Fig. 1 CFHT photometry converted into spectral reflectivity obtained on UT (Universal Time) 22 and 25 October 2014, is shown in comparison to the VLT reflectivity spectrum obtained on UT 18 November 2014. Data beyond 0.9 μm were affected by bright night sky emission lines that could not be subtracted satisfactorily; they are included for comparison with the CFHT data. Two independent methods were used to process the spectra (#1 and #2). The spectra have been binned to increase the signal-to-noise ratio. The location of the 1-μm band characteristic of S-type asteroids is shown, and the spectra of six S-type asteroids with a shallow 1-μm feature are shown for comparison (17, 32); the star symbols denote the S(IV)-type asteroids. All spectra are normalized to 0.65 μm. The data for C/2014 S3 are consistent with these S-type asteroids.
Fig. 2 Images of C/2014 S3 (PANSTARRS) obtained on 24 September 2014 (left) and 25 October 2014 (right) with the CFHT. The background stars have been processed out of these composites. The comet was at heliocentric distances (r) of 2.11 and 2.22 AU, moving outward from its perihelion at 2.05 AU on 13 August 2014. The syndynes (black; grain sizes are expressed in micrometers) and synchrones (red; positions noted in days before the observations) map out the expected position of the dust released from the nucleus under the influence of solar radiation pressure. Different lines indicate the locus of dust of different sizes released at different times; the marked change between the two epochs reflects very different viewing geometries. The blue isophotes are equally spaced on a logarithmic scale. The insets are at the same scale as the main images. The arrows indicate the directions of North and East and of the antisolar and negative of the heliocentric velocity vectors (−V). Dec, declination; RA, right ascension; Δ, geocentric distance.
Fig. 3 Water ice sublimation models compared to measured r-band brightness as a function of position along the orbit [true anomaly (TA) = 0o is at perihelion]. The solid line shows the total brightness contribution from the nucleus and the dust, and the dashed line shows the contribution from the nucleus only. Models for a low-albedo comet nucleus surface and a brighter S-type asteroid surface are shown. By TA = 41.7o, the activity had significantly decreased. No combination of nucleus size and activity level can reproduce all the data without assuming a decrease in activity; the best fit is presented. The error bar–like symbol at TA = −70o shows a possible maximum rotational brightness amplitude. The star symbol shows an upper limiting magnitude from searching the PS1 database for prediscovery images. The gray shading indicates times when C/2014 S3 was not observable because it was in solar conjunction.
Supplementary Materials
Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/2/4/e1600038/DC1
S1. Solar system formation model predictions
S2. Details of the observations
S3. Data reduction
S4. Conceptual ice sublimation model
S5. Finson-Probstein dust models
S6. Statistical assessment: Manx observations and dynamical models
table S1. Observing circumstances.
References (33–53)
Additional Files
Supplementary Materials
This PDF file includes:
- S1. Solar system formation model predictions
- S2. Details of the observations
- S3. Data reduction
- S4. Conceptual ice sublimation model
- S5. Finson-Probstein dust models
- S6. Statistical assessment: Manx observations and dynamical models
- table S1. Observing circumstances.
- References (33–53)
Files in this Data Supplement:
- S1. Solar system formation model predictions
