Principles and Applications of the Synchronous Network of Remote Telescopes

Zhilyaev, B. E.; Romanyuk, Ya. O.; Svyatogorov, O. A.; Verlyuk, I. A.

doi:10.1515/astro-2017-0081

Cited by 11 publications

(20 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We also note that, after a rapid decline in error as the S/N increases, the asymptotic behavior of σm for very large S/N may explain, in part, why it is so difficult to achieve photometric precisions smaller than a few milli-mag. While at S/N ∼ 100 we predict σm ∼ 11 [mmag], at S/N ∼ 200 we would have σm ∼ 5 [mmag], consistent with actual measurements, as quoted by Zhilyaev et al (2005) (see also Warner (2006, Section 4 and Table 4.1)).…”

Section: Analysis and Interpretation Of The 2d Cramér-rao Boundsupporting

confidence: 89%

Analysis of the Cramér-Rao Bound in the Joint Estimation of Astrometry and Photometry

Mendez

Silva²,

Orostica³

et al. 2014

Publications of the Astronomical Society of the Pacific

View full text Add to dashboard Cite

In this paper we use the Cramér-Rao lower uncertainty bound to estimate the maximum precision that could be achieved on the joint simultaneous (or 2D) estimation of photometry and astrometry of a point source measured by a linear CCD detector array.1 On leave at the European Southern Observatory, Casilla 19001, Santiago, Chile.-2 -We develop exact expressions for the Fisher matrix elements required to compute the Cramér-Rao bound in the case of a source with a Gaussian light profile. From these expressions we predict the behavior of the Cramér-Rao astrometric and photometric precision as a function of the signal and the noise of the observations, and compare them to actual observations -finding a good correspondence between them.From the Cramér-Rao bound we obtain the well known fact that the uncertainty in flux on a Poisson-driven detector, such as a CCD, goes approximately as the square root of the flux. However, more generally, higher order correction factors that depend on the ratio B/F or F/B (where B is the background flux per pixel and F is the total flux of the source), as well as on the properties of the detector (pixel size) and the source (width of the light profile), are required for a proper calculation of the minimum expected uncertainty bound in flux. Overall the Cramér-Rao bound predicts that the uncertainty in magnitude goes as (S/N ) −1 under a broad range of circumstances.As for the astrometry we show that its Cramér-Rao bound also goes as (S/N ) −1 but, additionally, we find that this bound is quite sensitive to the value of the backgroundsuppressing the background can greatly enhance the astrometric accuracy.We present a systematic analysis of the elements of the Fisher matrix in the case when the detector adequately samples the source (oversampling regime), leading to closed-form analytical expressions for the Cramér-Rao bound. We show that, in this regime, the joint parametric determination of photometry and astrometry for the source become decoupled from each other, and furthermore, it is possible to write down expressions (approximate to first order in the small quantities F/B or B/F ) for the expected minimum uncertainty in flux and position. These expressions are shown to be quite resilient to the oversampling condition, and become thus very valuable benchmark tools to estimate the approximate behavior of the maximum photometric and astrometric precision attainable under pre-specified observing conditions and detector properties.

show abstract

Section: Analysis and Interpretation Of The 2d Cramér-rao Boundsupporting

confidence: 89%

Analysis of the Cramér-Rao Bound in the Joint Estimation of Astrometry and Photometry

Mendez

Silva²,

Orostica³

et al. 2014

Publications of the Astronomical Society of the Pacific

View full text Add to dashboard Cite

show abstract

“…Possibly, the 160 s periodic oscillations observed by Houdebine et al (1993) observed by Zhilyaev et al (2000) in EV Lac flares have the same nature.…”

Section: Introductionmentioning

confidence: 78%

Acoustic oscillations in solar and stellar flaring loops

Nakariakov

Tsiklauri

Kelly

et al. 2004

A&A

109

111

View full text Add to dashboard Cite

Abstract. Evolution of a coronal loop in response to an impulsive energy release is numerically modelled. It is shown that the loop density evolution curves exhibit quasi-periodic perturbations with the periods given approximately by the ratio of the loop length to the average sound speed, associated with the second standing harmonics of an acoustic wave. The density perturbations have a maximum near the loop apex. The corresponding field-aligned flows have a node near the apex. We suggest that the quasi-periodic pulsations with periods in the range 10-300 s, frequently observed in flaring coronal loops in the radio, visible light and X-ray bands, may be produced by the second standing harmonic of the acoustic mode.

show abstract

“…The cited Crimean results have been obtained from the flare monitoring with a rather low time resolution of about 20 s. The technique of digital filtering recently employed by Zhilyaev et al (2000) allows the time resolution to improve by 2 orders of magnitude. The first application of the technique resulted in the discovery of HFO in brightness and colors of the detected flares (Zhilyaev et al 2000(Zhilyaev et al , 2003.…”

Section: Introductionmentioning

confidence: 99%

Fast colorimetry of the flare star EV Lacertae fromUBVRIobservations in 2004

Zhilyaev

Romanyuk

Svyatogorov

et al. 2007

A&A

Self Cite

View full text Add to dashboard Cite

Aims. We report results of a quantitative colorimetric UBVRI analysis of two flare events on the red dwarf EV Lac. The photometric data were obtained in September 2004, during the multi-site synchronous monitoring from the four observatories in Ukraine, Russia, Greece, and Bulgaria. These observations confirmed the presence of small-scale high-frequency oscillations (HFO) initially detected by Rodonó (1974, A&A, 32, 337) and recently reconfirmed by the authors. Here we discuss the color characteristics of flares and HFO. Methods. Colorimetric analysis had been performed with the help of the time tracks in the UBVRI color-color diagrams from the earliest phase of flare development. Digital filtering technique was used to evaluate the time-dependent color indices. Results. As can be clearly seen in the diagrams, color indices oscillate on a time scale of seconds, far exceeding instrumental errors. Regarding the HFO, we conclude that the bulk of a flare oscillates during a major part of its lifetime between the states of hydrogen plasma opaque and transparent in the Balmer continuum. We find that at the peaks of oscillations the color tracks drift into the regions of color-color diagrams corresponding to a blackbody radiation, which provides an estimate of color temperatures from 17 000 to 22 000 K. We also find that flares cover ∼1% of the stellar disc.

show abstract

Principles and Applications of the Synchronous Network of Remote Telescopes

Cited by 11 publications

References 0 publications

Analysis of the Cramér-Rao Bound in the Joint Estimation of Astrometry and Photometry

Analysis of the Cramér-Rao Bound in the Joint Estimation of Astrometry and Photometry

Acoustic oscillations in solar and stellar flaring loops

Fast colorimetry of the flare star EV Lacertae fromUBVRIobservations in 2004

Contact Info

Product

Resources

About