The GAPS programme with HARPS-N at TNG Borsa, F.; Scandariato, G.; Rainer, M. ...
Astronomy and astrophysics (Berlin),
06/2015, Volume:
578
Journal Article
Peer reviewed
Open access
Aims. We observed the τ Boo system with the HARPS-N spectrograph to test a new observational strategy aimed at jointly studying asteroseismology, the planetary orbit, and star-planet magnetic ...interaction. Methods. We collected high-cadence observations on 11 nearly consecutive nights and for each night averaged the raw FITS files using a dedicated software. In this way we obtained spectra with a high signal-to-noise ratio, used to study the variation of the Ca ii H&K lines and to have radial velocity values free from stellar oscillations, without losing the oscillations information. We developed a dedicated software to build a new custom mask that we used to refine the radial velocity determination with the HARPS-N pipeline and perform the spectroscopic analysis. Results. We updated the planetary ephemeris and showed the acceleration caused by the stellar binary companion. Our results on the stellar activity variation suggest the presence of a high-latitude plage during the time span of our observations. The correlation between the chromospheric activity and the planetary orbital phase remains unclear. Solar-like oscillations are detected in the radial velocity time series: we estimated asteroseismic quantities and found that they agree well with theoretical predictions. Our stellar model yields an age of 0.9 ± 0.5 Gyr for τ Boo and further constrains the value of the stellar mass to 1.38 ± 0.05 M⊙.
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The GAPS programme with HARPS-N at TNG Damasso, M.; Esposito, M.; Nascimbeni, V. ...
Astronomy and astrophysics (Berlin),
09/2015, Volume:
581
Journal Article
Peer reviewed
Open access
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 MJup 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.
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The GAPS Programme with HARPS-N at TNG Mancini, L.; Esposito, M.; Covino, E. ...
Astronomy and astrophysics (Berlin),
07/2015, Volume:
579
Journal Article
Peer reviewed
Open access
Context. Orbital obliquity is thought to be a fundamental parameter in tracing the physical mechanisms that cause the migration of giant planets from the snow line down to roughly 10-2 au from their ...host stars. We are carrying out a large programme to estimate the spin-orbit alignment of a sample of transiting planetary systems to study what the possible configurations of orbital obliquity are and whether they correlate with other stellar or planetary properties. Aims. We determine the true and the projected obliquity of HAT-P-36 and WASP-11/HAT-P-10 systems, respectively, which are both composed of a relatively cool star (with effective temperature Teff< 6100 K) and a hot-Jupiter planet. Methods. Thanks to the high-resolution spectrograph HARPS-N, we observed the Rossiter-McLaughlin effect for both systems by acquiring precise (3−8 m s-1) radial-velocity measurements during planetary transit events. We also present photometric observations comprising six light curves that cover five transit events, which were obtained using three medium-class telescopes. One transit of WASP-11/HAT-P-10 was followed simultaneously from two observatories. The three transit light curves of HAT-P-36 b show anomalies that are attributable to starspot complexes on the surface of the parent star, in agreement with the analysis of its spectra that indicates moderate activity ( log R′HK = −4.65 dex). By analysing the complete HATNet data set of HAT-P-36, we estimated the stellar rotation period by detecting a periodic photometric modulation in the light curve caused by star spots, obtaining Prot = 15.3 ± 0.4 days, which implies that the inclination of the stellar rotational axis with respect to the line of sight is i⋆ = 65° ± 34°. Results. We used the new spectroscopic and photometric data to revise the main physical parameters and measure the sky-projected misalignment angle of the two systems. We found λ = −14° ± 18° for HAT-P-36 and λ = 7° ± 5° for WASP-11/HAT-P-10, indicating in both cases a good spin-orbit alignment. In the case of HAT-P-36, we were also able to estimate an upper limit of its real obliquity, which turned out to be ψ< 63 degrees.
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The measurement of the Rossiter-McLaughlin effect for transiting exoplanets places constraints on the orientation of the orbital axis with respect to the stellar spin axis, which can shed light on ...the mechanisms shaping the orbital configuration of planetary systems. Here we present the interesting case of the Saturn-mass planet HAT-P-18b, which orbits one of the coolest stars for which the Rossiter-McLaughlin effect has been measured so far. We acquired a spectroscopic time-series, spanning a full transit, with the HARPS-N spectrograph mounted at the TNG telescope. The very precise radial velocity measurements delivered by the HARPS-N pipeline were used to measure the Rossiter-McLaughlin effect. Complementary new photometric observations of another full transit were also analysed to obtain an independent determination of the star and planet parameters. We find that HAT-P-18b lies on a counter-rotating orbit, the sky-projected angle between the stellar spin axis and the planet orbital axis being λ = 132 ± 15 deg. By joint modelling of the radial velocity and photometric data we obtain new determinations of the star (M⋆ = 0.770 ± 0.027 M⊙; R⋆ = 0.717 ± 0.026 R⊙; VsinI⋆ = 1.58 ± 0.18 km s-1) and planet (Mp = 0.196 ± 0.008 MJ; Rp = 0.947 ± 0.044 RJ) parameters. Our spectra provide for the host star an effective temperature Teff = 4870 ± 50 K, a surface gravity of log g⋆ = 4.57 ± 0.07 cm s-2, and an iron abundance of Fe/H = 0.10 ± 0.06. HAT-P-18b is one of the few planets known to transit a star with Teff ≲ 6250 K on a retrograde orbit. Objects such as HAT-P-18b (low planet mass and/or relatively long orbital period) most likely have a weak tidal coupling with their parent stars, therefore their orbits preserve any original misalignment. As such, they are ideal targets to study the causes of orbital evolution in cool main-sequence stars.
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The GAPS programme with HARPS-N at TNG Covino, E.; Esposito, M.; Barbieri, M. ...
Astronomy and astrophysics (Berlin),
06/2013, Volume:
554
Journal Article
Peer reviewed
Open access
Context. Our understanding of the formation and evolution of planetary systems is still fragmentary because most of the current data provide limited information about the orbital structure and ...dynamics of these systems. The knowledge of the orbital properties for a variety of systems and at different ages yields information on planet migration and on star-planet tidal interaction mechanisms. Aims. In this context, a long-term, multi-purpose, observational programme has started with HARPS-N at TNG and aims to characterise the global architectural properties of exoplanetary systems. The goal of this first paper is to fully characterise the orbital properties of the transiting system Qatar-1 as well as the physical properties of the star and the planet. Methods. We exploit HARPS-N high-precision radial velocity measurements obtained during a transit to measure the Rossiter-McLaughlin effect in the Qatar-1 system, and out-of-transit measurements to redetermine the spectroscopic orbit. New photometric-transit light-curves were analysed and a spectroscopic characterisation of the host star atmospheric parameters was performed based on various methods (line equivalent width ratios, spectral synthesis, spectral energy distribution). Results. We achieved a significant improvement in the accuracy of the orbital parameters and derived the spin-orbit alignment of the system; this information, combined with the spectroscopic determination of the host star properties (rotation, Teff, log g, metallicity), allows us to derive the fundamental physical parameters for star and planet (masses and radii). The orbital solution for the Qatar-1 system is consistent with a circular orbit and the system presents a sky-projected obliquity of λ = − 8.4 ± 7.1 deg. The planet, with a mass of 1.33 ± 0.05 MJ, is found to be significantly more massive than previously reported. The host star is confirmed to be metal-rich (Fe/H = 0.20 ± 0.10) and slowly rotating (vsinI = 1.7 ± 0.3 km s-1), though moderately active, as indicated by the strong chromospheric emission in the Ca ii H&K line cores (log R'HK ≈ -4.60). Conclusions. We find that the system is well aligned and fits well within the general λ versus Teff trend. We can definitely rule out any significant orbital eccentricity. The evolutionary status of the system is inferred based on gyrochronology, and the present orbital configuration and timescale for orbital decay are discussed in terms of star-planet tidal interactions.
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Due to the peculiarity of the Large Binocular Telescope optics (two 8.4 m mirrors on the same mounting), two wide-field imagers will be located at the prime loci of the telescope. The twin cameras ...will obtain an equivalent of two images of 6000 x 6000 pixels, which will be read out in 10 s. Due to the number of pixels/s that will be produced by the twin cameras, the handling, archiving, and reduction of data are a complex task. Proposed solutions are introduced. (Author)
Abell 611 Romano, A.; Fu, L.; Giordano, F. ...
Astronomy and astrophysics (Berlin),
05/2010, Volume:
514
Journal Article
Peer reviewed
Open access
Aims. The Large Binocular Cameras (LBC) are two twin wide field cameras (FOV ~ 23' × 25') mounted at the prime foci of the 8.4 m Large Binocular Telescope (LBT). We performed a weak lensing analysis ...of the z = 0.288 cluster Abell 611 on g-band data obtained by the blue-optimized LBC in order to estimate the cluster mass. Methods. Owing to the complexity of the PSF of LBC, we decided to use two different approaches, KSB and shapelets, to measure the shape of background galaxies and to derive the shear signal produced by the cluster. Then we estimated the cluster mass with both aperture densitometry and parametric model fits. Results. The combination of the large aperture of the telescope and the wide field of view allowed us to map a region well beyond the expected virial radius of the cluster and to get a high surface density for background galaxies (23 galaxies/arcmin2). This made it possible to estimate an accurate mass for Abell 611. We find that the mass within 1.5 Mpc is (8±3)× 1014 $M_\odot$ from the aperture mass technique and (5±1)× 1014 $M_\odot$ using the model fitting by an NFW mass density profile for both shapelet and KSB methods. This analysis demonstrates that LBC is a powerful instrument for weak gravitational lensing studies.
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The projected ellipticities of 34 populous SMC star clusters have been derived by means of PDS 1010A scans and a computer interactive method of reduction implemented on an Apollo 570 workstation. A ...pair of J and R plates taken with the 1.2 m UK Schmidt telescope in Australia were used. Radial ellipticity variations within individual globular clusters seem to be a common phenomenon for the SMC clusters, similar to that observed in the LMC clusters where the innerparts are more elliptical than the outer ones in 95 percent of the cases. The derived ellipticities which correspond to the innermost part of the cluster at radial distances near to half-mass radii have been found to be statistically more elliptical than those of the LMC, known to be more elliptical than those of the Galaxy. The dynamical masses of the clusters seem to correlate with ellipticities supporting the hypothesis that, either the gravitational field of the parent galaxy being a dominant factor affect slower the shape of the high mass clusters and/or the most massive clusters, being dynamically younger, retain their original shape.
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