J/A+A/511/A49 Lightcurves of 12 NEAs (Kwiatkowski+, 2010)
Photometric survey of the very small near-Earth asteroids with the SALT
telescope.
III. Lightcurves and periods for 12 objects and negative detections.
Kwiatkowski T., Polinska M., Loaring N., Buckley D.A.H., O'Donoghue D.,
Kniazev A., Romero Colmenero E.
<Astron. Astrophys. 511, A49 (2010)>
=2010A&A...511A..49K 2010A&A...511A..49K
ADC_Keywords: Surveys ; Solar system ; Minor planets ; Photometry, CCD
Keywords: techniques: photometric - minor planets, asteroids: general
Abstract:
Very small asteroids (VSAs) are thought to be the building blocks of
larger asteroids and, as such, are interesting to study. Many of these
monolithic or deeply fractured objects display rapid rotations with
periods as short as several minutes. Observations of such asteroids
can reveal their spin limits, which can be related to the tensile
strength of their interiors. The evolution of the spins of these
objects is primarily shaped by the YORP effect, the theory of which
needs comparison with observations.
With the 10m SALT telescope, we observed VSAs belonging to near-Earth
asteroids. The obtained lightcurves were used to derive synodical
periods of rotation, amplitudes, and elongations of these bodies.
Results for 14 rapidly rotating asteroids were reported in the first
paper in this series. Here we show lightcurves of 2 fast rotators, 9
objects with periods ≥1h, and a possible non-principal axis rotator.
We also list negative detections that most probably indicate asteroids
with long periods and/or low amplitudes. Combining our results with
the data from the literature, we obtain a set of 79 near-Earth VSAs
with a median period of 0.25h (15min). By adjusting the spin limits
predicted by theory to those observations, we find tentative evidence
that the tensile strengths of VSAs, after scaling them to the same
size, are of the same order as the minimum tensile strengths of stony
meteoroids that undergo fragmentation under the atmospheric load.
Description:
Time-series relative photometry for 12 near-Earth asteroids is
presented as well as the aspect data, the observing log, and the
derived rotation parameters. Objects for which no brightness
variations was recorded are also listed. For most asteroids several
lightcurves are reported, each of which was measured with a different
comparison star. For each asteroid a composite lightcurve is included,
obtained with the specified synodic rotation period. The period,
together with the shifts in magnitude of the individual data sets used
in the composite lightcurve, were obtained in a least-square fit of
the Fourier series of the specified order.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 88 23 Aspect data and observing log
table2.dat 37 12 Summary of the results
list.dat 62 37 List of all light curves
lc/* . 27 Individual light curves
clc/* . 10 Composite light curves
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See also:
J/A+A/509/A94 : Lightcurves of 14 NEAs (Kwiatkowski+, 2010)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Ast Designation of the asteroid
12- 15 F4.1 mag Hmag Absolute magnitude
17- 26 A10 "YYYY/MM/DD" Obs1.Date Date of observation
28- 32 A5 "h:m" Obs1.Time Observing time (beginning) (1)
34- 38 A5 "h:m" Obs2.Time Observing time (end) (1)
40- 45 F6.4 AU r Asteroid-Sun distance (2)
46- 51 F6.4 AU Delta Asteroid-Earth distance (2)
52- 55 F4.1 deg alpha Solar phase angle (2)
57- 61 F5.1 deg ELON Geocentric, ecliptic longitude (2)
63- 67 F5.1 deg ELAT Geocentric, ecliptic latitude (2)
69- 72 F4.1 mag Vmag Apparent magnitude
74- 77 F4.1 arcsec/min SkyMov Asteroid movement on the sky
79- 80 I2 s Exp Exposure time
82- 84 I3 --- N1 Number of exposures taken
86- 88 I3 --- N2 Number of exposures used
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Note (1): Observing runs which started on the next UTC night have hours
greater than 24 h.
Note (2): Coordinates given for the middle of the observation
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Ast Asteroid designation
12- 16 F5.3 h Per Rotation period
18- 22 F5.3 h e_Per Period uncertainty (max error/sigma)
24- 27 F4.2 mag Amp Peak-to-peak lightcurve amplitude
29- 31 F3.1 --- a/b Maximum elongation (1)
33- 37 F5.3 km Diam Effective diameter
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Note (1): Actual a/b elongation is not greater than the given value
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Ast Asteroid name
13- 26 A14 --- FileName Name of the file containing the light curve
31- 62 A32 --- Title Title of the file
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Byte-by-byte Description of file: lc/*
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Bytes Format Units Label Explanations
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1- 15 F15.7 d Time Julian date (1)
17- 22 F6.3 mag mag Relative magnitude
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Note (1): not corrected for the light travel time
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Byte-by-byte Description of file: clc/*
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Bytes Format Units Label Explanations
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1- 13 F13.7 d Phase Rotation phase
15- 19 F5.3 mag mag Relative magnitude
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Acknowledgements:
Tomasz Kwiatkowski, tkastr(at)vesta.astro.amu.edu.pl
References:
Kwiatkowski et al., Paper I 2010A&A...509A..94K 2010A&A...509A..94K, Cat. J/A+A/509/A94
Kwiatkowski, Paper II 2010A&A...509A..95K 2010A&A...509A..95K
(End) T. Kwiatkowski [Poznan Obs., Poland], Patricia Vannier [CDS] 05-Mar-2010