Abstract
The search for life in the Universe is a fundamental problem of astrobiology and modern science. The current progress in the detection of terrestrial-type exoplanets has opened a new avenue ...in the characterization of exoplanetary atmospheres and in the search for biosignatures of life with the upcoming ground-based and space missions. To specify the conditions favourable for the origin, development and sustainment of life as we know it in other worlds, we need to understand the nature of global (astrospheric), and local (atmospheric and surface) environments of exoplanets in the habitable zones (HZs) around G-K-M dwarf stars including our young Sun. Global environment is formed by propagated disturbances from the planet-hosting stars in the form of stellar flares, coronal mass ejections, energetic particles and winds collectively known as astrospheric space weather. Its characterization will help in understanding how an exoplanetary ecosystem interacts with its host star, as well as in the specification of the physical, chemical and biochemical conditions that can create favourable and/or detrimental conditions for planetary climate and habitability along with evolution of planetary internal dynamics over geological timescales. A key linkage of (astro)physical, chemical and geological processes can only be understood in the framework of interdisciplinary studies with the incorporation of progress in heliophysics, astrophysics, planetary and Earth sciences. The assessment of the impacts of host stars on the climate and habitability of terrestrial (exo)planets will significantly expand the current definition of the HZ to the biogenic zone and provide new observational strategies for searching for signatures of life. The major goal of this paper is to describe and discuss the current status and recent progress in this interdisciplinary field in light of presentations and discussions during the NASA Nexus for Exoplanetary System Science funded workshop ‘Exoplanetary Space Weather, Climate and Habitability’ and to provide a new roadmap for the future development of the emerging field of exoplanetary science and astrobiology.
ABSTRACT
In this paper, we report on the observational performance of the Swift Ultra-violet/Optical Telescope (UVOT) in response to the gravitational wave (GW) alerts announced by the Advanced Laser ...Interferometer Gravitational Wave Observatory and the Advanced Virgo detector during the O3 period. We provide the observational strategy for follow-up of GW alerts and provide an overview of the processing and analysis of candidate optical/UV sources. For the O3 period, we also provide a statistical overview and report on serendipitous sources discovered by Swift/UVOT. Swift followed 18 GW candidate alerts, with UVOT observing a total of 424 deg2. We found 27 sources that changed in magnitude at the 3σ level compared with archival u- or g-band catalogued values. Swift/UVOT also followed up a further 13 sources reported by other facilities during the O3 period. Using catalogue information, we divided these 40 sources into five initial classifications: 11 candidate active galactic nuclei (AGNs)/quasars, three cataclysmic variables (CVs), nine supernovae, 11 unidentified sources that had archival photometry, and six uncatalogued sources for which no archival photometry was available. We have no strong evidence to identify any of these transients as counterparts to the GW events. The 17 unclassified sources are likely a mix of AGN and a class of fast-evolving transient, and one source may be a CV.
We present the discovery and characterization of two sub-Neptunes in close orbits, as well as a tentative outer planet of a similar size, orbiting TOI-1260 – a low metallicity K6 V dwarf star. ...Photometry from Transiting Exoplanet Survey Satellite(TESS) yields radii of R(b) = 2.33 ± 0.10 and R(c) = 2.82 ± 0.15 Rꚛ, and periods of 3.13 and 7.49 d for TOI-1260 b and TOI-1260 c, respectively. We combined the TESS data with a series of ground-based follow-up observations to characterize the planetary system. From HARPS-N high-precision radial velocities we obtain M(b) = 8.6(+1.4,−1.5) and M(c) = 11.8(+3.4,−3.2) Mꚛ. The star is moderately active with a complex activity pattern, which necessitated the use of Gaussian process regression for both the light-curve detrending and the radial velocity modelling, in the latter case guided by suitable activity indicators. We successfully disentangle the stellar-induced signal from the planetary signals, underlining the importance and usefulness of the Gaussian process approach. We test the system’s stability against atmospheric photoevaporation and find that the TOI-1260 planets are classic examples of the structure and composition ambiguity typical for the 2–3 Rꚛ range.
Understanding the formation and evolution of giant planets (≥1
M
Jup
) at wide orbital separation (≥5 AU) is one of the goals of direct imaging. Over the past 15 yr, many surveys have placed strong ...constraints on the occurrence rate of wide-orbit giants, mostly based on non-detections, but very few have tried to make a direct link with planet formation theories. In the present work, we combine the results of our previously published VLT/NaCo large program with the results of 12 past imaging surveys to constitute a statistical sample of 199 FGK stars within 100 pc, including three stars with sub-stellar companions. Using Monte Carlo simulations and assuming linear flat distributions for the mass and semi-major axis of planets, we estimate the sub-stellar companion frequency to be within 0.75–5.70% at the 68% confidence level (CL) within 20–300 AU and 0.5–75
M
Jup
, which is compatible with previously published results. We also compare our results with the predictions of state-of-the-art population synthesis models based on the gravitational instability (GI) formation scenario with and without scattering. We estimate that in both the scattered and non-scattered populations, we would be able to detect more than 30% of companions in the 1–75
M
Jup
range (95% CL). With the threesub-stellar detections in our sample, we estimate the fraction of stars that host a planetary system formed by GI to be within 1.0–8.6% (95% CL). We also conclude that even though GI is not common, it predicts a mass distribution of wide-orbit massive companions that is much closer to what is observed than what the core accretion scenario predicts. Finally, we associate the present paper with the release of the Direct Imaging Virtual Archive (DIVA), a public database that aims at gathering the results of past, present, and future direct imaging surveys.
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ABSTRACT
We report the discovery and confirmation of the planetary system TOI-1288. This late G dwarf harbours two planets: TOI-1288 b and TOI-1288 c. We combine TESS space-borne and ground-based ...transit photometry with HARPS-N and HIRES high-precision Doppler measurements, which we use to constrain the masses of both planets in the system and the radius of planet b. TOI-1288 b has a period of $2.699835^{+0.000004}_{-0.000003}$ d, a radius of 5.24 ± 0.09 R⊕, and a mass of 42 ± 3 M⊕, making this planet a hot transiting super-Neptune situated right in the Neptunian desert. This desert refers to a paucity of Neptune-sized planets on short period orbits. Our 2.4-yr-long Doppler monitoring of TOI-1288 revealed the presence of a Saturn–mass planet on a moderately eccentric orbit ($0.13^{+0.07}_{-0.09}$) with a minimum mass of 84 ± 7 M⊕ and a period of $443^{+11}_{-13}$ d. The five sectors worth of TESS data do not cover our expected mid-transit time for TOI-1288 c, and we do not detect a transit for this planet in these sectors.
Context. Gravity modifies the spectral features of young brown dwarfs (BDs). A proper characterization of these objects is crucial for the identification of the least massive and latest-type objects ...in star-forming regions, and to explain the origin(s) of the peculiar spectrophotometric properties of young directly imaged extrasolar planets and BD companions. Aims. We obtained medium-resolution (R ~ 1500−1700) near-infrared (1.1−2.5 μm) spectra of seven young M9.5–L3 dwarfs classified at optical wavelengths. We aim to empirically confirm the low surface gravity of the objects in the near-infrared. We also test whether self-consistent atmospheric models correctly represent the formation and the settling of dust clouds in the atmosphere of young late-M and L dwarfs. Methods. We used the Infrared Spectrometer And Array Camera (ISAAC) at the Very Large Telescope (VLT) to obtain the spectra of the targets. We compared the spectra to those of mature and young BDs, and to young late-type companions to nearby stars with known ages to identify and study gravity-sensitive features. We computed spectral indices weakly sensitive to the surface gravity to derive near-infrared spectral types. Finally, we found the best fit between each spectrum and synthetic spectra from the BT-Settl 2010 and 2013 atmospheric models. Using the best fit, we derived the atmospheric parameters of the objects and identified which spectral characteristics the models do not reproduce. Results. We confirmed that our objects are young BDs and we found near-infrared spectral types in agreement with the ones determined at optical wavelengths. The spectrum of the L2γ dwarf 2MASSJ232252.99-615127.5 reproduces the spectrum of the planetary mass companion 1RXS J160929.1-210524b well. The BT-Settl models fit the spectra and the 1−5 μm spectral energy distribution of the L0–L3 dwarfs for temperatures between 1600−2000 K. But the models fail to reproduce the shape of the H band and the near-infrared slope of some of our targets. This fact, and the best-fit solutions found with super-solar metallicity, are indicative of a lack of dust, in particular at high altitude, in the cloud models. Conclusions. The modeling of the vertical mixing and of the grain growth will be revised in the next version of the BT-Settl models. These revisions may suppress the remaining non-reproducibilities. Our spectra provide additional templates for the characterization of the numerous young L-type companions that will be detected in the coming years by planet imaging instruments such as VLT/SPHERE, Gemini/GPI, Subaru/SCexAO, and LBTI/LMIRCam.
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Context. 51 Eridani b is an exoplanet around a young (20 Myr) nearby (29.4 pc) F0-type star, which was recently discovered by direct imaging. It is one of the closest direct imaging planets in ...angular and physical separation (~0.5′′, ~13 au) and is well suited for spectroscopic analysis using integral field spectrographs. Aims. We aim to refine the atmospheric properties of the known giant planet and to constrain the architecture of the system further by searching for additional companions. Methods. We used the extreme adaptive optics instrument SPHERE at the Very Large Telescope (VLT) to obtain simultaneous dual-band imaging with IRDIS and integral field spectra with IFS, extending the spectral coverage of the planet to the complete Y- to H-band range and providing additional photometry in the K12-bands (2.11, 2.25 μm). The object is compared to other known cool and peculiar dwarfs. The posterior probability distributions for parameters of cloudy and clear atmospheric models are explored using MCMC. We verified our methods by determining atmospheric parameters for the two benchmark brown dwarfs Gl 570D and HD 3651B. We used archival VLT-NACO (L′) Sparse Aperture Masking data to probe the innermost region for additional companions. Results. We present the first spectrophotometric measurements in the Y and K bands for the planet and revise its J-band flux to values 40% fainter than previous measurements. Cloudy models with uniform cloud coverage provide a good match to the data. We derive the temperature, radius, surface gravity, metallicity, and cloud sedimentation parameter fsed. We find that the atmosphere is highly super-solar (Fe/H = 1.0 ± 0.1 dex), and the low \hbox{${f_{\rm sed} = 1.26^{+0.36}_{-0.29}}$}fsed=1.26-0.29+0.36 value is indicative of a vertically extended, optically thick cloud cover with small sized particles. The model radius and surface gravity estimates suggest higher planetary masses of \hbox{${M_\mathrm{gravity} = 9.1^{+4.9}_{-3.3} \, {M}_\mathrm{J}}$}Mgravity=9.1-3.3+4.9 MJ. The evolutionary model only provides a lower mass limit of > 2 MJ (for pure hot-start). The cold-start model cannot explain the luminosity of the planet. The SPHERE and NACO/SAM detection limits probe the 51 Eri system at solar system scales and exclude brown-dwarf companions more massive than 20 MJ beyond separations of ~2.5 au and giant planets more massive than 2 MJ beyond 9 au.
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We previously reported the direct detection of a low-mass companion at a projected separation of 55 + or - 2 AU around the B9-type star Kappa Andromedae. The properties of the system make it a ...benchmark for understanding the formation and evolution of gas giant planets and brown dwarfs on wide orbits. We present new angular differential imaging (ADI) images of the system at 2.146 (Ksubs), 3.776 (L'), 4.052 (NB 4.05), and 4.78 mu m (M') obtained with Keck/NIRC 2 and LBTI/LMIRC am, as well as more accurate near-infrared photometry of the star with the MIMIR instrument. We aim to determine the near-infrared spectral energy distribution of the companion and use it to characterize the object. The mass of Kappa Andromedae b mostly falls in the brown-dwarf regime, owing to remaining uncertainties in age and in mass-luminosity models. According to the formation models, disk instability in a primordial disk may account for the position and a wide range of plausible masses of Kappa and b.
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We report the detection of a wide young hierarchical triple system where the primary has a candidate debris disc. The primary, TYC 5241-986-1 A, is a known Tycho star which we classify as a late-K ...star with emission in the X-ray, near- and far-ultraviolet (UV) and Hα suggestive of youth. Its proper motion, photometric distance (65-105 pc) and radial velocity lead us to associate the system with the broadly defined Local Association of young stars but not specifically with any young moving group. The presence of weak lithium absorption and X-ray and calcium H and K emission support an age in the 20 to ∼125 Myr range. The secondary is a pair of M4.5 ± 0.5 dwarfs with near- and far-UV and Hα emission separated by approximately 1 arcsec (∼65-105 au projected separation) which lie of 145 arcsec (9200-15200 au) from the primary. The primary has a Wide-field Infrared Survey Explorer (WISE) 22 μm excess and follow-up Herschel observations also detect an excess at 70 μm. The excess emissions are indicative of a 100-175 K debris disc. We also explore the possibility that this excess could be due to a coincident background galaxy and conclude that this is unlikely. Debris discs are extremely rare around stars older than 15 Myr, hence if the excess is caused by a disc this is an extremely novel system.
Context.
One of the goals of the Echelle Spectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO) Guaranteed Time Observations (GTO) consortium is the precise ...characterisation of a selected sample of planetary systems discovered by TESS. One such target is the K0V star HIP 29442 (TOI-469), already known to host a validated sub-Neptune companion TOI-469.01, which we followed-up with ESPRESSO.
Aims.
We aim to verify the planetary nature of TOI-469.01 by obtaining precise mass, radius, and ephemeris, and constraining its bulk physical structure and composition.
Methods.
Following a Bayesian approach, we modelled radial velocity and photometric time series to measure the dynamical mass, radius, and ephemeris, and to characterise the internal structure and composition of TOI-469.01.
Results.
We confirmed the planetary nature of TOI-469.01 (now renamed HIP 29442 b), and thanks to the ESPRESSO radial velocities we discovered two additional close-in companions. Through an in-depth analysis of the TESS light curve, we could also detect their low signal-to-noise transit signals. We characterised the additional companions, and conclude that HIP 29442 is a compact multi-planet system. The three planets have orbital periods
P
orb,b
= 13.63083 ± 0.00003,
P
orb,c
= 3.53796 ± 0.00003, and
P
orb,d
= 6.42975
−0.00010
+0.00009
days, and we measured their masses with high precision:
m
p,b
= 9.6 ± 0.8
M
⊕
,
m
p,c
= 4.5 ± 0.3
M
⊕
, and
m
p,d
= 5.1 ± 0.4
M
⊕
. We measured radii and bulk densities of all the planets (the 3
σ
confidence intervals are shown in parentheses):
R
p,b
= 3.48
−0.08(−0.28)
+0.07(+0.19)
R
⊕
and
ρ
p,b
= 1.3 ± 0.2(0.3)g cm
−3
;
R
p,c
= 1.58
−0.11(−0.34)
+0.10(+0.30)
R
⊕
and
ρ
p,c
= 6.3
−1.3(−2.7)
+1.7(+6.0)
g cm
−3
;
R
p,d
= 1.37 ± 0.11
(−0.43)
(+0.32)
R
⊕
and
ρ
p,d
= 11.0
−2.4(−6.3)
+3.4(+21.0)
g cm
−3
. Due to noisy light curves, we used the more conservative 3
σ
confidence intervals for the radii as input to the interior structure modelling. We find that HIP 29442 b appears as a typical sub-Neptune, likely surrounded by a gas layer of pure H-He with amass of 0.27
−0.17
+0.24
M
⊕
and a thickness of 1.4 ± 0.5
R
⊕
. For the innermost companions HIP 29442 c and HIP 29442 d, the model supports an Earth-like composition.
Conclusions.
The compact multi-planet system orbiting HIP 29442 offers the opportunity to study simultaneously planets straddling the gap in the observed radius distribution of close-in small-size exoplanets. High-precision photometric follow-up is required to obtain more accurate and precise radius measurements, especially for planets c and d. This, together with our determined high-precision masses, will provide the accurate and precise bulk structure of the planets, and enable an accurate investigation of the system’s evolution.
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