Search

Context. HAT-P-67 b is one of the lowest-density gas giants known to date, making it an excellent target for atmospheric characterisation through the transmission spectroscopy technique. Aims. In the framework of the GAPS large programme, we collected four transit events of HAT-P-67 b with the aim of studying the exoplanet atmosphere and deriving the orbital projected obliquity. Methods. We exploited the high-precision GIARPS (GIANO-B + HARPS-N) observing mode of the Telescopio Nazionale Galileo (TNG) along with additional archival TESS photometry to explore the activity level of the host star. We performed transmission spec-troscopy, both in the visible (VIS) and in the near-infrared (NIR) wavelength range, and we analysed the Rossiter–McLaughlin (RML) effect when fitting both the radial velocities and the Doppler shadow. Based on the TESS photometry, we redetermined the transit parameters of HAT-P-67 b. Results. By modelling the RML effect, we derived a sky-projected obliquity of (2.2 ± 0.4)°, indicating an aligned planetary orbit. The chromospheric activity index log R′HK, the CCF profile, and the variability in the transmission spectrum of the Hα line suggest that the host star shows signatures of stellar activity and/or pulsation. We found no evidence of atomic or molecular species in the optical transmission spectra, with the exception of pseudo-signals corresponding to Cr I, Fe I, Ha, Na I, and Ti I. In the NIR range, we found an absorption signal of the He I triplet of 5.56−0.30+0.29% (19.0σ), corresponding to an effective planetary radius of ~3 Rp (where Rp ~ 2 RJ), which extends beyond the planet's Roche lobe radius. Conclusions. Owing to the stellar variability and the high uncertainty of the model, we could not confirm the planetary origin of the signals found in the optical transmission spectrum. On the other hand, we were able to confirm previous detections of the infrared He I triplet, providing a 19.0σ detection. Our finding indicates that the planet's atmosphere is evaporating. [ABSTRACT FROM AUTHOR]

Context. Detecting and characterising exoworlds around very young stars (age ≤10 Myr) are key aspects of exoplanet demographic studies, especially for understanding the mechanisms and timescales of planet formation and migration. Any reliable theory for such physical phenomena requires a robust observational database to be tested. However, detection using the radial velocity method alone can be very challenging because the amplitude of the signals caused by the magnetic activity of such stars can be orders of magnitude larger than those induced even by massive planets. Aims. We observed the very young (~2 Myr) and very active star V830 Tau with the HARPS-N spectrograph between October 2017 and March 2020 to independently confirm and characterise the previously reported hot Jupiter V830 Tau b (Kb = 68 ± 11 m s−1; mb sin ib = 0.57 ± 0.10 MJup; Pb = 4.927 ± 0.008 d). Methods. Because of the observed ~1 km s−1 radial velocity scatter that can clearly be attributed to the magnetic activity of V830 Tau, we analysed radial velocities extracted with different pipelines and modelled them using several state-of-the-art tools. We devised injection-recovery simulations to support our results and characterise our detection limits. The analysis of the radial velocities was aided by a characterisation of the stellar activity using simultaneous photometric and spectroscopic diagnostics. Results. Despite the high quality of our HARPS-N data and the diversity of tests we performed, we were unable to detect the planet V830 Tau b in our data and cannot confirm its existence. Our simulations show that a statistically significant detection of the claimed planetary Doppler signal is very challenging. Conclusions. It is important to continue Doppler searches for planets around young stars, but utmost care must be taken in the attempt to overcome the technical difficulties to be faced in order to achieve their detection and characterisation. This point must be kept in mind when assessing their occurrence rate, formation mechanisms, and migration pathways, especially without evidence of their existence from photometric transits. [ABSTRACT FROM AUTHOR]

Aims. For more than 1.5 years we spectroscopically monitored the star KELT-6 (BD+31 2447), which is known to host the transiting hot-Saturn KELT-6 b, because a previously observed long-term trend in radial velocity time series suggested that there is an outer companion. Methods. We collected a total of 93 new spectra with the HARPS-N and TRES spectrographs. A spectroscopic transit of KELT-6 b was observed with HARPS-N, and simultaneous photometry was obtained with the IAC-80 telescope. Results. We proved the existence of an outer planet with a mininum mass Mpsin i = 3.71 ± 0.21 ... and a moderately eccentric orbit (e = 0.21-0.036+0.039) of period P ~ 3.5 years. We improved the orbital solution of KELT-6 b and obtained the first measurement of the Rossiter-McLaughlin effect, showing that the planet has a likely circular, prograde, and slightly misaligned orbit with a projected spin-orbit angle of λ = -36 ± 11 degrees. We improved the KELT-6 b transit ephemeris from photometry and provide new measurements of the stellar parameters. KELT-6 appears as an interesting case for studying the formation and evolution of multi-planet systems. [ABSTRACT FROM AUTHOR]

We update the TrES-4 system parameters using high-precision HARPS-N radial-velocity measurements and new photometric light curves. A combined spectroscopic and photometric analysis allows us to determine a spectroscopic orbit with a semi-amplitude K = 51 ± 3 ms-1. The derived mass of TrES-4b is found to be Mp = 0.49 ± 0.04 MJup, significantly lower than previously reported. Combined with the large radius (Rp = 1.84+0.08-0.09 RJup) inferred from our analysis, TrES-4b becomes the transiting hot Jupiter with the second-lowest density known. We discuss several scenarios to explain the puzzling discrepancy in the mass of TrES-4b in the context of the exotic class of highly inflated transiting giant planets. [ABSTRACT FROM AUTHOR]

Context. HD 144277 was previously discovered by Microvariability and Oscillations of Stars (MOST) space photometry to be a young and hot d Scuti star showing regular groups of pulsation frequencies. The first asteroseismic models required lower than solar metallicity to fit the observed frequency range based on a purely photometric analysis. Aims. The aim of the present paper is to determine, by means of high-resolution spectroscopy, fundamental stellar parameters required for the asteroseismic model of HD 144277, and subsequently, to refine it. Methods. High-resolution, high signal-to-noise spectroscopic data obtained with the HARPS spectrograph were used to determine the fundamental parameters and chemical abundances of HD 144277. These values were put into context alongside the results from asteroseismic models. Results. The effective temperature, Teff, of HD 144277 was determined as 8640 -100+300 K, log g is 4.14 ± 0.15 and the projected rotational velocity, v sin i, is 62.0 ± 2.0 kms-1. As the v sin i value is significantly larger than previously assumed, we refined the first asteroseimic model accordingly. The overall metallicity Z was determined to be 0.011 where the light elements He, C, O, Na, and S show solar chemical composition, but the heavier elements are significantly underabundant. In addition, the radius of HD 144277 was determined to be 1.55 ± 0.65 R⊙ from spectral energy distribution fitting, based on photometric data taken from the literature. Conclusions. From the spectroscopic observations, we could confirm our previous assumption from asteroseismic models that HD 144277 has less than solar metallicity. The fundamental parameters derived from asteroseismology, Teff, logg, L/L⊙ and R/R⊙ agree within one sigma to the values found from spectroscopic analysis. As the v sin i value is significantly higher than assumed in the first analysis, near-degeneracies and rotational mode coupling were taken into account in the new models. These suggest that HD 144277 has an equatorial rotational velocity of about 80 km s-1 and is seen equator-on. The observed frequencies are identified as prograde modes. [ABSTRACT FROM AUTHOR]

Aims. We aim to detect and interpret photometric and spectroscopic variability of the bright CoRoT B-type supergiant target HD46769 (V = 5.79). We also attempt to detect a magnetic field in the target. Methods. We analyse a 23-day oversampled CoRoT light curve after detrending and spectroscopic follow-up data using standard Fourier analysis and phase dispersion minimization methods. We determine the fundamental parameters of the star, as well as its abundances from the most prominent spectral lines. We perform a Monte Carlo analysis of spectropolarimetric data to obtain an upper limit of the polar magnetic field, assuming a dipole field. Results. In the CoRoT data, we detect a dominant period of 4.84 d with an amplitude of 87 ppm and some of its (sub-)multiples. Given the shape of the phase-folded light curve and the absence of binary motion, we interpret the dominant variability in terms of rotational modulation, with a rotation period of 9.69 d. Subtraction of the rotational modulation signal does not reveal any sign of pulsations. Our results are consistent with the absence of variability in the Hipparcos light curve. The spectroscopy leads to a projected rotational velocity of 72 ± 2 kms-1 and does not reveal periodic variability or the need to invoke macroturbulent line broadening. No signature of a magnetic field is detected in our data. A field stronger than ~500 G at the poles can be excluded, unless the possible non-detected field were more complex than dipolar. Conclusions. The absence of pulsations and macroturbulence of this evolved B-type supergiant is placed into the context of instability computations and of observed variability of evolved B-type stars. [ABSTRACT FROM AUTHOR]

Context. B-type stars are promising targets for asteroseismic modelling, since their frequency spectrum is relatively simple. Aims. We deduce and summarise observational constraints for the hybrid pulsator, HD 50230, earlier reported to have deviations from a uniform period spacing of its gravity modes. The combination of spectra and a high-quality light curve measured by the CoRoT satellite allow a combined approach to fix the position of HD 50230 in the HR diagram. Methods. To describe the observed pulsations, classical Fourier analysis was combined with short-time Fourier transformations and frequency spacing analysis techniques. Visual spectra were used to constrain the projected rotation rate of the star and the fundamental parameters of the target. In a first approximation, the combined information was used to interpret multiplets and spacings to infer the true surface rotation rate and a rough estimate of the inclination angle. Results. We identify HD 50230 as a spectroscopic binary and characterise the two components. We detect the simultaneous presence of high-order g modes and low-order p and g-modes in the CoRoT light curve, but were unable to link them to line profile variations in the spectroscopic time series. We extract the relevant information from the frequency spectrum, which can be used for seismic modelling, and explore possible interpretations of the pressure mode spectrum. [ABSTRACT FROM AUTHOR]