Isabella Pagano - Profile on Academia.edu (original) (raw)

Papers by Isabella Pagano

VLA Observations of dMe Stars (CD-ROM Directory: contribs/leto)

Astronomy and Astrophysics

We present new VLA radio observations of a sample of dMe stars in X, U, K, and Q bands (from 8.4 ... more We present new VLA radio observations of a sample of dMe stars in X, U, K, and Q bands (from 8.4 to 43 GHz) obtained during an observing campaign in 1996 April-June. The aim of the project was to determine the spectral energy distributions of late-type dwarf flare stars to investigate the possible existence of an inversion of the spectrum slope at frequencies higher than 8 GHz. We also tried to constrain the possible emission mechanism at radio frequencies. We have detections in X band (8.4 GHz), for three sources (UV Cet, V 1054 Oph, and EV Lac), while all of our other measurements are upper limits. We discuss how the weak radio emission of some sources (e.g. AU Mic) and the coronal plasma properties deduced from X-ray observations constrain the coronal magnetic field properties.

The RS CVn-type system II Pegasi was observed by ISOPHOT on ISO to derive spectrophotometric data... more The RS CVn-type system II Pegasi was observed by ISOPHOT on ISO to derive spectrophotometric data in the 2.5 - 12 micron range, and multifilter photometry between 3.6 and 200 microns. Contemporary to ISO observations we also secured: - millimeter data with the IRAM interferometer; - near infrared and optical photometry with the 91 cm and the 80 cm APT, respectively, at Catania Observatory. Preliminary data on the spectral distribution in the full 2.5 - 200 micron range indicate the presence of a remarkably well defined IR excess whose nature is under investigation.

Astronomy & Astrophysics, 2015

We report the spectroscopic confirmation of the Kepler object of interest KOI-183b (also known as... more We report the spectroscopic confirmation of the Kepler object of interest KOI-183b (also known as KOI-183.01), a half-Jupiter mass planet transiting an old solar-like star every 2.7 days. Our analysis is the first to combine the full Kepler photometry (quarters 1-17) with high-precision radial velocity measurements taken with the FIES spectrograph at the Nordic Optical Telescope. We simultaneously modelled the photometric and spectroscopic data-sets using Bayesian approach coupled with Markov chain Monte Carlo sampling. We found that the Kepler pre-search data conditioned light curve of KOI-183 exhibits quarter-to-quarter systematic variations of the transit depth, with a peak-to-peak amplitude of ∼4.3 % and seasonal trends reoccurring every four quarters. We attributed these systematics to an incorrect assessment of the quarterly variation of the crowding metric. The host star KOI-183 is a G4 dwarf with M = 0.85 ± 0.04 M , R = 0.95 ± 0.04 R , T eff = 5560 ± 80 K, [M/H]=−0.10±0.05 dex, and with an age of 11 ± 2 Gyr. The planet KOI-183b has a mass of M p = 0.595 ± 0.081 M Jup and a radius of R p = 1.192 ± 0.052 R Jup , yielding a planetary bulk density of ρ p = 0.459 ± 0.083 g cm −3 . The radius of KOI-183b is consistent with both theoretical models for irradiated coreless giant planets and expectations based on empirical laws. The inclination of the stellar spin axis suggests that the system is aligned along the line of sight. We detected a tentative secondary eclipse of the planet at a 2-σ confidence level (∆F ec = 14.2 ± 6.6 ppm) and found that the orbit might have a small non-zero eccentricity of 0.019 +0.028 −0.014 . With a Bond albedo of A B = 0.037 ± 0.019, KOI-183b is one of the gas-giant planets with the lowest albedo known so far.

World Space Observatory UltraViolet (WSO-UV) is a multipurpose space observatory, made by a 170 c... more World Space Observatory UltraViolet (WSO-UV) is a multipurpose space observatory, made by a 170 cm aperture telescope, capable of UV high-resolution spectroscopy, long slit low-resolution spectroscopy, and deep UV and optical imaging. With a nominal mission life time of 5 years, and a planned extension to 10 years, from a geosynchronous orbit with an inclination of 51.8 degrees, WSO-UV will provide observations of exceptional importance for the study of many unsolved astrophysical problems. WSO-UV is implemented in the framework of a collaboration between Russia (chair), China, Germany, Italy, Spain, and Ukraine. This book illustrates the results of the feasibility study for the Field Camera Unit (FCU), a multi-spectral radial instrument on the focal plane of WSO-UV. The book provides an overview of the key science topics that are drivers to the participation of the Italian astronomical community in the WSO-UV project. The science drivers here illustrated have been used to define th...

Context. Our understanding of the formation and evolution of planetary systems is still fragmenta... more 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, T eff , 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 M J , 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 sin I = 1.7 ± 0.3 km s −1 ), though moderately active, as indicated by the strong chromospheric emission in the Ca  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 T eff 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.

Hot Planets and Cool Stars, 2013

Ground based radial velocity (RV) searches continue to discover exoplanets below Neptune mass dow... more Ground based radial velocity (RV) searches continue to discover exoplanets below Neptune mass down to Earth mass. Furthermore, ground based transit searches now reach milli-mag photometric precision and can discover Neptune size planets around bright stars. These searches will find exoplanets around bright stars anywhere on the sky, their discoveries representing prime science targets for further study due to the proximity and brightness of their host stars. A mission for transit follow-up measurements of these prime targets is currently lacking. The first ESA S-class mission CHEOPS (CHaracterizing ExoPlanet Satellite) will fill this gap. It will perform ultra-high precision photometric monitoring of selected bright target stars almost anywhere on the sky with sufficient precision to detect Earth sized transits. It will be able to detect transits of RV-planets by photometric monitoring if the geometric configuration results in a transit. For Hot Neptunes discovered from the ground, CHEOPS will be able to improve the transit light curve so that the radius can be determined precisely. Because of the host stars' brightness, high precision RV measurements will be possible for all targets. All planets observed in transit by CHEOPS will be validated and their masses will be known. This will provide valuable data for constraining the mass-radius relation of exoplanets, especially in the Neptune-mass regime. During the planned 3.5 year mission, about 500 targets will be observed. There will be 20% of open time available for the community to develop new science programmes. a

Proceedings of the International Astronomical Union, 2011

Division XI is organized by astronomers and astrophysicists who are mainly involved in space astr... more Division XI is organized by astronomers and astrophysicists who are mainly involved in space astronomy and their relevant research fields. Thus the Division XI members represent a very broad community, including radio, infrared, optical, ultraviolet, X-ray, and gamma ray, as well as cosmic ray observers and theorests. The topics of interest to the Division were extended to the study neutrino, astrophysical particles and gravitational waves, but these are currently under-represented in the Divisional membership. The relevant investigations cover almost all astronomical topics from our Solar System, stellar, Galactic and extragalactic research to studies of the deep space Universe and cosmology. This implies that communication and cooperation among the Division members, and cross-fertilization with members of other Divisions, are important and helpful to promote new space and ground based observatories and to enhance their scientific value.

Astrophysics and Space Science, 2006

Astronomy & Astrophysics, 2011

Context. The CoRoT satellite has recently discovered a hot Jupiter that transits across the disc ... more Context. The CoRoT satellite has recently discovered a hot Jupiter that transits across the disc of a F9 main-sequence star called CoRoT-6 with a period of 8.886 days. Aims. We model the photospheric activity of the star and use the maps of the active regions to study stellar differential rotation and the star-planet interaction. Methods. We apply a maximum entropy spot model to fit the optical modulation as observed by CoRoT during a uninterrupted interval of ∼ 140 days. Photospheric active regions are assumed to consist of spots and faculae in a fixed proportion with solar-like contrasts.

Astronomy & Astrophysics, 2013

We performed an intensive radial velocity monitoring of XO-2S, the wide companion of the transiti... more We performed an intensive radial velocity monitoring of XO-2S, the wide companion of the transiting planet-host XO-2N, using HARPS-N at TNG in the framework of the GAPS programme. The radial velocity measurements indicate the presence of a new planetary system formed by a planet that is slightly more massive than Jupiter at 0.48 au and a Saturn-mass planet at 0.13 au. Both planetary orbits are moderately eccentric and were found to be dynamically stable. There are also indications of a long-term trend in the radial velocities. This is the first confirmed case of a wide binary whose components both host planets, one of which is transiting, which makes the XO-2 system a unique laboratory for understanding the diversity of planetary systems.

Astronomy and Astrophysics, 2009

Context. The space experiment CoRoT has recently detected transits by a hot Jupiter across the di... more Context. The space experiment CoRoT has recently detected transits by a hot Jupiter across the disk of an active G7V star (CoRoT-Exo-2a) that can be considered as a good proxy for the Sun at an age of approximately 0.5 Gyr. Aims. We present a spot modelling of the optical variability of the star during 142 days of uninterrupted observations performed by CoRoT with unprecedented photometric precision. Methods. We apply spot modelling approaches previously tested in the case of the Sun by modelling total solar irradiance variations, a good proxy for the optical flux variations of the Sun as a star. The best results in terms of mapping of the surface brightness inhomogeneities are obtained by means of maximum entropy regularized models. To model the light curve of CoRoT-Exo-2a, we take into account both the photometric effects of cool spots as well as those of solar-like faculae, adopting solar analogy. Results. Two active longitudes initially on opposite hemispheres are found on the photosphere of CoRoT-Exo-2a with a rotation period of 4.522 ± 0.024 days. Their separation changes by ≈ 80 • during the time span of the observations. From this variation, a relative amplitude of the surface differential rotation lower than ∼ 1 percent is estimated. Individual spots form within the active longitudes and show an angular velocity about ∼ 1 percent smaller than that of the longitude pattern. The total spotted area shows a cyclic oscillation with a period of 28.9 ± 4.3 days, which is close to 10 times the synodic period of the planet as seen by the rotating active longitudes. We discuss the effects of solar-like faculae on our models, finding indication of a facular contribution to the optical flux variations of CoRoT-Exo-2a being significantly smaller than in the present Sun.

Experimental Astronomy

The EChO core science will be based on a three tier survey, each with increasing sensitivity, in ... more The EChO core science will be based on a three tier survey, each with increasing sensitivity, in order to study the population of exo-planets from super-Earths to Jupiter-like planets, in the very hot to temperate zones (temperatures of 300 K - 3000 K) of F to M-type host stars. To achieve a meaningful outcome an accurate selection of the target sample is needed. In this paper we analyse the targets, suitable for EChO observations, expected to result from a sample of present and forthcoming detection surveys. Exoplanets currently known are already sufficient to provide a large and diverse sample. However we expect the results from these surveys to increase the sample of smaller planets that will allow us to optimize the EChO sample selection.