Context.
The bright star
π
Men was chosen as the first target for a radial velocity follow-up to test the performance of ESPRESSO, the new high-resolution spectrograph at the European Southern ...Observatory’s Very Large Telescope. The star hosts a multi-planet system (a transiting 4
M
⊕
planet at ~0.07 au and a sub-stellar companion on a ~2100-day eccentric orbit), which is particularly suitable for a precise multi-technique characterization.
Aims.
With the new ESPRESSO observations, which cover a time span of 200 days, we aim to improve the precision and accuracy of the planet parameters and search for additional low-mass companions. We also take advantage of the new photometric transits of
π
Men c observed by TESS over a time span that overlaps with that of the ESPRESSO follow-up campaign.
Methods.
We analysed the enlarged spectroscopic and photometric datasets and compared the results to those in the literature. We further characterized the system by means of absolute astrometry with H
IPPARCOS
and
Gaia
. We used the high-resolution spectra of ESPRESSO for an independent determination of the stellar fundamental parameters.
Results.
We present a precise characterization of the planetary system around
π
Men. The ESPRESSO radial velocities alone (37 nightly binned data with typical uncertainty of 10 cm s
−1
) allow for a precise retrieval of the Doppler signal induced by
π
Men c. The residuals show a root mean square of 1.2 m s
−1
, which is half that of the HARPS data; based on the residuals, we put limits on the presence of additional low-mass planets (e.g. we can exclude companions with a minimum mass less than ~2
M
⊕
within the orbit of
π
Men c). We improve the ephemeris of
π
Men c using 18 additional TESS transits, and, in combination with the astrometric measurements, we determine the inclination of the orbital plane of
π
Men b with high precision (
i
b
=45.8
−1.1
+1.4
deg). This leads to the precise measurement of its absolute mass
m
b
=14.1
−0.4
+0.5
M
Jup
, indicating that
π
Men b can be classified as a brown dwarf.
Conclusions.
The
π
Men system represents a nice example of the extreme precision radial velocities that can be obtained with ESPRESSO for bright targets. Our determination of the 3D architecture of the
π
Men planetary system and the high relative misalignment of the planetary orbital planes put constraints on and challenge the theories of the formation and dynamical evolution of planetary systems. The accurate measurement of the mass of
π
Men b contributes to make the brown dwarf desert a bit greener.
One of the most efficient methods used for exoplanet detection is the analysis of the radial velocity measurements of the host star, over a period of time. A newly proposed approach to analyze the ...radial velocity data is based on artificial neural networks (ANNs). The method is inspired from pattern recognition, a domain where ANNs are widely used. Preliminary results show the degree of similarity of the measured radial velocities to the theoretically computed effect of a multi-planetary system on a star. The present analysis can be the starting point for further classification of planetary systems using radial velocity curves.
Context.
Ground-based high-resolution spectrographs are key instruments for several astrophysical domains, such as exoplanet studies. Unfortunately, the observed spectra are contaminated by the ...Earth’s atmosphere and its large molecular absorption bands. While different techniques (forward radiative transfer models, principle component analysis (PCA), or other empirical methods) exist to correct for telluric lines in exoplanet atmospheric studies, in radial velocity (RV) studies, telluric lines with an absorption depth of >2% are generally masked, which poses a problem for faint targets and M dwarfs as most of their RV content is present where telluric contamination is important.
Aims.
We propose a simple telluric model to be embedded in the Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO) data reduction software (DRS). The goal is to provide telluric-free spectra and enable RV measurements through the cross-correlation function technique (and others), including spectral ranges where telluric lines fall.
Methods.
The model is a line-by-line radiative transfer code that assumes a single atmospheric layer. We use the sky conditions and the physical properties of the lines from the HITRAN database to create the telluric spectrum. This high-resolution model is then convolved with the instrumental resolution and sampled to the instrumental wavelength grid. A subset of selected telluric lines is used to robustly fit the spectrum through a Levenberg-Marquardt minimization algorithm.
Results.
We computed the model to the H
2
O lines in the spectral range of ESPRESSO. When applied to stellar spectra from A0- to M5-type stars, the residuals of the strongest water lines are below the 2% peak-to-valley (P2V) amplitude for all spectral types, with the exception of M dwarfs, which are within the pseudo-continuum. We then determined the RVs from the telluric-corrected ESPRESSO spectra of Tau Ceti and Proxima. We created telluric-free masks and compared the obtained RVs with the DRS RVs. In the case of Tau Ceti, we identified that micro-telluric lines introduce systematics up to an amplitude of 58 cm s
−1
and with a period of one year if not corrected. For Proxima, the impact of micro-telluric lines is negligible due to the low flux below 5900 A. For late-type stars, the gain in spectral content at redder wavelengths is equivalent to a gain of 25% in photon noise or a factor of 1.78 in exposure time. This leads to better constraints on the semi-amplitude and eccentricity of Proxima d, which was recently proposed as a planet candidate. Finally, we applied our telluric model to the O
2
γ
-band and we obtained residuals below the 2% P2V amplitude.
Conclusions.
We propose a simple telluric model for high-resolution spectrographs to correct individual spectra and to achieve precise RVs. The removal of micro-telluric lines, coupled with the gain in spectral range, leads to more precise RVs. Moreover, we showcase that our model can be applied to other molecules, and thus to other wavelength regions observed by other spectrographs, such as NIRPS.
We analyse spectroscopic and photometric transits of the hot Jupiters WASP-52 b and HAT-P30 b obtained with ESPRESSO, Eulercam and NGTS for both targets, and additional TESS data for HAT-P-30. Our ...goal is to update the system parameters and refine our knowledge of the host star surfaces. For WASP-52, the companion planet has occulted starspots in the past, and as such our aim was to use the reloaded Rossiter-McLaughlin technique to directly probe its starspot properties. Unfortunately, we find no evidence for starspot occultations in the datasets herein. Additionally, we searched for stellar surface differential rotation (DR) and any centre-to-limb variation (CLV) due to convection, but return a null detection of both. This is unsurprising for WASP-52, given its relatively cool temperature, high magnetic activity (which leads to lower CLV), and projected obliquity near 0° (meaning the transit chord is less likely to cross several stellar latitudes). For HAT-P-30, this result was more surprising given its hotter effective temperature, lower magnetic field, and high projected obliquity (near 70°). To explore the reasons behind the null DR and CLV detection for HAT-P-30, we simulated a variety of scenarios. We find that either the CLV present on HAT-P-30 is below the solar level or the presence of DR prevents a CLV detection given the precision of the data herein. A careful treatment of both DR and CLV is required, especially for systems with high impact factors, due to potential degeneracies between the two. Future observations and/or a sophisticated treatment of the red noise present in the data (likely due to granulation) is required to refine the DR and CLV for these particular systems; such observations would also present another opportunity to try to examine starspots on WASP-52.
Context.
An accurate characterization of the known exoplanet population is key to understanding the origin and evolution of planetary systems. Determining true planetary masses through the radial ...velocity (RV) method is expected to experience a great improvement thanks to the availability of ultra-stable echelle spectrographs.
Aims.
We took advantage of the extreme precision of the new-generation echelle spectrograph ESPRESSO to characterize the transiting planetary system orbiting the G2V star K2-38 located at 194 pc from the Sun with
V
~ 11.4. This system is particularly interesting because it could contain the densest planet detected to date.
Methods.
We carried out a photometric analysis of the available K2 photometric light curve of this star to measure the radius of its two known planets, K2-38b and K2-38c, with
P
b
= 4.01593 ± 0.00050 d and
P
c
= 10.56103 ± 0.00090 d, respectively. Using 43 ESPRESSO high-precision RV measurements taken over the course of 8 months along with the 14 previously published HIRES RV measurements, we modeled the orbits of the two planets through a Markov chain Monte Carlo analysis, significantly improving their mass measurements.
Results.
Using ESPRESSO spectra, we derived the stellar parameters,
T
eff
= 5731 ± 66, log
g
= 4.38 ± 0.11 dex, and Fe/H = 0.26 ± 0.05 dex, and thus the mass and radius of K2-38,
M
⋆
= 1.03
−0.02
+0.04
M
⊕
and
R
⋆
= 1.06
−0.06
+0.09
R
⊕
. We determine new values for the planetary properties of both planets. We characterize K2-38b as a super-Earth with
R
P
= 1.54 ± 0.14
R
⊕
and
M
p
= 7.3
−1.0
+1.1
M
⊕
, and K2-38c as a sub-Neptune with
R
P
= 2.29 ± 0.26
R
⊕
and
M
p
= 8.3
−1.3
+1.3
M
⊕
. Combining the radius and mass measurements, we derived a mean density of
ρ
p
= 11.0
−2.8
+4.1
g cm
−3
for K2-38b and
ρ
p
= 3.8
−1.1
+1.8
g cm
−3
for K2-38c, confirming K2-38b as one of the densest planets known to date.
Conclusions.
The best description for the composition of K2-38b comes from an iron-rich Mercury-like model, while K2-38c is better described by a rocky-model with H2 envelope. The maximum collision stripping boundary shows how giant impacts could be the cause for the high density of K2-38b. The irradiation received by each planet places them on opposite sides of the radius valley. We find evidence of a long-period signal in the RV time-series whose origin could be linked to a 0.25–3
M
J
planet or stellar activity.
Study of negligibly senescent animals may provide clues that lead to better understanding of the cardiac aging process. To elucidate mechanisms of successful cardiac aging, we investigated ...age-related changes in proteasome activity, oxidative protein damage and expression of heat shock proteins, inflammatory factors, and mitochondrial complexes in the heart of the ocean quahog Arctica islandica, the longest-lived noncolonial animal (maximum life span potential: 508 years). We found that in the heart of A. islandica the level of oxidatively damaged proteins did not change significantly up to 120 years of age. No significant aging-induced changes were observed in caspase-like and trypsin-like proteasome activity. Chymotrypsin-like proteasome activity showed a significant early-life decline, then it remained stable for up to 182 years. No significant relationship was observed between the extent of protein ubiquitination and age. In the heart of A. islandica, an early-life decline in expression of HSP90 and five mitochondrial electron transport chain complexes was observed. We found significant age-related increases in the expression of three cytokine-like mediators (interleukin-6, interleukin-1β, and tumor necrosis factor-α) in the heart of A. islandica. Collectively, in extremely long-lived molluscs, maintenance of protein homeostasis likely contributes to the preservation of cardiac function. Our data also support the concept that low-grade chronic inflammation in the cardiovascular system is a universal feature of the aging process, which is also manifest in invertebrates.
We assess whether reactive oxygen species production and resistance to oxidative stress might be causally involved in the exceptional longevity exhibited by the ocean quahog Arctica islandica. We ...tested this hypothesis by comparing reactive oxygen species production, resistance to oxidative stress, antioxidant defenses, and protein damage elimination processes in long-lived A islandica with the shorter-lived hard clam, Mercenaria mercenaria. We compared baseline biochemical profiles, age-related changes, and responses to exposure to the oxidative stressor tert-butyl hydroperoxide (TBHP). Our data support the premise that extreme longevity in A islandica is associated with an attenuated cellular reactive oxygen species production. The observation of reduced protein carbonyl concentration in A islandica gill tissue compared with M mercenaria suggests that reduced reactive oxygen species production in long-living bivalves is associated with lower levels of accumulated macromolecular damage, suggesting cellular redox homeostasis may determine life span. Resistance to aging at the organismal level is often reflected in resistance to oxidative stressors at the cellular level. Following TBHP exposure, we observed not only an association between longevity and resistance to oxidative stress-induced mortality but also marked resistance to oxidative stress-induced cell death in the longer-living bivalves. Contrary to some expectations from the oxidative stress hypothesis, we observed that A islandica exhibited neither greater antioxidant capacities nor specific activities than in M mercenaria nor a more pronounced homeostatic antioxidant response following TBHP exposure. The study also failed to provide support for the exceptional longevity of A islandica being associated with enhanced protein recycling. Our findings demonstrate an association between longevity and resistance to oxidative stress-induced cell death in A islandica, consistent with the oxidative stress hypothesis of aging and provide justification for detailed evaluation of pathways involving repair of free radical-mediated macromolecular damage and regulation of apoptosis in the world's longest-living non-colonial animal.
Previous studies suggest that the age-related decline in circulating growth hormone (GH) and insulin-like growth factor-1 (IGF-1) levels significantly contribute to vascular dysfunction in aging by ...impairing cellular oxidative stress resistance pathways. Obesity in elderly individuals is increasing at alarming rates, and there is evidence suggesting that elderly individuals are more vulnerable to the deleterious cardiovascular effects of obesity than younger individuals. However, the specific mechanisms through which aging, GH/IGF-1 deficiency, and obesity interact to promote the development of cardiovascular disease remain unclear. To test the hypothesis that low circulating GH/IGF-1 levels exacerbate the pro-oxidant and proinflammatory vascular effects of obesity, GH/IGF-1-deficient Lewis dwarf rats and heterozygous control rats were fed either a standard diet or a high-fat diet (HFD) for 7 months. Feeding an HFD resulted in similar relative weight gains and increases in body fat content in Lewis dwarf rats and control rats. HFD-fed Lewis dwarf rats exhibited a relative increase in blood glucose levels, lower insulin, and impaired glucose tolerance as compared with HFD-fed control rats. Analysis of serum cytokine expression signatures indicated that chronic GH/IGF-1 deficiency exacerbates HFD-induced inflammation. GH/IGF-1 deficiency also exacerbated HFD-induced endothelial dysfunction, oxidative stress, and expression of inflammatory markers (tumor necrosis factor-α, ICAM-1) in aortas of Lewis dwarf rats. Overall, our results are consistent with the available clinical and experimental evidence suggesting that GH/IGF-1 deficiency renders the cardiovascular system more vulnerable to the deleterious effects of obesity.
We present HARPS spectroscopy of μ Arae (HD 160691) performed for studying the origin of the metallicity excess in this planet-hosting stars. The asteroseismologic campaign led to the previously ...reported discovery of a 14 earth mass planetary companion (Santos et al. 2004b, A&A, 426, L19). The present analysis reinforces this interpretation by excluding other possible processes for explaining the observed Doppler variation and leads to the identification of up to 43 p-mode oscillations with l = 0–3, frequencies in the range 1.3–2.5 mHz and amplitudes in the range 10–40 cm s-1.
Context.The μ Arae planetary system is fairly complex, because it contains two already known planets, μ Arae b with $P=640$ days and μ Arae c with $P=9.64$ days , and a third companion on a wide, but ...still poorly defined, orbit. Aims.Even with three planets in the system, the data points keep anomalously high dispersion around the fitted solution. The high residuals are only partially due to the strong p-mode oscillations of the host star. We therefore studied the possible presence of a fourth planet in this system. Methods.During the past years we carried out additional and extremely precise radial-velocity measurements with the HARPS spectrograph. These data turned out to be highly important for constraining the many free parameters in a four-planet orbital fit. Nevertheless, the search for the best solution remains difficult in this complex and multi-dimensional parameter space. The new Stakanof software, that uses an optimized genetic algorithm, helped us considerably in this task and made our search extremely efficient and successful. Results.We provide a full orbital solution of the planetary system around μ Arae. It turns out to be the second system known to harbor 4 planetary companions. Before this study, μ Arae b was already well known and characterized. Thanks to the new data points acquired with HARPS we can confirm the presence of μ Arae c at $P=9.64$ days, which produces a coherent RV signal over more than two years. The new orbital fit sets the mass of μ Arae c to 10.5 $M_{\oplus}$. Furthermore, we present the discovery of μ Arae d, a new planet on an almost circular 310 day-period and with a mass of 0.52 MJup. Finally, we give completely new orbital parameters for the longest-period planet, μ Arae e. It is the first time that this companion has been constrained by radial-velocity data into a dynamical stable orbit, which leaves no doubt about its planetary nature. We take this opportunity to discuss naming conventions for poorly characterized planets.
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