Spin Rate of Comet 333P/LINEAR (2007 VA85)
ATel #8905; Michael Hicks (JPL/Caltech), Beverly Thackeray (Cal State San Bernardino)
on 4 Apr 2016; 21:51 UT
Credential Certification: Michael D. Hicks (Michael.Hicks@jpl.nasa.gov)
Subjects: Optical, Comet, Solar System Object
Comet 333P/LINEAR was discovered as the near-Earth asteroid 2007 VA85 by the LINEAR asteroid survey (MPEC 2007-V72). Although the object's orbital elements, particularly the exceptionally high inclination, (a,e,i = 4.22 AU, 0.736, 132 deg) were recognized as consistent with the Jupiter-family comets, no coma was detected during the discovery apparition (IAUC 8894 ). With more favorable observational geometry, cometary activity was observed early in the 2015-16 return (MPEC 2016-A101). We planned to target this comet once observable from our latitude in anticipation that low-cometary activity may facilitate the detection of rotational variability embedded within time resolved integrated photometry.
We obtained seven partial nights of Bessel R-band photometry of 333P/Linear with the JPL Table Mountain Observatory 0.6-m telescope, as summarized in Table 1. The expected visual magnitudes, appropriate for asteroids, were generated using standard IAU conventions assuming H=15.1, G=0.15 (determined during the 2007 apparition), while the comet's approximate apparent visual total magnitudes were generated assuming M1=17.2, k1=11 (derived during the 2015/2016 apparition).
Figure 1 shows the observed R mag as a function of time, and includes the expected brightness assuming the object was asteroid
al shown as a dashed line. A secular brightening trend was apparent as the comet moved closer to perihelion. A typical azimuthly averaged radial profile is shown in Figure 2, with a Gaussian point spread function (FWHM=2â) included for comparison. The coma of 333P/LINEAR was more compact (~ r^-1.8) than expected from a steady state coma model (~r^-1), which assumes dust ejected at constant velocity.
The secular cometary brightening trend shown in Figure 1 was corrected to first order using the T-mag and V estimates listed in Table 1. Applying standard Fourier techniques, we found a best-fit period of ~21 hr, assuming a double-peaked lightcurve [
Figure 3]. If the short term variability is caused by a single active area rotating into and out of sunlight, the rotational
period of the nucleus is likely half that value (~10.5 hr).
Copyright 2016. All rights reserved. The research described in this telegram was carried out at the Jet Propulsion Laboratory, under a contract with the National Aeronautics and Space Administration.
Table 1: Observational Circumstances.
Num.
UT Time r delta phase V T-mag Exp.
[AU] [AU] [deg] [mag] [mag]
../telegram
2016 02 14.17 1.307 0.529 42.9 15.97 14.79 31
2016 02 16.19 1.293 0.539 44.9 16.05 14.78 27
2016 02 20.21 1.267 0.581 49.0 16.28 14.85 25
2016 02 21.18 1.261 0.595 49.9 16.35 14.88 34
2016 02 25.17 1.237 0.665 52.9 16.64 15.03 37
2016 02 26.14 1.231 0.686 53.5 16.71 15.07 11
2016 02 28.14 1.220 0.727 54.3 16.84 15.16 12