Context.
In photometry, the short-timescale stellar variability (“flicker”), such as that caused by granulation and solar-like oscillations, can reach amplitudes comparable to the transit depth of ...Earth-sized planets and is correlated over the typical transit timescales. It can introduce systematic errors on the inferred planetary parameters when a small number of transits are observed.
Aims.
The objective of this paper is to characterize the statistical properties of the flicker noise and quantify its impact on the inferred transit parameters.
Methods.
We used the extensive solar observations obtained with SoHO/VIRGO to characterize flicker noise. We simulated realistic transits across the solar disk using SDO/HMI data and used these to obtain transit light curves, which we used to estimate the errors made on the transit parameters due to the presence of real solar noise. We make these light curves publicly available. To extend the study to a wider parameter range, we derived the properties of flicker noise using
Kepler
observations and studied their dependence on stellar parameters. Finally, we predicted the limiting stellar apparent magnitude for which the properties of the flicker noise can be extracted using high-precision CHEOPS and PLATO observations.
Results.
Stellar granulation is a stochastic colored noise, and is stationary with respect to the stellar magnetic cycle. Both the flicker correlation timescales and amplitudes increase with the stellar mass and radius. If these correlations are not taken into account when fitting for the parameters of transiting exoplanets, this can bias the inferred parameters. In particular, we find errors of up to 10% on the ratio between the planetary and stellar radius (
R
p
∕
R
s
) for an Earth-sized planet orbiting a Sun-like star.
Conclusions.
Flicker will significantly affect the inferred parameters of transits observed at high precision with CHEOPS and PLATO for F and G stars. Dedicated modeling strategies need to be developed to accurately characterize both the star and the transiting exoplanets.
The benchmark hot Jupiter HD 189733 b has been a key target, used to lay out the foundations of comparative planetology for giant exo-planets. As such, HD 189733 b has been extensively studied across ...the electromagnetic spectrum. Here we report the observation and analysis of three transit light curves of HD 189733 b obtained with
Hubble/
STIS in the near-ultraviolet (NUV), the last remaining unexplored spectral window to be probed with present-day instrumentation for this planet. The NUV is a unique window for atmospheric mass-loss studies owing to the strong resonance lines and large photospheric flux. Overall, from a low-resolution analysis (
R
= 50) we found that the planet’s NUV spectrum is well characterized by a relatively flat baseline, consistent with the optical-infrared transmission, plus two regions at ~2350 and ~2600 Å that exhibit a broad and significant excess absorption above the continuum. From an analysis at a higher resolution (
R
= 4700), we found that the transit depths at the core of the magnesium resonance lines are consistent with the surrounding continuum. We discarded the presence of Mg
II
absorption in the upper atmosphere at a ~2–4
σ
confidence level, whereas we could place no significant constraint for Mg I absorption. These broad absorption features coincide with the expected location of Fe II bands; however, solar-abundance hydrodynamic models of the upper atmosphere are not able to reproduce the amplitude of these features with iron absorption. This scenario would require a combination of little to no iron condensation in the lower atmosphere super-solar metallicities and a mechanism to enhance the absorption features (such as zonal wind broadening). The true nature of this feature remains to be confirmed.
The K2-33 planetary system hosts one transiting ~5
R
⊕
planet orbiting the young M-type host star. The planet’s mass is still unknown, with an estimated upper limit of 5.4
M
J
. The extreme youth of ...the system (<20 Myr) gives the unprecedented opportunity to study the earliest phases of planetary evolution, at a stage when the planet is exposed to an extremely high level of high-energy radiation emitted by the host star. We perform a series of 1D hydrodynamic simulations of the planet’s upper atmosphere considering a range of possible planetary masses, from 2 to 40
M
⊕
, and equilibrium temperatures, from 850 to 1300 K, to account for internal heating as a result of contraction. We obtain temperature profiles mostly controlled by the planet’s mass, while the equilibrium temperature has a secondary effect. For planetary masses below 7–10
M
⊕
, the atmosphere is subject to extremely high escape rates, driven by the planet’s weak gravity and high thermal energy, which increase with decreasing mass and/or increasing temperature. For higher masses, the escape is instead driven by the absorption of the high-energy stellar radiation. A rough comparison of the timescales for complete atmospheric escape and age of the system indicates that the planet is more massive than 10
M
⊕
.
The Dlg4 gene encodes for post-synaptic density protein 95 (PSD95), a major synaptic protein that clusters glutamate receptors and is critical for plasticity. PSD95 levels are diminished in ageing ...and neurodegenerative disorders, including Alzheimer's disease and Huntington's disease. The epigenetic mechanisms that (dys)regulate transcription of Dlg4/PSD95, or other plasticity genes, are largely unknown, limiting the development of targeted epigenome therapy. We analysed the Dlg4/PSD95 epigenetic landscape in hippocampal tissue and designed a Dlg4/PSD95 gene-targeting strategy: a Dlg4/PSD95 zinc finger DNA-binding domain was engineered and fused to effector domains to either repress (G9a, Suvdel76, SKD) or activate (VP64) transcription, generating artificial transcription factors or epigenetic editors (methylating H3K9). These epi-editors altered critical histone marks and subsequently Dlg4/PSD95 expression, which, importantly, impacted several hippocampal neuron plasticity processes. Intriguingly, transduction of the artificial transcription factor PSD95-VP64 rescued memory deficits in aged and Alzheimer's disease mice. Conclusively, this work validates PSD95 as a key player in memory and establishes epigenetic editing as a potential therapy to treat human neurological disorders.
Context. In photometry, the short-timescale stellar variability (“flicker”), such as that caused by granulation and solar-like oscillations, can reach amplitudes comparable to the transit depth of ...Earth-sized planets and is correlated over the typical transit timescales. It can introduce systematic errors on the inferred planetary parameters when a small number of transits are observed. Aims. The objective of this paper is to characterize the statistical properties of the flicker noise and quantify its impact on the inferred transit parameters. Methods. We used the extensive solar observations obtained with SoHO/VIRGO to characterize flicker noise. We simulated realistic transits across the solar disk using SDO/HMI data and used these to obtain transit light curves, which we used to estimate the errors made on the transit parameters due to the presence of real solar noise. We make these light curves publicly available. To extend the study to a wider parameter range, we derived the properties of flicker noise using Kepler observations and studied their dependence on stellar parameters. Finally, we predicted the limiting stellar apparent magnitude for which the properties of the flicker noise can be extracted using high-precision CHEOPS and PLATO observations. Results. Stellar granulation is a stochastic colored noise, and is stationary with respect to the stellar magnetic cycle. Both the flicker correlation timescales and amplitudes increase with the stellar mass and radius. If these correlations are not taken into account when fitting for the parameters of transiting exoplanets, this can bias the inferred parameters. In particular, we find errors of up to 10% on the ratio between the planetary and stellar radius (Rp∕Rs) for an Earth-sized planet orbiting a Sun-like star. Conclusions. Flicker will significantly affect the inferred parameters of transits observed at high precision with CHEOPS and PLATO for F and G stars. Dedicated modeling strategies need to be developed to accurately characterize both the star and the transiting exoplanets.
The GAPS Programme at TNG Guilluy, G.; Giacobbe, P.; Carleo, I. ...
Astronomy and astrophysics (Berlin),
09/2022, Letnik:
665
Journal Article
Recenzirano
Odprti dostop
Context.
The field of exo-atmospheric characterisation is progressing at an extraordinary pace. Atmospheric observations are now available for tens of exoplanets, mainly hot and warm inflated gas ...giants, and new molecular species continue to be detected, revealing a richer atmospheric composition than previously expected. Thanks to its warm equilibrium temperature (963 ± 18 K) and low density (0.219 ± 0.031 g cm
−3
), the close-in gas giant WASP-69b represents a golden target for atmospheric characterisation.
Aims.
With the aim of searching for molecules in the atmosphere of WASP-69b and investigating its properties, we performed high-resolution transmission spectroscopy with the GIANO-B near-infrared spectrograph at the Telescopio Nazionale Galileo.
Methods.
We observed three transit events of WASP-69b. During a transit, the planetary lines are Doppler-shifted due to the large change in the planet’s radial velocity, allowing us to separate the planetary signal from the quasi-stationary telluric and stellar spectrum.
Results.
Considering the three nights together, we report the detection of CH
4
, NH
3
, CO, C
2
H
2
, and H
2
O, at more than a 3.3a- level. We did not identify the presence of HCN or CO
2
with confidence a level higher than 3a. This is the first time that five molecules have been simultaneously detected in the atmosphere of a warm giant planet. These results suggest that the atmosphere of WASP-69b is possibly carbon-rich and characterised by the presence of disequilibrium chemistry.
We present here the signal-to-noise (S/N) calculator developed for the Colorado Ultraviolet Transit Experiment (CUTE) mission. CUTE is a 6U CubeSat operating in the near-ultraviolet (NUV) observing ...exoplanetary transits to study their upper atmospheres. CUTE was launched into a low-Earth orbit in September 2021 and it is currently gathering scientific data. As part of the S/N calculator, we also present the error propagation for computing transit depth uncertainties starting from the S/N of the original spectroscopic observations. The CUTE S/N calculator is currently extensively used for target selection and scheduling. The modular construction of the CUTE S/N calculator enables its adaptation and can be used also for other missions and instruments.
Ultraviolet (UV) transmission spectroscopy probes atmospheric escape, which has a significant impact on planetary atmospheric evolution. If unaccounted for, interstellar medium absorption (ISM) at ...the position of specific UV lines might bias transit depth measurements, and thus potentially affect the (non-)detection of features in transmission spectra. Ultimately, this is connected to the so called ``resolution-linked bias'' (RLB) effect. We present a parametric study quantifying the impact of unresolved or unconsidered ISM absorption in transit depth measurements at the position of the MgII h&k resonance lines (i.e. 2802.705 Å and 2795.528 Å respectively) in the near-ultraviolet spectral range. We consider main-sequence stars of different spectral types and vary the shape and amount of chromospheric emission, ISM absorption, and planetary absorption, as well as their relative velocities. We also evaluate the role played by integration bin and spectral resolution. We present an open-source tool enabling one to quantify the impact of unresolved or unconsidered MgII ISM absorption in transit depth measurements. We further apply this tool to a few already or soon to be observed systems. On average, we find that ignoring ISM absorption leads to biases in the MgII transit depth measurements comparable to the uncertainties obtained from the observations published to date. However, considering the bias induced by ISM absorption might become necessary when analysing observations obtained with the next generation space telescopes with UV coverage (e.g. LUVOIR, HABEX), which will provide transmission spectra with significantly smaller uncertainties compared to what obtained with current facilities (e.g. HST).
The GAPS Programme at TNG Basilicata, M.; Giacobbe, P.; Bonomo, A. S. ...
Astronomy and astrophysics (Berlin),
6/2024, Letnik:
686
Journal Article
Recenzirano
Context. The atmospheric characterisation of hot and warm Neptune-size exoplanets is challenging mainly due to their relatively small radius and atmospheric scale height, which reduce the amplitude ...of atmospheric spectral features. The warm-Neptune HAT-P-11 b is a remarkable target for atmospheric characterisation because of the large brightness of its host star ( V = 9.46 mag; H = 7.13 mag). Aims. The aims of this work are to review the main physical and architectural properties of the HAT-P-11 planetary system, and to probe the presence of eight molecular species in the atmosphere of HAT-P-11 b through near-infrared (NIR) high-resolution transmission spectroscopy. Methods. We reviewed the physical and architectural properties of the HAT-P-11 planetary system by analysing transits and occultations of HAT-P-11 b from the Kepler data set as well as HIRES at Keck archival radial-velocity data. We modelled the latter with Gaussian-process regression and a combined quasi-periodic and squared-exponential kernel to account for stellar variations on both (short-term) rotation and (long-term) activity-cycle timescales. In order to probe the atmospheric composition of HAT-P-11 b, we observed four transits of this target with the NIR GIANO-B at TNG spectrograph and cross-correlated the data with template atmospheric transmission spectra. Results. We find that the long-period radial-velocity signal previously attributed to the HAT-P-11 c planet ( P ~ 9.3 yr; M p sin i ~ 1.6 M J ; e ~ 0.6) is more likely due to the stellar magnetic activity cycle. Nonetheless, the H IPPARCOS - Gaia difference in the proper-motion anomaly suggests that an outer-bound companion might still exist. For HAT-P-11 b, we measure a radius of R p = 0.4466 ± 0.0059 R J , a mass of M p = 0.0787 ± 0.0048 M J , a bulk density of ρ p = 1.172 ± 0.085 g cm −3 , and an orbital eccentricity of e = 0.2577 −0.0025 +0.0033 . These values are compatible with those from the literature. Probing its atmosphere, we detect the presence of two molecular species, H 2 O and NH 3 , with a S/N of 5.1 and 5.3, and a significance of 3.4 σ and 5.0 σ , respectively. We also tentatively detect the presence of CO 2 and CH 4 , with a S/N of 3.0 and 4.8, and a significance of 3.2 σ and 2.6 σ , respectively. Conclusions. We revisit the HAT-P-11 planetary system, confirm the presence of H 2 O, and report the detection of NH 3 in the atmosphere of HAT-P-11 b, also finding hints for the presence of CO 2 and CH 4 that need to be confirmed by further observations.
The GAPS Programme at TNG Basilicata, M; Giacobbe, P; Bonomo, A S ...
Astronomy and astrophysics (Berlin),
06/2024, Letnik:
686
Journal Article
Recenzirano
Context. The atmospheric characterisation of hot and warm Neptune-size exoplanets is challenging mainly due to their relatively small radius and atmospheric scale height, which reduce the amplitude ...of atmospheric spectral features. The warm-Neptune HAT-P-11 b is a remarkable target for atmospheric characterisation because of the large brightness of its host star (V = 9.46 mag; H = 7.13 mag). Aims. The aims of this work are to review the main physical and architectural properties of the HAT-P-11 planetary system, and to probe the presence of eight molecular species in the atmosphere of HAT-P-11 b through near-infrared (NIR) high-resolution transmission spectroscopy. Methods. We reviewed the physical and architectural properties of the HAT-P-11 planetary system by analysing transits and occultations of HAT-P-11 b from the Kepler data set as well as HIRES at Keck archival radial-velocity data. We modelled the latter with Gaussian-process regression and a combined quasi-periodic and squared-exponential kernel to account for stellar variations on both (short-term) rotation and (long-term) activity-cycle timescales. In order to probe the atmospheric composition of HAT-P-11 b, we observed four transits of this target with the NIR GIANO-B at TNG spectrograph and cross-correlated the data with template atmospheric transmission spectra. Results. We find that the long-period radial-velocity signal previously attributed to the HAT-P-11 c planet (P ~ 9.3 yr; Mp sin i ~ 1.6 MJ; e ~ 0.6) is more likely due to the stellar magnetic activity cycle. Nonetheless, the HIPPARCOS-Gaia difference in the proper-motion anomaly suggests that an outer-bound companion might still exist. For HAT-P-11 b, we measure a radius of Rp = 0.4466 ± 0.0059 RJ, a mass of Mp = 0.0787 ± 0.0048 MJ, a bulk density of ρp = 1.172 ± 0.085 g cm−3, and an orbital eccentricity of e = 0.2577−0.0025+0.0033. These values are compatible with those from the literature. Probing its atmosphere, we detect the presence of two molecular species, H2O and NH3, with a S/N of 5.1 and 5.3, and a significance of 3.4 σ and 5.0 σ, respectively. We also tentatively detect the presence of CO2 and CH4, with a S/N of 3.0 and 4.8, and a significance of 3.2 σ and 2.6 σ, respectively. Conclusions. We revisit the HAT-P-11 planetary system, confirm the presence of H2O, and report the detection of NH3 in the atmosphere of HAT-P-11 b, also finding hints for the presence of CO2 and CH4 that need to be confirmed by further observations.
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