The TESS mission has reported a wealth of new planetary systems around bright and nearby stars amenable for detailed characterizations of planet properties and atmospheres. However, not all ...interesting TESS planets orbit around bright host stars. TOI-263 b is a validated ultra-short-period substellar object in a 0.56-day orbit around a faint (
V
= 18.97) M 3.5 dwarf star. The substellar nature of TOI-263 b was explored using multicolor photometry: a true radius of 0.87 ± 0.21
R
J
was determined, establishing TOI-263 b ’s nature as somewhere between an inflated Neptune and a brown dwarf. The orbital period-radius parameter space occupied by TOI-263 b is quite unique, which prompted a further characterization of its true nature. Here, we report radial velocity measurements of TOI-263 obtained with three VLT units and the ESPRESSO spectrograph to retrieve the mass of TOI-263 b. We find that TOI-263 b is a brown dwarf with a mass of 61.6 ± 4.0
M
Jup
. Additionally, the orbital period of the brown dwarf is found to be synchronized with the rotation period of the host star, and the system is found to be relatively active, possibly revealing a star–brown dwarf interaction. All these findings suggest that the system’s formation history might be explained via disk fragmentation and a later migration to close-in orbits. If the system is found to be unstable, TOI-263 will be an excellent target to test the migration mechanisms before the brown dwarf becomes “engulfed” by its parent star.
Ultra-hot jupiters (UHJs) are giant planets on short orbital periods with high equilibrium temperature (
T
eq
) values. Their hot, extended atmospheres are perfect laboratories for transmission ...spectroscopy studies based on high-resolution spectrographs. In recent years, a variety of atoms and molecules were found in their atmospheres, using different methods such as cross-correlation or transmission and emission spectroscopy. Here, we present the studies of six ultra-hot Jupiters: HAT-P-57b, KELT-7b, KELT-17b, KELT-21b, MASCARA-1b, and WASP-189b, based on high-resolution observations obtained with HARPS-N and HARPS spectrographs. By applying line and cross-correlation transmission spectroscopy methods, we searched for the absorption features of a broad range of atomic and molecular species. We did not detect any absorption features in our sample of UHJs, with the exception of WASP-189b, for which we detected Fe
I
, Fe
II
, and Ti
I
using cross-correlation. The transmission spectroscopy of single lines for WASP-189b revealed several absorption features (including H
α
, H
β,
and Ca H&K), but they remain tentative pending a better modeling of the gravity darkening deformation of the Rossiter-McLaughlin effect. The non-detections with regard to the rest of the planets can be explained via a combination of stellar pulsations and the Rossiter-McLaughlin effect, which mask possible planetary signals for most of the planets, and by the low signal-to-noise ratios of the observations for KELT-21b. Here, we compare our results with the known population of planets for which atmospheric detections have been reported in the literature. We find that the empirical frontier between hot and ultra-hot planets, based on the detection of atomic and ionized species in their atmospheres, can be established as
T
eq
=
2150 K.
Ultra-hot Jupiters orbit very close to their host star and consequently receive strong irradiation, causing their atmospheric chemistry to be different from the common gas giants. Here, we have ...studied the atmosphere of one of these particular hot planets, MASCARA-2b/KELT-20b, using four transit observations with high resolution spectroscopy facilities. Three of these observations were performed with HARPS-N and one with CARMENES. Additionally, we simultaneously observed one of the transits with MuSCAT2 to monitor possible spots in the stellar surface. At high resolution, the transmission residuals show the effects of Rossiter-McLaughlin and centre-to-limb variations from the stellar lines profiles, which we have corrected to finally extract the transmission spectra of the planet. We clearly observe the absorption features of CaII, FeII, NaI, H
α
, and H
β
in the atmosphere of MASCARA-2b, and indications of H
γ
and MgI at low signal-to-noise ratio. In the case of NaI, the true absorption is difficult to disentangle from the strong telluric and interstellar contamination. The results obtained with CARMENES and HARPS-N are consistent, measuring an H
α
absorption depth of 0.68 ± 0.05 and 0.59 ± 0.07%, and NaI absorption of 0.11 ± 0.04 and 0.09 ± 0.05% for a 0.75 Å passband, in the two instruments respectively. The H
α
absorption corresponds to ~1.2
R
p
, which implies an expanded atmosphere, as a result of the gas heating caused by the irradiation received from the host star. For H
β
and H
γ
only HARPS-N covers this wavelength range, measuring an absorption depth of 0.28 ± 0.06 and 0.21 ± 0.07%, respectively. For CaII, only CARMENES covers this wavelength range measuring an absorption depth of 0.28 ± 0.05, 0.41 ± 0.05 and 0.27 ± 0.06% for CaII
λ
8498Å,
λ
8542Å and
λ
8662Å lines, respectively. Three additional absorption lines of FeII are observed in the transmission spectrum by HARPS-N (partially covered by CARMENES), measuring an average absorption depth of 0.08 ± 0.04% (0.75 Å passband). The results presented here are consistent with theoretical models of ultra-hot Jupiters atmospheres, suggesting the emergence of an ionised gas on the day-side of such planets. Calcium and iron, together with other elements, are expected to be singly ionised at these temperatures and be more numerous than its neutral state. The Calcium triplet lines are detected here for the first time in transmission in an exoplanet atmosphere.
In this work, we use long-slit spectroscopy observations of a transit event of the close-in orbiting planet WASP-43b (Msubp=2.034 Msub Jup, Rsubp=1.036 RsubJup in an effort to detect its atmosphere. ...We used the Gran Telescopio Canarias (GTC) instrument OSIRIS to obtain long-slit spectra in the optical range 520-1040 nm of the planetary host star WASP-43 and of a reference star during a full primary transit event and four partial transit observations. We measure a mean planet-to-star radius ratio in the white light curve of 0.15988sub -0 .00145sup +0 .00133. Using broadband filters, we detect the color signature of WASP-43. We present a tentative detection in the planet-to-star radius ratio around the Na I doublet (lambda 588.9, 589.5 nm) when compared to the nearby continuum at the 2.9sigma level. As previous results, this hints to the orbital decay of this planet although a timing analysis over several years needs to be made to confirm this.
Understanding the role of optical absorbers is critical for linking the properties of the dayside and terminator atmospheres of hot Jupiters. This study aims to identify the signatures of optical ...absorbers in the atmosphere of the hot Jupiter HAT-P-41b. We conducted five transit observations of this planet to obtain its optical transmission spectra using the Gran Telescopio Canarias (GTC). We performed atmospheric retrievals assuming free abundances of 12 chemical species. Our Bayesian model comparisons revealed strong evidence for TiO absorption (∆ ln = 21.02), modest evidence for CrH (∆ ln = 3.73), and weak evidence for MgH (∆ ln = 2.32). When we combined the GTC transmission spectrum with previously published
Hubble
Space Telescope and
Spitzer
data, the retrieval results and model inferences remained consistent. In conclusion, HAT-P-41b has a metal-rich atmosphere with no high-altitude clouds or hazes. Further observations of its dayside atmosphere should be made to confirm the hints of a thermal inversion in the upper atmosphere suggested by our results.
Context.
Exoplanet atmospheres are the key to understanding the nature of exoplanets. To this end, transit spectrophotometry provides us opportunities to investigate the physical properties and ...chemical compositions of exoplanet atmospheres.
Aims.
We aim to detect potential atmospheric signatures in 12 gaseous giant exoplanets using transit spectrophotometry and we try to constrain their atmospheric properties.
Methods.
The targets of interest were observed using transit spectrophotometry with the GTC OSIRIS instrument. We estimated the transit parameters and obtained the optical transmission spectra of the target planets using a Bayesian framework. We analyzed the spectral features in the transmission spectra based on atmospheric retrievals.
Results.
Most of the observed transmission spectra were found to be featureless, with only the spectrum of CoRoT-1b showing strong evidence for atmospheric features. However, in combination with the previously published near-infrared transmission spectrum, we found multiple interpretations for the atmosphere of CoRoT-1b due to the lack of decisive evidence for alkali metals or optical absorbers.
Conclusions.
Featureless spectra are not necessarily indicative of cloudy atmospheres if they poorly constrain the altitudes of cloud decks. Precise constraints on the models of hazes and clouds strongly depend on the significance of the observed spectral features. Further investigations on these exoplanets, especially CoRoT-1b, are required to confirm the properties of their atmospheres.
The star HD 144548 (=HIP 78977; TYP 6212-1273-1) has been known as a detached eclipsing binary and a bona-fide member of the Upper Scorpius OB association. Continuous photometry from the K2 mission ...on Campaign Two has revealed the presence of additional eclipses due to the presence of a third star in the system. These are explained by a system composed of the two previously known members of the eclipsing system (Ba and Bb) with a period of 1.63 d, orbiting around an F7-F8V star with a period of 33.945 ± 0.002 d in an eccentric orbit (eA = 0.2652 ± 0.0003). The timing of the eclipses of Ba and Bb reveals the same 33.9 d periodicity, which we interpret as the combination of a light time effect combined with dynamical perturbations on the close system. Here we combine radial velocities and analytical approximations for the timing of the eclipses to derive masses and radii for the three components of the system. We obtain a mass of 1.44 ± 0.04 M⊙ and radius of 2.41 ± 0.03 R⊙ for the A component, and almost identical masses and radii of about 0.96 M⊙ and 1.33 R⊙ for each of the two components of the close binary. HD 144548 is the first triply eclipsing system for which radial velocities of all components could be measured.
High resolution transit spectroscopy has proven to be a reliable technique for the characterization of the chemical composition of exoplanet atmospheres. Taking advantage of the broad spectral ...coverage of the CARMENES spectrograph, we initiated a survey aimed at characterizing a broad range of planetary systems. Here, we report our observations of three transits of GJ 3470 b with CARMENES in search of He (2
3
S) absorption. On one of the nights, the He
I
region was heavily contaminated by OH
−
telluric emission and, thus, it was not useful for our purposes. The remaining two nights had a very different signal-to-noise ratio (S/N) due to weather. They both indicate the presence of He (2
3
S) absorption in the transmission spectrum of GJ 3470 b, although a statistically valid detection can only be claimed for the night with higher S/N. For that night, we retrieved a 1.5 ± 0.3% absorption depth, translating into a
R
p
(
λ
)∕
R
p
= 1.15 ± 0.14 at this wavelength. Spectro-photometric light curves for this same night also indicate the presence of extra absorption during the planetary transit with a consistent absorption depth. The He (2
3
S) absorption is modeled in detail using a radiative transfer code, and the results of our modeling efforts are compared to the observations. We find that the mass-loss rate,
Ṁ
, is confined to a range of 3 × 10
10
g s
−1
for
T
= 6000 K to 10 × 10
10
g s
−1
for
T
= 9000 K. We discuss the physical mechanisms and implications of the He
I
detection in GJ 3470 b and put it in context as compared to similar detections and non-detections in other Neptune-size planets. We also present improved stellar and planetary parameter determinations based on our visible and near-infrared observations.
Context.
Ground-based transit observations are affected by both telluric absorption and instrumental systematics, which can affect the final retrieved transmission spectrum of an exoplanet. To ...account for these effects, a better understanding of the impact of different data analyses is needed to improve the accuracy of the retrieved transmission spectra.
Aims.
We propose validating ground-based low-resolution transmission spectroscopy using transiting white dwarfs. These targets are selected to have transit parameters comparable with typical transiting hot Jupiters but nondetectable transmission signals due to their extremely high surface gravities. The advantage here is that we know beforehand what the final transmission spectrum should be: a featureless flat spectrum.
Methods.
We analyzed two transiting white dwarfs analogous to hot Jupiters, KIC 10657664B and KIC 9164561B. We used various noise models to account for the systematic noise in their spectroscopic light curves following common procedures of transmission spectroscopy analyses. We compared the derived transmission spectra with the broadband transit depth to determine whether there are any artificial offsets or spectral features arising from light-curve fitting.
Results.
The results show a strong model dependence, and the transmission spectra exhibit considerable discrepancies when they are computed with different noise models, different reference stars, and different common-mode removal methods. Nonetheless, we can still derive relatively accurate transmission spectra based on a Bayesian model comparison.
Conclusions.
With current ground-based instrumentation, the systematics in transit light curves can easily contaminate a transmission spectrum, introducing a general offset or some spurious spectral features and thus leading to a biased interpretation on the planetary atmosphere. Therefore, we suggest that any wiggle within the measurement errors in a transmission spectrum should be interpreted with caution. It is necessary to determine the dependence of results on the adopted noise model through model comparison. The model inferences should be examined through multiple observations and different instruments.
We study multiple notions of Hilbert spaces of functions which, via the respective inner products, reproduce function values, or differences of function values. We do this by extending results from ...the more familiar settings of reproducing kernel Hilbert spaces, RKHSs. Our main results deal with operations on infinite graphs
of vertices and edges, and associated Hilbert spaces. For electrical network models, the differences
represent voltage differences for pairs of vertices x, y. In these cases, relative RKHSs will depend on choices of conductance functions c, where an appropriate function c is specified as a positive function defined on the edge-set E from G. Our present study of higher order differences, using choices of relative RKHSs, is motivated in part by existing numerical algorithms for discretization of PDEs. Our approach to higher order differences uses both combinatorial operations on graphs, and operator theory for the respective RKHSs. Starting with a graph
, we introduce an induced graph
such that the vertices in
are the edges in E from G, while the edges in
are pairs of neighboring edges from G.
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