scholarly journals Optical Photometry of Flares and Flare Statistics

1983 ◽  
Vol 71 ◽  
pp. 157-174
Author(s):  
Patrick B. Byrne
Keyword(s):  
Flare Star ◽  
Present Review ◽  
Optical Observations ◽  
Solar Neighbourhood ◽  
Flare Activity ◽  
Optical Photometry ◽  
Flare Phenomenon ◽  
Spectroscopic Observations ◽  
The Past ◽  
Flare Stars

This review discusses optical observations of flares and the results gleaned from these. Excellent reviews of flare activity have been published in the past and one might mention in particular Kunkel (1975), Gershberg (1978) and Gurzadyan (1980). In general these have been more broadly based than the present review incorporating other aspects of flare stars e.g. BY Dra variability, spectroscopic observations, etc. Since these other aspects of flare star behaviour are being covered elsewhere in this volume we will confine ourselves exclusively to optical photometry of the flare phenomenon itself. We will also confine ourselves to the solar-neighbourhood flare stars (i.e. the UV Ceti stars) since other contributors will discuss the T-Taurl, RS CVn, BY Dra and other flaring objects.

scholarly journals High-Speed Photometry of Cluster Flare Stars

1975 ◽  
Vol 67 ◽  
pp. 69-73
Author(s):  
M. Rodonò
Keyword(s):  
High Speed ◽  
Activity Level ◽  
Flare Star ◽  
Solar Neighbourhood ◽  
High Occurrence ◽  
High Speed Photometry ◽  
Flare Stars ◽  
Photoelectric Observations ◽  
Absolute Luminosity

Recent photoelectric observations made at Catania Observatory show a high occurrence of short-lived faint flares on the Hyades member II Tau (H II 2411). Its activity level turns out to be higher than for UV Cet-type stars of equal absolute luminosity.II Tau could represent a transition prototype between UV Cet-type flare star in the solar neighbourhood and cluster ones.The importance of coordinated photoelectric patrol of properly selected flare stars in clusters of different age is emphasized.

The BVIT: from Flare Stars to the Search for ET

2017 ◽  
Vol 14 (S339) ◽  
pp. 7-11
Author(s):  
B. Y. Welsh ◽  
J. Vallerga ◽  
O. H. W. Siegmund ◽  
J. Wheatley ◽  
M. Kotze
Keyword(s):  
Time Scales ◽  
Flare Star ◽  
Extraterrestrial Intelligence ◽  
Visible Image ◽  
Image Tube ◽  
The Past ◽  
Flare Stars ◽  
Astrophysical Phenomena

AbstractThe Berkeley Visible Image Tube (BVIT) has been a user instrument on the SALT 10-m telescope for the past six years. It can observe transient astrophysical phenomena occurring on time-scales of micro-seconds. This overview presented some recent observations of a dMe flare star, and discussed the recent results of our optical Search for Extraterrestrial Intelligence (OSETI) around nearby exoplanet-hosting stars.

scholarly journals Flare Star Observations in the Praesepe Region

1977 ◽  
Vol 42 ◽  
pp. 120-125
Author(s):  
I. Jankovics
Keyword(s):  
Observational Data ◽  
Flare Star ◽  
Flare Activity ◽  
List Type ◽  
The Sun ◽  
Type Number ◽  
Orion Association ◽  
Order Of Magnitude ◽  
Photographic Survey ◽  
Flare Stars

In a program of systematic search for flare stars in clusters and associations we have carried out a photographic survey in the region of Praesepe. The previously obtained interesting results in the Pleiades cluster and the Orion association stimulated us to continue the work of Haro (1968) and Rosino (1966) in Praesepe. The importance of observations in this cluster is obvious if we consider the following circumstances: 1. Praesepe and Pleiades have nearly the same distance from the Sun, 160 and 125 pc, respectively.2. There exists a difference in age between the 2 clusters of at least one order of magnitude.3. The use of Schmidt telescopes allows observations in large cluster regions.A great number of observational data are desirable for comparison of flare activity in the regions of Pleiades and Praesepe.

scholarly journals X-Ray and Optical Observations of the X-Ray Source EX0020528+1454.8

1987 ◽  
Vol 93 ◽  
pp. 697-700
Author(s):  
R. Hudec ◽  
W. Wenzel ◽  
W. Goetz ◽  
B. Valníček ◽  
R. Peřestý ◽  
...  
Keyword(s):  
Optical Observations ◽  
X Rays ◽  
Optical Counterpart ◽  
Optical Photometry ◽  
X Ray ◽  
Preliminary Results ◽  
Flare Stars

AbstractWe present preliminary results of the EXOSAT X-ray observations and quasisimultaneous and simultaneous optical photometry of the X-ray source EX0020528+1454.8 = 1E0205+149 found independently as an serendipitous source both with Einstein and EXOSAT satellites. The optical counterpart is a pair of dMe stars, Our results indicate that the object is variable both in X-rays and optical wavelenghts, and probably belongs to dMe flare stars.

scholarly journals BD+47°819, an A-type Flare Star with Peculiar Spectroscopic Variation

1995 ◽  
Vol 151 ◽  
pp. 101-102
Author(s):  
Jun-Jie Wang
Keyword(s):  
Emission Line ◽  
Exposure Time ◽  
Spectral Type ◽  
Open Cluster ◽  
Astronomical Observatory ◽  
Flare Star ◽  
Quiescent State ◽  
Spectroscopic Observations ◽  
Stellar Flares ◽  
Flare Stars

Stellar flares are one of the most challenging problems in astrophysics. Up to now, most of the detected flare stars are of late spectral type (e.g. UV Cet type stars etc.). Non-classical flare stars with early spectral type are very rare.Recently, an A5-type flare star BD+47°819, near the open cluster α Persei, was discovered (Wang 1993). The flare U amplitude was 1m.5 in ten minutes. The V magnitude of the star was 9m.25 during the quiescent state.On 1993 February 28 and March 1, spectroscopic observations of BD+47°819 were madewithn the 2.16 m telescope of Beijing Astronomical Observatory. A grating with a dispersion of 5nm/mm was used. Figs. 1 (a) and (b) show the observed spectra in the two nights. The exposure time for each spectrum was 15 minutes. Fig. 1 (a) shows a strange feature, an “emission line” at around 676 nm. Is this a real feature?

scholarly journals Photometric Research of Pre-flare and Extra-flare Activity of Flare Stars

1995 ◽  
Vol 151 ◽  
pp. 110-111
Author(s):  
G. Roizman ◽  
L. Pustil’nik ◽  
D. Pundak
Keyword(s):  
Spectral Lines ◽  
Flare Star ◽  
Flare Activity ◽  
Jordan Valley ◽  
Preliminary Results ◽  
Regional College ◽  
Flare Stars ◽  
Ev Lac ◽  
Low Amplitude

Preliminary results of a photometric search for non-flare activity of the flare star EV Lac during June-August 1994 are presented. These observations are part of the long-term project entitled “Investigation of pre-flare processes on flare stars” being carried out at the Observatory of the Jordan Valley Regional College since July 1994. The project was motivated by reports of the existence of slow, low-amplitude non-periodic variability of both spectral lines and continuum outside/between flares (Rodono et al. 1979, Roizman et al. 1984).

scholarly journals Short-Time Flare Events of EV Lac

1995 ◽  
Vol 151 ◽  
pp. 80-81 ◽  
Author(s):  
B.E. Zhilyaev ◽  
I.A. Verlyuk
Keyword(s):  
High Altitude ◽  
Sea Level ◽  
Time Resolution ◽  
Flare Star ◽  
Flare Activity ◽  
Flare Stars ◽  
Ev Lac ◽  
Short Time

Moffett (1972) pointed out the existence of short-time outbursts in flare stars as long ago as 1972. Gershberg & Petrov (1986) had registered a flare in EV Lac with a duration of 28.4 and an amplitude of 38.4 in 1984 with ASTRON. In recent years, a few reports appeared about observations of short-time outbursts in EV Lac with a duration in the range from 08.1 to several seconds. These results were summarized briefly by Zhilyaev (1993). Our observations confirm the existence of short-time flare activity on EV Lac.The observations reported here were obtained at the 60 cm telescope at the Peak Terskol high-altitude Observatory (3 100 m above sea level) with a highspeed two-channel photometer (Zhilyaev et al. 1992) in B as well as simultaneously in both, U and V bands, with a time resolution down to 08.1. A new prefiltering technique (Zhilyaev 1995) has been used for the detection of smallscale activity of the flare star EV Lac.

scholarly journals Continued Analysis of EUVE and Optical Observations of a Flare on AD Leonis

1996 ◽  
Vol 152 ◽  
pp. 153-158
Author(s):  
S.L. Cully ◽  
G.H. Fisher, ◽  
S.L. Hawley, ◽  
T. Simon
Keyword(s):  
Emission Measure ◽  
Flare Star ◽  
Optical Observations ◽  
Physical Parameters ◽  
Differential Emission Measure ◽  
Optical Photometry

The flare star AD Leo (dM3.5e, 4.9 pc) was observed by EUVE from 1993 March 1-March 3 UT. A flare was detected by the EUVE DS/S and seen in optical photometry on 1993 March 2 UT. We summarize an analysis of the flare’s physical parameters, and present differential emission measure (DEM) curves calculated for the quiescent, flare peak and flare decay phases of the observation.

Recent Advances in Therapeutic Applications of Bisbenzimidazoles

2020 ◽  
Vol 16 (4) ◽  
pp. 454-486 ◽  
Author(s):  
Smita Verma ◽  
Vishnuvardh Ravichandiran ◽  
Nihar Ranjan ◽  
Swaran J.S. Flora
Keyword(s):  
Heterocyclic Compounds ◽  
Wide Spectrum ◽  
Dna Recognition ◽  
Present Review ◽  
Pharmacological Activities ◽  
Structural Motifs ◽  
Therapeutic Applications ◽  
The Past ◽  
Recent Advances

Nitrogen-containing heterocycles are one of the most common structural motifs in approximately 80% of the marketed drugs. Of these, benzimidazoles analogues are known to elicit a wide spectrum of pharmaceutical activities such as anticancer, antibacterial, antiparasitic, antiviral, antifungal as well as chemosensor effect. Based on the benzimidazole core fused heterocyclic compounds, crescent-shaped bisbenzimidazoles were developed which provided an early breakthrough in the sequence-specific DNA recognition. Over the years, a number of functional variations in the bisbenzimidazole core have led to the emergence of their unique properties and established them as versatile ligands against several classes of pathogens. The present review provides an overview of diverse pharmacological activities of the bisbenzimidazole analogues in the past decade with a brief account of its development through the years.

Synthesis of nontronite and other Fe-rich smectites: a critical review

Clay Minerals ◽  
2017 ◽  
Vol 52 (4) ◽  
pp. 469-483 ◽  
Author(s):  
S. Petit ◽  
F. Baron ◽  
A. Decarreau
Keyword(s):  
Clay Minerals ◽  
Critical Review ◽  
Present Review ◽  
Chemical Compositions ◽  
Natural Environments ◽  
The Past

AbstractThe synthesis of clay minerals has been studied for decades in an attempt to better understand their formation in natural environments and more recently to obtain clay minerals with controlled compositions and properties. Even though nontronite has been synthesized successfully since 1935, the process is not a straightforward and has been poorly documented. In the present review concerning the synthesis of nontronite and other Fe-rich smectites, the experiments attempted in the past are discussed critically in light of the most recent data. Most notably, the application of relationships established recently, thanks to synthetic smectitic series, have allowed us to refine the chemical compositions of some nontronites synthesized previously.

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