85 research outputs found
The strange case of Na I in the atmosphere of HD 209458 b: reconciling low- and high-resolution spectroscopic observations
Stars and planetary system
High-resolution transmission spectroscopic studies of hot and ultra-hot Jupiters
Stars and planetary system
CARMENES detection of the Ca II infrared triplet and possible evidence of He I in the atmosphere of WASP-76b
Casasayas-Barris, N., et al.Ultra-hot Jupiters are highly irradiated gas giants with equilibrium temperatures typically higher than 2000 K. Atmospheric studies of these planets have shown that their transmission spectra are rich in metal lines, with some of these metals being ionised due to the extreme temperatures. Here, we use two transit observations of WASP-76b obtained with the CARMENES spectrograph to study the atmosphere of this planet using high-resolution transmission spectroscopy. Taking advantage of the two channels and the coverage of the red and near-infrared wavelength ranges by CARMENES, we focus our analysis on the study of the Ca II infrared triplet (IRT) at 8500 Å and the He I triplet at 10 830 Å. We present the discovery of the Ca II IRT at 7¿ in the atmosphere of WASP-76b using the cross-correlation technique, which is consistent with previous detections of the Ca II H&K lines in the same planet, and with the atmospheric studies of other ultra-hot Jupiters reported to date. The low mass density of the planet, and our calculations of the XUV (X-ray and EUV) irradiation received by the exoplanet, show that this planet is a potential candidate to have a He I evaporating envelope and, therefore, we performed further investigations focussed on this aspect. The transmission spectrum around the He I triplet shows a broad and red-shifted absorption signal in both transit observations. However, due to the strong telluric contamination around the He I lines and the relatively low signal-to-noise ratio of the observations, we are not able to unambiguously conclude if the absorption is due to the presence of helium in the atmosphere of WASP-76b, and we consider the result to be only an upper limit. Finally, we revisit the transmission spectrum around other lines such as Na I, Li I, H¿, and K I. The upper limits reported here for these lines are consistent with previous studies.We acknowledge funding from the European Research Council
under the European Union’s Horizon 2020 research and innovation program
under grant agreement no. 694513, the Agencia Estatal de Investigación of
the Ministerio de Ciencia, Innovación y Universidades and the ERDF through
projects PID2019-109522GB-C5[1:4]/AEI/10.13039/501100011033, PID2019-
110689RB-I00/AEI/10.13039/501100011033, ESP2017-87143-R, and ESP2016-
80435-C2-2-R, and the Centre of Excellence “Severo Ochoa” and “María de
Maeztu” awards to the Instituto de Astrofísica de Canarias (CEX2019-000920-
S), Instituto de Astrofísica de Andalucía (SEV-2017-0709), and Centro de
Astrobiología (MDM-2017-0737), and the Generalitat de Catalunya/CERCA programme. T.H. acknowledges support by the European Research Council under
the Horizon 2020 Framework Program via the ERC Advanced Grant Origins
83 24 28. G.M. has received funding from the European Union’s Horizon 2020
research and innovation programme under the Marie Skłodowska-Curie grant
agreement No. 895525
Non-detection of He I in the atmosphere of GJ1214b with Keck/NIRSPEC, at a time of minimal telluric contamination
Observations of helium in exoplanet atmospheres may reveal the presence of
large gaseous envelopes, and indicate ongoing atmospheric escape. Orell-Miquel
et al. (2022) used CARMENES to measure a tentative detection of helium for the
sub-Neptune GJ 1214b, with a peak excess absorption reaching over 2% in transit
depth at 10830 Angstroms. However, several non-detections of helium had
previously been reported for GJ 1214b. One explanation for the discrepancy was
contamination of the planetary signal by overlapping telluric absorption- and
emission lines. We used Keck/NIRSPEC to observe another transit of GJ 1214b at
10830 Angstroms, at a time of minimal contamination by telluric lines, and did
not observe planetary helium absorption. Accounting for correlated noise in our
measurement, we place an upper limit on the excess absorption size of 1.22%
(95% confidence). We find that the discrepancy between the CARMENES and NIRSPEC
observations is unlikely to be caused by using different instruments or stellar
activity. It is currently unclear whether the difference is due to correlated
noise in the observations, or variability in the planetary atmosphere.Comment: Accepted for publication in ApJ
High-resolution transmission spectroscopy study of ultra-hot Jupiters HAT-P-57b, KELT-17b, KELT-21b, KELT-7b, MASCARA-1b, and WASP-189b
Stars and planetary system
On the study of atmospheric escape of exoplanets using the new window of the He 10830 line
Stars and planetary system
Characterisation of the upper atmospheres of HAT-P-32 b, WASP-69 b, GJ 1214 b, and WASP-76 b through their He I triplet absorption
Characterisation of atmospheres undergoing photo-evaporation is key to
understanding the formation, evolution, and diversity of planets. However, only
a few upper atmospheres that experience this kind of hydrodynamic escape have
been characterised. Our aim is to characterise the upper atmospheres of the hot
Jupiters HAT-P-32 b and WASP-69 b, the warm sub-Neptune GJ 1214 b, and the
ultra-hot Jupiter WASP-76 b through high-resolution observations of their HeI
triplet absorption. In addition, we also reanalyse the warm Neptune GJ 3470 b
and the hot Jupiter HD 189733 b. We used a spherically symmetric 1D
hydrodynamic model coupled with a non-local thermodynamic equilibrium model.
Comparing synthetic absorption spectra with observations, we constrained the
main parameters of the upper atmosphere of these planets and classify them
according to their hydrodynamic regime. Our results show that HAT-P-32 b
photo-evaporates at (13070)10 gs with a hot (12
4002900 K) upper atmosphere; WASP-69 b loses its atmosphere at
(0.90.5)10 gs and 5250750 K; and GJ 1214 b,
with a relatively cold outflow of 3750750 K, photo-evaporates at
(1.31.1)10 gs. For WASP-76 b, its weak absorption
prevents us from constraining its temperature and mass-loss rate significantly;
we obtained ranges of 6000-17 000\,K and 23.521.510
gs. Our reanalysis of GJ 3470 b yields colder temperatures, 3400350
K, but practically the same mass-loss rate as in our previous results. Our
reanalysis of HD 189733 b yields a slightly higher mass-loss rate,
(1.40.5)10 gs, and temperature, 12 700900 K
compared to previous estimates. Our results support that photo-evaporated
outflows tend to be very light
The atmosphere of WASP-76b seen with CARMENES: looking for CaII IRT and HeI
Stars and planetary system
HD 191939 revisited: New and refined planet mass determinations, and a new planet in the habitable zone
HD 191939 (TOI-1339) is a nearby (d = 54 pc), bright (V = 9 mag), and inactive Sun-like star (G9 V) known to host a multi-planet transiting system. Ground-based spectroscopic observations confirmed the planetary nature of the three transiting sub-Neptunes (HD 191939 b, c, and d) originally detected by TESS and were used to measure the masses for planets b and c with 3\ucf precision. These previous observations also reported the discovery of an additional Saturn-mass planet (HD 191939 e) and evidence for a further, very long-period companion (HD 191939 f). Here, we report the discovery of a new non-transiting planet in the system and a refined mass determination of HD 191939 d. The new planet, HD 191939 g, has a minimum mass of 13.5\ub12.0 M- and a period of about 280 days. This period places the planet within the conservative habitable zone of the host star, and near a 1:3 resonance with HD 191939 e. The compilation of 362 radial velocity measurements with a baseline of 677 days from four different high-resolution spectrographs also allowed us to refine the properties of the previously known planets, including a 4.6\ucf mass determination for planet d, for which only a 2\ucf upper limit had been set until now. We confirm the previously suspected low density of HD 191939 d, which makes it an attractive target for attempting atmospheric characterisation. Overall, the planetary system consists of three sub-Neptunes interior to a Saturn-mass and a Uranus-mass planet plus a high-mass long-period companion. This particular configuration has no counterpart in the literature and makes HD 191939 an exceptional multi-planet transiting system with an unusual planet demographic worthy of future observation
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