Short time-scale variability in the spectrum of the hot B3V star ηUMa

2020 ◽  
Vol 10 (1) ◽  
pp. 3-6
Author(s):  
S. Pokhvala
Keyword(s):  
Time Resolution ◽  
Stellar Wind ◽  
Time Scale ◽  
Atmospheric Oxygen ◽  
Short Time Scale ◽  
Low Resolution ◽  
Balmer Lines ◽  
Hydrogen Lines ◽  
Short Time ◽  
Radial Pulsations

We report the results of observations of short time-scale variability in the Hydrogen Balmer lines and HeI lines in the hot B star ηUMa. Spectral observations were carried out with the low-resolution slitless spectrograph (R∼200) installed on the 60 cm Carl Zeiss telescope in the Andrushivka Observatory, Ukraine. Spectra were obtained with a time resolution in the sub-second range. It has been found that the hot B star ηUMa shows rapid variations in the Hydrogen lines Hβ, Hγ, Hδ, Hε and the Helium lines HeI 5016Å HeI 5047Å, as well as variations in the atmospheric oxygen lines. This can be interpreted that their variations are non-radial pulsations and strong stellar wind.

Radio-Astronomical Evidence for Magneto-Hydrodynamical Pulsations in the Corona

1971 ◽  
Vol 43 ◽  
pp. 652-655 ◽  
Author(s):  
Hans Rosenberg
Keyword(s):  
Time Resolution ◽  
Time Scale ◽  
Small Amplitude ◽  
Broad Band ◽  
Striking Feature ◽  
Short Time Scale ◽  
Type Iv ◽  
Long Duration ◽  
Stationary Type ◽  
Short Time

At Utrecht Observatory a 60-channel solar radiospectrograph has been in regular operation since the fall of 1968, in the bandwidth 160–320 MHz, with a time resolution of 0s.03 (DeGroot and Van Nieuwkoop, 1968). In addition to all generally known and classified emissions as noise storms, type IV bursts, type III bursts, type IV continua, a number of unclassified emissions have been observed. The spectrograph is particularly well suited to study short time scale fluctuations, even of small amplitude. One striking feature is an often recurring broad band (> 80 MHz) weak, quasiperiodic fluctuation superimposed on a type IV-like continuum (Figure 1). Since no interferometric measurements were available, it is not known whether it is a stationary or a moving type IV burst. However, due to the sometimes very long duration, we expect it to be a stationary type IV.

scholarly journals High-frequency variations of hydrogen spectral lines in the B3V star η UMa

2015 ◽  
Vol 5 (1) ◽  
pp. 21-23
Author(s):  
S. Pokhvala
Keyword(s):  
Time Resolution ◽  
High Frequency ◽  
Atmospheric Oxygen ◽  
Spectral Lines ◽  
Spectral Class ◽  
Balmer Lines ◽  
Hydrogen Lines ◽  
Frequency Variations

We reported the detection of high-frequency variations in the hydrogen Balmer lines in the hot star η UMa of spectral class B3V. Spectral observations of η UMa were carried out with slitless spectrograph (R∼100) installed on the 60 cm Carl Zeiss telescope in the Andrushivka Observatory. Spectra were obtained with a time resolution in the sub-second range. It has been found that the η UMa shows rapid variations in the hydrogen lines Hα, Hβ, Hγ, as well as variations in the atmospheric oxygen lines. The intensity variations in the hydrogen lines varies from 0.2% to 0.5%, and that of the oxygen lines is approximately 2%.

scholarly journals Is HR 9070 Really Pulsating?

1987 ◽  
Vol 92 ◽  
pp. 78-81
Author(s):  
Sareyan J.P. ◽  
Alvarez M. ◽  
Chauville J. ◽  
Le Contel J.M. ◽  
Michel R. ◽  
...  
Keyword(s):  
Time Resolution ◽  
Time Scale ◽  
Short Time Scale ◽  
Be Stars ◽  
Time Constants ◽  
Systematic Survey ◽  
Short Time

As Be stars and classical β CMa variables both have a distribution peak at B2, one can wonder if there is a connection between these two phenomena. A way to solve this problem could be to carry out a systematic survey of emission on short periodic B variables,over months and years.Another way, chosen by our grouns in Nice, Ensenada and Meudon, is to improve time resolution in photometric and spectrographic observations on the Be stars already known to have short time scale variations. Special attention is paid to longitude cooperation, essential to detect or measure longer time constants.

Periodic Variations in the Coronal Green Line Intensity and their Connection with the White-light Coronal Structures

2000 ◽  
Vol 179 ◽  
pp. 197-200
Author(s):  
Milan Minarovjech ◽  
Milan Rybanský ◽  
Vojtech Rušin
Keyword(s):  
Time Resolution ◽  
White Light ◽  
Short Time Scale ◽  
High Time Resolution ◽  
Green Line ◽  
Periodic Intensity ◽  
Coronal Green Line ◽  
Significant Intensity ◽  
Short Time ◽  
Coronal Structures

AbstractWe present an analysis of short time-scale intensity variations in the coronal green line as obtained with high time resolution observations. The observed data can be divided into two groups. The first one shows periodic intensity variations with a period of 5 min. the second one does not show any significant intensity variations. We studied the relation between regions of coronal intensity oscillations and the shape of white-light coronal structures. We found that the coronal green-line oscillations occur mainly in regions where open white-light coronal structures are located.

An Alternative Test Using Algal Cultures for Testing Chemicals for Toxicity

1993 ◽  
Vol 21 (2) ◽  
pp. 196-201
Author(s):  
Søren Achim Nielsen ◽  
Thomas Hougaard
Keyword(s):  
Size Distribution ◽  
Mitotic Activity ◽  
Time Scale ◽  
Test System ◽  
Short Time Scale ◽  
Toxic Substances ◽  
Alternative Test ◽  
Short Time ◽  
Algal Cultures ◽  
Test Cultures

An alternative test is presented, in which algal cultures are used for testing toxic substances. This test system is based on variations in the size distribution of cells in test cultures as a measurement of growth. Thus, inhibition of mitotic activity is used as a measurement for toxic effects. The test can be performed on a short time-scale and is very sensitive to even weak toxic doses.

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