scholarly journals The stellar occultations by the largest satellite of the dwarf planet Haumea, Hi'iaka

2021 ◽  
Author(s):  
Estela Fernández-Valenzuela ◽  
Jose Luis Ortiz ◽  
Bryan Holler ◽  
Monica Vara-Lubiano ◽  
Nicolas Morales ◽  
...  
Keyword(s):  
Light Curve ◽  
North Africa ◽  
High Accuracy ◽  
The Body ◽  
Light Curves ◽  
Effective Diameter ◽  
Preliminary Results ◽  
Stellar Occultations ◽  
The Times ◽  
Triaxial Shape

<p>Two stellar occultations by the largest satellite of the dwarf planet Haumea, Hi'iaka, were predicted to happen on April, 6th and 16th, 2021. Additional high accuracy astrometric analysis was carried out in order to refine the prediction for April 6th, using several telescopes in the 1.2-m to 2-m range, with the final shadow path crossing North Africa. We successfully detected the first event from TRAPPIST-North telescope at Oukaïmeden Observatory (Morocco). Although it was recorded from only one site, this first detection allowed us to improve the prediction for the second that crossed North America from East to West. We had a good success recording six positive detections and several negative detections that constrain the shape and size of the body. The light curves obtained from the different observatories provide the time at which the star disappears and reappears, which are translated into chords (the projected lines on the sky-plane as observed from each location). Additionally, we carried out a campaign to study Hi'iaka's rotational light-curve, studying the residuals of Haumea's rotational light-curve to a four-order Fourier fit. We obtained the rotational phases at the times of the occultations, which is critical for the analysis of the occultations, given that Hi’iaka is clearly non-spherical. Our preliminary results show that Hi'iaka indeed has a triaxial shape with a larger effective diameter than what has been published so far. The preliminary results and their implications will be discussed in this talk. </p>

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.

scholarly journals Structure of the Gaseous Disk in RX Cas

1980 ◽  
Vol 88 ◽  
pp. 269-270
Author(s):  
S. Kříž
Keyword(s):  
Light Curve ◽  
Light Curves ◽  
Bright Spot ◽  
Period Increase ◽  
Long Period ◽  
Short Period ◽  
Observational Errors ◽  
The Times ◽  
Image Position

RX Cas appers to be a long-period Algol-like binary with very fast mass exchange (Struve 1944). In the period 1975-1977, this star was observed photometrically by Arsenijevič, Grygar, Harmanec, Horn, Koubský, Kříž and Pavlovski at Hvar Observatory (Yugoslavia) and by Zverko at Skalnaté Pleso Observatory (Czechoslovakia). The resulting UBV light curves seem to be rather peculiar, for the following reasons:1) Combining our observations with the older ones, we obtain the following formula for the times of minima: The period increase is surprisingly high.2) The scatter of observed points is considerable (about 0.2 mag.) and cannot be caused by observational errors. It corresponds to short period light variations on the time scale of several days.3) After J.D. 24422660, the brightness of the whole system decreased in all colours. This decrease is about 0.2 mag. in V colour and 0.5 mag. in U colour. Only after J.D. 2442900 the brightness increased again. Such a behaviour confirms the reality of old observations by Gaposchkin (1944) and Martynov (1950) who found a long-term light variation with a period of approximately 500 days.4) The part of the light curve around the phase 0.75 is definitely much lower than the corresponding part around the phase 0.25. This effect is most pronounced in the ultraviolet; the depression around the phase 0.75 is much deeper than the secondary minimum. This behaviour is opposite to the behaviour of dwarf novae. Instead of a bright shoulder connected with a bright spot, we observe some darkening.

scholarly journals Meteors with multi-modal light curves: observations and qualitative models

2018 ◽  
pp. 48-55
Author(s):  
P. Kozak
Keyword(s):  
Light Curve ◽  
Body Shape ◽  
The Body ◽  
Light Curves ◽  
Mass Center ◽  
Video Registration ◽  
Qualitative Models ◽  
The Moment ◽  
The Given ◽  
Final Confirmation

The problem of TV or video registration of meteors with anomalous light curves, in particular with multimodal and bimodal types is considered. The results of observations of two meteors from Perseid shower, obtained with the help of TV systems of super-isocon type are presented. The initial velocities of meteors were typical for Perseid shower meteors: 62.4 km/s and 58.4 km/s. One of the meteors has a light curve of a multimodal character, which can be explained by the fragmentation of the body. Another light curve has an evident bimodal type, which has no final explanation for the present. In opposite to most of registered for the moment meteors with bimodal light curves the given meteor from Perseid shower demonstrates the first peak of illumination to be much more intensive, and the second one to be significantly lower. The maximal brightness in the first peak was +2 magnitude, in the second one +3.5 magnitude, and in depression +4.5 magnitude which almost corresponds to the sky background, while the sensitivity of our observational instruments was +5.5 magnitude; but nevertheless the entire radiation disappearance was not happen. The qualitative models for interpretation of the meteor with bimodal light curve are proposed. One of them stipulates for different variants of realization of the 2-components composition of a meteoroid, when a body as the matter of fact consists of two particles. One of particles, inner as a rule, is high melting, for example a stone of iron; another one, the cover, is lower melting, for example a mix of dust and ice. Other types of the models use the cases of uniform monolith meteoroid of specific geometric shape. It is also intended that the meteoroid can rotate during its motion dependently on changing body shape or shifting its mass center. The proposed models are the simplest in accordance with the number of varying parameters, and can therefore pretend to their reality after successful application of quantitative analysis and according numerical modeling. It is noted that the final confirmation or abolishment of the model type will be possible after carrying out parallel spectral observations of meteors.

scholarly journals OJ 287: A Blazar with Everything

1994 ◽  
Vol 159 ◽  
pp. 409-409
Author(s):  
L.O. Takalo
Keyword(s):  
Correlation Analysis ◽  
Light Curve ◽  
Observational Data ◽  
Light Curves ◽  
Simple Correlation ◽  
Data Set ◽  
Preliminary Results ◽  
Blazar Oj 287

We have collected all the observations available to us of blazar OJ 287. Here we will present preliminary results from our investigation of these data. The photometric light curves show large outbursts occuring (quasi)simultaneously in all frequences. The largest outbursts occured during 1972 and 1983. The B-band light curve can be extended to the year 1894. This being the longest available observational data set of all blazars. Polarization light curves in optical show random variations in all timescales. In the radio bands the polarization observations show well defined structure in the light curves. Light curves and simple correlation analysis based on the light curves on different frequences will be presented.

scholarly journals Frequency analysis of multiperiodic δ Scuti stars

1993 ◽  
Vol 139 ◽  
pp. 149-149 ◽  
Author(s):  
L. Mantegazza ◽  
E. Poretti ◽  
F.M. Zerbi
Keyword(s):  
Light Curve ◽  
Frequency Analysis ◽  
Curve Analysis ◽  
Light Curves ◽  
Light Curve Analysis ◽  
Preliminary Results ◽  
Long Time ◽  
Scuti Star ◽  
Scuti Stars ◽  
Δ Scuti Stars

We report some of the recent results of our studies on δ Scuti star pulsation which are based on observations made at Merate and La Silla Observatories, sometimes in two site campaigns. Our recent experiences on X Caeli and 44 Tauri have shown that quite complicate light curves can be resolved even with observations obtained from one site only, if compact and accurate datasets are collected on sufficiently long time baselines (Mantegazza and Poretti, 1992; Poretti et al., 1992). Here we report the preliminary results of the light curve analysis of three more stars surveyed for more than 120 hours each: BI CMi, HD 18878 and HD 224639.BI CMi has been observed in a two-site campaign in January-February 1991, the observations being collected during 17 nights. The frequency analysis of the light curve allowed us to identify unambiguously 4 pulsation modes at 8.247, 8.863, 8.514 and 7.424 c/d with semi-amplitudes of 22, 19, 5 and 5 mmag respectively.

scholarly journals Physical model of near-Earth asteroid (1917) Cuyo from ground-based optical and thermal-IR observations

2019 ◽  
Vol 627 ◽  
pp. A172
Author(s):  
A. Rożek ◽  
S. C. Lowry ◽  
B. Rozitis ◽  
S. F. Green ◽  
C. Snodgrass ◽  
...  
Keyword(s):  
Light Curve ◽  
Physical Properties ◽  
Physical Model ◽  
Spin State ◽  
Physical Modelling ◽  
Light Curves ◽  
Compositional Variation ◽  
Effective Diameter ◽  
Surface Material ◽  
Earth Asteroid

Context. The near-Earth asteroid (1917) Cuyo was subject to radar and light curve observations during a close approach in 1989, and observed up until 2008. It was selected as one of our ESO Large Programme targets, aimed at observational detections of the Yarkovsky-O’Keefe-Radzievskii-Paddack (YORP) effect through long-term light curve monitoring and physical modelling of near-Earth asteroids. Aims. We aim to constrain the physical properties of Cuyo: shape, spin-state, and spectroscopic and thermo-physical properties of the surface. Methods. We acquired photometric light curves of Cuyo spanning the period between 2010 and 2013, which we combined with published light curves from 1989 to 2008. Our thermal-infrared observations were obtained in 2011. Rotationally resolved optical spectroscopy data were acquired in 2011 and combined with all available published spectra to investigate any surface material variegation. Results. We developed a convex light curve-inversion shape of Cuyo that suggests the presence of an equatorial ridge, typical for an evolved system close to shedding mass due to fast rotation. We determine limits of YORP strength through light curve-based spin-state modelling, including both negative and positive acceleration values, between − 0.7 × 10−8 and 1.7 × 10−8 rad day−2. Thermo-physical modelling with the ATPM provides constraints on the geometric albedo, pV = 0.24 ± 0.07, the effective diameter, Deff = 3.15 ± 0.08 km, the thermal inertia, Γ = 44 ± 9 J m−2 s−1∕2 K−1, and a roughness fraction of 0.52  ±  0.26. This enabled a YORP strength prediction of ν = (−6.39 ± 0.96) × 10−10 rad day−2. We also see evidence of surface compositional variation. Conclusions. The low value of YORP predicted by means of thermo-physical analysis, consistent with the results of the light curve study, might be due to the self-limiting properties of rotational YORP, possibly involving movement of sub-surface and surface material. This may also be consistent with the surface compositional variation that we see. The physical model of Cuyo can be used to investigate cohesive forces as a way to explain why some targets survive rotation rates faster than the fission limit.

scholarly journals Starspot modelling of the TESS light curve of CVSO 30

2021 ◽  
Vol 647 ◽  
pp. L1
Author(s):  
C. Koen
Keyword(s):  
Light Curve ◽  
High Accuracy ◽  
Light Curves ◽  
Modelling Technique ◽  
Photometric Variability ◽  
Periodic Components ◽  
Planetary Transits

Aims. I aim to investigate whether the photometric variability in the candidate host star CVSO 30 can be explained by starspots. Methods. The Transiting Exoplanet Survey Satellite (TESS) light curve of CVSO 30 is separated into two independent non-sinusoidal periodic components. A starspot modelling technique is applied to each of these components. Results. Combined, the two model light curves reproduce the TESS observations to a high accuracy, obviating the need to invoke planetary transits to describe part of the variability.

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.

scholarly journals Changes in the Soft and Hard X-Ray Light Curves of the AM Her Object E1405−451

1987 ◽  
Vol 93 ◽  
pp. 643-649
Author(s):  
J.P. Osborne ◽  
M. Cropper ◽  
S. Cristiani
Keyword(s):  
Phase Shift ◽  
Light Curve ◽  
Light Curves ◽  
Optical Observations ◽  
X Ray ◽  
Preliminary Results ◽  
Optical Light Curve

AbstractThe preliminary results of EXOSAT and contemporaneous optical observations of E1405−451 (V834 Cen) in 1985 and 1986 are presented. In the latter of the two observations the soft X-ray light curve was observed to be quite different to that seen in all previous observations, but similar to the optical light curve and the new soft X-ray light curve of E2003+225. A phase shift of the broad soft X-ray eclipse was also observed. The hard X-ray and optical light curves have also undergone small changes.

scholarly journals Revisiting the exomoon candidate signal around Kepler-1625 b

2018 ◽  
Vol 617 ◽  
pp. A49 ◽  
Author(s):  
Kai Rodenbeck ◽  
René Heller ◽  
Michael Hippke ◽  
Laurent Gizon
Keyword(s):  
Light Curve ◽  
Bayesian Information Criterion ◽  
Additional Data ◽  
Statistical Significance ◽  
Model Fitting ◽  
Information Criterion ◽  
High Accuracy ◽  
Light Curves ◽  
Orbital Dynamics ◽  
Large Object

Context. Transit photometry of the Jupiter-sized exoplanet candidate Kepler-1625 b has recently been interpreted as showing hints of a moon. This exomoon, the first of its kind, would be as large as Neptune and unlike any moon we know from the solar system. Aims. We aim to clarify whether the exomoon-like signal is indeed caused by a large object in orbit around Kepler-1625 b, or whether it is caused by stellar or instrumental noise or by the data detrending procedure. Methods. To prepare the transit data for model fitting, we explore several detrending procedures using second-, third-, and fourth-order polynomials and an implementation of the Cosine Filtering with Autocorrelation Minimization (CoFiAM). We then supply a light curve simulator with the co-planar orbital dynamics of the system and fit the resulting planet–moon transit light curves to the Kepler data. We employ the Bayesian information criterion (BIC) to assess whether a single planet or a planet–moon system is a more likely interpretation of the light curve variations. We carry out a blind hare-and-hounds exercise using many noise realizations by injecting simulated transits into different out-of-transit parts of the original Kepler-1625 light curve: (1) 100 sequences with three synthetic transits of a Kepler-1625 b-like Jupiter-size planet and (2) 100 sequences with three synthetic transits of a Kepler-1625 b-like planet with a Neptune-sized moon. Results. The statistical significance and characteristics of the exomoon-like signal strongly depend on the detrending method (polynomials versus cosines), the data chosen for detrending, and the treatment of gaps in the light curve. Our injection-retrieval experiment shows evidence of moons in about 10% of those light curves that do not contain an injected moon. Strikingly, many of these false-positive moons resemble the exomoon candidate, that is, a Neptune-sized moon at about 20 Jupiter radii from the planet. We recover between about one third and one half of the injected moons, depending on the detrending method, with radii and orbital distances broadly corresponding to the injected values. Conclusions. A ΔBIC of − 4.9 for the CoFiAM-based detrending is indicative of an exomoon in the three transits of Kepler-1625 b. This solution, however, is only one out of many and we find very different solutions depending on the details of the detrending method. We find it concerning that the detrending is so clearly key to the exomoon interpretation of the available data of Kepler-1625 b. Further high-accuracy transit observations may overcome the effects of red noise but the required amount of additional data might be large.

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