scholarly journals Surface Imaging of El Eri

1991 ◽  
Vol 130 ◽  
pp. 321-325 ◽  
Author(s):  
T. Hackman ◽  
N.E. Piskunov ◽  
M. Poutanen ◽  
K.G. Strassmeier ◽  
I. Tuominen
Keyword(s):  
Temperature Distribution ◽  
Imaging Technique ◽  
Light Curves ◽  
Surface Imaging ◽  
Photometric Observations ◽  
Temperature Maps

AbstractWe present maps of the temperature distribution on the spotted RS CVn-type binary EI Eri (HD 26337), obtained by means of the surface imaging technique described in the Colloquium (Piskunov, 1991). Images were calculated for two separate lines for two epochs of observation. For one epoch we also calculated an image using a blend of several lines. The reliability of the maps is confirmed by comparing the simultaneous photometric observations with the light curves calculated from the temperature maps.

scholarly journals Circular Polarimetry of AM Herculis

1983 ◽  
Vol 72 ◽  
pp. 207-210
Author(s):  
V. Piirola ◽  
O. Vilhu ◽  
I. Tuominen
Keyword(s):  
Circular Polarization ◽  
Magnetic Axis ◽  
Light Curves ◽  
Short Term ◽  
Probable Explanation ◽  
Photometric Observations ◽  
Peak Value

ABSTRACTCircular polarimetry in the red and simultaneous photometric observations in the UBVRI bands during the period June 1-3, 1981, are discussed. The peak value of negative circular polarization PV ~ -15 % is stronger than observed in 1976-79. Variations in the shape of the polarization and light curves occur from night to night. The positive crossover and reversal of the sign of the circular polarization are only marginal. A probable explanation of the short term variations seems to be the changing shape and position of the accretion columns with respect to the magnetic axis

scholarly journals Optical photometric variable stars towards Cygnus OB7

2019 ◽  
Vol 487 (2) ◽  
pp. 1765-1776 ◽  
Author(s):  
Somnath Dutta ◽  
Soumen Mondal ◽  
Santosh Joshi ◽  
Ramkrishna Das
Keyword(s):  
Variable Stars ◽  
T Tauri Stars ◽  
Light Curves ◽  
Main Sequence Stars ◽  
Star Forming ◽  
Rotation Rates ◽  
T Tauri ◽  
Photometric Observations ◽  
Sky Survey ◽  
Magnitude Diagram

ABSTRACT We present optical I-band light curves of the stars towards a star-forming region Cygnus OB7 from 17-night photometric observations. The light curves are generated from a total of 381 image frames with very good photometric precision. From the light curves of 1900 stars and their periodogram analyses, we detect 31 candidate variables including five previously identified. 14 out of 31 objects are periodic and exhibit the rotation rates in the range of 0.15–11.60 d. We characterize those candidate variables using optical/infrared colour–colour diagram and colour–magnitude diagram (CMD). From spectral indices of the candidate variables, it turns out that four are probably Classical T-Tauri stars (CTTSs), rest remain unclassified from present data, they are possibly field stars or discless pre-main-sequence stars towards the region. Based on their location on the various CMDs, the ages of two T Tauri Stars were estimated to be ∼5 Myr. The light curves indicate at least five of the periodic variables are eclipsing systems. The spatial distribution of young variable candidates on Planck 857 GHz (350 $\mu$m) and 2MASS (Two Micron All Sky Survey) Ks images suggest that at least two of the CTTSs are part of the active star-forming cloud Lynds 1003.

scholarly journals A photometric and spectroscopic study of R Coronae Borealis stars in the LMC

1991 ◽  
Vol 148 ◽  
pp. 351-352
Author(s):  
W. A. Lawson ◽  
P. L. Cottrell ◽  
K. R. Pollard
Keyword(s):  
High Resolution ◽  
Spectroscopic Study ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Light Curves ◽  
Photometric Observations ◽  
R Coronae Borealis Stars

Over the last several years we have obtained photometric observations of the four suspected (W Men, HV 5637, HV 12671, HV 12842) R Coronae Borealis (RCB) stars in the Large Magellanic Cloud (LMC). Fourier analyses of the light curves has revealed some periodicity in HV 12842, where there appear to be at least two closely spaced periods of 55 and 60 d. High resolution spectra of HV 12842, obtained with the Ango-Australian Telescope (AAT), indicate that it has similar atmospheric properties to a number of warmer galactic RCB and hydrogen-deficient Carbon (HdC) stars, e.g. R CrB, RY Sgr and XX Cam.

Mapping the Non-Radial Pulsations

2000 ◽  
Vol 175 ◽  
pp. 268-271
Author(s):  
S.V. Berdyugina ◽  
H. Korhonen ◽  
C. Schrijvers ◽  
J.H. Telting
Keyword(s):  
High Resolution ◽  
Imaging Technique ◽  
Temperature Fluctuations ◽  
Dominant Mode ◽  
Type Star ◽  
Surface Imaging ◽  
Pulsation Mode ◽  
Radial Pulsations

AbstractWe apply the surface imaging technique to high-resolution spectra of the rapidly rotating β Cep-type star ω1 Sco. Assuming only temperature fluctuations due to pulsations, we obtain a map of the surface corotating with the dominant pulsation mode. Prom the map we identify the dominant mode and find traces of a second pulsation mode. We conclude that the traditional surface imaging technique can be successfully used for mapping stellar non-radial pulsations.

Fundamental validation for surface texture imaging using a microsphere as a laser-trapping-based microprobe

2014 ◽  
Vol 3 (4) ◽  
Author(s):  
Masaki Michihata ◽  
Kosuke Takami ◽  
Terutake Hayashi ◽  
Yasuhiro Takaya
Keyword(s):  
Surface Texture ◽  
Imaging Technique ◽  
Focal Point ◽  
Objective Lens ◽  
Surface Imaging ◽  
Laser Trapping ◽  
Imaging Characteristics ◽  
Virtual Images ◽  
Engineered Surfaces

AbstractA surface imaging technique using a laser-trapped microsphere is proposed. The goal of this research is to image the surface texture, while simultaneously measuring the position of the engineered surfaces using the laser-trapping-based microprobe. This paper presents an investigation of imaging characteristics for the microsphere technique. Depending on the distance from the surface to the microsphere, the available images could be either real or virtual. Virtual images had a higher contrast than real images. Contrast and magnification varies depending on the positions of the focal point of the objective lens and surface.

Study of Pulsations in the Nova-like Variable KR Aur and the Intermediate Polar BG CMi

1991 ◽  
Vol 9 (2) ◽  
pp. 279-280
Author(s):  
J. Singh ◽  
P. C. Agrawal ◽  
M. V. K. Apparao ◽  
R. K. Manchanda ◽  
P. Vivekananda Rao ◽  
...  
Keyword(s):  
Neutron Star ◽  
White Dwarf ◽  
Accretion Disc ◽  
Light Curves ◽  
Pulsation Period ◽  
Variable Amplitude ◽  
X Ray ◽  
Photometric Observations ◽  
The Times ◽  
Made In

AbstractFast photometric observations of a nova-like variable KR Aurigae and the intermediate polar BG CMi (3A0729+103) were made in the B and U bands during 1984–89 to study pulsations in them. The light curves of KR Aur show large amplitude quasi-periodic pulsations with periods in the range 500–800s which can be ascribed to inhomogeneities in the accretion disc. The light curves of the X-ray emitting intermediate polar BG CMi show variable amplitude pulsations with 913s period. From the times of maxima of the pulsations obtained from observations over the period 1984–1989, the pulsation period is derived to be 0.010572966 ± 8 days and the spin-up rate to be (−5.7 ± 0.5) × 10−11 ss−1. The spin-up rate is consistent with the pulsating source being a white dwarf and not a neutron star.

scholarly journals Resolving Io’s Volcanoes from a Mutual Event Observation at the Large Binocular Telescope

2021 ◽  
Vol 2 (6) ◽  
pp. 227
Author(s):  
Katherine de Kleer ◽  
Michael Skrutskie ◽  
Jarron Leisenring ◽  
Ashley G. Davies ◽  
Al Conrad ◽  
...  
Keyword(s):  
Temperature Distribution ◽  
Spatial Resolution ◽  
High Spatial Resolution ◽  
Temporal Evolution ◽  
Light Curves ◽  
Lava Flows ◽  
Volcanic Center ◽  
Active Volcanism ◽  
Geological Processes ◽  
Areal Coverage

Abstract Unraveling the geological processes ongoing at Io’s numerous sites of active volcanism requires high spatial resolution to, for example, measure the areal coverage of lava flows or identify the presence of multiple emitting regions within a single volcanic center. In de Kleer et al. (2017) we described observations with the Large Binocular Telescope during an occultation of Io by Europa at ∼6:17 UT on 2015 March 8 and presented a map of the temperature distribution within Loki Patera derived from these data. Here we present emission maps of three other volcanic centers derived from the same observation: Pillan Patera, Kurdalagon Patera, and the vicinity of Ulgen Patera/PV59/N Lerna Regio. The emission is localized by the light curves and resolved into multiple distinct emitting regions in two of the cases. Both Pillan and Kurdalagon Paterae had undergone eruptions in the months prior to our observations, and the location and intensity of the emission are interpreted in the context of the temporal evolution of these eruptions observed from other facilities. The emission from Kurdalagon Patera is resolved into two distinct emitting regions separated by only a few degrees in latitude that were unresolved by Keck observations from the same month.

scholarly journals Long-term spot monitoring of the young solar analogue V889 Herculis

2019 ◽  
Vol 622 ◽  
pp. A170 ◽  
Author(s):  
T. Willamo ◽  
T. Hackman ◽  
J. J. Lehtinen ◽  
M. J. Käpylä ◽  
I. Ilyin ◽  
...  
Keyword(s):  
Magnetic Activity ◽  
Doppler Imaging ◽  
Mean Temperature ◽  
Photometric Observations ◽  
Crucial Information ◽  
The Mean ◽  
Magnetic Cycles ◽  
Temperature Maps ◽  
Weak Tendency

Context. Starspots are important manifestations of stellar magnetic activity. By studying their behaviour in young solar analogues, we can unravel the properties of their magnetic cycles. This gives crucial information of the underlying dynamo process. Comparisons with the solar cycle enable us to infer knowledge about how the solar dynamo has evolved during the Sun’s lifetime. Aims. Here we study the correlation between photometric brightness variations, spottedness, and mean temperature in V889 Her, a young solar analogue. Our data covers 18 years of spectroscopic and 25 years of photometric observations. Methods. We use Doppler imaging to derive temperature maps from high-resolution spectra. We use the Continuous Period Search method to retrieve mean V-magnitudes from photometric data. Results. Our Doppler imaging maps show a persistent polar spot structure varying in strength. This structure is centred slightly off the rotational pole. The mean temperature derived from the maps shows an overall decreasing trend, as does the photometric mean brightness, until it reaches its minimum around 2017. The filling factor of cool spots, however, shows only a weak tendency to anti-correlate with the decreasing mean brightness. Conclusions. We interpret V889 Her to have entered into a grand maximum in its activity. The clear relation between the mean temperature of the Doppler imaging surface maps and the mean magnitude supports the reliability of the Doppler images. The lack of correlation between the mean magnitude and the spottedness may indicate that bright features in the Doppler images are real.

scholarly journals X-ray Timing Studies of GRS 1915+105

1998 ◽  
Vol 188 ◽  
pp. 394-395
Author(s):  
B. Paul ◽  
P. C. Agrawal ◽  
A. R. Rao ◽  
M. N. Vahia ◽  
J. S. Yadav ◽  
...  
Keyword(s):  
Power Density ◽  
Light Curves ◽  
Energy Bands ◽  
X Ray ◽  
Photometric Observations ◽  
Different Types

We have made photometric observations of the galactic superluminal jet source GRS 1915+105 in the energy bands of 2-6 and 6-18 keV during 1997 June 12-29 and August 8-10. During our observations, different types of very intense, quasi-regular X-ray bursts have been observed from this source. We present here the light curves and the power density spectra of our observation of this source in its bright state.

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