun is used as our best laboratory to calibrate our understanding of stellar heterogeneities (âThe Sun as the Stellar Benchmarkâ), (ii) how stars other than the Sun extend our knowledge of heterogeneities (âSurface Heterogeneities of Other Starsâ), and (iii) how to incorporate information gathered for the Sun and other stars into transit studies (âMapping Stellar Knowledge to Transit Studiesâ). In this invited review, we largely reproduce the final report of SAG21 as a contribution to the peer-reviewed literature