The asteroid (7132) Casulli is a binary system

ATel #13590; Lorenzo Franco (A81 - Balzaretto Observatory, Rome - Italy), Alessandro Marchini, Giacomo Bonnoli (K54 - Astronomical Observatory, Department of Physical Sciences, Earth and Environment, University of Siena - Italy), Riccardo Papini (K49 - WBRO Carpione Observatory, San Casciano Val di Pesa, Florence - Italy), Paolo Bacci, Martina Maestripieri (104 - San Marcello Pistoiese Observatory, Pistoia - Italy), Nello Ruocco (C82 - Osservatorio Astronomico Nastro Verde, Sorrento - Italy), Nico Montigiani, Massimiliano Mannucci (A57 - Margherita Hack Observatory, Florence - Italy), Giulio Scarfi (K78 - iota Scorpii Observatory, La Spezia - Italy)
on 25 Mar 2020; 16:28 UT
Credential Certification: Giacomo Bonnoli (giacomo.bonnoli@unisi.it)

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(7132) Casulli is a main belt asteroid discovered on 1993 Sept. 17 by A. Vagnozzi at Stroncone (Italy) and is named in honor of Silvano Casulli (1944 - 2018), who was the first amateur astronomer in the world to obtain precise astrometric positions of minor planets using a CCD camera (Minor Planet Circular 30800). It orbits with a semi-major axis of about 2.309 AU, eccentricity 0.209, and a period of 3.51 years; it has an absolute magnitude H = 13.6 , a diameter D = 9.015 +/- 0.064 km and a geometric albedo of 0.089 +/- 0.003 (JPL Small-Body Database Browser - ssd.jpl.nasa.gov/sbdb.cgi, 2020; Masiero et al., Main-belt Asteroids with WISE/NEOWISE: Near-infrared Albedos, Astrophys. J., 791, 2014).

Collaborative photometric observations carried out from 2020 February 20 to 2020 March 20 within the Asteroid Research Section of the UAI (Italian Amateur Astronomers Union) reveal that the minor planet (7132) Casulli is a binary system with an orbital period of 36.54 +/- 0.02 h.
The rotational light curve of the primary has a period of 3.5238 +/- 0.0002 h with an amplitude of 0.14 mag, suggesting a nearly spheroidal shape. Mutual eclipse/occultation events that are 0.11 to 0.16 mag deep indicate a secondary-to-primary mean-diameter ratio of 0.21 +/- 0.04.

Differential photometry measurements and dual-period search were performed using MPO Canopus. The phase plots for the primary (rotational) and secondary (orbital) periods of the system are available at this page: https://www.dsfta.unisi.it/it/notizie/il-telescopio-delluniversita-di-siena-scopre-che-lasteroide-7132-casulli-e-un-sistema

Instrumentation used for this campaign is listed below:
- K54 - Astronomical Observatory, DSFTA - University of Siena: 0.30 m f/5.6 MCT, SBIG STL-6303e CCD
- K49 - WBRO Carpione Observatory: 0.23 m SCT f/10 SBIG ST8-XME CCD
- 104 - San Marcello Pistoiese Observatory: 0.60 m f/4 NRT, apogee U6 CCD
- C82 - Osservatorio Astronomico Nastro Verde: 0.35 m f/10 SCT, ST10 CCD
- A57 - Margherita Hack Observatory: SCT 0.35 m, ST10XME CCD
- K78 - iota Scorpii Observatory : 0.40 m f/8 RCT, SBIG STXL-6303E CCD
(Telescopes MCT: Maksutov-Cassegrain, NRT: Newtonian Reflector, RCT: Ritchey-Chretien, SCT: Schmidt-Cassegrain).

Any enquiry on these observations may be sent to Lorenzo Franco (lor_franco -at- libero.it).

Rotational and orbital phase plots for (7132) Casulli