J/ApJ/883/L21 LC of the TNO Varuna (Fernandez-Valenzuela+, 2019)
The changing rotational light-curve amplitude of Varuna and evidence for a
close-in satellite.
Fernandez-Valenzuela E., Ortiz J.L., Morales N., Santos-Sanz P., Duffard R.,
Aznar A., Lorenzi V., Pinilla-Alonso N., Lellouch E.
<Astrophys. J., 883, L21 (2019)>
=2019ApJ...883L..21F 2019ApJ...883L..21F
ADC_Keywords: Solar system ; Minor planets ; Photometry; Optical
Keywords: Small solar system bodies; Solar system formation; CCD photometry;
Trans-Neptunian objects; Observational astronomy; Optical observation
Abstract:
From CCD observations carried out with different telescopes, we
present short-term photometric measurements of the large
trans-Neptunian object Varuna in 10 epochs, spanning around 19 years.
We observe that the amplitude of the rotational light curve has
changed considerably during this period of time from 0.41 to 0.55mag.
In order to explain this variation, we constructed a model in which
Varuna has a simple triaxial shape, assuming that the main effect
comes from the change of the aspect angle as seen from Earth, due to
Varuna's orbital motion in the 19yr time span. The best fits to the
data correspond to a family of solutions with axial ratios b/a between
0.56 and 0.60. This constrains the pole orientation in two different
ranges of solutions presented here as maps. Apart from the remarkable
variation of the amplitude, we have detected changes in the overall
shape of the rotational light curve over shorter timescales. After the
analysis of the periodogram of the residuals to a 6.343572hr
double-peaked rotational light-curve fit, we find a clear additional
periodicity. We propose that these changes in the rotational
light-curve shape are due to a large and close-in satellite whose
rotation induces the additional periodicity. The peak-to-valley
amplitude of this oscillation is in the order of 0.04mag. We estimate
that the satellite orbits Varuna with a period of 11.9819hr (or
23.9638hr), assuming that the satellite is tidally locked, at a
distance of ∼1300km (or ∼2000km) from Varuna, outside the Roche limit.
Description:
We carried out eight observing campaigns from 2005 to 2019 using four
different Spanish telescopes: the 1.5m telescope at the Sierra Nevada
Observatory (OSN) in Granada; the 1.23m and 2.2m telescopes at Calar
Alto Observatory (CAHA) in Almeria and the 3.58m Telescopio Nazionale
Galileo (TNG) at the Roque de los Muchachos Observatory in Canary Islands.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 51 1224 Results from the relative photometry and
observational circumstances
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See also:
J/AJ/154/241 : Phot. of a Kuiper Belt object: 2002 CC249 (Thirouin+, 2017)
J/AJ/157/228 : Cold Classical TNOs: LCs & rotational data (Thirouin+, 2019)
J/ApJS/236/18 : OSSOS. VII. TNOs complete data release (Bannister+, 2018)
J/ApJS/244/19 : OSSOS. XII. Subaru/HSC obs. of 65 TNOs (Alexandersen+, 2019)
J/AJ/157/120 : TNOs and Centaurs observed within DES (Banda-Huarca+, 2019)
J/AJ/159/133 : Orbital elements of TNOs from DES (Khain+, 2020)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 11 F11.3 d JD Julian date of observation
13- 21 F9.6 mag mag [-0.35/0.45] Relative magnitude
23- 28 F6.4 mag e_mag [0.012/0.16] Uncertainty in mag
30- 36 F7.4 au rH [43.25/43.93] Heliocentric distance
38- 44 F7.4 au Delta [42.36/43.91] Topocentric distance
46- 51 F6.4 deg alpha [0.15/1.32] Phase angle
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 10-Mar-2021