scholarly journals Flare Activity in the NGC 1275 Nucleus

1996 ◽  
Vol 171 ◽  
pp. 420-420 ◽  
Author(s):  
N.I. Merkulova ◽  
L.P. Metik
Keyword(s):  
Light Curve ◽  
Seyfert Galaxies ◽  
Crimean Astrophysical Observatory ◽  
Light Curves ◽  
Flare Activity ◽  
Different Types ◽  
Ngc 1275 ◽  
First Time

The simultaneous UBVRI – observations of some Seyfert galaxies have been carried out at Crimean Astrophysical Observatory using the 1.25m telescope. Photometric errors are less than 0.01 mag. By analysis of the NGC 1275 light curves within one night we are discovered at least two types of variability: 1) The flares with the maximal amplitudes of 5 – 30 % in the U-band and durations of 15 – 30 minutes. 2) For the first time we have found rapid red flares. For instance, the red flare on the light curve 22-23.10.1992 lasted ∼ 65 minutes (see Figure. Vertical axes are in magnitudes). The amplitude in the filter I is ∼ 25 % (top panel). The light curve in the U-band is on the bottom panel. Fluxes in the U,B,V-bands were almost constant. One can see the flux decreasing in some filters before this flare. We conclude, that light curve of NGC 1275 nucleus could be represented by a superposition of rapid flares of different types.

scholarly journals TESS photometry of extreme helium stars PV Tel and V821 Cen

2020 ◽  
Vol 495 (1) ◽  
pp. L135-L138 ◽  
Author(s):  
C Simon Jeffery ◽  
Geert Barentsen ◽  
Gerald Handler
Keyword(s):  
Light Curve ◽  
Time Scales ◽  
Characteristic Time ◽  
Satellite Observations ◽  
Light Curves ◽  
Single Site ◽  
Helium Stars ◽  
First Time

ABSTRACT PV Tel variables are extreme helium (EHe) stars known to be intrinsic light and velocity variable on characteristic time-scales of 0.1–25 d. With two exceptions, they are best described as irregular. Light curves have invariably been obtained from single-site terrestrial observatories. We present Transiting Exoplanet Survey Satellite observations of two bright EHe stars, Popper’s star (V821 Cen) and Thackeray’s star (PV Tel). PV Tel is variable on time-scales previously reported. V821 Cen is proven to be variable for the first time. Neither light curve shows any evidence of underlying regularity. Implications are considered.

scholarly journals BVRcIc Observations and Analysis of the Near-Contact Solar Type Eclipsing Binary, V530 Andromedae

2013 ◽  
Vol 2013 ◽  
pp. 1-8
Author(s):  
Ronald G. Samec ◽  
Daniel Flaaten ◽  
James Kring ◽  
Danny R. Faulkner
Keyword(s):  
Light Curve ◽  
Undergraduate Research ◽  
Initial Period ◽  
Light Curves ◽  
Eclipsing Binary ◽  
Massive Component ◽  
Solar Type ◽  
First Time ◽  
Curve Solution ◽  
Light Curve Solution

We present the first precision UBVRcIc light curves, an initial period study, and a simultaneous light curve solution for the near-contact solar type eclipsing binary V530 And. Our observations were taken with the 0.81 m Lowell reflector on 27 and 29 September, 2011, with time being granted from the National Undergraduate Research Observatory (NURO). Our Wilson Devinney Program solution yields a semidetached, V1010 Oph configuration: the more massive component is filling its Roche lobe. The system is apparently approaching contact for the first time. It is not a classic Algol.

Light curve analysis of six totally eclipsing W UMa binaries

2020 ◽  
Author(s):  
Olivera Latković ◽  
Atila Čeki
Keyword(s):  
Light Curve ◽  
Parameter Space ◽  
Curve Analysis ◽  
Light Curves ◽  
Evolutionary Status ◽  
Search Procedure ◽  
Light Curve Analysis ◽  
Short Period ◽  
Mass Ratios ◽  
First Time

Abstract We analyze multicolor light curves of six totally eclipsing, short-period W UMa binaries and derive, for the first time, their orbital and stellar parameters. The mass ratios are established robustly through an automated q-search procedure that performs an heuristic survey of the parameter space. Five stars belong to the W and one to the A subtype. The mass ratios range from 0.23 to 0.51 and the fillouts from $10\%$ to $15\%$. We estimate the ages and discuss the evolutionary status of these objects in comparison with a sample of other short-period W UMa binaries from the literature.

Phase difference between long-term magnetic feature activity and flare activity of solar-type stars

2018 ◽  
Vol 13 (S340) ◽  
pp. 217-220 ◽  
Author(s):  
Han He ◽  
Huaning Wang ◽  
Mei Zhang ◽  
Ahmad Mehrabi ◽  
Yan Yan ◽  
...  
Keyword(s):  
Light Curve ◽  
Phase Difference ◽  
Light Curves ◽  
Magnetic Feature ◽  
Flare Activity ◽  
Source Regions ◽  
Rotational Modulation ◽  
Stellar Flares ◽  
Solar Type

AbstractIn the light curves of some solar-type stars, both rotational modulation (caused by corotating bright or dark magnetic features) and flare phenomena can be seen simultaneously. Based on these light curve observations, the relation between stellar magnetic feature activity (reflected by the rotational modulation component of the light curves) and flare activity can be investigated. Here, we analyze the light curve data of a flare-abundant solar-type star, KIC 6034120, observed with Kepler space telescope, and describe magnetic feature activity property by fluctuation range of light curves and flare activity property by time occupation ratio of flares. Distinct phase difference between long-term magnetic feature activity and flare activity is found for this star, which indicates that the source regions of stellar flares (e.g., starspots) on this star do not dominate the rotational modulation of light curves, yet they might be related to a same stellar dynamo process.

scholarly journals The Nature of V1464 Aql: A New Ellipsoidal Variable with a δ Scuti Component

2013 ◽  
Vol 30 ◽  
Author(s):  
H. A. Dal ◽  
E. Sipahi
Keyword(s):  
Primary Component ◽  
Light Curves ◽  
The Other ◽  
Close Binaries ◽  
Mass Ratio ◽  
Pulsating Stars ◽  
Different Types ◽  
Scuti Star ◽  
Linear Fit ◽  
First Time

AbstractTaking into account the results obtained from the models and analyses of the BVRI light curves, we discuss the nature of V1464 Aql. The analyses indicated that the mass ratio of the system is q = 0.71 ± 0.02, while the inclination of the system (i) is 38°.45 ± 0°.22. Taking the primary component’s temperature as 7420 ± 192 K, we found that the temperature of the secondary is 6232 ± 161 K. The mass of the primary component was found to be 1.74 ± 0.05 M⊙, while it is 1.23 ± 0.01 M⊙ for the secondary. The primary component’s radius was found to be 2.10 ± 0.05 R⊙, while it was found as 1.80 ± 0.01 R⊙ for the secondary. Revealing that the system should not exhibit any eclipses, we demonstrated that the main variation with large amplitude should be caused due to the ellipsoidal effect. Indeed, the Fourier analysis also supported the result. For the first time in the literature, we revealed that the primary component is a δ Scuti star. The period of pulsation was found to be 58.482 ± 0.002, 58.482 ± 0.001, 60.966 ± 0.002, and 60.964 ± 0.003 min in BVRI bands, respectively. We plotted V1464 Aql in the log (Porb)–log (Ppulse) plane. Using more than 160 binaries, whose one or both components are pulsating, we derived a new linear fit in the log (Porb)–log (Ppulse) plane for each type of binary. Using the linear fit of each group, we obtained new calibrations between log (Porb) and log (Ppulse) for different types of pulsating stars. In addition, a calibration has been obtained for the first time for the pulsating stars with spectral types O and B. V1464 Aql seems to be located near the other ellipsoidal and close binaries. Thus, we listed V1464 Aql as a new candidate for the ellipsoidal variables with a δ Scuti component.

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.

Probabilistic Assessment of Reliability and Risk Values by Certification Results

2020 ◽  
pp. 52-67
Author(s):  
Vladimir A. Lapin ◽  
Erken S. Aldakhov ◽  
S. D. Aldakhov ◽  
A. B. Ali
Keyword(s):  
Seismic Risk ◽  
Housing Stock ◽  
Seismic Resistance ◽  
Probabilistic Assessment ◽  
Quantitative Estimates ◽  
Different Types ◽  
Reduce Risk ◽  
First Time ◽  
Structural Solutions ◽  
Practical Recommendations

For the first time in Almaty full passport of apartment stock of multiapartment building was carried out. The structure of the housing stock was revealed with the allocation of groups of buildings according to structural solutions and assessment of their seismic resistance. Based on the results of certification, quantitative estimates of failure probability values for different types of buildings were obtained. Formulas for estimation of quantitative value of seismic risk are obtained. The number of deaths in the estimated zem-shakes was estimated. The results of the assessments will be used for practical recommendations to reduce risk and expected losses in possible earthquakes.

The Small State Challenge

2018 ◽  
Author(s):  
Jack Corbett ◽  
Wouter Veenendaal
Keyword(s):  
Comparative Politics ◽  
Institutional Design ◽  
Small States ◽  
Small State ◽  
Informal Politics ◽  
Different Types ◽  
Approach Method ◽  
Key Terms ◽  
First Time

Chapter 1 introduces the main arguments of the book; outlines the approach, method, and data; defines key terms; and provides a chapter outline. Global theories of democratization have systematically excluded small states, which make up roughly 20 per cent of countries. These cases debunk mainstream theories of why democratization succeeds or fails. This book brings small states into the comparative politics fold for the first time. It is organized thematically, with each chapter tackling one of the main theories from the democratization literature. Different types of data are examined—case studies and other documentary evidence, interviews and observation. Following an abductive approach, in addition to examining the veracity of existing theory, each chapter is also used to build an explanation of how democracy is practiced in small states. Specifically, we highlight how small state politics is shaped by personalization and informal politics, rather than formal institutional design.

scholarly journals An extensive photometric study of the Blazhko RR Lyrae star RZ Lyr*

2012 ◽  
Vol 423 (2) ◽  
pp. 993-1005 ◽  
Author(s):  
J. Jurcsik ◽  
Á. Sódor ◽  
G. Hajdu ◽  
B. Szeidl ◽  
Á. Dózsa ◽  
...  
Keyword(s):  
Light Curve ◽  
Light Curves ◽  
Stellar Structure ◽  
Time Base ◽  
Photometric Method ◽  
Physical Parameters ◽  
Component Solution ◽  
Rr Lyrae ◽  
Curve Variation ◽  
Type Variable

Abstract The analysis of recent, extended multicolour CCD and archive photoelectric, photographic and visual observations has revealed several important properties of RZ Lyr, an RRab-type variable exhibiting large-amplitude Blazhko modulation. On the time base of ∼110 yr, a strict anticorrelation between the pulsation- and modulation-period changes is established. The light curve of RZ Lyr shows a remarkable bump on the descending branch in the small-amplitude phase of the modulation, similarly to the light curves of bump Cepheids. We speculate that the stellar structure temporally suits a 4:1 resonance between the periods of the fundamental and one of the higher order radial modes in this modulation phase. The light-curve variation of RZ Lyr can be correctly fitted with a two-modulation-component solution; the 121-d period of the main modulation is nearly but not exactly four times longer than the period of the secondary modulation component. Using the inverse photometric method, the variations in the pulsation-averaged values of the physical parameters in different phases of both modulation components are determined.

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