Cosmos 462 (1971-106A): Orbit determination and analysis

1979 ◽  
Vol 292 (1396) ◽  
pp. 473-512 ◽  
Keyword(s):  
Rotation Rate ◽  
Optical Observations ◽  
Positional Accuracy ◽  
Orbital Parameters ◽  
East Wind ◽  
Average Rotation ◽  
The 1960S ◽  
Similar Accuracy ◽  
Geopotential Harmonic Coefficients ◽  
Density Scale

Cosmos 462 (1971-106A) was launched on 3 December 1971 into an orbit inclined at 65.75° to the equator, with a perigee height of 230 km and apogee height of 1800 km. The satellite remained in orbit for 40 months and decayed on 4 April 1975. Orbital parameters have been determined at 85 epochs by using the R.A.E. orbit refinement program PROP, with 6635 radar and optical observations, including 197 from the Hewitt cameras. The average standard deviation in eccentricity and inclination corresponded to a positional accuracy of about 100 m. In addition, orbits of similar accuracy were determined daily for the last 15 days of the life, from 2000 NORAD observations. During its slow decay, the orbit passed through 14:1,29:2 and 15:1 resonances with the Earth’s gravitational field. The variations in inclination and eccentricity at these resonances have been analysed in detail to evaluate lumped geopotential harmonic coefficients of order 14, 29 and 15. The variation of inclination between resonances has been analysed to obtain four values of the average atmospheric rotation rate at heights of 200-250 km in 1972-5. The values of A show a seasonal dependence, being greater in winter than in summer, and the average rotation rate is lower than in the 1960s, being near 1.0 rev/day. Analysis of the inclination in the last 15 days of the satellite’s life indicates a weak west-to-east wind at high latitude (54-62° N). The variation of perigee height has been analysed to obtain 24 values of density scale height H , including eight in the last 15 days. Comparison with values from CIRA 1972 shows a bias difference of only 1 % and r.m.s. difference of 10%, so CIRA 1972 provides a good approximation to the values of H in 1972-5.

scholarly journals Evidence of angular momentum transport in main-sequence solar-like stars

2015 ◽  
Vol 11 (A29B) ◽  
pp. 661-666
Author(s):  
Othman Benomar ◽  
Masao Takata ◽  
Hiromoto Shibahashi ◽  
Tugdual Ceillier ◽  
Rafael A. García
Keyword(s):  
Angular Momentum ◽  
Rotation Rate ◽  
Main Sequence ◽  
Light Variation ◽  
Momentum Transport ◽  
Angular Momentum Transport ◽  
Surface Rotation ◽  
Average Rotation ◽  
The Difference ◽  
Few Data

AbstractThe rotation rates in the interior and at the surface is determined for the 22 main-sequence stars with masses between 1.0 and 1.6 M⊙. The average interior rotation is measured using asteroseismology, while the surface rotation is measured by the spectroscopic v sin i or the periodic light variation due to surface structures, such as spots. It is found that the difference between the surface rotation rate determined by spectroscopy and the average rotation rate for most of stars is small enough to suggest that an efficient process of angular momentum transport operates during and/or before the main-sequence stage of stars. By comparing the surface rotation rate measured from the light variation with those measured by spectroscopy, we found hints of latitudinal differential rotation. However, this must be confirmed by a further study because our result is sensitive to a few data points.

Three-dimensional finite-amplitude solutions in plane Couette flow: bifurcation from infinity

1990 ◽  
Vol 217 ◽  
pp. 519-527 ◽  
Author(s):  
M. Nagata
Keyword(s):  
Couette Flow ◽  
Rotation Rate ◽  
Three Dimensional ◽  
Finite Amplitude ◽  
Narrow Gap ◽  
Plane Couette Flow ◽  
Bifurcation Problem ◽  
Bifurcation From Infinity ◽  
Flow Bifurcation ◽  
Average Rotation

Finite-amplitude solutions of plane Couette flow are discovered. They take a steady three-dimensional form. The solutions are obtained numerically by extending the bifurcation problem of a circular Couette system between co-rotating cylinders with a narrow gap to the case with zero average rotation rate.

scholarly journals Determination of Resonance terms using Optical Observations of Two Meteosat Satellites

1997 ◽  
Vol 165 ◽  
pp. 355-360
Author(s):  
U. Hugentobler ◽  
T. Schildknecht ◽  
G. Beutler
Keyword(s):  
Radiation Pressure ◽  
Ccd Camera ◽  
Least Square ◽  
Optical Observations ◽  
Laser Ranging ◽  
Time Interval ◽  
Orbital Parameters ◽  
Adjustment Procedure ◽  
Relative Errors

AbstractDuring an observation campaign in winter 94/95 astrometric positions from Meteosat 4 and 5 were acquired at the Zimmerwald observatory using a CCD camera mounted in the prime focus of the 0.5 m Satellite Laser Ranging telescope. The measurements cover a time interval of four months, their precision is of the order of .The modeling of radiation pressure for the small, cylindrically shaped satellites is relatively easy and they are therefore excellent objects to probe the geopotential. The orbital parameters and the radiation pressure coefficients for the two satellites as well as the resonant coefficients C22, S22 of the geopotential were determined by a single least square adjustment procedure including all the Zimmerwald observations. The relative errors estimated for the terms C22 and S22 are of the order of 1 ÷ 3 · 10−4.

The average rotation rate of a fiber in the linear flow of a semidilute suspension

1990 ◽  
Vol 2 (12) ◽  
pp. 2093-2102 ◽  
Author(s):  
Donald L. Koch ◽  
Eric S. G. Shaqfeh
Keyword(s):  
Rotation Rate ◽  
Linear Flow ◽  
Average Rotation

scholarly journals Explaining temporal variations in the jet position angle of the blazar OJ 287 using its binary black hole central engine model

2021 ◽  
Author(s):  
Lankeswar Dey ◽  
Mauri J Valtonen ◽  
A Gopakumar ◽  
Rocco Lico ◽  
José L Gómez ◽  
...  
Keyword(s):  
Black Hole ◽  
Position Angle ◽  
Temporal Variations ◽  
Optical Observations ◽  
High Angular Resolution ◽  
Orbital Parameters ◽  
Engine Model ◽  
Binary Black Hole ◽  
Central Engine ◽  
Blazar Oj 287

Abstract The bright blazar OJ 287 is the best-known candidate for hosting a supermassive black hole binary system. It inspirals due to the emission of nanohertz gravitational waves (GWs). Observations of historical and predicted quasi-periodic high-brightness flares in its century-long optical lightcurve, allow us to determine the orbital parameters associated with the binary black hole (BBH) central engine. In contrast, the radio jet of OJ 287 has been covered with Very Long Baseline Interferometry (VLBI) observations for only about 30 years and these observations reveal that the position angle (PA) of the jet exhibits temporal variations at both millimetre and centimetre wavelengths. Here we associate the observed PA variations in OJ 287 with the precession of its radio jet. In our model, the evolution of the jet direction can be associated either with the primary black hole (BH) spin evolution or with the precession of the angular momentum direction of the inner region of the accretion disc. Our Bayesian analysis shows that the BBH central engine model, primarily developed from optical observations, can also broadly explain the observed temporal variations in the radio jet of OJ 287 at frequencies of 86, 43, and 15 GHz. Ongoing Global mm-VLBI Array (GMVA) observations of OJ 287 have the potential to verify our predictions for the evolution of its 86 GHz PA values. Additionally, thanks to the extremely high angular resolution that the Event Horizon Telescope (EHT) can provide, we explore the possibility to test our BBH model through the detection of the jet in the secondary black hole .

scholarly journals Blind Search Methods for Binary Gamma-ray Pulsars

2017 ◽  
Vol 13 (S337) ◽  
pp. 382-383
Author(s):  
Lars Nieder ◽  
Colin J. Clark ◽  
Holger J. Pletsch
Keyword(s):  
Gamma Ray ◽  
Optical Observations ◽  
Large Area ◽  
Search Methods ◽  
Companion Star ◽  
Orbital Parameters ◽  
Radio Data ◽  
Blind Search

AbstractGamma-ray observations by the Fermi Large Area Telescope (LAT) have been used very successfully in the last 9 years to detect more than 200 gamma-ray pulsars. Sixty of these have been found by directly searching for pulsations in the gamma-ray data, but only one binary MSP has been found this way. Pulsars in binaries are often difficult to detect in radio data because of large eclipses, and some binary MSPs may even be radio quiet. For those, a gamma-ray blind search might be the only possibility for detection. While searches for isolated pulsars up to kilohertz frequencies are already computationally very challenging, blind searches for binary gamma-ray pulsars are simply infeasible without further knowledge of their orbital parameters. Here we present methods with which we can conduct searches for candidate binary gamma-ray pulsars for which orbital constraints are known from optical observations of a likely companion star. We also highlight some example sources where these methods have been used.

scholarly journals Flare Stars in a Field Near the North Galactic Pole: ROSAT and Optical Observations

1995 ◽  
Vol 151 ◽  
pp. 69-72
Author(s):  
G.A. Richter ◽  
H.-J. Bräuer ◽  
J. Greiner
Keyword(s):  
Optical Observations ◽  
Positional Accuracy ◽  
X Ray ◽  
The North ◽  
Optical Position ◽  
Sky Survey ◽  
Objective Prism ◽  
Flare Stars ◽  
North Galactic ◽  
Calar Alto

In a field of 100 square degrees around 26 Com, 238 X-ray sources have been discovered by ROSAT during the All-Sky-Survey observations. These sources were identified using objective prism spectrograms taken with the Hamburg Schmidt telescope on Calar Alto (courtesy N. Bade) and including the positional accuracy of typically 30" and the X-ray to optical luminosity ratio. In an ongoing investigation of these X-ray sources on more than 400 plates of the Sonneberg astrographs 400/1600 mm and 400/2000 mm, a total of 5 of the M type counterparts were found to be flare stars. In Table 1 we give the ROSAT name (column 1), the new designation as a Sonneberg variable (2), the position of the optical counterpart (3), the magnitude range of the newly discovered flare stars (4), the ROSAT PSPC countrate during the All-Sky-Survey (5), the distance D between X-ray and optical position (6). All 5 objects had not been known to be flaring. The real amplitudes must be larger than those given in column 3 because the (unknown) duration of the flares is usually much shorter than the exposure time of the plates. The figures give APM finding charts of these new flare stars.

The rotation and interior of Ganymede

2020 ◽  
Author(s):  
Tim Van Hoolst ◽  
Rose-Marie Baland ◽  
Alexis Coyette ◽  
Marie Yseboodt
Keyword(s):  
Rotation Rate ◽  
Interior Structure ◽  
Small Deviations ◽  
Icy Moons ◽  
Explorer Mission ◽  
Low Degree ◽  
Orbital Phase ◽  
Average Rotation ◽  
Tidal Deformations ◽  
Ice Shell

<p>The rotation rate of Ganymede, the largest satellite of Jupiter, is on average equal to its orbital mean motion but cannot be constant on orbital time scale as a result of the gravitational torque exerted by Jupiter on the moon. Here we discuss small deviations from the average rotation rate, evaluate polar motion, and discuss Ganymede's obliquity. We examine different time scales, from diurnal to long-period, and assess the potential of using rotation as probes of the interior structure.</p><p>The ESA JUICE (JUpiter ICy moons Explorer) mission will accurately measure the rotation of Ganymede during its orbital phase around the satellite starting in 2032. We report on different theoretical aspects of the rotation for realistic models of the interior of Ganymede, include tidal deformations and take into account the low-degree gravity field and topography of Ganymede. We assess the advantages of a joint use of rotation and tides to constrain the satellite's interior structure, in particular its ice shell and ocean.</p>

scholarly journals Accretion disc by Roche lobe overflow in the supergiant fast X-ray transient IGR J08408−4503

2019 ◽  
Vol 631 ◽  
pp. A135 ◽  
Author(s):  
L. Ducci ◽  
P. Romano ◽  
L. Ji ◽  
A. Santangelo
Keyword(s):  
Binary Systems ◽  
Dynamic Range ◽  
Compact Object ◽  
Accretion Disc ◽  
Roche Lobe ◽  
Optical Observations ◽  
Optical Data ◽  
X Ray ◽  
Orbital Parameters ◽  
Large Size

Supergiant fast X-ray transients (SFXTs) are X-ray binary systems with a supergiant companion and likely a neutron star, which show a fast (∼103 s) and high variability with a dynamic range up to 105−6. Given their extreme properties, they are considered among the most valuable laboratories to test accretion models. Recently, the orbital parameters of a member of this class, IGR J08408−4503, were obtained from optical observations. We used this information, together with X-ray observations from previous publications and new results from X-ray and optical data collected by INTEGRAL and presented in this work, to study the accretion mechanisms at work in IGR J08408−4503. We found that the high eccentricity of the compact object orbit and the large size of the donor star imply Roche lobe overflow (RLO) around the periastron. It is also likely that a fraction of the outer layers of the photosphere of the donor star are lost from the Lagrangian point L2 during the periastron passages. On the basis of these findings, we discuss the flaring variability of IGR J08408−4503 assuming the presence of an accretion disc. We point out that IGR J08408−4503 may not be the only SFXT with an accretion disc fueled by RLO. These findings open a new scenario for accretion mechanisms in SFXTs, since most of them have so far been based on the assumption of spherically symmetric accretion.

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