L. Di Fabrizio

Metal abundances of RR Lyrae stars in the bar of the Large Magellanic Cloud

Metallicities ((Fe/H)) from low resolution spectroscopy obtained with the Very Large Telescope (VLT) are presented for 98 RR Lyrae and 3 short period Cepheids in the bar of the Large Magellanic Cloud. Our metal abundances have typical errors of ±0.17 dex. The average metallicity of the RR Lyrae stars is (Fe/H) = −1.48 ± 0.03 ± 0.06 on the scale of Harris (1996). The star-to-star scatter (0.29 dex) is larger than the observational errors, indicating a real spread in metal abundances. The derived metallicities cover the range −2.12 −1. For the ab-type variables we compared our spectroscopic abundances with those obtained from the Fourier decomposition of the light curves. We find good agreement between the two techniques, once the systematic offset of 0.2 dex between the metallicity scales used in the two methods is taken into account. The spectroscopic metallicities were combined with the dereddened apparent magnitudes of the variables to derive the slope of the luminosity-metallicity relation for the LMC RR Lyrae stars: the resulting value is 0.214 ± 0.047 mag/dex. Finally, the 3 short period Cepheids have (Fe/H) values in the range −2.0 < (Fe/H) < −1.5. They are more metal-poor than typical LMC RR Lyrae stars, thus they are more likely to be Anomalous Cepheids rather than the short period Classical Cepheids that are often found in a number of dwarf Irregular galaxies.

The GAPS programme with HARPS-N at TNG - I. Observations of the Rossiter-McLaughlin effect and characterisation of the transiting system Qatar-1

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 di erent 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 e ect 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, Te , logg, 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 = 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 (v sinI = 1:7 0:3 km s 1 ), though moderately active, as indicated by the strong chromospheric emission in the Caii H&K line cores (logR 0 4:60). Conclusions. We find that the system is well aligned and fits well within the general versus Te 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.

CU Comae: A New Field Double-Mode RR Lyrae Variable, the Most Metal-poor Discovered to Date*

We report the discovery of a new double-mode RR Lyrae variable (RRd) in the field of our Galaxy: CU Comae. CU Com is the sixth such RRd identified to date and is the most metal-poor RRd ever detected. Based on BVI CCD photometry spanning 11 years of observations, we find that CU Com has periods P0 = 0.5441641 days (±0.0000049) and P1 = 0.4057605 days (±0.0000018). The amplitude of the primary (first overtone) period of CU Com is about twice the amplitude of the secondary (fundamental) period. The combination of the fundamental period of pulsation P0 and the period ratio of P1/P0 = 0.7457 places the variable on the metal-poor side of the Petersen diagram, in the region occupied by M68 and M15 RRds. A mass of 0.83 M⊙ is estimated for CU Com using an updated theoretical calibration of the Petersen diagram. High-resolution spectroscopy (R = 30,000) covering the full pulsation cycle of CU Com was obtained with the 2.7 m telescope of the McDonald Observatory and has been used to build up the radial velocity curve of the variable. An abundance analysis performed on the four spectra taken near minimum light (0.54 < < 0.71) confirms the metal-poor nature of CU Com, for which we derive [Fe/H] = -2.38 ± 0.20. This value places this new RRd at the extreme metal-poor edge of the metallicity distribution of the RR Lyrae variables in our Galaxy.

The GAPS programme with HARPS-N at TNG - XI. Pr 0211 in M 44: the first multi-planet system in an open cluster

Open cluster (OC) stars share the same age and metallicity, and, in general, their age and mass can be estimated with higher precision than for field stars. For this reason, OCs are considered an important laboratory to study the relation between the physical properties of the planets and those of their host stars, and the evolution of planetary systems. We started an observational campaign within the GAPS collaboration to search for and characterize planets in OCs We monitored the Praesepe member Pr0211 to improve the eccentricity of the Hot-Jupiter (HJ) already known to orbit this star and search for additional planets. An eccentric orbit for the HJ would support a planet-planet scattering process after its formation. From 2012 to 2015, we collected 70 radial velocity (RV) measurements with HARPS-N and 36 with TRES of Pr0211. Simultaneous photometric observations were carried out with the robotic STELLA telescope in order to characterize the stellar activity. We discovered a long-term trend in the RV residuals that we show to be due to the presence of a second, massive, outer planet. Orbital parameters for the two planets are derived by simultaneously fitting RVs and photometric light curves, with the activity signal modelled as a series of sinusoids at the rotational period of the star and its harmonics. We confirm that Pr0211b has a nearly circular orbit (

Berkeley 29, the most distant old open cluster

e = 0.02 \pm 0.01

The activity of comet C/2007 D1 (LINEAR) at 9.7 AU from the Sun

), with an improvement of a factor two with respect to the previous determination of its eccentricity, and estimate that Pr0211c has a mass

The old anticentre open cluster Berkeley 32: membership and fundamental parameters★

M_p\sin i = 7.9 \pm 0.2 M_J

Observational results for eight long-period comets observed far from the Sun

, a period

Optical pulsations from a transitional millisecond pulsar

P>

The GAPS programme with HARPS-N at TNG - IX. The multi-planet system KELT-6: Detection of the planet KELT-6 c and measurement of the Rossiter-McLaughlin effect for KELT-6 b

3500 days and a very eccentric orbit (