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 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 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 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 Third Preliminary Catalogue of Stars Observed With the Photoelectric Astrolabe

1990 ◽  
Vol 141 ◽  
pp. 495-496
Author(s):  
Lu Lizhi
Keyword(s):  
Spectral Type ◽  
Astronomical Observatory ◽  
Single Passage ◽  
The Mean

On the basis of the data observed with the Photoelectric Astrolabe Mark II of the Beijing Astronomical Observatory during the period from 1982 to 1988, residuals of 355 fundamental stars and 2921 catalogue stars are reduced and analyzed. The relations between the residuals V and the magnitude M, and the spectral type S of FK5 stars are discussed. The position corrections (PACP3—FK5), Δα′s and Δδ′s, from the double passage of the stars are determined. There are 910 in Δα and 696 in Δδ. The mean precisions of Δα′s and Δδ′s are ±3.9 ms and ±0″.067, respectively. Under certain conditions 328 Δα′s and 12 Δδ′s from the observed single passage of the stars are determined. Finally systematic corrections of PACP3—FK5 are given.

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.

A Discussion on astronomy in the ultraviolet - The Celescope survey and the galactic distribution of interstellar absorption

1975 ◽  
Vol 279 (1289) ◽  
pp. 345-354 ◽  
Keyword(s):  
Interstellar Dust ◽  
Interstellar Extinction ◽  
Astronomical Observatory ◽  
Digital Television ◽  
National Observatory ◽  
Interstellar Absorption ◽  
The Galaxy ◽  
Galactic Distribution

The Celescope experiment consisted of four 31 cm aperture telescopes equipped with digital television photometers, installed in the Orbiting Astronomical Observatory, launched 7 December 1968. We used this instrument to conduct a survey in four ultraviolet colours: U l (2100-3200 A), U2 (1550—3200 A), U3 (1350— 2150 A) and U4 (1050-2150 A). We have published the observational results in the Celescope catalog of ultraviolet stellar observations (Davis, Deutschman & Haramundanis 1973). I have studied these results, together with relevant ground-based data, to determine the distribution of interstellar dust and variations of the interstellar extinction law with the position in the galaxy. Results from the data contained in the Celescope catalogue have been prepared for publication (Peytremann & Davis 1974)- These results have now been refined and expanded to include new ground-based U, B, V, and H(3 photometry acquired at Kitt Peak National Observatory, as well as new observations by W. A. Deutschman and R. Schild at Cerro Tololo Inter-American Observatory

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.

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 A new spectropolarimeter for the San Pedro Martir National Observatory

2013 ◽  
Vol 9 (S302) ◽  
pp. 154-155
Author(s):  
E. Iñiguez-Garín ◽  
D. Hiriart ◽  
J. Ramirez-Velez ◽  
J. M. Núñez-Alfonso ◽  
J. Herrera ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Linear Polarization ◽  
Astronomical Observatory ◽  
Point Sources ◽  
Spectral Lines ◽  
National Observatory ◽  
San Pedro ◽  
Magnetic Stars ◽  
Star Images ◽  
The Magnetic Field

AbstractWe present the design of a stellar spectropolarimeter to measure the magnetic field of point sources. The polarization module interfaces the Boller and Chivens (B&Ch) intermediate-low resolution (R ~ 500 − 4000) spectrograph to the 2.1-m telescope of the San Pedro Martir National Astronomical Observatory in Mexico. The module uses a Savart plate to split the beam into two orthogonal states of polarization and a quarter (half) waveplate to measure circular (linear) polarization. The module is mounted to the telescope and it feeds the spectrograph through a set of four fibers, two for the polarized star images and two for the spectrograph calibration lamp. The instrument will be capable of measuring polarization in spectral lines to determine the longitudinal and transversal fields in magnetic stars.

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