Data reduction for stellar speckle interferograms of binary stars based on the shift-and-add method

Shift-and-add (SAA) is a simple image processing procedure. SAA was devised to reconstruct a diffraction-limited image from atmospherically degraded stellar images. Recently SAA has been applied to biological imaging. There are several variants of SAA. Here proposed is an SAA procedure incorporated with unsharp masking (USM). The SAA procedure proposed here encompasses an extended version of USM. The proposed SAA method retains the simplicity and easiness, and the basic features of SAA. The effectiveness of the proposed method is examined by restoring atmospherically degraded solar images. It is shown that the USM SAA reconstructed image exhibits high contrast and reveals fine structures blurred by atmospheric turbulence. It is also shown that the USM SAA performs better with a data frame selection scheme.

As an astronomical image post-processing technique, deconvolution from wavefront sensing (DWFS) is a powerful and low cost method for adaptive optics (AO) images reduction. It is based on deconvolution of short exposure images and simultaneous measuring wavefront sensor data, both are provided by adaptive optics system to improve the quality of images. However, for extended or dim sources observing, limited precision of the Wave Front Sensor (WFS) will lead to inferior correction quality of AO images, also these can hardly enhanced by DWFS method. We show here a simple and efficient solution, which combines the DWFS method with a shift-and-add (SAA) image reconstruction technique, designed for reduction of astronomical data obtained with AO system, especially extended objects. This scheme has been applied to the upgraded 61-actuator Shack-Hartmann based adaptive optics system, partially primary corrected extended object images at Yunnan observatory 1.2m telescope for astronomical high resolution imaging. Experimental result of Mars was presented.

Video recordings of images of binary stars at the focus of a 0.36m telescope have been used to select images recorded in instants of good seeing. The selected images have been analysed to give separations and position angles for the binary systems which are in good agreement with values predicted from previous observations. In these exploratory observations it has been shown that separations of 0.9 arcseconds can be measured with an accuracy of ~2% and position angles to ~1–2 degrees when the average seeing was ~1.3 arcseconds. These observations demonstrated that the diffraction limit of the telescope could be reached when the seeing was a factor of 2–3 greater than it. A binary with three magnitudes difference in the brightness of its components has been measured with comparable accuracy although difficulties are anticipated for binaries with components closer than ~2 arcseconds with this magnitude difference. The limiting magnitude is determined by the need to limit exposure times of individual frames to be comparable with or less than the atmospheric coherence time.

We present 549 observations of 181 primarily southern binary stars. Of these, 32 are high-quality nondetections, meaning that, if binary, the system had a separation below the diffraction limit at the time of the observation, and relative astrometry is presented for the remaining 517 observations. In addition, a magnitude difference measure is reported in 312 cases in which the observation was judged to be of sufficient quality to have little decorrelation of the speckle pattern of the secondary relative to the primary star. These data were obtained from speckle observations taken at the Lowell-Tololo 0.6 m telescope at Cerro Tololo Inter-American Observatory using a fast-readout CCD detector during 2001 November. Results from an astrometric measurement precision study indicate that the measures have typical uncertainties of 12.2 ± 1.4 mas in separation and 128 ± 021 in position angle with little systematic error. The magnitude differences presented show good agreement with values in the Hipparcos catalog where comparisons can be made. Their uncertainties are also characterized; they show a typical value of 0.18 mag per 2 minute observation. Four systems of particular interest are discussed.

Context. Eclipsing, spectroscopic double-lined (SB2) binaries remain the prime source of precise and accurate fundamental properties of stars. Furthermore, high-cadence spectroscopic observations of the eclipse phases allow us to resolve the Rossiter-McLaughlin (RM) effect, whose modelling offers the means to probe spin-orbit misalignment in binaries. Aims. We aim to develop a method that provides precise and accurate measurements of radial velocities (RVs) of both binary components, including the in-eclipse orbital phases where line profiles are subject to large distortions due to the RM effect. We also intend to separate spectral contributions of the primary and secondary components in the velocity space in order that a time series of the separated spectroscopic signals can be obtained throughout the binary orbit, preserving any line-profile variability (LPV) that might be present in either or both of those spectroscopic contributions. Methods. In this study, we provide a generalisation of the least-squares deconvolution (LSD) method to SB2 systems. Our LSD-Binary algorithm is capable of working with both in-eclipse and out-of-eclipse spectra as input, and delivers the LSD profiles, LSD-based model spectra, and precise RVs of both binary components as output. We offer an option to account for the RM effect in the calculation of the initial guess LSD profiles and components’ flux ratio, such that the effect can be modelled within the algorithm itself. In that case, the algorithm delivers both the LSD profiles and RVs, which are no longer distorted by the RM effect. Otherwise, when geometry of the RM effect is ignored in the calculation of the initial guess, the LSDBinary algorithm delivers an RV curve that contains contributions from both the orbital motion of the star and spectral line distortions due to the RM effect. Results. In this study, we provide an extensive test of the LSDBinary software package on simulated spectra of artificial binaries resembling Algol-type systems and detached binaries with similar components. We study the effects of signal-to-noise ratios (S/N) of input spectra, the resolving power of the instrument, uncertain atmospheric parameters of stars, and orbital properties of the binary system on the resulting LSD profiles and RVs measured from them. We find that atmospheric parameters have a negligible effect on the shape of the computed LSD profiles while affecting mostly their global scaling. High-resolution (R ≳ 60 000) spectroscopic observations are required in order to investigate the RM effect in detail, although a medium resolving power of R ≈ 25 000–30 000 might suffice when the amplitude of the effect is large. Our results are barely sensitive to the S/N of the input spectra provided they contain a sufficient number of spectral lines, such as in A-type and later stars. Finally, the orbital inclination angle and the components’ radii ratio are found to have the largest effect on the shapes of the LSD profiles and RV curves extracted from them. Conclusions. The LSDBinary algorithm is specifically developed to perform detailed spectroscopic studies of eclipsing SB2 systems whose orbital configuration and components’ atmospheric parameters are estimated by other means. The algorithm is well suited to study the RM effect, as well as to compute the separated LSD profiles of both binary components from the observed composite in-eclipse spectra of SB2 systems.

Binary Transneptunian Objects (TNOs) have remained virtually unaltered since the formation of the solar system. They can therefore provide valuable insights into the history and properties of objects from the outer solar system, such as object compositions and dynamical history, including the effects of planetary migration on primordial planetesimal populations. Benecchi et al. 2009 measured the colours of 23 TNO binaries using the Hubble Space Telescope (HST), reporting a strong correlation between primary-secondary F606W-F814W colours. Marsset et al. 2020 extended this work into the NIR, adding a further three TNO binary objects with accurate colour measurements made using the Gemini-North telescope which indicated a similar colour correlation in the infrared.   We aim to increase the number of binary TNOs with accurate NIR colour measurements by reprocessing data available in the HST archive using a consistent MCMC-based point spread function (PSF)-fitting algorithm. We explore both the position and brightness parameter space for the binary components. Tiny Tim (Krist et al., 2011) PSFs are generated for each component and planted in a model image that is compared with the HST archive image to identify best-fit PSF parameter values. These values are then used to produce and subtract a final model image, providing accurate likelihood estimates for the in-image position and photometric brightness of each component.   We will present the results of applying the algorithm to archival data of 24 known binaries, including both optical and NIR colour measurements of both binary components. We will also provide a measure of our sensitivity to binary component separations and brightness ratios. Our results will be compared to the correlated colours observed by Benecchi et al. (2009) and Marsset et al. (2020). 

Die Serie Communications in Asteroseismology (CoAst) stellt eine international gefragte Plattform für wissenschaftliche Publikationen der neuesten Forschungsergebnisse auf dem Gebiet der Asteroseismologie dar. Forschungsgegenstand der Asteroseismologie sind veränderliche und pulsierende Sterne. Neben den halbjährlich erscheinenden regulären Ausgaben mit Beiträgen aus der laufenden Forschung werden auch Sonderausgaben für Konferenzberichte bzw. Programmhandbücher herausgegeben. Volume 153 beinhaltet eine Vielzahl von Arbeiten mit Ergebnissen aus erdgebundenen und satellitengestüzten Beobachtungen pulsierender Sterne sowie über den Vergleich mit theoretischen Modellen. Erstmals berichtet auch das von der EU eingerichtete Forschungsnetzwerk HELAS - European Helio- and Asteroseismology Network - über neue Instrumente und Strukturen für den Daten- und Wissensaustausch unter Astronomen.

GW170817 is the very first observation of gravitational waves originating from the coalescence of two compact objects in the mass range of neutron stars, accompanied by electromagnetic counterparts, and offers an opportunity to directly probe the internal structure of neutron stars. We perform Bayesian model selection on a wide range of theoretical predictions for the neutron star equation of state. For the binary neutron star hypothesis, we find that we cannot rule out the majority of theoretical models considered. In addition, the gravitational-wave data alone does not rule out the possibility that one or both objects were low-mass black holes. We discuss the possible outcomes in the case of a binary neutron star merger, finding that all scenarios from prompt collapse to long-lived or even stable remnants are possible. For long-lived remnants, we place an upper limit of 1.9 kHz on the rotation rate. If a black hole was formed any time after merger and the coalescing stars were slowly rotating, then the maximum baryonic mass of non-rotating neutron stars is at most , and three equations of state considered here can be ruled out. We obtain a tighter limit of for the case that the merger results in a hypermassive neutron star.

view Abstract Citations (6) References (7) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Anomalous flare activity on UV Ceti. Lacy, C. H. ; Evans, D. S. ; Quigley, R. J. ; Sandmann, W. H. Abstract During monitoring of UV Ceti for flare activity in the fall of 1976 an interval of anomalous activity characterized by fewer flares of greater intensity, but preserving the same total flare energy, was observed. The phenomena are unrelated to change in the separation between the binary components, and the cause is at present unknown. Publication: The Astrophysical Journal Supplement Series Pub Date: July 1978 DOI: 10.1086/190530 Bibcode: 1978ApJS...37..313L Keywords: Astronomical Photometry; Binary Stars; Flare Stars; Anomalies; Energy Distribution; Statistical Analysis; Tables (Data); Ubv Spectra; Astrophysics; Flare Stars:Visual Binaries full text sources ADS | data products SIMBAD (1)

During a last decade also, the coal seam gas (CSG) industry in Australia, particular in Queensland has grown rapidly due to large export-oriented LNG projects. Consequently, many CSG fields were developed to meet the necessary gas demand for these LNG plants as well as to supply domestic need. A key requirement in gas supply from the CSG reservoirs, important for conditioning the feed and operating conditions of the LNG plants is the correct forecasting of the gas quality variation with time. In particular, CO2 concentration in the produced gas is likely to trend upwards in the long term. The impact of this dictates the LNG plant gas pre-conditioning and may also raise environmental concerns. Because of these investment sensitive and environmentally crucial reasons, it is important to predict how this is likely to play out.The main objective of this study is to find a method to enable prediction of gas concentration profile as it evolves with time. Most of the previous methods in the literature roughly predict future gas concentrations, but the models are subject to considerable uncertainties, and are not underpinned by solid experimental data on multi-component gas sorption in real coals. This study seeks to utilized both experimental (single and binary components) data and available field observed data to provide further insight into this issue.Adsorption is the main storage mechanism whereas desorption, diffusion and Darcy flow are key production and transport processes in coals investigated in this study using experimental methods and numerical simulation.For diffusion and desorption, coals from different areas were utilized and the single component isotherms for CH4 and CO2 were measured. These isotherms were used with existing theory, namely Ideal Adsorption Solution and correlations to validate measured binary component Isotherms. Using the methodology and workflow, the attempt was made to predict binary component isotherms with different feed ratios of adsorbed initial CH4:CO2. The resultant binary isotherms with different CH4:CO2 ratios were used in the numerical model as input to model to predict of long term CH4:CO2 production profiles.As part of coal characterisation, coal physical properties serve as input to the mathematical modelling. experimental coal physical properties and sorption characteristics are used to generate the coal Diffusivity coefficient. The intention is to compare the results from the numerical model using Diffusivity coefficient against the alternative input, namely the desorption time constant (measured as desorption days in a canister test). Two types of coals used in this study originated from Surat Basin. Unsurprisingly, the results of the using Diffusivity coefficient provide much more accurate results.In the simulation study, the results from numerical model matched reasonable well with actual production data and the forecast gas concentration production trends for long term are taken to be reasonably accurate.There are some limitations in the method used to obtain the binary component Isotherm machine (using a BG Belsorp), which can be improved in future study similar to this work.The current study can be extended to multicomponent version with more accurate experimental measurements. However, the outcome from the present study provides a useful reservoir monitoring tool to understand the long term binary gas production trends (CH4:CO2) and the relation with coal physical properties as well as coal seam gas transport mechanism due to pressure and saturation changes during production life span.

In this paper we calculate the probability that existing binaries in various stellar systems have suffered exchange collisions with single stars. After such a collision the former single star is one of the new binary components while the star it replaces is ejected from the binary. In the solar neighborhood, about one visual binary in 10/sup 3/ has a nonprimordial stellar component which it captured from the general field. The two stellar components of such a binary can have very different ages and chemical compositions. Dynamically, such binaries are indistinguishable from primordial binaries except for their high average orbital eccentricities. It is likely that many of the x-ray binaries in the Galactic disk and bulge have captured their relativistic components by exchange collisions. In open clusters most binaries with semimajor axes aapproximately-greater-than10/sup 3/ AU have suffered one or more exchange collisions. In the cores of dense globular clusters, this is true for binaries with aapproximately-greater-than1 AU.

As a part of a larger program to measure physical properties of PMS binary systems, we have observed the PMS quadruple system HD 98800 (aka TW Hya 4A) with the Keck Interferometer (KI), and resolved the two separate spectroscopic binary components of the system. In particular we have observed the HD 98800 North (B) binary component on multiple epochs, and integrating our data with the double-lined spectroscopic orbit from Torres et al [15]s has allowed us to estimate a physical orbit for the B system. This orbit in turn yields relatively accurate (8%) mass estimates of the component stars, and an independent system distance and component luminosity estimates. Comparisons between the estimated physical parameters for the low-mass HD 98800 B components with mass-luminosity models of PMS stars, and implications for the age of HD 98800 are discussed.

Magnetic activity signatures in the atmosphere of active stars can be used to place constrains on the underlying processes of flux transport and dynamo operation in its convective envelope. The ‘solar paradigm’ for magnetic activity suggests that the magnetic field is amplified and stored at the base of the convection zone. Once a critical field strength is exceeded, perturbations initiate the onset of instabilities and the growth of magnetic flux loops, which rise through the convection zone, emerge at the stellar surface, and eventually lead to the formation of starspots and active regions. In close binaries, the proximity of the companion star breaks the rotational symmetry. Although the magnitude of tidal distortions is rather small, non‐linear MHD simulations have nevertheless shown in the case of main‐sequence binary components that they can cause non‐uniform surface distributions of flux tube eruptions. The present work extends the investigation to post‐mainsequence components to explore the specific influence of the stellar structure on the surface pattern of erupting flux tubes. In contrast to the case of main‐sequence components, where the consistency between simulation results and observations supports the presumption of a solar‐like dynamo mechanism, the numerical results here do not recover the starspot properties frequently observed on evolved binary components. This aspect points out an insufficiency of the applied flux tube model and leads to the conclusion that additional flux transport and possibly amplification mechanisms have to be taken into account. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The numerical investigation of the stability of motion of a mass element ejected from a component of a binary star system has been made. The small mass element is initially taken as rest and the binary components are assumed to be revolving in a circular orbit around the center of mass. Only planar motion has been considered. The stability of motion has been investigated using the Poincare surface of section method

Eclipsing binary stars are gratifying objects because of their unique geometrical properties upon which all important physical parameters such as masses, radii, temperatures, luminosities and distance may be obtained in absolute scale. This poses strict demand on the model to be free of systematic effects that would influence the results later used for calibrations, catalogs and evolution theory. We present an objective scheme of obtaining individual temperatures of both binary system components by means of color-index constraining, with the only requirement that the observational data-set is acquired in a standard photometric system. We show that for a modest case of two similar main-sequence components the erroneous approach of assuming the temperature of the primary star from the color index yields temperatures which are systematically wrong by ∼ 100K.