Astronomical Observatory of the Autonomous Region of the Aosta Valley

Nus, Italy

Astronomical Observatory of the Autonomous Region of the Aosta Valley

Nus, Italy

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Carry B.,University Pierre and Marie Curie | Carry B.,European Space Agency | Matter A.,Max Planck Institute for Radio Astronomy | Matter A.,CNRS Grenoble Institute for Particle Astrophysics and Cosmology Laboratory | And 32 more authors.
Icarus | Year: 2015

In understanding the composition and internal structure of asteroids, their density is perhaps the most diagnostic quantity. We aim here at characterizing the surface composition, mutual orbit, size, mass, and density of the small main-belt binary asteroid (939) Isberga. For that, we conduct a suite of multi-technique observations, including optical lightcurves over many epochs, near-infrared spectroscopy, and interferometry in the thermal infrared. We develop a simple geometric model of binary systems to analyze the interferometric data in combination with the results of the lightcurve modeling. From spectroscopy, we classify Ibserga as a Sq-type asteroid, consistent with the albedo of 0.14-0.06+0.09 (all uncertainties are reported as 3- σ range) we determine (average albedo of S-types is 0.197. ±. 0.153, see Pravec et al. (Pravec et al. [2012]. Icarus 221, 365-387). Lightcurve analysis reveals that the mutual orbit has a period of 26.6304. ±. 0.0001. h, is close to circular (eccentricity lower than 0.1), and has pole coordinates within 7° of (225°, +86°) in Ecliptic J2000, implying a low obliquity of 1.5-1.5+6.0deg. The combined analysis of lightcurves and interferometric data allows us to determine the dimension of the system and we find volume-equivalent diameters of 12.4-1.2+2.5km and 3.6-0.3+0.7km for Isberga and its satellite, circling each other on a 33. km wide orbit. Their density is assumed equal and found to be 2.91-2.01+1.72gcm-3, lower than that of the associated ordinary chondrite meteorites, suggesting the presence of some macroporosity, but typical of S-types of the same size range (Carry [2012]. Planet. Space Sci. 73, 98-118). The present study is the first direct measurement of the size of a small main-belt binary. Although the interferometric observations of Isberga are at the edge of MIDI capabilities, the method described here is applicable to others suites of instruments (e.g., LBT, ALMA). © 2014 Elsevier Inc.


Mottola S.,German Aerospace Center | Di Martino M.,National institute for astrophysics | Erikson A.,German Aerospace Center | Gonano-Beurer M.,German Aerospace Center | And 7 more authors.
Astronomical Journal | Year: 2011

We present the results of a Jupiter Trojans' light curve survey aimed at characterizing the rotational properties of Trojans in the approximate size range 60-150km. The survey, which was designed to provide reliable and unbiased estimates of rotation periods and amplitudes, resulted in light curves for a total of 80 objects, 56 of which represent the first determinations published to date and nine of which supersede previously published erroneous values. Our results more than double the size of the existing database of rotational properties of Jovian Trojans in the selected size range. The analysis of the distributions of the rotation periods and light curve amplitudes is the subject of companion papers. © 2011. The American Astronomical Society. All rights reserved.


Giacobbe P.,University of Trieste | Damasso M.,Astronomical Observatory of the Autonomous Region of the Aosta Valley | Damasso M.,University of Padua | Sozzetti A.,National institute for astrophysics | And 7 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2012

We present the results of a year-long photometric monitoring campaign of a sample of 23 nearby (d < 60pc), bright (J < 12) dM stars carried out at the Astronomical Observatory of the Autonomous Region of the Aosta Valley, in the western Italian Alps. This programme represents a 'pilot study' for a long-term photometric transit search for planets around a large sample of nearby M dwarfs, due to start with an array of identical 40-cm class telescopes by the Spring of 2012. In this study, we set out to (i) demonstrate the sensitivity to <4R ⊕ transiting planets with periods of a few days around our programme stars, through a two-fold approach that combines a characterization of the statistical noise properties of our photometry with the determination of transit detection probabilities via simulations; and (ii) where possible, improve our knowledge of some astrophysical properties (e.g. activity, rotation) of our targets by combining spectroscopic information and our differential photometric measurements. We achieve a typical nightly root mean square (RMS) photometric precision of ~5 mmag, with little or no dependence on the instrumentation used or on the details of the adopted methods for differential photometry. The presence of correlated (red) noise in our data degrades the precision by a factor of ~1.3 with respect to a pure white noise regime. Based on a detailed stellar variability analysis (i) we detected no transit-like events (an expected result, given the sample size); (ii) we determined photometric rotation periods of ~0.47 and ~0.22d for LHS 3445 and GJ 1167A, respectively; (iii) these values agree with the large projected rotational velocities (~25 and ~33 kms -1, respectively) inferred for both stars based on the analysis of archival spectra; (iv) the estimated inclinations of the stellar rotation axes for LHS 3445 and GJ 1167A are consistent with those derived using a simple spot model; and (v) short-term, low-amplitude flaring events were recorded for LHS 3445 and LHS 2686. Finally, based on simulations of transit signals of given period and amplitude injected in the actual (nightly reduced) photometric data for our sample, we derive a relationship between transit detection probability and phase coverage. We find that, using the Box-fitting Least Squares search algorithm, even when the phase coverage approaches 100per cent, there is a limit to the detection probability of ≈90per cent. Around programme stars with phase coverage > 50per cent, we would have had >80per cent chances of detecting planets with P < 1 d inducing fractional transit depths > 0.5per cent, corresponding to minimum detectable radii in the range ~1.0-2.2R ⊕. These findings are illustrative of our high readiness level ahead of the main survey start. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.


Nascimbeni V.,University of Padua | Nascimbeni V.,US Space Telescope Science Institute | Nascimbeni V.,National institute for astrophysics | Piotto G.,University of Padua | And 7 more authors.
Astronomy and Astrophysics | Year: 2011

TASTE (The Asiago Search for Transit timing variations of Exoplanets) project is collecting high-precision, short-cadence light curves for a selected sample of transiting exoplanets. It has been claimed that the hot jupiter HAT-P-13b suddenly deviated from a linear ephemeris by ~20 min, implying that there is a perturber in the system. Using five new transits, we discuss the plausibility of this transit time variation (TTV), and show that a periodic signal should not be excluded. More follow-up observations are required to constrain the mass and the orbit of the hypothetical perturber. © ESO, 2011.


Nascimbeni V.,University of Padua | Nascimbeni V.,US Space Telescope Science Institute | Piotto G.,University of Padua | Bedin L.R.,US Space Telescope Science Institute | And 2 more authors.
Astronomy and Astrophysics | Year: 2011

A promising method for detecting earth-sized exoplanets is the timing analysis of a known transit. The technique allows a search for variations in either the transit duration or the center induced by the perturbation of a third body, e.g. a second planet or an exomoon. By applying this method, the TASTE (The Asiago search for transit timing variations of Exoplanets) project will collect high-precision, short-cadence light curves for a selected sample of transits by using imaging differential photometry at the Asiago 1.82 m telescope. The first light curves show that our project can achieve a competitive timing accuracy, as well as a significant improvement of the orbital parameters.We derived refined ephemerides for HAT-P-3b and HAT-P-14b with a timing accuracy of 11 and 25 s, respectively. © ESO 2011.


Nascimbeni V.,University of Padua | Nascimbeni V.,US Space Telescope Science Institute | Piotto G.,University of Padua | Bedin L.R.,US Space Telescope Science Institute | And 2 more authors.
Astronomy and Astrophysics | Year: 2011

A promising method for detecting earth-sized exoplanets is the timing analysis of a known transit. The technique allows a search for variations in either the transit duration or the center induced by the perturbation of a third body, e.g. a second planet or an exomoon. By applying this method, the TASTE (The Asiago search for transit timing variations of Exoplanets) project will collect high-precision, short-cadence light curves for a selected sample of transits by using imaging di fferential photometry at the Asiago 1.82 m telescope. The first light curves show that our project can achieve a competitive timing accuracy, as well as a significant improvement of the orbital parameters.We derived refined ephemerides for HAT-P-3b and HAT-P-14b with a timing accuracy of 11 and 25 s, respectively. © ESO 2011.


Granata V.,University of Padua | Granata V.,National institute for astrophysics | Nascimbeni V.,University of Padua | Nascimbeni V.,National institute for astrophysics | And 11 more authors.
Astronomische Nachrichten | Year: 2014

We present four new light curves of the transiting exoplanets WASP-1b and HAT-P-20b, observed within the TASTE (The Asiago Search for Transit timing variations of Exoplanets) project. We re-analyzed light curves from the literature in a homogeneous way, calculating a refined ephemeris and orbital-physical parameters for both objects. WASP-1b does not show any significant Transit Timing Variation signal at the 120 s level. As for HAT-P-20b, we detected a deviation from our re-estimated linear ephemeris that could be ascribed to the presence of a perturber or, more probably, to a previously unnoticed high level of stellar activity. The rotational period of HAT-P-20 A that we obtained from archival data (Prot ≃ 14.5 d), combined with its optical variability and strong emission of Ca ii H & K lines, is consistent with a young stellar age (<1 Gyr) and support the hypothesis that stellar activity may be responsible of the measured deviations of the transit times. ( © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Damasso M.,Astronomical Observatory of the Autonomous Region of the Aosta Valley | Damasso M.,University of Padua | Giacobbe P.,University of Trieste | Calcidese P.,Astronomical Observatory of the Autonomous Region of the Aosta Valley | And 5 more authors.
Publications of the Astronomical Society of the Pacific | Year: 2010

We present the results of a site characterization study carried out at the Astronomical Observatory of the Autonomous Region of the Aosta Valley (OAVdA), in the western Italian Alps, aimed at establishing its potential to host a photometric transit search for small-size planets around a statistically significant sample of nearby cool M dwarfs. For the purpose of the site testing campaign, we gathered photometric and seeing measurements utilizing different instruments available at the site. As in any search for new locations for astronomical observations, we gauged site-dependent observing conditions such as night-sky brightness, photometric precision, and seeing properties. Public meteorological data were also used in order to help in the determination of the actual number of useful observing nights per year. The measured zenithal V-band night-sky brightness is typical of that of very good, very dark observing sites. The extinction registered at the V-band is not dissimilar from that of other sites. The median seeing over the period of in situ observations is found to be ∼1.7″. Given the limited duration of the observations, we did not probe any possible seeing seasonal patterns or the details of its possible dependence on other meteorological parameters, such as wind speed and direction. Moreover, our data show that the seeing at the observatory was reasonably stable during most of the nights. The fraction of fully clear nights per year amounts to 39%, while the total of useful nights increases to 57%, assuming a (conservative) cloud cover of not more than 50% of the night. Based on the analysis of photometric data collected over the period of 2009 May-August for three stellar fields centered on the transiting planet hosts WASP-3, HAT-P-7, and Gliese 436, we achieve seeing-independent best-case photometric precision σ ph ≤3 mmag (rms) in several nights for bright stars (R ≤ 11 mag). A median performance σ ph-6 mmag during the observing period is obtained for stars with R ≤ 13 mag. A by-product of the significant amount of photometric data collected in the stellar fields of WASP-3 and HAT-P-7 was the identification of a handful of new variable stars, four of which are presented and discussed here. Our results demonstrate that the OAVdA site is well poised to conduct an upcoming long-term photometric survey for transiting low-mass, small-size planets around a well-defined sample of M dwarfs in the solar neighborhood. © 2010. The Astronomical Society of the Pacific. All rights reserved.


Sozzetti A.,National institute for astrophysics | Bernagozzi A.,Astronomical Observatory of the Autonomous Region of the Aosta Valley | Bertolini E.,Astronomical Observatory of the Autonomous Region of the Aosta Valley | Calcidese P.,Astronomical Observatory of the Autonomous Region of the Aosta Valley | And 13 more authors.
EPJ Web of Conferences | Year: 2013

First, we summarize the four-year long efforts undertaken to build the final setup of the APACHE Project, a photometric transit search for small-size planets orbiting bright, low-mass M dwarfs. Next, we describe the present status of the APACHE survey, officially started in July 2012 at the site of the Astronomical Observatory of the Autonomous Region of the Aosta Valley, in the Western Italian Alps. Finally, we briefly discuss the potentially far-reaching consequences of a multi-technique characterization program of the (potentially planet-bearing) APACHE targets. © Owned by the authors, published by EDP Sciences, 2013.


Christille J.-M.,Astronomical Observatory of the Autonomous Region of the Aosta Valley | Christille J.-M.,University of Perugia | Bernagozzi A.,Astronomical Observatory of the Autonomous Region of the Aosta Valley | Bertolini E.,Astronomical Observatory of the Autonomous Region of the Aosta Valley | And 13 more authors.
EPJ Web of Conferences | Year: 2013

Small-size ground-based telescopes can effectively be used to look for transiting rocky planets around nearby low-mass M stars using the photometric transit method, as recently demonstrated for example by the MEarth project. Since 2008 at the Astronomical Observatory of the Autonomous Region of Aosta Valley (OAVdA), we have been preparing for the long-term photometric survey APACHE, aimed at finding transiting small-size planets around thousands of nearby early and mid-M dwarfs. APACHE (A PAthway toward the Characterization of Habitable Earths) is designed to use an array of five dedicated and identical 40-cm Ritchey-Chretien telescopes and its observations started at the beginning of summer 2012. The main characteristics of the survey final set up and the preliminary results from the first weeks of observations will be discussed. © Owned by the authors, published by EDP Sciences, 2013.

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