The Aosta Valley Astronomical Observatory

6 p.International audienceOAVdA stands for Astronomical Observatory of the Autonomous Region of the Aosta Valley (Italy). The centre is located in the northwestern Italian Alps, near the border with France and Switzerland (Lat: 45° 47′ 22″ N, Long: 7° 28′ 42″ E), at 1675 m above sea level in the Saint- Barthélemy Valley and is managed by the "Fondazione Clément Fillietroz", with funding from local administrations. OAVdA was opened in 2003 as a centre for the popularization of astronomy but, since 2006, the main activity has been scientific research, as a consequence of an official cooperation agreement established with the Italian National Institute for Astrophysics (INAF). In 2009, a planetarium was built near the observatory with a 10-meter dome and 67 seats, which is currently used for educational astronomy. In the year 2009 about 15,200 people visited OAVdA and the planetarium. The staff in 2010 was made up of 12 people, including a scientific team of 5 physicists and astronomers on ESF (European Social Fund) grants and permanently residing at the observatory

Spinning and color properties of the active asteroid (6478) Gault

We report on accurate $BVR_{c}$ observations of (6478) Gault, a 5-6 km diameter inner main-belt asteroid in the Phocaea family, notable for its sporadic, comet-like ejection of dust. This curious behavior has been mainly interpreted as reconfigurations after YORP spin-up, although merging of a contact binary system cannot be fully excluded. We collected optical observations along the 2019 March-April period, at orbital phase angles between $12^{\circ}-21^{\circ}$, to search for direct evidence of asteroid quick spinning rotation. A prevailing period value of $3.34 \pm 0.02$ hours is supported by our and other photometric observations. In the YORP spin-up hypothesis, this period points to a bulk density $\rho \approx 1$ $\textrm{g}/\textrm{cm}^3$. The mean colors are $B-V = +0.82_{\pm 0.3}$, $V-R_{c} = +0.28_{\pm 0.06}$ and $B-R_{c} = +1.11_{\pm 0.4}$, but we have observed a strong bluer color during the April session, with about $\Delta (B-V) \sim 0.35 \pm 0.09$~mag. This color change can be due to asteroid rotation and support the hypothesis that there is a bluer surface under the Gault's dust, as indicated by spectroscopic observations made on 2019 March 31 and April 8 by Marsset et al. (2019).Comment: 8 pages, 12 figures, submitted to Mon. Not. R. Astron. So

Computation of a possible Tunguska's strewn field

On June 30, 1908 at about 0h 14.5m UTC what is known today as the Tunguska Event (TE) occurred, most likely caused by the fall of a small rocky asteroid of about 50-60 meters in diameter over the basin of the Tunguska River (Central Siberia). Unfortunately the first expedition was made by Kulik 19 years after the event and macroscopic meteorites have never been found in epicenter site. After considering the Chelyabinsk event as a guide, because it is the most energetic impact event observed after TE, we estimated the strewn field of possible macroscopic fragments of the asteroid responsible of the TE: we have reason to believe that there might be fragments with enough strength to survive the airburst and reach the ground. The strewn field, which is located about 16 to 19 km North-West from the epicenter, should be considered for the search of macroscopic bodies, even if the mud and vegetation could have made any trace disappear. Cheko Lake, which by some authors is considered an impact crater, falls several km outside these areas and, based on our results, it is unlikely that it could be a real impact crater: only if the cosmic body's trajectory had an azimuth of about $150^\circ - 180^\circ$ would be in the strewn field area, but it is not consistent with the most likely trajectory.Comment: 13 pages, 5 figures, draft of a work in progres

Dynamical properties of the Molniya satellite constellation: long-term evolution of orbital eccentricity

The aim of this work is to analyze the orbital evolution of the mean eccentricity given by the Two-Line Elements (TLE) set of the Molniya satellites constellation. The approach is bottom-up, aiming at a synergy between the observed dynamics and the mathematical modeling. Being the focus the long-term evolution of the eccentricity, the dynamical model adopted is a doubly-averaged formulation of the third-body perturbation due to Sun and Moon, coupled with the oblateness effect on the orientation of the satellite. The numerical evolution of the eccentricity, obtained by a two-degree-of-freedom model assuming different orders in the series expansion of the third-body effect, is compared against the mean evolution given by the TLE. The results show that, despite being highly elliptical orbits, the second order expansion catches extremely well the behavior. Also, the lunisolar effect turns out to be non-negligible for the behavior of the longitude of the ascending node and the argument of pericenter. The role of chaos in the timespan considered is also addressed. Finally, a frequency series analysis is proposed to show the main contributions that can be detected from the observational data

New Variable Stars Discovered by the APACHE Survey. II. Results After the Second Observing Season

Routinely operating since July 2012, the APACHE survey has celebrated its second birthday. While the main goal of the Project is the detection of transiting planets around a large sample of bright, nearby M dwarfs in the northern hemisphere, the APACHE large photometric database for hundreds of different fields represents a relevant resource to search for and provide a first characterization of new variable stars. We celebrate here the conclusion of the second year of observations by reporting the discovery of 14 new variables.Comment: 25 pages, accepted for publication on The Journal of the American Association of Variable Star Observers (JAVVSO

Cinque anni di Media Inaf: report 2015-2019

In questo report, inizialmente realizzato in occasione della presentazione dei prodotti di Terza missione per la VQR 2015-2019, sono illustrate la linea editoriale della testata Media Inaf, le principali attività redazionali e i risultati conseguiti nel quinquennio di riferimento. Per i risultati quantitativi, in particolare, sono esplicitati e descritti gli indicatori utilizzati

Erratum to nodal management and upstaging of disease. Initial results from the Italian VATS Lobectomy Registry

[This corrects the article DOI: 10.21037/jtd.2017.06.12.]

(704) Interamnia: a transitional object between a dwarf planet and a typical irregular-shaped minor body

Context. With an estimated diameter in the 320–350 km range, (704) Interamnia is the fifth largest main belt asteroid and one of the few bodies that fills the gap in size between the four largest bodies with D > 400 km (Ceres, Vesta, Pallas and Hygiea) and the numerous smaller bodies with diameter ≤200 km. However, despite its large size, little is known about the shape and spin state of Interamnia and, therefore, about its bulk composition and past collisional evolution. Aims. We aimed to test at what size and mass the shape of a small body departs from a nearly ellipsoidal equilibrium shape (as observed in the case of the four largest asteroids) to an irregular shape as routinely observed in the case of smaller (D ≤ 200 km) bodies. Methods. We observed Interamnia as part of our ESO VLT/SPHERE large program (ID: 199.C-0074) at thirteen different epochs. In addition, several new optical lightcurves were recorded. These data, along with stellar occultation data from the literature, were fed to the All-Data Asteroid Modeling algorithm to reconstruct the 3D-shape model of Interamnia and to determine its spin state. Results. Interamnia’s volume-equivalent diameter of 332 ± 6 km implies a bulk density of ρ = 1.98 ± 0.68 g cm−3, which suggests that Interamnia – like Ceres and Hygiea – contains a high fraction of water ice, consistent with the paucity of apparent craters. Our observations reveal a shape that can be well approximated by an ellipsoid, and that is compatible with a fluid hydrostatic equilibrium at the 2σ level. Conclusions. The rather regular shape of Interamnia implies that the size and mass limit, under which the shapes of minor bodies with a high amount of water ice in the subsurface become irregular, has to be searched among smaller (D ≤ 300 km) less massive (m ≤ 3 × 1019 kg) bodies

Physical properties of the trans-Neptunian binary 2000 YW₁₃₄

The study of trans-Neptunian binaries (TNBs) remains one of the most active areas of progress in understanding the solar system beyond Neptune. TNBs have been found in every dynamical population of the trans-Neptunian region (Noll et al. 2020), with proportions ranging from 29 % in the cold classical population to 5.5 % for the remaining classes combined (Brunini 2020). The formation of the contact TNB Arrokoth is one of the challenges that formation models face nowadays. The current angular momentum of Arrokoth is too low and the current binary formation scenarios, by either rotational fission or streaming instability (Nesvorný et al. 2019), require also loss of angular momentum (McKinnon et al. 2020). Additionally, formation mechanisms of close binaries may be distinct from those for the wider pairs. As the angular momentum of a system approaches that of an object spinning near its critical rotation period, rotational fission is the most likely explanation for their formation (Descamps et al. 2008), which is thought to be the case for the proposed satellites of Varuna and 2002 TC302 systems (Fernández-Valenzuela et al. 2019; Ortiz et al. 2020). If close TNBs turn out to be common for objects rotating close to the breakup limit, that could reveal important clues about angular momentum evolution during accretion for TNOs (Petit et al. 2011). However, characterizing binary systems at such distances is challenging. From the ~120 known TNBs, only around 40 have their mutual orbit fully determined, let alone physical characterization. 2000 YW134 is a TNB in a 3:8 resonance with an orbital semi-major axis of 57.4 au (a rare occurrence). On February 23rd, 2022, it occulted the Gaia EDR3 star 627356458358636544 (V = 17.1 mag). The stellar occultation was initially predicted using the JPL orbit solution #24, and updated using data from the 1.5-m and 1.23-m telescopes at Sierra Nevada and Calar Alto Observatories, using the same methodology as explained in Ortiz et al (2020). From the 17 observatories involved, seven reported positive chords, with five of them corresponding to the main body and the other two chords corresponding to its satellite. We are currently working on the analysis of these data in order to obtain the physical properties that characterize the system. Preliminary results show that the lower limit for the equivalent projected diameter of the satellite is twice the previously estimated size from HST observations (Stephens et al. 2006). We will also compare our results with the area-equivalent diameter and albedo obtained using thermal data from Herschel and Spitzer observations (Farkas-Takács et al. 2020)