Polarimetric survey of main-belt asteroids

Abstract

Aims. We present the first results of a polarimetric survey of main-belt asteroids at Complejo Astronómico El Leoncito (Casleo), San Juan, Argentina. The aims of this survey are to increase the database of asteroid polarimetry, to estimate diversity in polarimetric properties of asteroids that belong to different taxonomic classes, and to search for objects that exhibit anomalous polarimetric properties, similar to those shown by the asteroid (234) Barbara. Methods. The data were obtained with the Torino and CASPROF polarimeters at the 2.15 m telescope. The Torino polarimeter is an instrument that allows the simultaneous measurement of polarization in five different bands, and the CASPROF polarimeter is a two-hole aperture polarimeter with rapid modulation. Results. The survey began in 2003, and up to 2009 data on a sample of more than 170 asteroids were obtained. In this paper the results of 57 S-, L-, and K-type objects are presented, most of them are being polarimetrically observed for the first time. Using these data we find phase-polarization curves and polarimetric parameters for these taxonomic classes. Furthermore, we also find two candidates, (397) Vienna and (458) Hercynia, that could have a phase-polarization curve with a large inversion angle.

Polarimetric survey of main-belt asteroids

“…This includes computations of the position angle of the scattering plane and of the polarization parameter P r . The overall data reduction pipeline is essentially identical to that previously used in Gil-Hutton et al (2017). As a test of the data reduction process, we analyzed the distribution of the ratio between the U component of linear polarization and its error and found that it is centered at zero, while all points differ from this value by less than a few σ, which supports the reliability of the polarimetric measurements.…”

“…Figure 2 shows the observations obtained for three T -types and six D-types objects (four and eight observations, respectively), and it seems that the D-types show a bimodality in their polarimetric behavior where two asteroids, (565) Marbachia and (1481) Tubingia, seem to have phase-polarization curves with large inversion angles. Recently, Gil-Hutton et al (2017) reported that this polarimetric behavior is also observed for (2579) Spartacus, a V-type object, so if this bimodality is confirmed in the future for D-types, it would indicate that the Barbarian group of asteroids is present in different taxonomic classes and is not an exclusivity of L-, Ld-, and K-types.…”

“…If we analyze all the asteroid polarimetric data available today, including the data in the Asteroid Polarimetric Database (APD; Lupishko 2014) and that from papers not included in the APD (Cellino et al 2005;Masiero et al 2007;Rosenbush et al 2009;Masiero 2010;Cellino et al 2014;Zaitsev et al 2014;Gil-Hutton et al 2014;Bagnulo et al 2016;Belskaya et al 2017;Devogèle et al 2017;Gil-Hutton et al 2017, and the present paper), the total number of polarimetric measurements available in V-or R-band is 3028 for 515 asteroids, of which it is possible to obtain polarimetric parameters of good quality for 121 objects considering only measurements with σ < 0.25% 3 . The polarimetric parameters were obtained by fitting the observations to a phase-polarization curve using the function proposed by Kaasalainen et al (2003) and Muinonen et al (2009):…”

A polarimetric study of asteroids in comet-like orbits

“…4). We used the h values of asteroids provided in the catalog of the asteroid polarization curves (Gil-Hutton et al 2017). The applied slope h values from the catalog are determined in the V band.…”