scholarly journals The wind-wind collision hole in eta Car

2016 ◽  
Vol 12 (S329) ◽  
pp. 186-190
Author(s):  
A. Damineli ◽  
M. Teodoro ◽  
N. D. Richardson ◽  
T. R. Gull ◽  
M. F. Corcoran ◽  
...  
Keyword(s):  
Light Curve ◽  
Accurate Determination ◽  
Physical Parameters ◽  
Electromagnetic Spectrum ◽  
Orbital Eccentricity ◽  
Orbital Parameters ◽  
Eta Carinae ◽  
Secondary Star ◽  
Reflected Light

AbstractEta Carinae is one of the most massive observable binaries. Yet determination of its orbital and physical parameters is hampered by obscuring winds. However the effects of the strong, colliding winds changes with phase due to the high orbital eccentricity. We wanted to improve measures of the orbital parameters and to determine the mechanisms that produce the relatively brief, phase-locked minimum as detected throughout the electromagnetic spectrum. We conducted intense monitoring of the He ii λ4686 line in η Carinae for 10 months in the year 2014, gathering ~300 high S/N spectra with ground- and space-based telescopes. We also used published spectra at the FOS4 SE polar region of the Homunculus, which views the minimum from a different direction. We used a model in which the He ii λ4686 emission is produced by two mechanisms: a) one linked to the intensity of the wind-wind collision which occurs along the whole orbit and is proportional to the inverse square of the separation between the companion stars; and b) the other produced by the ‘bore hole’ effect which occurs at phases across the periastron passage. The opacity (computed from 3D SPH simulations) as convolved with the emission reproduces the behavior of equivalent widths both for direct and reflected light. Our main results are: a) a demonstration that the He ii λ4686 light curve is exquisitely repeatable from cycle to cycle, contrary to previous claims for large changes; b) an accurate determination of the longitude of periastron, indicating that the secondary star is ‘behind’ the primary at periastron, a dispute extended over the past decade; c) a determination of the time of periastron passage, at ~4 days after the onset of the deep light curve minimum; and d) show that the minimum is simultaneous for observers at different lines of sight, indicating that it is not caused by an eclipse of the secondary star, but rather by the immersion of the wind-wind collision interior to the inner wind of the primary.

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

2020 ◽  
Vol 29 (1) ◽  
pp. 72-80 ◽  
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.

scholarly journals Active Compensation of Radiation Effects on Optical Fibers for Sensing Applications

Sensors ◽  
2021 ◽  
Vol 21 (24) ◽  
pp. 8193
Author(s):  
Sohel Rana ◽  
Austin Fleming ◽  
Nirmala Kandadai ◽  
Harish Subbaraman
Keyword(s):  
Optical Fibers ◽  
Radiation Effects ◽  
Accurate Determination ◽  
Radiation Environment ◽  
Physical Parameters ◽  
Air Cavity ◽  
Sensing Applications ◽  
Fabry Perot ◽  
Radiation Induced

Neutron and gamma irradiation is known to compact silica, resulting in macroscopic changes in refractive index (RI) and geometric structure. The change in RI and linear compaction in a radiation environment is caused by three well-known mechanisms: (i) radiation-induced attenuation (RIA), (ii) radiation-induced compaction (RIC), and (iii) radiation-induced emission (RIE). These macroscopic changes induce errors in monitoring physical parameters such as temperature, pressure, and strain in optical fiber-based sensors, which limit their application in radiation environments. We present a cascaded Fabry–Perot interferometer (FPI) technique to measure macroscopic properties, such as radiation-induced change in RI and length compaction in real time to actively account for sensor drift. The proposed cascaded FPI consists of two cavities: the first cavity is an air cavity, and the second is a silica cavity. The length compaction from the air cavity is used to deduce the RI change within the silica cavity. We utilize fast Fourier transform (FFT) algorithm and two bandpass filters for the signal extraction of each cavity. Inclusion of such a simple cascaded FPI structure will enable accurate determination of physical parameters under the test.

scholarly journals Orbital stability of S-type circumbinary planets

2021 ◽  
Vol 2145 (1) ◽  
pp. 012014
Author(s):  
N Nantanoi ◽  
N Nantanoi ◽  
S Awiphan ◽  
S Komonjinda ◽  
T Bunfong
Keyword(s):  
Orbital Stability ◽  
Physical Parameters ◽  
Orbital Eccentricity ◽  
Stable Orbit ◽  
Orbital Parameters ◽  
Inaccurate Measurement ◽  
Roche Limit ◽  
Orbital Instability ◽  
Circumbinary Planets

Abstract Nowadays, more than 4,000 exoplanets have been discovered, including a hundred of circumbinary planets. In the following work, the orbital variations of 67 S-type circumbinary planets have been studied. Their orbital evolutions for a thousand years are simulated using the REBOUND package. The published physical and orbital parameters of the systems are used to computed the systems’ orbital instability limits: Roche limit and Hill’s sphere. From 67 systems, there are two unstable circumbinary systems: Kepler-420 and GJ 86. Kepler-420 Ab orbit passes into the system’s Roche limit due to its high orbital eccentricity. For GJ 86 Ab, the planet orbits outside its Hill’s sphere. The instability of GJ 86 Ab might be caused by an inaccurate measurement of GJ 86 A physical parameters. Using the GJ 86 A mass obtained from Farihi et al., the planet orbits in the stable orbit zone.

scholarly journals Ground-Based and Space Observations of Interacting Binaries

2011 ◽  
Vol 7 (S282) ◽  
pp. 21-26
Author(s):  
Panagiotis G. Niarchos
Keyword(s):  
Binary Systems ◽  
Accurate Determination ◽  
Space Missions ◽  
Light Curves ◽  
Physical Parameters ◽  
Multi Wavelength ◽  
Low Mass ◽  
Space Observations

AbstractMulti-wavelength observational data, obtained from ground-based and space observations are used to compute the physical parameters of the observed Interacting Binaries (IBs) and study the interactions and physical processes in these systems. In addition, the database of IBs from ground-based surveys and space missions will provide light curves for many thousands of new binary systems for which extensive follow up ground-based observations can be carried out. In certain cases, light curves of superior quality will allow studies of fine effects of stellar activity and very accurate determination of stellar parameters. Moreover, many new discoveries of interesting systems are expected from ground-based all-sky surveys and space missions, including low mass binaries and star-planet binary systems. The most important current and future programs of observations of IBs from ground and space are presented.

scholarly journals The supergiant O + O binary system HD 166734: a new study

2016 ◽  
Vol 12 (S329) ◽  
pp. 402-402 ◽  
Author(s):  
E. Gosset ◽  
L. Mahy ◽  
Y. Damerdji ◽  
C. Nitschelm ◽  
H. Sana ◽  
...  
Keyword(s):  
Binary System ◽  
Light Curve ◽  
Radial Velocity ◽  
Velocity Curve ◽  
Physical Parameters ◽  
Radial Velocity Curve ◽  
X Ray ◽  
Orbital Parameters

AbstractWe present here a modern study of the radial velocity curve and of the photometric light curve of the very interesting supergiant O7.5If + O9I(f) binary system HD 166734. The physical parameters of the stars and the orbital parameters are carefully determined. We also perform the analysis of the observed X-ray light curve of this colliding-wind binary.

scholarly journals The influence of starspots activity on the determination of planetary transit parameters

2009 ◽  
Vol 5 (S264) ◽  
pp. 440-442 ◽  
Author(s):  
Adriana Silva-Válio
Keyword(s):  
Light Curve ◽  
Major Axis ◽  
The Other ◽  
Semi Major Axis ◽  
Active Star ◽  
Orbital Parameters ◽  
Correct Determination ◽  
The Times ◽  
Parent Star

AbstractAs a planet eclipses its parent star, dark spots on the surface of the star may be occulted, causing a detectable variation in the transit light curve. There are basically two effects caused by the presence of spots on the surface of the star which can alter the shape of the light curve during transits and thus preclude the correct determination of the planet physical and orbital parameters. The first one is that the presence of many spots within the latitude band occulted by the planet will cause the depth of the transit in the light curve to be shallower. This will erroneously result in a smaller radius for the planet. The other effect is that generated by spots located close to the limb of the star. In this case, the spots will interfere in the light curve during the times of ingress or egress of the planet, causing a decrease in the transit duration. This in turn will provide a larger value for the semi-major axis of the planetary orbit. Qualitative estimates of both effects are discussed and an example provided for a very active star, such as CoRoTo-2.

scholarly journals First measurement of the total gravitational quadrupole moment of a black widow companion

2020 ◽  
Vol 494 (3) ◽  
pp. 4448-4453
Author(s):  
Guillaume Voisin ◽  
C J Clark ◽  
R P Breton ◽  
V S Dhillon ◽  
M R Kennedy ◽  
...  
Keyword(s):  
Quadrupole Moment ◽  
Accurate Determination ◽  
Light Curves ◽  
Orbital Eccentricity ◽  
Black Widow ◽  
Companion Star ◽  
Quadrupole Component ◽  
Timing Data ◽  
Orbital Precession

ABSTRACT We present the first measurement of the gravitational quadrupole moment of the companion star of a spider pulsar, namely the black widow PSR J2051–0827. To this end, we have re-analysed radio timing data using a new model that is able to account for periastron precession caused by tidal and centrifugal deformations of the star as well as by general relativity. The model allows for a time-varying component of the quadrupole moment, thus self-consistently accounting for the ill-understood orbital period variations observed in these systems. Our analysis results in the first detection of orbital precession in a spider system at $\dot{\omega } = -68{_{.}^{\circ}}6_{-0{_{.}^{\circ}}5}^{+0{_{.}^{\circ}}9}$ yr−1 and the most accurate determination of orbital eccentricity for PSR J2051–0827 with e = (4.2 ± 0.1) × 10−5. We show that the variable quadrupole component is about 100 times smaller than the average quadrupole moment $\bar{Q} = -2.2_{-1}^{+0.6} \times 10^{41} \ {\rm kg\,m^2}$. We discuss how accurate modelling of high-precision optical light curves of the companion star will allow its apsidal motion constant to be derived from our results.

scholarly journals CoRoT target HD 51844: a δ Scuti star in a binary system with periastron brightening

2013 ◽  
Vol 9 (S301) ◽  
pp. 59-62 ◽  
Author(s):  
Markus Hareter ◽  
Margit Paparó
Keyword(s):  
Binary System ◽  
Light Curve ◽  
Radial Velocity ◽  
Frequency Analysis ◽  
Significant Variation ◽  
Orbital Motion ◽  
The Other ◽  
Physical Parameters ◽  
Reflected Light ◽  
Scuti Star

AbstractThe star HD 51844 was observed in the CoRoT LRa02 as a target in the seismology field, which turned out to be an SB2 system. The 117-day light curve revealed δ Scuti pulsations in the range of 6 to 15 d−1 where four frequencies have amplitudes larger than 1.4 mmag, and a rich frequency spectrum with amplitudes lower than 0.6 mmag. Additionally, the light curve exhibits a 3-mmag brightening event recurring every 33.5 days with a duration of about 5 days. The radial velocities from spectroscopy confirmed that the star is an eccentric binary system with nearly identical masses and physical parameters. The brightening event in the light curve coincides with the maximum radial-velocity separation showing that the brightening is in fact caused by tidal distortion and/or reflected light. One component displays large line-profile variations, while the other does not show significant variation. The frequency analysis revealed a quintuplet structure of the four highest-amplitude frequencies, which is due to the orbital motion of the pulsating star.

scholarly journals Semi-Empirical Determination of the Position of RRAB Stars on The H-R Diagram

1998 ◽  
Vol 11 (1) ◽  
pp. 373-373
Author(s):  
J. Jurcsik ◽  
G. Kovács
Keyword(s):  
Light Curve ◽  
Light Curves ◽  
The Other ◽  
Physical Parameters ◽  
Present Sample ◽  
Large Numbers ◽  
Empirical Determination ◽  
The Absolute ◽  
Semi Empirical

In a recent series of papers, it was shown that the metallicity and the absolute V, I and K mean magnitudes of RRab stars can be accurately calculated using only their periods and the low order Fourier parameters of the V light curves. The application of these formulae in conjunction with the synthetic colours of the model atmospheres and with the theoretical pulsation periods enables us to determine all the basic physical parameters (i.e. logL, logT, logM and [Fe/H]) of any variable with an accurate light curve. As a result, we might trace evolutionary tracks on the H—R diagram by plotting the stars with the same mass and metallicity. From a present sample of nearly 300 stars, signs of differences in the evolutionary statescan be suspected but not yet proven. The accumulation of large numbers of precise light and colour curves, onthe one hand, will further improve the empirical formulae and therefore theaccuracy of the derived parameters and, on the other hand, will increase our chances of constructing better-populated empirical evolutionary tracks.

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