scholarly journals International multiwavelength campaigns on short-term variability of OB stars: optical polarimetry

1994 ◽  
Vol 162 ◽  
pp. 530-531
Author(s):  
D. McDavid
Keyword(s):  
Optical Spectroscopy ◽  
Linear Polarization ◽  
Wide Band ◽  
Be Stars ◽  
Short Term ◽  
Ob Stars ◽  
Intensive Monitoring ◽  
Polarization Measurements ◽  
Ultraviolet Observations ◽  
Short Term Variability

From 1986 through 1992, wide-band optical (B or V filter) linear polarization measurements of eight Be stars and seven O stars were obtained simultaneously with ultraviolet observations from IUE and worldwide ground-based optical spectroscopy and photometry in a series of campaigns designed to study the short-term variability of these objects. Each campaign consisted of intensive monitoring of a few carefully chosen stars over a period of several days and nights, with the greatest possible continuity subject to the limitations of instrument scheduling, weather, and the longitudes of the observing sites.

scholarly journals Polarization Measurements of Some Herbig Ae/Be Stars

1990 ◽  
Vol 140 ◽  
pp. 323-324
Author(s):  
S. K. Jain ◽  
H.C. Bhatt ◽  
Ram Sagar
Keyword(s):  
Linear Polarization ◽  
Wavelength Dependence ◽  
Be Stars ◽  
Polarization Measurements

We have measured the linear polarization of 8 bright Herbig Ae/Be stars in UBVRI bands. No unique wavelength dependence of polarization magnitude as well as direction is found in these measurements.

scholarly journals Short Term Photometric and Spectroscopic Variability of a Sample of Be Stars

1987 ◽  
Vol 92 ◽  
pp. 74-77
Author(s):  
M. Alvarez ◽  
R. Michel
Keyword(s):  
Be Stars ◽  
Short Term ◽  
Preliminary Results ◽  
Cooperative Program ◽  
Short Term Variability

Previous studies of variable Be stars show that the short-term variability is a common, but not well understood phenomena. From a list of ‘candidates’ given by Alvarez (1980) and Schuster & Alvarez (1983) under a cooperative program between France and México, we choose some interesting Be objects to study their behaviour both in spectroscopy and photometry. We are reporting some preliminary results of our observations.

scholarly journals Photometric studies of Be star variability

1994 ◽  
Vol 162 ◽  
pp. 299-300
Author(s):  
John R. Percy
Keyword(s):  
Time Scales ◽  
Balmer Line ◽  
Radial Pulsation ◽  
Be Stars ◽  
Photometric Study ◽  
Short Term ◽  
Hot Stars ◽  
Be Star ◽  
Short Term Variability

Be stars are hot stars which have shown emission in at least one Balmer line on at least one occasion. As the definition implies, the Be phenomenon can be variable with time: on time scales of days to decades as the circumstellar disc develops and disperses; on time scales of days to months in a few Be stars which are interacting binaries; on time scales of 0.2 to 2 days due to non-radial pulsation or possibly rotation. The Be stars are worthy of photometric study because they are bright and numerous; the nature of the short-term variability is not yet agreed upon; the cause of the development of the disc - and its relationship to the short-term variability - is also not yet known.

scholarly journals Short-term variability and mass loss in Be stars

2016 ◽  
Vol 588 ◽  
pp. A56 ◽  
Author(s):  
D. Baade ◽  
Th. Rivinius ◽  
A. Pigulski ◽  
A. C. Carciofi ◽  
Ch. Martayan ◽  
...  
Keyword(s):  
Mass Loss ◽  
Be Stars ◽  
Short Term ◽  
Short Term Variability

scholarly journals Short-term variability and mass loss in Be stars

2016 ◽  
Vol 593 ◽  
pp. A106 ◽  
Author(s):  
Th. Rivinius ◽  
D. Baade ◽  
A. C. Carciofi
Keyword(s):  
Mass Loss ◽  
Be Stars ◽  
Short Term ◽  
Short Term Variability

scholarly journals Some Important Results From Two Photometric Campaigns on Short Term Variability in Be Stars

1987 ◽  
Vol 92 ◽  
pp. 90-92
Author(s):  
C.R. Stagg
Keyword(s):  
Be Stars ◽  
Short Term ◽  
Be Star ◽  
Comparison Stars ◽  
Set Up ◽  
Short Term Variability

In 1983 and 1984 a programme of UBV observations was carried out to set up a network of standard stars, identify short term variables, and analyse the variability of the 86 bright (V ≳ 6.5) southern (δ < -20°) Be stars.The timing of the observations was designed specifically to reveal short term variability. Each group of Be and comparison stars was observed at least four times. Where possible, the first two sets of observations were made on one night and the next two sets on the next night (and sometimes a fifth set of observations was also made). Eleven Be stars were identified as possible short or intermediate term variables (Stagg, in preparation). These included the Be star 28 ω CMa, whose V and B-V (but not U-B) variations were consistent with the spectroscopic period of 1.37 days found by Baade (1982).

scholarly journals Chinese and Japanese Participation in B/Be Star Campaigns

2000 ◽  
Vol 175 ◽  
pp. 364-371
Author(s):  
J. Hao
Keyword(s):  
Astronomical Observatory ◽  
Be Stars ◽  
Short Term ◽  
Be Star ◽  
Short Term Variability

AbstractIn the early 1980’s, astronomers at the Beijing Astronomical Observatory (BAO) entered a collaboration in a long term photometric observing project on Be stars which included about 30 stars. For example, in 1983 the group at BAO organized a multi-site campaign to measure the short term variability of EW Lac, KX And, KY And, o And, and LQ And. In 1989, 48 Per was selected to be one of the targets of MuSiCoS campaign in which many stellar astronomers at the BAO participated. In 1991, the Be group at the BAO joined a campaign on the prototypical nonradially pulsating B star, 53 Per. In 1992, French & Chinese astronomers proposed a joint campaign on o And and EW Lac. Astronomers in Japan are also active in Be star campaigns and in 1993-5 they organized several campaigns on few well known Be stars (ζ Oph, EW Lac, ϒ Cas, λ Eri and 28 Cyg).

scholarly journals Searching for Magnetospheres around Herbig Ae/Be Stars

Universe ◽  
2021 ◽  
Vol 7 (12) ◽  
pp. 489
Author(s):  
Mikhail Pogodin ◽  
Natalia Drake ◽  
Nina Beskrovnaya ◽  
Sergei Pavlovskiy ◽  
Swetlana Hubrig ◽  
...  
Keyword(s):  
Accretion Disks ◽  
Be Stars ◽  
Early Type ◽  
Short Term ◽  
The Third ◽  
Disk Star ◽  
T Tauri ◽  
Be Star ◽  
Magnetospheric Accretion ◽  
Short Term Variability

We describe four different approaches for the detection of magnetospheric accretion among Herbig Ae/Be stars with accretion disks. Studies of several unique objects have been carried out. One of the objects is the Herbig Ae star HD 101412 with a comparatively strong magnetic field. The second is the early-type Herbig B6e star HD 259431. The existence of a magnetosphere in these objects was not recognized earlier. In both cases, a periodicity in the variation of some line parameters, originating near the region of the disk/star interaction, has been found. The third object is the young binary system HD 104237, hosting a Herbig Ae star and a T Tauri star. Based on the discovery of periodic variations of equivalent widths of atmospheric lines in the spectrum of the primary, we have concluded that the surface of the star is spotted. Comparing our result with an earlier one, we argue that these spots can be connected with the infall of material from the disk onto the stellar surface through a magnetosphere. The fourth example is the Herbig Ae/Be star HD 37806. Signatures of magnetospheric accretion in this object have been identified using a different method. They were inferred from the short-term variability of the He i λ5876 line profile forming in the region of the disk/star interaction.

scholarly journals Polarization Measurements Across the Balmer Lines of Be and Shell Stars

1976 ◽  
Vol 70 ◽  
pp. 261-275 ◽  
Author(s):  
I. S. McLean ◽  
D. Clarke
Keyword(s):  
Line Profile ◽  
Linear Polarization ◽  
New Method ◽  
Degree Of Polarization ◽  
Be Stars ◽  
Intrinsic Polarization ◽  
Polarization Effects ◽  
Polarization Measurements ◽  
Balmer Lines ◽  
The Continuum

We have made linear polarization measurements of several Be and shell stars across the Hα and Hβ lines, all of the stars exhibiting polarization in the continuum, the emphasis here being on measurements made of ζ Tau, 48 Per, φ Per, and γ Cas. Three types of results ensue: some stars show no significant change of polarization across the Balmer features (e.g., 48 Per, X Per); some stars show a reduced polarization across the features (e.g., γ Cas, ζ Tau) indicating the presence of intrinsic polarization; some stars show a change in the degree of polarization but with a marked rotation of the direction of vibration (e.g., φ Per, 48 Lib) which can be attributed to a combination of non-aligned intrinsic (circumstellar) and interstellar polarizations. Interpretations of these results are discussed, and we demonstrate the potential power of line profile polarimetry/photometry as an important new method for separating intrinsic and interstellar polarization effects, thus enabling polarization observations to be used as a constraint on models of Be stars.

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