In the age of JWST, temperate terrestrial exoplanets transiting nearby late-type M dwarfs provide unique opportunities for characterising their atmospheres, as well as searching for biosignature ...gases. We report here the discovery and validation of two temperate super-Earths transiting LP 890-9 (TOI-4306, SPECULOOS-2), a relatively low-activity nearby (32 pc) M6V star. The inner planet, LP 890-9b, was first detected by TESS (and identified as TOI-4306.01) based on four sectors of data. Intensive photometric monitoring of the system with the SPECULOOS Southern Observatory then led to the discovery of a second outer transiting planet, LP 890-9c (also identified as SPECULOOS-2c), previously undetected by TESS. The orbital period of this second planet was later confirmed by MuSCAT3 follow-up observations. With a mass of 0.118±0.002 M⊙, a radius of 0.1556±0.0086 R⊙, and an effective temperature of 2850±75 K, LP 890-9 is the second-coolest star found to host planets, after TRAPPIST-1. The inner planet has an orbital period of 2.73 d, a radius of 1.320+0.053−0.027 R⊕, and receives an incident stellar flux of 4.09±0.12 S⊕. The outer planet has a similar size of 1.367+0.055−0.039 R⊕ and an orbital period of 8.46 d. With an incident stellar flux of 0.906 ± 0.026 S⊕, it is located within the conservative habitable zone, very close to its inner limit. Although the masses of the two planets remain to be measured, we estimated their potential for atmospheric characterisation via transmission spectroscopy using a mass-radius relationship and found that, after the TRAPPIST-1 planets, LP 890-9c is the second-most favourable habitable-zone terrestrial planet known so far. The discovery of this remarkable system offers another rare opportunity to study temperate terrestrial planets around our smallest and coolest neighbours.
We report the detection of two very eccentric planets orbiting HD4113 and HD156846 with the CORALIE Echelle spectrograph mounted on the 1.2-m Euler Swiss telescope at La Silla. The first planet, ...HD4113b, has minimum mass of \(m\sin{i}=1.6\pm0.2 M_{\rm Jup}\), a period of \(P=526.59\pm0.21\) days and an eccentricity of \(e=0.903\pm0.02\). It orbits a metal rich G5V star at \(a=1.28\) AU which displays an additional radial velocity drift of 28 m s\(^{-1}\)/yr observed during 8 years. The combination of the radial-velocity data and the non-detection of any main sequence stellar companion in our high contrast images taken at the VLT with NACO/SDI, characterizes the companion as a probable brown dwarf or as a faint white dwarf. The second planet, \object{HD 156846 b}, has minimum mass of \(m\sin{i}=10.45\pm0.05\) M\(_{\rm Jup}\), a period of \(P=359.51\pm0.09 \) days, an eccentricity of \(e=0.847\pm0.002\) and is located at \(a=1.0\) AU from its parent star. HD156846 is a metal rich G0 dwarf and is also the primary of a wide binary system (\(a>250\) AU, \(P>4000\) years). Its stellar companion, \object{IDS 17147-1914 B}, is a M4 dwarf. The very high eccentricities of both planets can be explained by Kozai oscillations induced by the presence of a third object.
We present Spitzer Space Telescope infrared photometry of a secondary eclipse of the hot Neptune GJ436b. The observations were obtained using the 8-micron band of the InfraRed Array Camera (IRAC). ...The data spanning the predicted time of secondary eclipse show a clear flux decrement with the expected shape and duration. The observed eclipse depth of 0.58 mmag allows us to estimate a blackbody brightness temperature of T_p = 717 +- 35 K at 8 microns. We compare this infrared flux measurement to a model of the planetary thermal emission, and show that this model reproduces properly the observed flux decrement. The timing of the secondary eclipse confirms the non-zero orbital eccentricity of the planet, while also increasing its precision (e = 0.14 +- 0.01). Additional new spectroscopic and photometric observations allow us to estimate the rotational period of the star and to assess the potential presence of another planet.
55 Cnc e is a transiting super-Earth (radius $1.88\rm\,R_\oplus$ and mass $8\rm\, M_\oplus$) orbiting a G8V host star on a 17-hour orbit. Spitzer observations of the planet's phase curve at 4.5 µm ...revealed a time-varying occultation depth, and MOST optical observations are consistent with a time-varying phase curve amplitude and phase offset of maximum light. Both broadband and high-resolution spectroscopic analyses are consistent with either a high mean molecular weight atmosphere or no atmosphere for planet e. A long term photometric monitoring campaign on an independent optical telescope is needed to probe the variability in this system. We seek to measure the phase variations of 55 Cnc e with a broadband optical filter with the 30 cm effective aperture space telescope CHEOPS and explore how the precision photometry narrows down the range of possible scenarios. We observed 55 Cnc for 1.6 orbital phases in March of 2020. We designed a phase curve detrending toolkit for CHEOPS photometry which allows us to study the underlying flux variations of the 55 Cnc system. We detected a phase variation with a full-amplitude of $72 \pm 7$ ppm but do not detect a significant secondary eclipse of the planet. The shape of the phase variation resembles that of a piecewise-Lambertian, however the non-detection of the planetary secondary eclipse, and the large amplitude of the variations exclude reflection from the planetary surface as a possible origin of the observed phase variations. They are also likely incompatible with magnetospheric interactions between the star and planet but may imply that circumplanetary or circumstellar material modulate the flux of the system. Further precision photometry of 55 Cnc from CHEOPS will measure variations in the phase curve amplitude and shape over time this year.
The CHEOPS space mission dedicated to exoplanet follow-up was launched in December 2019, equipped with the capacity to perform photometric measurements at the 20 ppm level. As CHEOPS carries out its ...observations in a broad optical passband, it can provide insights into the reflected light from exoplanets and constrain the short-wavelength thermal emission for the hottest of planets by observing occultations and phase curves. Here, we report the first CHEOPS observation of an occultation, namely, that of the hot Jupiter WASP-189 b, a MP ≈ 2MJ planet orbiting an A-type star. We detected the occultation of WASP-189 b at high significance in individual measurements and derived an occultation depth of dF = 87.9 ± 4.3 ppm based on four occultations. We compared these measurements to model predictions and we find that they are consistent with an unreflective atmosphere heated to a temperature of 3435 ± 27 K, when assuming inefficient heat redistribution. Furthermore, we present two transits of WASP-189 b observed by CHEOPS. These transits have an asymmetric shape that we attribute to gravity darkening of the host star caused by its high rotation rate. We used these measurements to refine the planetary parameters, finding a ~25% deeper transit compared to the discovery paper and updating the radius of WASP-189 b to 1.619 ± 0.021RJ. We further measured the projected orbital obliquity to be λ = 86.4-4.4+2.9°, a value that is in good agreement with a previous measurement from spectroscopic observations, and derived a true obliquity of Ψ = 85.4 ± 4.3°. Finally, we provide reference values for the photometric precision attained by the CHEOPS satellite: for the V = 6.6 mag star, and using a 1-h binning, we obtain a residual RMS between 10 and 17 ppm on the individual light curves, and 5.7 ppm when combining the four visits.
The TRAPPIST-1 planetary system represents an exceptional opportunity for the atmospheric characterization of temperate terrestrial exoplanets with the upcoming James Webb Space Telescope (JWST). ...Assessing the potential impact of stellar contamination on the planets' transit transmission spectra is an essential precursor step to this characterization. Planetary transits themselves can be used to scan the stellar photosphere and to constrain its heterogeneity through transit depth variations in time and wavelength. In this context, we present our analysis of 169 transits observed in the optical from space with K2 and from the ground with the SPECULOOS and Liverpool telescopes. Combining our measured transit depths with literature results gathered in the mid/near-IR with Spitzer/IRAC and HST/WFC3, we construct the broadband transmission spectra of the TRAPPIST-1 planets over the 0.8-4.5 \(\mu\)m spectral range. While planets b, d, and f spectra show some structures at the 200-300ppm level, the four others are globally flat. Even if we cannot discard their instrumental origins, two scenarios seem to be favored by the data: a stellar photosphere dominated by a few high-latitude giant (cold) spots, or, alternatively, by a few small and hot (3500-4000K) faculae. In both cases, the stellar contamination of the transit transmission spectra is expected to be less dramatic than predicted in recent papers. Nevertheless, based on our results, stellar contamination can still be of comparable or greater order than planetary atmospheric signals at certain wavelengths. Understanding and correcting the effects of stellar heterogeneity therefore appears essential to prepare the exploration of TRAPPIST-1's with JWST.
Background: The prognosis of liver iron overload is highly dependent on liver iron content (LIC) and the extent of liver fibrosis. Liver biopsy is the invasive reference method for fibrosis ...evaluation but with several limitations. Non-invasive biological methods (FibroTest, APRI) are not applicable in blood diseases. Transient elastography (TE) is a new non-invasive and rapid bedside method used to measure liver stiffness.This technique has been extensively studied with success in evaluation of liver fibrosis in HCV infection (Ziol, Hepatology 2005; Castera, Gastroenterology 2005). Until now, no data are available on evaluation of liver fibrosis by TE in highly transfused patients with iron overload.
Methods: We assessed liver stiffness (kPa) by elastography measurement (Fibroscan; Echosens, Paris, France). Ishak's and Metavir's scales were used to stage fibrosis and hepatitis activity; LIC was measured by atomic absorption spectometry in a central laboratory (Rennes, France) and by MRI procedure according to Gandon (Lancet 2004). Cardiac MRI T2* (indirect estimation of iron heart content) was also measured by MRI according to Anderson (Eur Heart J 2001). Serum ferritin level and HCV serology were assayed in all cases. Correlation statistical analysis used Spearman's Rho and Pearson tests and mean comparisons were done by a non-parametric Mann-Whitney test.
Results: 15 liver samples (weight >1mg except 1) from monthly transfused patients (13 major beta Thalassemia, 1 sickle cell disease, 1 myelodysplastic syndrome) were analyzed. Median age was 37 years (7–75). Histological results were: 3 cirrhosis (METAVIR F=4 (F4), or Ishak's Staging =6 (IS6)) among 5 patients with severe fibrosis (F3,F4) or (IS4-6) and 10 patients with no or mild fibrosis (F0-2) or (IS0-3). Mean ferritin was 2579 ng/ml CI 95% 1372–3786. 2 patients were HCV positive. Correlation between LIC and ferritin was 0.82 (p<0,05); between LIC and MRI LIC: 0.88 (p<0,05); LIC and MRI Heart T2*: 0.72(p<0,05); METAVIR F score and Ishak's grading score: 0.86 (p<0,05). A correlation was also observed between METAVIR F and elastography: 0.60(p<0,05); and mean values of elastography were significally different in patients with severe fibrosis: 9.1kPa CI95% 4.5–13.7 vs 5.9kPa CI95% 4.6–7.2 in those without sever fibrosis (p<0,05) (fig). A value of elastography above 6.25kPa (Se=80%; Sp=70%; AUROC=0.820) identified patients at risk for severe fibrosis (F3,F4 or IS 4–6) (Negative Predictive Value = 88%; Positive Predictive Value = 57%).
Conclusion: A significant correlation between Metavir Fibrosis scale and elastography values was found. This new non-invasive method would be helpful to evaluate liver fibrosis and to determine patients who could avoid invasive procedures in particular in regularly transfused low risk myelodysplastic patients at risk of bleeding due to abnormal platelet function. These preliminary results will have to be confirmed in a larger population.
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We report high-precision interferometric and radial velocity (RV) observations of the M-dwarf binary Gl 268. Combining measurements conducted using the IOTA interferometer and the ELODIE and Harvard ...Center for Astrophysics RV instruments leads to a mass of 0.22596 plus-minus 0.00084 Mass compared to the sun for component A and 0.19230 plus-minus 0.00071 Mass compared to the sun for component B. The system parallax as determined by these observations is 0.1560 plus-minus 0.0030 arcsec - a measurement with 1.9% uncertainty in excellent agreement with Hipparcos (0.1572 plus-minus 0.0033). The absolute H-band magnitudes of the component stars are not well constrained by these measurements; however, we can place an approximate upper limit of 7.95 and 8.1 for Gl 268A and B, respectively.We test these physical parameters against the predictions of theoretical models that combine stellar evolution with high fidelity, non-gray atmospheric models. Measured and predicted values are compatible within 2sigma. These results are among the most precise masses measured for visual binaries and compete with the best adaptive optics and eclipsing binary results.
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