scholarly journals Rapid spike flares on AD Leo and EV Lac

1990 ◽  
Vol 137 ◽  
pp. 27-30
Author(s):  
K. P. Panov ◽  
M. S. Ivanova ◽  
A. Antov
Keyword(s):  
Astronomical Observatory ◽  
Monitoring Time ◽  
Flare Stars ◽  
Ev Lac

Photoelectric U - band observations of the flare stars A Leo and EV Lac during the last 9 years obtained at the Bulgarian National Astronomical Observatory revealed 8 rapid spike flares on AD Leo and 9 rapid spike flares on EV Lac which duration is less than 6 seconds. The corresponding total monitoring time is 173.6 hours for AD Leo and 173.3 hours for EV Lac.

scholarly journals Long-Term Spot Photometry and Differential Rotation of the Spotted Flare Stars Ev Lac and by Dra

1993 ◽  
Vol 157 ◽  
pp. 157-159
Author(s):  
K.P. Panov
Keyword(s):  
Differential Rotation ◽  
Astronomical Observatory ◽  
Light Curves ◽  
Rotational Period ◽  
Rotational Modulation ◽  
Balmer Lines ◽  
Flare Stars ◽  
Ev Lac ◽  
Image Position

Ev Lac = Gliese 873 (dM4.5e) is a well-known flare star with hydrogen Balmer lines as well as with Ca II lines in emission. Rotational modulation by starspots has been discovered by Pettersen (1980) who determined the photometric (rotational) period P = 4.378 d. Spot photometry of EV Lac was obtained with the 60 cm telescope of the Bulgarian National Astronomical Observatory in the years 1983–87 and 1989–91. For these years (except for 1989 and 1990) light curves are available in the V and B bands. From the BNAO-data and the data published by Pettersen (1980) a new ephemerishas been derived which shows a slight revision of the period.

scholarly journals Flare Stars Investigations at the Department of Astronomy and the Rozhen National Astronomical Observatory

1989 ◽  
Vol 104 (2) ◽  
pp. 151-154
Author(s):  
M.K. Tsvetkov ◽  
B.Zh. Kovachev
Keyword(s):  
Spectral Type ◽  
Astronomical Observatory ◽  
National Observatory ◽  
Flare Stars ◽  
Nonstable Star

In the frames of the programme of nonstable star investigations in the Department, of Astronomy and National Astronomical Observatory the investigations of flare stars- stars of spectral type dK - dM whose nonstabi1ity appears first of all through the quick brightness increases take an essential place. The programme of systematic observations was initiated in 1979 with setting into operation of the telescopes of the Rozhen National Observatory.

scholarly journals Analysis of the Machine-Readable Version of the Tonantzintla Catalogue of the Pleiades Flare Stars

1989 ◽  
Vol 104 (2) ◽  
pp. 147-150
Author(s):  
M.K. Tsvetkov ◽  
K.Y. Stavrev ◽  
K.P. Tsvetkova
Keyword(s):  
Astronomical Observatory ◽  
International Programme ◽  
Intensive Observations ◽  
Flare Stars ◽  
The Creation ◽  
Machine Readable

The results of the intensive observations of the Pleiades flare stars for more than 20 years (≈ 3000 h effective observational time) were compiled and published by G.Haro and collaborators in a catalogue (Haro et al.,1982) including the flare stars discovered in the Pleiades region up to 1981. The catalogue contains the data far 519 flare stars.In the frame of the international programme for the study of flare stars in stellar aggregates the Department of Astronomy and the National Astronomical Observatory have carried out patrol observations in the Pleiades since 1979. Parallel to the observations, work on the creation of machine-readable versions of the published flare stars catalogues has begun. As a firatstep, a machine—readable version of the Tonantzintla catalogue (TC of the Pleiades flare stars has been prepared (Tsvetkov et al., 1987).

scholarly journals New EUV Selected Flare Stars

1995 ◽  
Vol 151 ◽  
pp. 67-68
Author(s):  
Bill Ball ◽  
Gordon Bromage
Keyword(s):  
South African ◽  
Direct Evidence ◽  
Line Emission ◽  
Astronomical Observatory ◽  
Balmer Line ◽  
Wide Field ◽  
Comparison Stars ◽  
Flare Stars ◽  
Photometric Monitoring

The ROSAT Wide Field Camera all-sky EUV survey of 1990-91 identified over 200 active late-type stars (Pounds et al. 1993). Most of these were not known to be active prior to the survey and follow-up optical spectroscopy has been successful in selecting the most active dMe stars. These stars are characterized by their Balmer line emission which is direct evidence for an active chromosphere. We present photometric monitoring data for 4 new dMe stars, including the discovery of flaring activity on all 4 stars.The observations were made at the South African Astronomical Observatory at Sutherland near Capetown in October 1994, using the 0.5m and 1.9m telescopes for photometry and spectrometry, respectively. The 0.5m telescope is equipped with an automated, pulse-counting photometer. Flare monitoring of all the stars was done in the U-band with either 5 or 10 s integration times. All the stars monitored were between magnitude V = 11 and 13. A total of 15 flares were detected, including at least one on each star (Table 1). Comparison stars were measured in standard UBVRI photometric bands for each star.

scholarly journals Statistics of flares observed for UV Ceti type stars YZ CMi, AD Leo, and EV Lac at the Okayama Observatory

1990 ◽  
Vol 137 ◽  
pp. 43-47
Author(s):  
K. Ishida
Keyword(s):  
Time Resolution ◽  
High Time ◽  
High Time Resolution ◽  
Ceti Type ◽  
Flare Stars ◽  
Ev Lac

Photoelectric monitoring of flare stars YZ CMi, AD Leo, and EV Lac has been done at the Okayama Observatory since early 1970s. This is a simultaneous UBV observations with a high time resolution. Some statistics of the flares of the UV Ceti type stars are presented.

Long-Term Changes of the Flare Stars EV Lac and by Dra

1982 ◽  
pp. 253-276 ◽  
Author(s):  
L. N. Mavridis ◽  
G. Asteriadis ◽  
F. M. Mahmoud
Keyword(s):  
Long Term Changes ◽  
Flare Stars ◽  
Ev Lac

Rapid UBVRI photometry of the active flare stars EV Lac and AD Leo

2000 ◽  
Vol 44 (10) ◽  
pp. 689-695
Author(s):  
I. Yu. Alekseev ◽  
V. E. Chalenko ◽  
D. N. Shakhovskoi
Keyword(s):  
Ubvri Photometry ◽  
Flare Stars ◽  
Ev Lac

scholarly journals Quiescent And Flaring Radio Emission From dMe Stars

1983 ◽  
Vol 71 ◽  
pp. 273-286 ◽  
Author(s):  
D. M. Gibson
Keyword(s):  
Radio Emission ◽  
Solar Flares ◽  
Expected Value ◽  
Detection Thresholds ◽  
Significant Interest ◽  
Radio Studies ◽  
Flare Stars ◽  
Ev Lac ◽  
M Dwarf

In reviewing radio studies of M-dwarf flare stars one is struck by the curious way in which the field developed. Indeed, that is twenty years old may be the greatest surprise, for if one imagines the largest solar flares occurring at distances comparable to the nearest stars the expected flux densities would be < 10 mJy. Yet, despite the fact that detection thresholds in 1963 were about two orders of magnitude higher than the expected value, Lovell et al. (1963) made extensive observations and reported the. detection of UV Ceti. This remarkable discovery was followed immediately by detections of V371 Ori (Slee et al., 1963) and EV Lac (Lovell et al., 1964). One might have thought that these unexpected discoveries would have spurred significant interest in this new field but they did not.

scholarly journals Closing remarks

1990 ◽  
Vol 137 ◽  
pp. 393-393
Author(s):  
Charles J. Lada
Keyword(s):  
New York ◽  
Nobel Prize ◽  
Stellar Evolution ◽  
Astronomical Observatory ◽  
Flare Star ◽  
Pablo Neruda ◽  
The Subject ◽  
Flare Stars ◽  
Galactic Astronomy ◽  
First Time

A number of years ago, the nobel-prize winning Chilean poet Pablo Neruda paid a visit to the Byurakan and wrote these comments in his Memoirs (1978:Penguin Books, New York, pg. 243.): “I shall never forget my visit to the astronomical observatory of Byurakan, where I saw the writing of stars for the first time. The trembling light of the stars was picked up; very fine mechanisms were taking down the palpitation of the stars in space, like an electrocardiogram of the sky. In those graphics I observed that each star has its own distinct way of writing, tremulous and fascinating, but unintelligible to the eyes of an earthbound poet” Unintelligible to the eyes of a poet, but as we have seen from this symposium, to the eyes of the astronomer, the phenomenon of flare stars is becoming more and more comprehensible. Before I came here to Byurakan I must confess that I (like Neruda) knew very little about the flare star phenomenon. As a result of this symposium I have learned much about these objects and now have a keen appreciation for their importance for studies of early stellar evolution. In this regard, I find it a particular priviledge and extremely appropriate to have a meeting on the subject of flare stars here at the Byurakan Observatory, where so much seminal work on this topic has been done. I have been impressed by the dedicated efforts of the astronomers at the Byurakan Observatory in flare star research. Their efforts represent an important contribution to galactic astronomy.

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