scholarly journals Optical polarimetry and photometry of young sun-like star LO Peg

2010 ◽  
Vol 6 (S273) ◽  
pp. 455-459
Author(s):  
J. C. Pandey ◽  
B. J. Medhi ◽  
R. Sagar
Keyword(s):  
Radiation Field ◽  
Position Angle ◽  
Degree Of Polarization ◽  
Circumstellar Envelope ◽  
The Sun ◽  
Photometric Study ◽  
V Band ◽  
Stellar Radiation ◽  
Photometric Observations

AbstractWe have carried out the B,V and R-band polarimetric and V-band photometric study of the star LO Peg. Our analysis reveal that LO Peg is highly polarized among the sun-like stars. The degree of polarization and polarization position angle are found to be rotationally modulated. The levels of polarization observed in LO Peg could be the result of scattering of an anisotropic stellar radiation field by an optically thin circumstellar envelope or scattering of the stellar radiation by prominence-like structures. The long term photometric observations of LO Peg indicate three independent groups of spots are present on the surface of LO Peg.

scholarly journals A Spectroscopic and Photometric Study of the Shell Star EW Lac

2000 ◽  
Vol 175 ◽  
pp. 554-557
Author(s):  
Huilai Cao ◽  
Zhongwei Li ◽  
Lin Huang ◽  
Yulian Guo
Keyword(s):  
Active Phase ◽  
Anomalous Behavior ◽  
Absorption Lines ◽  
Photometric Study ◽  
Short Term ◽  
Photometric Observations ◽  
Shell Star

AbstractWe report on combined spectroscopic and photometric observations of EW Lac during its outburst of 1983. At this time the star’s Hα and Hβ lines showed strong doubled-peaked emission profiles which were variable with time. UBV photometry exhibited a long-term and frequent erratic short-term variations. The amplitude of U, B and V variations reached about 0.3 magnitude on October 15, 1983. Both Hβ emission and the structure of the shell absorption lines of the star also displayed anomalous behavior in 1983. It is evident that this star was in a strong active phase at that time.

A New Approach to the Long-Term Activity Behavior of DM UMa

2012 ◽  
Vol 21 (4) ◽  
Author(s):  
G. Taş ◽  
S. Evren
Keyword(s):  
Broad Band ◽  
Color Variation ◽  
Time Interval ◽  
Period Analysis ◽  
New Approach ◽  
V Band ◽  
Photometric Observations ◽  
Color Data ◽  
Using Data

AbstractA long-term activity character of DM UMa (K0-1 IV-III), which is one of the most active members of the RS CVn type variables, is examined using the multicolor photometric observations which spread to the time interval between 1980 and 2009. In this work, we present a new approximation for the long-term light and color variation of DM UMa using data obtained by combining our own observations obtained in the Johnson broad-band U,B,V,R filters between the years 1997 and 2008 and data published in literature. Available light and color data were examined for the long-term and seasonal variations using PERIOD04 program. The period analysis of the V-band data reveals the period estimations of 51.2±2.8 years and 15.1±0.7 years superposed on it. The U-B, B-V and V-R colors do not show correlation with the longer period, but they show variations with a period similar to the shorter one, except for B-V color. The amplitude variation also does not exhibit any correlation with the V light and color curves. It is found that the movement of the spot minima phases in years also indicates the migration period of nearly 15 years, similar to the period derived from the analysis of the long-term photometric observations in V-band.

scholarly journals Polarization in CH Cygni During Quiet and Active Phases

1988 ◽  
Vol 103 ◽  
pp. 229-230
Author(s):  
M.H. Rodriguez
Keyword(s):  
Sharp Increase ◽  
Wide Band ◽  
Position Angle ◽  
Degree Of Polarization ◽  
Standard Errors ◽  
Circumstellar Envelope ◽  
Mean Values ◽  
Photon Noise ◽  
Colour Excess ◽  
Noise Statistics

Our wide-band polarimetric observations of CH Cyg began in 1974 and continued In 1976 and 1984. During the first two observational seasons the star was in quiet phase between two outbursts, in 1984 the latest outburst that began in 1977 was declining. Figure shows mean values of the degree of polarization P and the position angle θ for the different observational periods. Standard errors calculated by photon noise statistics are 0.02–0.04% for P and 1–5% for θ.In 1974 (October 12 - December 1) polarization parameters did not change significantly. Sharp increase of the degree of polarization in the shortwave region of the spectrum and change with wavelength of the degree of polarization are typical for many cool luminous stars and indicate existence of an asymmetric circumstellar envelope around CH Cyg. Interstellar polarization in the direction of CH Cyg should be quite small [1,2],as its distance is 330 pc and colour-excess EB-V does not exceed 0.07m.

scholarly journals Optical light curves of FUor and FUor-like objects

2016 ◽  
Vol 12 (S325) ◽  
pp. 266-269
Author(s):  
Evgeni Semkov ◽  
Stoyanka Peneva ◽  
Sunay Ibryamov
Keyword(s):  
Light Curve ◽  
Photographic Plate ◽  
Light Curves ◽  
Curve Shape ◽  
Photometric Study ◽  
Maximum Light ◽  
Photometric Observations ◽  
Rate Of Increase ◽  
Photometric Monitoring

AbstractUsing recent data from photometric monitoring and data from the photographic plate archives we aim to study, the long-term photometric behavior of FUors. The construction of the historical light curves of FUors could be very important for determining the beginning of the outburst, the time to reach the maximum light, the rate of increase and decrease in brightness, the pre-outburst variability of the star. Our CCD photometric observations were performed with the telescopes of the Rozhen (Bulgaria) and Skinakas (Crete, Greece) observatories. Most suitable for long-term photometric study are the plate archives of the big Schmidt telescopes, as the telescopes at Kiso Observatory, Asiago Observatory, Palomar Observatory and others. In comparing our results with light curves of the well-studied FUors, we conclude that every new FUor object shows different photometric behavior. Each known FUor has a different rate of increase and decrease in brightness and a different light curve shape.

scholarly journals Long-Term Multicolour Photometry of the Young Stellar Objects FHO 26, FHO 27, FHO 28, FHO 29, and V1929 Cygni

2015 ◽  
Vol 32 ◽  
Author(s):  
S. I. Ibryamov ◽  
E. H. Semkov ◽  
S. P. Peneva
Keyword(s):  
Gulf Of Mexico ◽  
Young Stellar Objects ◽  
Main Sequence Stars ◽  
Stellar Objects ◽  
Photometric Variability ◽  
The North ◽  
Dense Molecular Cloud ◽  
Photometric Observations ◽  
All Optical

AbstractResults from long-term multicolour optical photometric observations of the pre-main-sequence stars FHO 26, FHO 27, FHO 28, FHO 29, and V1929 Cyg collected during the period from 1997 June to 2014 December are presented. The objects are located in the dense molecular cloud L935, named ‘Gulf of Mexico’, in the field between the North America and Pelican nebulae. All stars from our study exhibit strong photometric variability in all optical passbands. Using our BVRI observations and data published by other authors, we tried to define the reasons for the observed brightness variations. The presented paper is a part of our long-term photometric study of the young stellar objects in the region of ‘Gulf of Mexico’.

scholarly journals ESTIMATION OF PERIOD OF LONG-TERM OSCILLATIONS OF FACULAR FORMATIONS ON THE SUN

2019 ◽  
Author(s):  
P.V. Strekalova ◽  
◽  
A.A. Solov’ev ◽  
V.V. Smirnova ◽  
Y.A. Nagovitsyn ◽  
...  
Keyword(s):  
The Sun

scholarly journals Closing up onto our sun: solar imaging

2020 ◽  
Vol 240 ◽  
pp. 07011
Author(s):  
Kushagra Shrivastava ◽  
Keith Wen Kai Chia ◽  
Kang Jun Wong ◽  
Alfred Yong Liang Tan ◽  
Hwee Tiang Ning
Keyword(s):  
Solar Activity ◽  
The Sun ◽  
Research Needs ◽  
Large Numbers ◽  
Wide Range ◽  
Future Science ◽  
Insight Into ◽  
Term Data ◽  
Made In

Solar activity research provides insight into the Sun’s past, future (Science Daily, 2018). The solar activity includes observations of large numbers of intense sunspots, flares, and other phenomena; and demands a wide range of techniques and measurements on the observations. This research needs long term data collection before critical analyses can occur, to generate meaningful learning and knowledge. In this project, we will use solar imaging to make observations of solar activity, and take our baby steps to make contributions in citizen science. Observations will be made in 3 wavelengths to gain a more thorough analysis by looking at different perspectives of the Sun, namely H-Alpha, Calcium-K, and white light.

scholarly journals Long-term evolution of coronal holes on the Sun and occurrence frequencies of magnetic storms with gradual commencements

2021 ◽  
Vol 2103 (1) ◽  
pp. 012038
Author(s):  
S Veretenenko ◽  
M Ogurtsov ◽  
V Obridko ◽  
A Tlatov
Keyword(s):  
Coronal Holes ◽  
Long Term Evolution ◽  
Magnetic Storms ◽  
Time Shift ◽  
Time Interval ◽  
The Sun ◽  
Close Link ◽  
Sunspot Numbers ◽  
Term Evolution

Abstract Long-term evolution of areas with open configuration of magnetic field (coronal holes) on the Sun reconstructed on the basis of H-alpha synoptic charts for the period 1887-2016 was studied and compared with annual occurrence frequencies of magnetic storms with gradual (GC) commencements. It was found that correlation between yearly values of coronal hole (CH) areas and sunspot numbers with no time shift is negative and not strong, but increases up to ∼0.6-0.7 when CH areas are delayed by 4-5 years relative to sunspot numbers. Temporal variations of CH areas in the Northern and Southern hemispheres are characterized by dominant ∼11-year periodicities; however, they differ significantly on the multidecadal time scale. The wavelet spectra of CH areas in the Southern hemisphere, unlike those in the Northern one, reveal persistent periodicities of ∼30-35 years on the studied time interval. Similar periodicities of ∼30-35 years are observed in annual occurrences of GC magnetic storms which are caused by high-speed streams of solar wind from coronal holes. The results of cross wavelet analysis of annual occurrence frequencies of GC magnetic storms and areas of coronal holes revealed common periodicities ∼11, ∼35 and ∼60 years which confirmed a close link of these storms with the evolution of large-scale magnetic fields on the Sun.

scholarly journals Simultaneous Five Color (UBVRI) Polarimetry of VV Puppis

1987 ◽  
Vol 93 ◽  
pp. 203-203
Author(s):  
V. Piirola ◽  
A. Reiz ◽  
G.V. Coyne
Keyword(s):  
Circular Polarization ◽  
Linear Polarization ◽  
Wavelength Dependence ◽  
Position Angle ◽  
Orbital Inclination ◽  
V Band ◽  
Highly Active ◽  
Phase Interval ◽  
In The Beginning ◽  
Bright Phase

AbstractObservations of linear and circular polarization in five colour bands during a highly active state of VV Puppis in January 86 are reported. A strong linear polarization pulse with the maximum in the blue, PB ≈ 22%, is observed at the end of the bright phase when the active pole is at the limb and a weaker secondary pulse, PB ≈ 7%, is seen in the beginning of the bright phase, when the active pole reappears. Strong positive circular polarization is also observed in the blue and the ultraviolet, РU ≈ PB ≈ 18%, PV ≈ 10% during the bright phase. The circular polarization reverses the sign in the B and V bands during the faint phase and a negative polarization hump is seen when the active pole crosses the limb. The circular polarization in the V band reaches the value PV ≈ −10% at the hump, after which it remains near PV ≈ −5% during the faint phase. This is probably due to radiation coming from the second, less active pole and accretion thus takes place onto both poles. The wavelength dependences of the positive and negative parts of the circular polarization curve are different and no polarization reversal is seen in the U band. The position angle of the linear polarization is well determined during a large portion of the cycle, especially in the V band, thanks to the activity from both poles. A best fit to the position angle curve, taking into account also the duration of the positive circular polarization phase interval ΔΦ = 0.40 (in the V band), yields the values of orbital inclination i = 78° ± 2° and the colatitude of the active magnetic pole ß = 146° ± 2°. The relatively good fit to the position angle data indicates that the simple dipole model is nearly correct in the case of VV Puppis. Some wavelength dependence is, however, seen in the position angle curves, especially in the I band where the slope Δθ/ΔΦ at the main pulse is considerably smaller than in the other bands. The shape of the position angle curves changes also in the blue and the ultraviolet around the middle of the bright phase. This is probably due to optical thickness effects as the side of the accretion column which is toward the observer changes near this phase.

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