Non-Vestoid candidate asteroids in the inner main belt

Abstract

Context. Most howardite-eucrite-diogenite (HED) meteorites (analogues to V-type asteroids) are thought to originate from the asteroid (4) Vesta. However some HEDs show distinct oxygen isotope ratios and therefore are thought to originate from other asteroids. In this study we try to identify asteroids that may represent parent bodies of those mismatching HEDs. Aims. The main goal of this study is to test the hypothesis that there might be V-type asteroids in the inner main asteroid belt unrelated to (4) Vesta. In order to evolve outside the Vesta family and became Vesta fugitives, asteroids should produce the correct Yarkovsky drift. The direction of which is dependent on asteroid sense of rotation. Therefore we focus on determining sense of rotation for asteroids outside the Vesta family to better understand their origin. Methods. We performed photometric observations using the 1.1 m and 1.8 m telescopes at Lowell Observatory to determine rotational synodic periods of selected objects before, at, and after opposition. Prograde rotators show a minimum in synodic period at opposition while retrograde rotators show a maximum. This is known as the "drifting minima" method. Changes in the rotational period are on the order of seconds and fractions of seconds and depend on the rotational pole of the object and the asteroid-observer-Sun geometry at opposition. Results. We have determined sense of rotation for eight asteroids and retrieved spin states for three objects from literature. For one asteroid we were not able to determine the sense of rotation. In total our sample includes 11 V-type asteroids and one S-type (test object). We have revised rotation periods for three objects. Five V-types in our sample can be explained by migration from the Vesta family. Two show spin states that are inconsistent with migration from Vesta. The origin of the remaining objects is ambiguous. Conclusions. We found two objects with rotations inconsistent with migration from Vesta. Assuming that the YORP effect and random collisions did not substantially modify their sense of rotation, those objects are candidates for non-Vestoids in the inner asteroid belt. Finding more non-Vestoids is crucial in testing the formation and migration theory of differentiated parent bodies.

PHOTOMETRYPIPELINE: An automated pipeline for calibrated photometry

“…In order to test the reliability of the pipeline, PP is run over V band imaging data of asteroid (2704) Julian Loewe taken with Lowell Observatory's 42-inch telescope (Oszkiewicz et al, 2016) transformation from 2MASS near-infrared magnitudes to optical magnitudes (Binzel, 2004) due to a lack of other calibration stars. The resulting lightcurve from PP and the comparison to the MPO Canopus results are displayed in Figure 4.…”

Lava Worlds: From Early Earth to Exoplanets

“…Enrichment of heavy isotopes of Si and Mg in planets with re-spect to chondritic meteorites has been interpreted as evidence for isotopic fractionation during evaporation from molten planetesimals (Young et al, 2019). There have been several surveys that have identified a few basaltic asteroids that, unlike the "Vestoid" asteroid family, cannot be dynamically linked to Vesta (Lazzaro et al, 2000;Moskovitz et al, 2008;Roig et al, 2008;Oszkiewicz et al, 2017). Finds and falls of unique basaltic as well as the anorthosite-rich meteorites (Bland et al, 2009;Frossard et al, 2019) also hint at additional diversity in similar bodies, obscured, in part, by the effects of space weathering (Yamamoto et al, 2018).…”

Physical and dynamical properties of the unusual V-type asteroid (2579) Spartacus

“…Generally the inner main belt is considered to be the main source region of meteorites. Oszkiewicz et al (2015) and Oszkiewicz et al (2017) show that some V-type prograde rotators in the inner main belt have Yarkovsky drift direction that is inconsistent with origin in the Vesta family and may represent parent bodies of those anomalous HEDs. Spectroscopic surveys of this region (Burbine et al 2001;Moskovitz et al 2010;Mayne et al 2011) have yet to unambiguously identify V-type asteroids that are not related to Vesta.…”