A FOURIER OPTICS METHOD FOR CALCULATING STELLAR OCCULTATION LIGHT CURVES BY OBJECTS WITH THIN ATMOSPHERES

2012 ◽  
Vol 144 (2) ◽  
pp. 32 ◽  
Author(s):  
E. F. Young
Keyword(s):  
Light Curves ◽  
Fourier Optics ◽  
Stellar Occultation

An investigation of Pluto’s troposphere using stellar occultation light curves and an atmospheric radiative–conductive–convective model

Icarus ◽  
2011 ◽  
Vol 214 (2) ◽  
pp. 685-700 ◽  
Author(s):  
Angela M. Zalucha ◽  
Xun Zhu ◽  
Amanda A.S. Gulbis ◽  
Darrell F. Strobel ◽  
J.L. Elliot
Keyword(s):  
Light Curves ◽  
Stellar Occultation ◽  
Convective Model

scholarly journals Pluto’s ephemeris from ground-based stellar occultations (1988–2016)

2019 ◽  
Vol 625 ◽  
pp. A43 ◽  
Author(s):  
J. Desmars ◽  
E. Meza ◽  
B. Sicardy ◽  
M. Assafin ◽  
J. I. B. Camargo ◽  
...  
Keyword(s):  
Impact Parameter ◽  
Light Curves ◽  
Reference Star ◽  
Stellar Occultation ◽  
Stellar Occultations ◽  
Star Position

Context. From 1988 to 2016, several stellar occultations have been observed to characterise Pluto’s atmosphere and its evolution. From each stellar occultation, an accurate astrometric position of Pluto at the observation epoch is derived. These positions mainly depend on the position of the occulted star and the precision of the timing. Aims. We present 19 Pluto’s astrometric positions derived from occultations from 1988 to 2016. Using Gaia DR2 for the positions of the occulted stars, the accuracy of these positions is estimated at 2−10 mas, depending on the observation circumstances. From these astrometric positions, we derive an updated ephemeris of Pluto’s system barycentre using the NIMA code. Methods. The astrometric positions were derived by fitting the light curves of the occultation by a model of Pluto’s atmosphere. The fits provide the observed position of the centre for a reference star position. In most cases other publications provided the circumstances of the occultation such as the coordinates of the stations, timing, and impact parameter, i.e. the closest distance between the station and centre of the shadow. From these parameters, we used a procedure based on the Bessel method to derive an astrometric position. Results. We derive accurate Pluto’s astrometric positions from 1988 to 2016. These positions are used to refine the orbit of Pluto’system barycentre providing an ephemeris, accurate to the milliarcsecond level, over the period 2000−2020, allowing for better predictions for future stellar occultations.

scholarly journals Search for small trans-Neptunian objects by the TAOS project

2006 ◽  
Vol 2 (S236) ◽  
pp. 65-68 ◽  
Author(s):  
W.P. Chen ◽  
C. Alcock ◽  
T. Axelrod ◽  
F.B. Bianco ◽  
Y.I. Byun ◽  
...  
Keyword(s):  
Solar System ◽  
Detection Rate ◽  
Light Curves ◽  
Wide Field ◽  
Stellar Photometry ◽  
Stellar Occultation ◽  
Icy Bodies ◽  
Photometric Measurements ◽  
Readout Scheme ◽  
Effective Analysis

AbstractThe Taiwan-America Occultation Survey (TAOS) aims to determine the number of small icy bodies in the outer reach of the Solar System by means of stellar occultation. An array of 4 robotic small (D=0.5 m), wide-field (f/1.9) telescopes have been installed at Lulin Observatory in Taiwan to simultaneously monitor some thousand of stars for such rare occultation events. Because a typical occultation event by a TNO a few km across will last for only a fraction of a second, fast photometry is necessary. A special CCD readout scheme has been devised to allow for stellar photometry taken a few times per second. Effective analysis pipelines have been developed to process stellar light curves and to correlate any possible flux changes among all telescopes. A few billion photometric measurements have been collected since the routine survey began in early 2005. Our preliminary result of a very low detection rate suggests a deficit of small TNOs down to a few km size, consistent with the extrapolation of some recent studies of larger (30–100 km) TNOs.

scholarly journals The first observed stellar occultations by the irregular satellite Phoebe (Saturn IX) and improved rotational period

2019 ◽  
Vol 492 (1) ◽  
pp. 770-781
Author(s):  
A R Gomes-Júnior ◽  
M Assafin ◽  
F Braga-Ribas ◽  
G Benedetti-Rossi ◽  
B E Morgado ◽  
...  
Keyword(s):  
3D Model ◽  
Rotation Period ◽  
Light Curves ◽  
Rotational Period ◽  
Shape Model ◽  
Stellar Occultation ◽  
Stellar Occultations ◽  
The Difference ◽  
The Moment ◽  
Gaia Dr2

ABSTRACT We report six stellar occultations by Phoebe (Saturn IX), an irregular satellite of Saturn, obtained between mid-2017 and mid-2019. The 2017 July 6 event was the first stellar occultation by an irregular satellite ever observed. The occultation chords were compared to a 3D shape model of the satellite obtained from Cassini observations. The rotation period available in the literature led to a sub-observer point at the moment of the observed occultations where the chords could not fit the 3D model. A procedure was developed to identify the correct sub-observer longitude. It allowed us to obtain the rotation period with improved precision compared to the currently known value from literature. We show that the difference between the observed and the predicted sub-observer longitude suggests two possible solutions for the rotation period. By comparing these values with recently observed rotational light curves and single-chord stellar occultations, we can identify the best solution for Phoebe’s rotational period as 9.27365 ± 0.00002 h. From the stellar occultations, we also obtained six geocentric astrometric positions in the ICRS as realized by the Gaia DR2 with uncertainties at the 1-mas level.

scholarly journals The large trans-Neptunian object 2002 TC302 from combined stellar occultation, photometry, and astrometry data

2020 ◽  
Vol 639 ◽  
pp. A134 ◽  
Author(s):  
J. L. Ortiz ◽  
P. Santos-Sanz ◽  
B. Sicardy ◽  
G. Benedetti-Rossi ◽  
R. Duffard ◽  
...  
Keyword(s):  
Physical Properties ◽  
Sierra Nevada ◽  
Thermal Flux ◽  
Absolute Magnitude ◽  
The Body ◽  
Light Curves ◽  
Effective Diameter ◽  
Near Misses ◽  
Considerable Uncertainty ◽  
Stellar Occultation

Context. Deriving physical properties of trans-Neptunian objects is important for the understanding of our Solar System. This requires observational efforts and the development of techniques suitable for these studies. Aims. Our aim is to characterize the large trans-Neptunian object (TNO) 2002 TC302. Methods. Stellar occultations offer unique opportunities to determine key physical properties of TNOs. On 28 January 2018, 2002 TC302 occulted a mv ~ 15.3 star with designation 593-005847 in the UCAC4 stellar catalog, corresponding to Gaia source 130957813463146112. Twelve positive occultation chords were obtained from Italy, France, Slovenia, and Switzerland. Also, four negative detections were obtained near the north and south limbs. This represents the best observed stellar occultation by a TNO other than Pluto in terms of the number of chords published thus far. From the 12 chords, an accurate elliptical fit to the instantaneous projection of the body can be obtained that is compatible with the near misses. Results. The resulting ellipse has major and minor axes of 543 ± 18 km and 460 ± 11 km, respectively, with a position angle of 3 ± 1 degrees for the minor axis. This information, combined with rotational light curves obtained with the 1.5 m telescope at Sierra Nevada Observatory and the 1.23 m telescope at Calar Alto observatory, allows us to derive possible three-dimensional shapes and density estimations for the body based on hydrostatic equilibrium assumptions. The effective diameter in equivalent area is around 84 km smaller than the radiometrically derived diameter using thermal data from Herschel and Spitzer Space Telescopes. This might indicate the existence of an unresolved satellite of up to ~300 km in diameter, which is required to account for all the thermal flux, although the occultation and thermal diameters are compatible within their error bars given the considerable uncertainty of the thermal results. The existence of a potential satellite also appears to be consistent with other ground-based data presented here. From the effective occultation diameter combined with absolute magnitude measurements we derive a geometric albedo of 0.147 ± 0.005, which would be somewhat smaller if 2002 TC302 has a satellite. The best occultation light curves do not show any signs of ring features or any signatures of a global atmosphere.

Distance to SN 1987A and the LMC

1999 ◽  
Vol 190 ◽  
pp. 549-554
Author(s):  
Nino Panagia
Keyword(s):  
Angular Size ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Light Curves ◽  
Distance Modulus ◽  
Absolute Size ◽  
Sn 1987A

Using the new reductions of the IUE light curves by Sonneborn et al. (1997) and an extensive set of HST images of SN 1987A we have repeated and improved Panagia et al. (1991) analysis to obtain a better determination of the distance to the supernova. In this way we have derived an absolute size of the ringRabs= (6.23 ± 0.08) x 1017cm and an angular sizeR″ = 808 ± 17 mas, which give a distance to the supernovad(SN1987A) = 51.4 ± 1.2 kpc and a distance modulusm–M(SN1987A) = 18.55 ± 0.05. Allowing for a displacement of SN 1987A position relative to the LMC center, the distance to the barycenter of the Large Magellanic Cloud is also estimated to bed(LMC) = 52.0±1.3 kpc, which corresponds to a distance modulus ofm–M(LMC) = 18.58±0.05.

Quasi-Periodic Oscillations in Dwarf Novae

1979 ◽  
Vol 46 ◽  
pp. 77-88
Author(s):  
Edward L. Robinson
Keyword(s):  
Binary Systems ◽  
Outer Edge ◽  
Light Curves ◽  
Close Binary ◽  
Bright Spot ◽  
Dwarf Novae ◽  
Periodic Oscillations ◽  
High Frequencies ◽  
Short Period ◽  
Typical Time

Three distinct kinds of rapid variations have been detected in the light curves of dwarf novae: rapid flickering, short period coherent oscillations, and quasi-periodic oscillations. The rapid flickering is seen in the light curves of most, if not all, dwarf novae, and is especially apparent during minimum light between eruptions. The flickering has a typical time scale of a few minutes or less and a typical amplitude of about .1 mag. The flickering is completely random and unpredictable; the power spectrum of flickering shows only a slow decrease from low to high frequencies. The observations of U Gem by Warner and Nather (1971) showed conclusively that most of the flickering is produced by variations in the luminosity of the bright spot near the outer edge of the accretion disk around the white dwarf in these close binary systems.

The Eclipsing Binary WX Eridani

1979 ◽  
Vol 46 ◽  
pp. 385
Author(s):  
M.B.K. Sarma ◽  
K.D. Abhankar
Keyword(s):  
Light Curve ◽  
Spectral Type ◽  
Orbital Period ◽  
Primary Component ◽  
Light Curves ◽  
Absorption Feature ◽  
Primary Star ◽  
Eclipsing Binary ◽  
The Times ◽  
Phase Angles

AbstractThe Algol-type eclipsing binary WX Eridani was observed on 21 nights on the 48-inch telescope of the Japal-Rangapur Observatory during 1973-75 in B and V colours. An improved period of P = 0.82327038 days was obtained from the analysis of the times of five primary minima. An absorption feature between phase angles 50-80, 100-130, 230-260 and 280-310 was present in the light curves. The analysis of the light curves indicated the eclipses to be grazing with primary to be transit and secondary, an occultation. Elements derived from the solution of the light curve using Russel-Merrill method are given. From comparison of the fractional radii with Roche lobes, it is concluded that none of the components have filled their respective lobes but the primary star seems to be evolving. The spectral type of the primary component was estimated to be F3 and is found to be pulsating with two periods equal to one-fifth and one-sixth of the orbital period.

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