J/ApJ/864/L33 Polarimetric survey of Phaethon with PICO (Shinnaka+, 2018)
Inversion angle of phase-polarization curve of near-Earth asteroid (3200)
Phaethon.
Shinnaka Y., Kasuga T., Furusho R., Boice D.C., Terai T., Noda H.,
Namiki N., Watanabe J.-I.
<Astrophys. J., 864, L33 (2018)>
=2018ApJ...864L..33S 2018ApJ...864L..33S
ADC_Keywords: Minor planets; Polarization; Optical
Keywords: minor planets, asteroids: general ;
minor planets, asteroids: individual ((3200) Phaethon) ;
techniques: polarimetric
Abstract:
As a function of the solar phase angle, α, the linear
polarization degree (referred to the scattering plane, Pr) of solar
system objects is a good diagnostic for understanding the scattering
properties of their surface materials. We report the Pr of Phaethon
over a wide range of α from 19.1° to 114.3°. The derived
phase-polarization curve shows that the maximum of Pr, Pmax, is
>42.4% at α>114.3°, a value significantly larger than those
of the moderate albedo asteroids (Pmax∼9%). The phase-polarization
curve classifies Phaethon as B-type as well as M- and K-type
asteroids, in the polarimetric taxonomy, being compatible with the
spectral property. We compute the geometric albedo, pv, of
0.14±0.04 independently by using an empirical slope-albedo relation,
and the derived pv is consistent with previous results determined
from mid-infrared spectra and thermophysical modeling. We find no
periodic variation of Pr in our polarimetric data in the range from
0 up to 7.208hr (e.g., less than twice the rotational period). We
also find significant differences between our Pr during the 2017
approach toward Earth and that in 2016, implying that Phaethon has a
region with different properties for light scattering near its
rotational pole.
Description:
The polarimetric survey of Phaethon was performed for 13 consecutive
nights from UT 2017 December 9 to 21 using the Polarimetric Imager for
Comets (PICO) mounted on the 50cm Telescope for Public Outreach at the
Mitaka Campus of the National Astronomical Observatory of Japan. We
used the standard Johnson-Cousins RC-band filter (its bandpass is
483-799nm) for all observations of Phaethon.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 51 812 Observational results acquired with the Polarimetric
Imager for Comets (PICO)
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See also:
J/A+A/607/A103 : Main-belt asteroids polarimetry. VI. (Gil-Hutton+, 2017)
J/AJ/154/168 : NEOWISE: thermal model fits for NEOs and MBAs (Masiero+, 2017)
J/A+A/626/A42 : Polarimetry of Main-Belt Asteroids (Lopez-Sisterna+, 2019)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 11 A11 "Y/M/D" Date UT date of the observation
13- 20 F8.4 d JD [97/109] Julian Date minus; JD-2458000 (1)
22- 28 F7.3 deg alpha [19.1/114.3] Solar phase angle α
30- 34 F5.2 % Pol [-2.1/54.4] Degree of linear polarization Pr
36- 39 F4.2 % e_Pol [0.1/6] Uncertainty in Pol
41- 45 F5.1 deg theta [1/180] Position angle in the scattering plane
θr
47- 51 F5.1 deg e_theta [0.3/305] Uncertainty in theta
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Note (1): At the middle time of the sequence.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 20-Aug-2019