J/A+A/663/A121 TNO (84922) 2003 VS2 light curve (Vara-Lubiano+, 2022)
The multichord stellar occultation on 2019 October 22 by the trans-Neptunian
object (84922) 2003VS2.
Vara-Lubiano M., Benedetti-Rossi G., Santos-Sanz P., Ortiz J.L., Sicardy B.,
Popescu M., Morales N., Rommel F.L., Morgado B., Pereira C.L.,
Alvarez-Candal A., Fernandez-Valenzuela E., Souami D., Ilic D., Vince O.,
Bachev R., Semkov E., Nedelcu D.A., Sonka A., Hudin L., Boaca M., Inceu V.,
Curelaru L., Gherase R., Turcu V., Moldovan D., Mircea L., Predatu M.,
Teodorescu M., Stoian L., Juravle A., Braga-Ribas F., Desmars J.,
Duffard R., Lecacheux J., Camargo J.I.B., Assafin M., Vieira-Martins R.,
Pribulla T., Husarik M., Sivanic P., Pal A., Szakats R., Kiss C.,
Alonso-Santiago J., Frasca A., Szabo G.M., Derekas A., Szigeti L.,
Drozdz M., Ogloza W., Skvarc J., Ciabattari F., Delincak P.,
Di Marcantonio P., Iafrate G., Coretti I., Baldini V., Baruffetti P.,
Klos O., Dumitrescu V., Mikuz H., Mohar A.
<Astron. Astrophys. 663, A121 (2022)>
=2022A&A...663A.121V 2022A&A...663A.121V (SIMBAD/NED BibCode)
ADC_Keywords: Minor planets ; Magnitudes ; Photometry, CCD
Keywords: Kuiper belt objects: individual: 2003 VS2 - methods: observational -
techniques: photometric
Abstract:
Stellar occultations have become one of the best techniques to gather
information about the physical properties of trans-Neptunian object
(TNOs), which are critical objects for understanding the origin and
evolution of our Solar System. The purpose of this work is to
determine, with better accuracy, the physical characteristics of the
TNO (84922) 2003 VS2 through the analysis of the multichord stellar
occultation on 2019 October 22 and photometric data collected
afterward. We predicted, observed, and analyzed the multichord stellar
occultation of the Second Gaia Data Release (Gaia DR2) source
3449076721168026624 (mv=14.1mag) by the plutino object 2003 VS2 on
2019 October 22. We performed aperture photometry on the images
collected and derived the times when the star disappeared and
reappeared from the observing sites that reported a positive
detection. We fit the extremities of such positive chords to an
ellipse using a Monte Carlo method. We also carried out photometric
observations to derive the rotational light curve amplitude and
rotational phase of 2003 VS2 during the stellar occultation. Combining
the results and assuming a triaxial shape, we derived the 3D shape of
2003 VS2. Out of the 39 observatories involved in the observational
campaign, 12 sites, located in Bulgaria (one), Romania (ten), and
Serbia (one), reported a positive detection; this makes it one of the
best observed stellar occultations by a TNO so far. Considering the
rotational phase of 2003 VS2 during the stellar occultation and the
rotational light curve amplitude derived (Deltam=0.264± 0.017mag),
we obtained a mean area-equivalent diameter of 545±13km and a
geometric albedo of 0.134±0.010. By combining the rotational light
curve information with the stellar occultation results, we derived the
best triaxial shape for 2003 VS2, which has semiaxes a = 339 ± 5 km,
b=235±6km, and c=226±8km. The derived aspect angle of 2003 VS2 is
theta=59±2deg or its supplementary theta=121±2deg, depending on
the north-pole position of the TNO. The spherical-volume equivalent
diameter is 524±7km. If we consider large albedo patches on its
surface, the semi-major axis of the ellipsoid could be ∼ 10 km
smaller. These results are compatible with the previous ones
determined from the single-chord 2013 and four-chord 2014 stellar
occultations and with the effective diameter and albedo derived from
Herschel and Spitzer data. They provide evidence that 2003 VS2's 3D
shape is not compatible with a homogeneous triaxial body in
hydrostatic equilibrium, but it might be a differentiated body and/or
might be sustaining some stress. No secondary features related to
rings or material orbiting around 2003 VS2 were detected.
Description:
Photometric data used to derive the rotational light curve of 2003
VS2. The images were obtained with the 1.23-m telescope at the Calar
Alto Observatory in Almeria (Spain) in two consecutive observing
nights, on the 2019 October 24 and 25. The images were taken with a
4kx4k CCD DLR-MKIII camera, which provides a field of view of
21.5'x21.5' and an image scale of 0.32"/pixel. We took 143 images in
2x2 binning mode and 400s of integration time using no filter. The
moonshine was 14% for the first night and 7% for the second. The
average measured full width at half maximum was 2.5 pixels (1.6") for
the first night and 2.3 pixels (1.5") for the second. The signal to
noise ratio was between 30 and 70 during the first night and between
20 and 80 during the second. Bias and flat-field frames were used for
standard calibration. We performed aperture photometry on 2003 VS2 and
16 reference stars. The selected reference stars were the same on both
nights. We chose different apertures for each observing day and then
combined the best photometry results. We used 55 images for the
rotational light curve since the rest had contamination from a nearby
star.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
data.dat 30 55 Photometric data of 2003 VS2
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Byte-by-byte Description of file: data.dat
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Bytes Format Units Label Explanations
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1- 16 F16.8 d JD Julian Date not corrected for light travel time
19- 23 F5.2 mag mag Relative magnitude in mag
27- 30 F4.2 mag e_mag Error of relative magnitude in mag
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Acknowledgements:
Monica Vara-Lubiano, mvara (at)iaa.es
(End) Patricia Vannier [CDS] 04-May-2022