scholarly journals Modelling energy-dependent pulsar light curves due to curvature radiation

2018 ◽  
Author(s):  
Monica Barnard ◽  
Christo Venter ◽  
Alice K. Harding ◽  
Constantinos Kalapotharakos
Keyword(s):  
Light Curves ◽  
Curvature Radiation ◽  
Energy Dependent

scholarly journals X-ray Flux and Spectral Variability of Blazar H 2356-309

Galaxies ◽  
2020 ◽  
Vol 8 (3) ◽  
pp. 59
Author(s):  
Kiran A. Wani ◽  
Haritma Gaur
Keyword(s):  
Spectral Analysis ◽  
Light Curves ◽  
Synchrotron Emission ◽  
Ratio Analysis ◽  
Power Law Model ◽  
Parabolic Model ◽  
Spectral Variability ◽  
X Ray ◽  
Flux Variability ◽  
Energy Dependent

We present the results of timing and spectral analysis of the blazar H 2356-309 using XMM-Newton observations. This blazar is observed during 13 June 2005–24 December 2013 in total nine observations. Five of the observations show moderate flux variability with amplitude 1.7–2.2%. We search for the intra-day variability timescales in these five light curves, but did not find in any of them. The fractional variability amplitude is generally lower in the soft bands than in the hard bands, which is attributed to the energy dependent synchrotron emission. Using the hardness ratio analysis, we search for the X-ray spectral variability along with flux variability in this source. However, we did not find any significant spectral variability on intra-day timescales. We also investigate the X-ray spectral curvature of blazar H 2356-309 and found that six of our observations are well described by the log parabolic model with α = 1.99–2.15 and β = 0.03–0.18. Three of our observations are well described by power law model. The break energy of the X-ray spectra varies between 1.97–2.31 keV. We investigate the correlation between various parameters that are derived from log parabolic model and their implications are discussed.

scholarly journals Modelling energy-dependent pulsar light curves

2017 ◽  
Vol 13 (S337) ◽  
pp. 120-123
Author(s):  
Christo Venter ◽  
Monica Barnard ◽  
Alice K. Harding ◽  
Constantinos Kalapotharakos
Keyword(s):  
Light Curve ◽  
Energy Range ◽  
Light Curves ◽  
Good Resolution ◽  
Pulsar Magnetosphere ◽  
Energy Bands ◽  
Light Cylinder ◽  
Energy Dependent

AbstractIn recent years, surprise discoveries of pulsed emission from the Crab and Vela pulsars above 100 GeV have drawn renewed attention to this largely unexplored region of the energy range. In this paper, we discuss example light curves due to curvature emission, with good resolution in the different energy bands. Continued light curve modelling may help to discriminate between different emission mechanisms, as well as constrain the location where emission is produced within the pulsar magnetosphere, including regions beyond the light cylinder.

scholarly journals X-ray variability of accreting black hole systems: propagating-fluctuation scenario

2006 ◽  
Vol 2 (S238) ◽  
pp. 319-320
Author(s):  
Patricia Arévalo ◽  
Phil Uttley ◽  
Ian McHardy
Keyword(s):  
Black Hole ◽  
Light Curves ◽  
Time Lags ◽  
Spectral Densities ◽  
Energy Bands ◽  
X Ray ◽  
Fundamental Properties ◽  
Power Spectral ◽  
Power Spectral Densities ◽  
Energy Dependent

AbstractPropagating fluctuation models can reproduce fundamental properties of the variability observed in the X-ray light curves of accreting black hole systems. We explore this type of model and show how extended emitting regions introduce at the same time energy dependent power spectral densities (PSD) and time lags between different energy bands.

scholarly journals Modelling Phase-resolved Spectra and Energy-dependent Light Curves of the Vela Pulsar to Scrutinize its GeV Emission Mechanism

2021 ◽  
Author(s):  
Monica Barnard ◽  
Christo Venter ◽  
Alice Kust Harding ◽  
Constantinos Kalapotharakos ◽  
Tyrel J. Johnson
Keyword(s):  
Light Curves ◽  
Emission Mechanism ◽  
Vela Pulsar ◽  
Energy Dependent

Distance to SN 1987A and the LMC

1999 ◽  
Vol 190 ◽  
pp. 549-554
Author(s):  
Nino Panagia
Keyword(s):  
Angular Size ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Light Curves ◽  
Distance Modulus ◽  
Absolute Size ◽  
Sn 1987A

Using the new reductions of the IUE light curves by Sonneborn et al. (1997) and an extensive set of HST images of SN 1987A we have repeated and improved Panagia et al. (1991) analysis to obtain a better determination of the distance to the supernova. In this way we have derived an absolute size of the ringRabs= (6.23 ± 0.08) x 1017cm and an angular sizeR″ = 808 ± 17 mas, which give a distance to the supernovad(SN1987A) = 51.4 ± 1.2 kpc and a distance modulusm–M(SN1987A) = 18.55 ± 0.05. Allowing for a displacement of SN 1987A position relative to the LMC center, the distance to the barycenter of the Large Magellanic Cloud is also estimated to bed(LMC) = 52.0±1.3 kpc, which corresponds to a distance modulus ofm–M(LMC) = 18.58±0.05.

Quasi-Periodic Oscillations in Dwarf Novae

1979 ◽  
Vol 46 ◽  
pp. 77-88
Author(s):  
Edward L. Robinson
Keyword(s):  
Binary Systems ◽  
Outer Edge ◽  
Light Curves ◽  
Close Binary ◽  
Bright Spot ◽  
Dwarf Novae ◽  
Periodic Oscillations ◽  
High Frequencies ◽  
Short Period ◽  
Typical Time

Three distinct kinds of rapid variations have been detected in the light curves of dwarf novae: rapid flickering, short period coherent oscillations, and quasi-periodic oscillations. The rapid flickering is seen in the light curves of most, if not all, dwarf novae, and is especially apparent during minimum light between eruptions. The flickering has a typical time scale of a few minutes or less and a typical amplitude of about .1 mag. The flickering is completely random and unpredictable; the power spectrum of flickering shows only a slow decrease from low to high frequencies. The observations of U Gem by Warner and Nather (1971) showed conclusively that most of the flickering is produced by variations in the luminosity of the bright spot near the outer edge of the accretion disk around the white dwarf in these close binary systems.

The Eclipsing Binary WX Eridani

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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