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

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.

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

10.5194/epsc2021-609 ◽

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 Ouka&#239;meden 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.&#160;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&#8217;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.&#160;</p>

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Analysis of the Light-Curve of Comet P/Halley in 1985–1986

International Astronomical Union Colloquium ◽

10.1017/s0252921100092630 ◽

1988 ◽

Vol 98 ◽

pp. 160-162

Author(s):

David Valls-Gabaud ◽

Angel Gómez

Keyword(s):

Light Curve ◽

Physical Properties ◽

Transition Phase ◽

Light Curves ◽

Equivalent Radius ◽

Semi Empirical

We analize the light curve of comet P/Halley resulting from 187 observations made by amateurs. We try to derive some constraints on the physical properties of the comet through the application of the semi-empirical photometric model (SEPM) developped by R.L. Newburn.The m1 (Fig. 2) and V(1,0) light curves show a clear transition phase in the pre-perihelion apparition, between ~ 1.9 and ~ 1.2 A.U. which supports the division into 3 parts made by Hasegawa. It is remarkable to find that the light curve obtained by amateurs is so close to those obtained by experienced observers.We derive an effective equivalent radius of β = 4.9 ± 0.8 (1σ) km, and a geometrical albedo of pυ = 0.06 ± 0.02 (1σ) using the method suggested by Delsemme and Rud.

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Shape model and spin state of non-principal axis rotator (5247) Krylov

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936808 ◽

2020 ◽

Vol 635 ◽

pp. A137

Author(s):

H.-J. Lee ◽

J. Ďurech ◽

M.-J. Kim ◽

H.-K. Moon ◽

C.-H. Kim ◽

...

Keyword(s):

Physical Model ◽

Spin State ◽

Principal Axis ◽

Light Curves ◽

Infrared Light ◽

Inversion Method ◽

Wide Field ◽

Angular Momentum Vector ◽

Axis Rotation ◽

Vector Orientation

Context. The study of non-principal axis (NPA) rotators can provide important clues to the evolution of the spin state of asteroids. However, very few studies to date have focused on NPA-rotating main belt asteroids (MBAs). One MBA known to be in an excited rotation state is asteroid (5247) Krylov. Aims. By using disk-integrated photometric data, we construct a physical model of (5247) Krylov including shape and spin state. Methods. We applied the light curve convex inversion method employing optical light curves obtained by using ground-based telescopes in three apparitions during 2006, 2016, and 2017, along with infrared light curves obtained by the Wide-field Infrared Survey Explorer satellite in 2010. Results. Asteroid (5247) Krylov is spinning in a short axis mode characterized by rotation and precession periods of 368.7 and 67.27 h, respectively. The angular momentum vector orientation of Krylov is found to be λL = 298° and βL = −58°. The ratio of the rotational kinetic energy to the basic spin-state energy E∕E0 ≃ 1.02 shows that the (5247) Krylov is about 2% excited state compared to the principal axis rotation state. The shape of (5247) Krylov can be approximated by an elongated prolate ellipsoid with a ratio of moments of inertia of Ia : Ib : Ic = 0.36 : 0.96 : 1. This is the first physical model of an NPA rotator among MBAs. The physical processes that led to the current NPA rotation cannot be unambiguously reconstructed.

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The atmosphere of WASP-17b: Optical high-resolution transmission spectroscopy

Astronomy and Astrophysics ◽

10.1051/0004-6361/201732029 ◽

2018 ◽

Vol 618 ◽

pp. A98 ◽

Cited By ~ 7

Author(s):

Sara Khalafinejad ◽

Michael Salz ◽

Patricio E. Cubillos ◽

George Zhou ◽

Carolina von Essen ◽

...

Keyword(s):

High Resolution ◽

Light Curve ◽

Physical Properties ◽

Transmission Spectrum ◽

Atmospheric Model ◽

Atmospheric Temperature ◽

Temporal Variations ◽

Light Curves ◽

Sodium Absorption ◽

Transmission Spectroscopy

High-resolution transmission spectroscopy is a method for understanding the chemical and physical properties of upper exoplanetary atmospheres. Due to large absorption cross-sections, resonance lines of atomic sodium D-lines (at 5889.95 and 5895.92 Å) produce large transmission signals. Our aim is to unveil the physical properties of WASP-17b through an accurate measurement of the sodium absorption in the transmission spectrum. We analyze 37 high-resolution spectra observed during a single transit of WASP-17b with the MIKE instrument on the 6.5 m Magellan Telescopes. We exclude stellar flaring activity during the observations by analyzing the temporal variations of Hα and Ca II infrared triplet (IRT) lines. We then obtain the excess absorption light curves in wavelength bands of 0.75, 1, 1.5, and 3 Å around the center of each sodium line (i.e., the light curve approach). We model the effects of differential limb-darkening, and the changing planetary radial velocity on the light curves. We also analyze the sodium absorption directly in the transmission spectrum, which is obtained by dividing in-transit by out-of-transit spectra (i.e., the division approach). We then compare our measurements with a radiative transfer atmospheric model. Our analysis results in a tentative detection of exoplanetary sodium: we measure the width and amplitude of the exoplanetary sodium feature to be σNa = (0.128 ± 0.078) Å and ANa = (1.7 ± 0.9)% in the excess light curve approach and σNa = (0.850 ± 0.034) Å and ANa = (1.3 ± 0.6)% in the division approach. By comparing our measurements with a simple atmospheric model, we retrieve an atmospheric temperature of 15501550 −200+700 K and radius (at 0.1 bar) of 1.81 ± 0.02 RJup for WASP-17b.

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

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038046 ◽

2020 ◽

Vol 639 ◽

pp. A134 ◽

Cited By ~ 2

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.

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The Eclipsing Binary WX Eridani

International Astronomical Union Colloquium ◽

10.1017/s0252921100073656 ◽

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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An extensive photometric study of the Blazhko RR Lyrae star RZ Lyr*

Monthly Notices of the Royal Astronomical Society ◽

10.1111/j.1365-2966.2012.20772.x ◽

2012 ◽

Vol 423 (2) ◽

pp. 993-1005 ◽

Cited By ~ 11

Author(s):

J. Jurcsik ◽

Á. Sódor ◽

G. Hajdu ◽

B. Szeidl ◽

Á. Dózsa ◽

...

Keyword(s):

Light Curve ◽

Light Curves ◽

Stellar Structure ◽

Time Base ◽

Photometric Method ◽

Physical Parameters ◽

Component Solution ◽

Rr Lyrae ◽

Curve Variation ◽

Type Variable

Abstract The analysis of recent, extended multicolour CCD and archive photoelectric, photographic and visual observations has revealed several important properties of RZ Lyr, an RRab-type variable exhibiting large-amplitude Blazhko modulation. On the time base of ∼110 yr, a strict anticorrelation between the pulsation- and modulation-period changes is established. The light curve of RZ Lyr shows a remarkable bump on the descending branch in the small-amplitude phase of the modulation, similarly to the light curves of bump Cepheids. We speculate that the stellar structure temporally suits a 4:1 resonance between the periods of the fundamental and one of the higher order radial modes in this modulation phase. The light-curve variation of RZ Lyr can be correctly fitted with a two-modulation-component solution; the 121-d period of the main modulation is nearly but not exactly four times longer than the period of the secondary modulation component. Using the inverse photometric method, the variations in the pulsation-averaged values of the physical parameters in different phases of both modulation components are determined.

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Evolutionary Changes in LUMINOUS STARS

Highlights of Astronomy ◽

10.1017/s1539299600020979 ◽

1998 ◽

Vol 11 (1) ◽

pp. 346-346

Author(s):

E. Zsldos

Keyword(s):

Light Curve ◽

19Th Century ◽

Stellar Evolution ◽

Colour Change ◽

Light Curves ◽

Appreciable Change ◽

Luminous Blue Variables ◽

Secular Changes ◽

Evolutionary Changes ◽

The 19Th Century

The light curves of luminous stars often show spectacular secular changes which can be connected to stellar evolution. Such events are, e.g. the outbursts of P Cygni in the 17th century and 77 Carinae in the last century. Both stars belong to the Luminous Blue Variables, but these changes are not restricted to blue stars. The light curve of HR 8752 (V509 Cassiopeiae) shows a certain similarity to that of the former two stars. When it was first catalogued in the middle of the 19th century, it had been a 6m star. During 100 years the star showed a secular brightening of lm. A similar yellow hypergiant, p Cassiopeiae produced at least two outbursts this century, though both have smaller amplitudes than it is in the case of the LBVs. Moreover, these yellow variables also have an apparently secular colour change: the B − V colour of HR 8752 is decreasing while that of ρ Cassiopeiae is increasing. In both cases evolutionary changes are possible but one cannot exclude other causes. Besides these well studied stars there are several other yellow hypergiants with promising light curves. One of the most interesting cases seems to be R Puppis, which was discovered to be variable in the last century, but then did not show any appreciable change in the following 70-80 years. In the late 1970s, however, it began to vary once more.

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Light-curve properties of SN 2017fgc and HV SNe Ia

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab254 ◽

2021 ◽

Vol 502 (3) ◽

pp. 4112-4124

Author(s):

Umut Burgaz ◽

Keiichi Maeda ◽

Belinda Kalomeni ◽

Miho Kawabata ◽

Masayuki Yamanaka ◽

...

Keyword(s):

Light Curve ◽

Near Infrared ◽

Light Curves ◽

Normal Velocity ◽

External Effects ◽

Band Maximum ◽

Bolometric Luminosity ◽

V Band ◽

Photometric And Spectroscopic Observations ◽

Type Ia

ABSTRACT Photometric and spectroscopic observations of Type Ia supernova (SN) 2017fgc, which cover the period from −12 to + 137 d since the B-band maximum are presented. SN 2017fgc is a photometrically normal SN Ia with the luminosity decline rate, Δm15(B)true = 1.10 ± 0.10 mag. Spectroscopically, it belongs to the high-velocity (HV) SNe Ia group, with the Si ii λ6355 velocity near the B-band maximum estimated to be 15 200 ± 480 km s−1. At the epochs around the near-infrared secondary peak, the R and I bands show an excess of ∼0.2-mag level compared to the light curves of the normal velocity (NV) SNe Ia. Further inspection of the samples of HV and NV SNe Ia indicates that the excess is a generic feature among HV SNe Ia, different from NV SNe Ia. There is also a hint that the excess is seen in the V band, both in SN 2017fgc and other HV SNe Ia, which behaves like a less prominent shoulder in the light curve. The excess is not obvious in the B band (and unknown in the U band), and the colour is consistent with the fiducial SN colour. This might indicate that the excess is attributed to the bolometric luminosity, not in the colour. This excess is less likely caused by external effects, like an echo or change in reddening but could be due to an ionization effect, which reflects an intrinsic, either distinct or continuous, difference in the ejecta properties between HV and NV SNe Ia.

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New Data on the Eclipsing Binary V1848 Ori and Improved Orbital and Light Curve Solutions

Open Astronomy ◽

10.1515/astro-2020-0013 ◽

2020 ◽

Vol 29 (1) ◽

pp. 72-80 ◽

Cited By ~ 1

Author(s):

Fatemeh Davoudi ◽

Atila Poro ◽

Fahri Alicavus ◽

Afshin Halavati ◽

Saeed Doostmohammadi ◽

...

Keyword(s):

Binary System ◽

Light Curve ◽

Mass Function ◽

Light Curves ◽

Complete Analysis ◽

Physical Parameters ◽

Mass Ratio ◽

Third Body ◽

Eclipsing Binary

AbstractNew observations of the eclipsing binary system V1848 Ori were carried out using the V filter resulting in a determination of new times of minima and new ephemeris were obtained. We presented the first complete analysis of the system’s orbital period behavior and analysis of O-C diagram done by the GA and MCMC approaches in OCFit code. The O-C diagram demonstrates a sinusoidal trend in the data; this trend suggests a cyclic change caused by the LITE effect with a period of 10.57 years and an amplitude of 7.182 minutes. It appears that there is a third body with mass function of f (m3) = 0.0058 M⊙ in this binary system. The light curves were analyzed using the Wilson-Devinney code to determine some geometrical and physical parameters of the system. These results show that V1848 Ori is a contact W UMa binary system with the mass ratio of q = 0.76 and a weak fillout factor of 5.8%. The O’Connell effect was not seen in the light curve and there is no need to add spot.

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