arXiv subjects

Andrew McNeill

Publications and source records attributed to Andrew McNeill.

21 records · Page 2Linked to original sources

arXiv2018

Infrared Lightcurves of Near Earth Objects

We present lightcurves and derive periods and amplitudes for a subset of 38 near earth objects (NEOs) observed at 4.5 microns with the IRAC camera on the the Spitzer Space Telescope, many of them having no previously reported rotation periods. This subset was chosen from about 1800 IRAC NEO observations as having obvious periodicity and significant amplitude. For objects where the period observed did not sample the full rotational period, we derived lower limits to these parameters based on sinusoidal fits. Lightcurve durations ranged from 42 to 544 minutes, with derived periods from 16 to 400 minutes. We discuss the effects of lightcurve variations on the thermal modeling used to derive diameters and albedos from Spitzer photometry. We find that both diameters and albedos derived from the lightcurve maxima and minima agree with our previously published results, even for extreme objects, showing the conservative nature of the thermal model uncertainties. We also evaluate the NEO rotation rates, sizes, and their cohesive strengths.

astro-ph.EP↗

arXiv2018

Constraints on the Density and Internal Strength of 1I/'Oumuamua

1I/'Oumuamua was discovered by the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS 1) on 19 October 2017. Unlike all previously discovered minor planets this object was determined to have eccentricity $e > 1.0$, suggesting an interstellar origin. Since this discovery and within the limited window of opportunity, several photometric and spectroscopic studies of the object have been made. Using the measured light curve amplitudes and rotation periods we find that, under the assumption of a triaxial ellipsoid, a density range $1500 < ρ< 2800$ kg m$^{-3}$ matches the observations and no significant cohesive strength is required. We also determine that an aspect ratio of $6\pm 1:1$ is most likely after accounting for phase-angle effects and considering the potential effect of surface properties. This elongation is still remarkable but less than some other estimates.

astro-ph.EP↗

arXiv2013

The Unusual Kuiper Belt Object 2003 SQ317

We report photometric observations of Kuiper belt object 2013 SQ317 obtained between 2011 August 21 and 2011 November 1 at the 3.58 m New Technology Telescope, La Silla. We obtained a rotational lightcurve for 2013 SQ317 with a large peak-to-peak photometric range 0.85+/-0.05 mag, and a periodicity, P=7.210+/-0.001 hr. We also measure a nearly neutral broadband colour B-R=1.05+/-0.18 mag and a phase function with slope beta=0.95+/-0.41 mag/deg. The large lightcurve range implies an extremely elongated shape for 2013 SQ317, possibly as a single elongated object but most simply explained as a compact binary. If modelled as a compact binary near hydrostatic equilibrium, the bulk density of 2013 SQ317 is near 2670 kg m^(-3). If 2003 SQ317 is instead a single, elongated object, then its equilibrium density is about 860 kg m^(-3). These density estimates become uncertain at the 30% level if we relax the hydrostatic assumption and account for solid, "rubble pile"-type configurations. 2013 SQ317 has been associated with the Haumea family based on its orbital parameters and near-infrared colour; we discuss our findings in this context. If confirmed as a close binary, 2013 SQ317 will be the second object of its kind identified in the Kuiper belt.

astro-ph.EP↗