Rapid Multicolour Variations of Selected Southern Be Stars

1994 ◽  
pp. 305-306
Author(s):  
S. Štefl ◽  
P. Harmanec ◽  
D. Baade
Keyword(s):  
Be Stars

scholarly journals Hα emission-line stars in molecular clouds

2019 ◽  
Vol 630 ◽  
pp. A90 ◽  
Author(s):  
Bertil Pettersson ◽  
Bo Reipurth
Keyword(s):  
Molecular Clouds ◽  
Young Stellar Objects ◽  
Be Stars ◽  
Stellar Objects ◽  
Strong Concentration ◽  
Ob Stars ◽  
Star Forming ◽  
Hα Emission ◽  
Objective Prism ◽  
Emission Stars

A deep objective-prism survey for Hα emission stars towards the Canis Major star-forming clouds was performed. A total of 398 Hα emitters were detected, 353 of which are new detections. There is a strong concentration of these Hα emitters towards the molecular clouds surrounding the CMa OB1 association, and it is likely that these stars are young stellar objects recently born in the clouds. An additional population of Hα emitters is scattered all across the region, and probably includes unrelated foreground dMe stars and background Be stars. About 90% of the Hα emitters are detected by WISE, of which 75% was detected with usable photometry. When plotted in a WISE colour–colour diagram it appears that the majority are Class II YSOs. Coordinates and finding charts are provided for all the new stars, and coordinates for all the detections. We searched the Gaia-DR2 catalogue and from 334 Hα emission stars with useful parallaxes, we selected a subset of 98 stars that have parallax errors of less than 20% and nominal distances in the interval 1050 to 1350 pc that surrounds a strong peak at 1185 pc in the distance distribution. Similarly, Gaia distances were obtained for 51 OB-stars located towards Canis Major and selected with the same parallax errors as the Hα stars. We find a median distance for the OB stars of 1182 pc, in excellent correspondence with the distance from the Hα stars. Two known runaway stars are confirmed as members of the association. Finally, two new Herbig-Haro objects are identified.

scholarly journals The Use of Terms and Definitions in the Study of Be Stars (Review Paper)

1987 ◽  
Vol 92 ◽  
pp. 3-21
Author(s):  
George W. Collins
Keyword(s):  
Review Paper ◽  
Be Stars ◽  
Basic Definition ◽  
The Subject ◽  
Definition Of ◽  
Incorrect Usage

AbstractIn this paper I shall examine the use and misuse of some astronomical terminology as it is commonly found in the literature. The incorrect usage of common terms, and sometimes the terms themselves, can lead to confusion by the reader and may well indicate misconceptions by the authors. A basic definition of the Be phenomena is suggested and other stellar characteristics whose interpretation may change when used for non-spherical stars, is discussed. Special attention is paid to a number of terms whose semantic nature is misleading when applied to the phenomena they are intended to represent. The use of model-dependent terms is discussed and some comments are offered which are intended to improve the clarity of communication within the subject.

scholarly journals The Possible Role of Radiative Acceleration in Supporting Extended Atmospheres in Be Stars

1976 ◽  
Vol 70 ◽  
pp. 377-382 ◽  
Author(s):  
R. L. Kurucz ◽  
R. E. Schild
Keyword(s):  
Effective Temperature ◽  
Detailed Calculation ◽  
Be Stars ◽  
Be Star ◽  
Hα Emission ◽  
Two Peaks ◽  
Radiative Acceleration ◽  
Emission Strength ◽  
Peaked Function

A detailed calculation of the radiative acceleration in B-type stars shows it to be a double-peaked function of effective temperature at small optical depths. The two peaks are shown to coincide approximately with peaks in the distribution of mean Hα emission strength as a function of B - V color in Be stars. These facts suggest that radiation may play an important role in the support of the Be star extended atmosphere.

scholarly journals Detection of accreting circumstellar gas around weak emission-line Herbig Ae/Be stars

1994 ◽  
Vol 212 (1-2) ◽  
pp. 107-114 ◽  
Author(s):  
C. A. Grady ◽  
M. R. P�rez ◽  
P. S. Th�
Keyword(s):  
Emission Line ◽  
Be Stars ◽  
Circumstellar Gas

scholarly journals Probing Be star disks: new insights from Hα spectroscopy and detailed numerical models

2010 ◽  
Vol 6 (S272) ◽  
pp. 398-399 ◽  
Author(s):  
Carol E. Jones ◽  
Christopher Tycner ◽  
Jessie Silaj ◽  
Ashly Smith ◽  
T. A. Aaron Sigut
Keyword(s):  
High Resolution ◽  
Numerical Models ◽  
Analytical Tool ◽  
High Resolution Spectroscopy ◽  
Be Stars ◽  
Line Shapes ◽  
Physical Conditions ◽  
Temperature Distributions ◽  
Inclination Angles ◽  
Be Star

AbstractHα high resolution spectroscopy combined with detailed numerical models is used to probe the physical conditions, such as density, temperature, and velocity of Be star disks. Models have been constructed for Be stars over a range in spectral types and inclination angles. We find that a variety of line shapes can be obtained by keeping the inclination fixed and changing density alone. This is due to the fact that our models account for disk temperature distributions self-consistently from the requirement of radiative equilibrium. A new analytical tool, called the variability ratio, was developed to identify emission-line stars at particular stages of variability. It is used in this work to quantify changes in the Hα equivalent widths for our observed spectra.

Continuum Energy Distribution of Bright Be Stars

2006 ◽  
Vol 306 (1-2) ◽  
pp. 93-98
Author(s):  
P. S. Goraya
Keyword(s):  
Energy Distribution ◽  
Be Stars ◽  
Continuum Energy

scholarly journals A catalogue of nebulæ and clusters of stars in the southern hemisphere, observed at Paramatta in New South Wales, by James Dunlop, Esq. In a letter addressed to Sir Thomas Makdougall Brisbane, Bart. K. C. B. late Governor of New South Wales. Presented to the Royal Society by John Frederick William Herschel, Esq. Vice President

1833 ◽  
Vol 2 ◽  
pp. 334-335
Keyword(s):  
New South ◽  
New South Wales ◽  
Vice President ◽  
Be Stars ◽  
East Side ◽  
South Wales ◽  
Dark Space ◽  
William Herschel ◽  
Right Ascension ◽  
Different Parts

The observations, of which the results are here given, were made by Mr. Dunlop in the open air, with a 9-feet reflecting telescope, having the clear aperture of the large mirror 9 inches, and fitted up as a meridian telescope; the position of which, and the index error, being ascertained by the passage of known stars. The drawings which accompany the paper were made at the time of observation of the appearances of a great number of nebulæ and clusters, and particularly of the nebulæ major and minor. The paper contains a catalogue and description of 629 nebulæ, arranged in the order of their south polar distance, and in zones for each degree in the order of their right ascension. A few observations are subjoined, describing more particularly the appearance of the nebula minor, which, seen through the telescope, resembles one of the brighter portions of the milky way; of the nebula major, which is brighter, more irregular, and composed of a great number of different parts; and of the dark space on the east side of the cross, or the black cloud, as it is called, which is occasioned by the almost total absence of stars. It is remarked by the author, that neither of the two nebulæ, major and minor, are at present in the place assigned to them by La Caille. He finds also that scarcely any nebulæ exist in a high state of condensation, and very few even in a state of moderate condensation towards the centre. Some have bright points in or near the centre, many of which may be stars; but the greater number of the nebulæ appear only as condensations of the general nebulous matter into faint nebulæ of various forms and magnitudes, generally not well defined; while many of the larger nebulous appearances are resolvable into stars of small magnitudes. But whether nebulæ are universally thus resolvable, is a question of which our instruments are yet incompetent to afford a direct solution, and in the discussion of which we have only analogy as our guide.

scholarly journals Spectropolarimetry of the Hα Line in Herbig Ae/Be Stars

2007 ◽  
Vol 667 (1) ◽  
pp. L89-L92 ◽  
Author(s):  
D. M. Harrington ◽  
J. R. Kuhn
Keyword(s):  
Be Stars
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