scholarly journals Some Blue Stars of Peculiar Type in the Region of the South Galactic Pole

1973 ◽  
Vol 50 ◽  
pp. 245-250
Author(s):  
J. A. Graham ◽  
A. Slettebak
Keyword(s):  
Classification Criteria ◽  
Type Star ◽  
Horizontal Branch ◽  
The South ◽  
B Stars ◽  
Subdwarf B Stars ◽  
Horizontal Branch Stars ◽  
Photometric Observations ◽  
Late Type Star ◽  
Objective Prism

uvby photometric observations have been used in conjunction with slit spectra to classify 90 stars which were noted as peculiar by Slettebak and Brundage in a recent objective prism survey of the South Galactic Pole region. In this paper, we review the photometric classification criteria and identify in the Slettebak-Brundage list, 8 subdwarf O stars, 10 subdwarf B stars, 10 horizontal branch stars, 1 white dwarf star and 26 late subdwarf stars. Three stars with outstanding peculiarities are SB (Slettebak-Brundage) 58 which is a helium subdwarf O star, SB 319 (CD–38°245), a late type star with extremely weak metal lines and SB 845 (BD–13°6465), an A type star with a very small Balmer discontinuity.

scholarly journals Progress in the study of pulsating subdwarf B stars

2015 ◽  
Vol 11 (A29B) ◽  
pp. 589-595
Author(s):  
M. D Reed
Keyword(s):  
Differential Rotation ◽  
Observational Constraints ◽  
Interior Structure ◽  
Horizontal Branch ◽  
B Stars ◽  
Subdwarf B Stars ◽  
Rotation Periods ◽  
Horizontal Branch Stars ◽  
Short Period

AbstractDuring Kepler's main mission, nearly 20 pulsating subdwarf B (sdB: extreme horizontal branch stars) were discovered. Many of these stars were observed for three years, accumulating over 1.5 million observations. Only through these extended observations have we been able to identify pulsation modes, applying constraints for structure models. Discoveries include nearly-evenly-spaced asymptotic period overtones which represent the interior structure and rotationally-induced frequency multiplets from which we have learned that rotation periods are long, even when in short-period binaries. This paper reviews progress on observational constraints and highlights some of our discoveries including radially differential rotation, conflicting stratification indicators and mode lifetimes.

scholarly journals The Distribution of Field Horizontal–Branch Stars in the Galactic Halo

1977 ◽  
Vol 4 (2) ◽  
pp. 73-74
Author(s):  
A. G. Davis Philip
Keyword(s):  
Density Distribution ◽  
Galactic Halo ◽  
Galactic Plane ◽  
Horizontal Branch ◽  
Schmidt Telescope ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Horizontal Branch Stars ◽  
General Program ◽  
Objective Prism

Since the time allowed per paper at this joint discussion is short only one aspect of the stellar distribution at high galactic latitudes will be presented here, namely the distribution of field horizontal-branch stars (FHB) in the galactic halo. First, the method by which FHB stars are found will be described. Second, the density distribution of FHB stars will be compared with that of the RR Lyrae stars.As part of a general program to study the stellar density distribution perpendicular to the galactic plane a number of possible FHB stars has been discovered. In each survey area objective prism plates (at a dispersion of 280 Å/mm. to a limiting magnitude of V = 14) are taken with the Michigan Curtis Schmidt telescope at Cerro Tololo Inter-American Observatory or the Schmidt telescope at the Warner and Swasey Observatory. A set of direct plates are taken also to obtain photographic magnitudes for the stars with spectral classifications.

scholarly journals Carbon Stars in the SMC

1994 ◽  
Vol 161 ◽  
pp. 513-515 ◽  
Author(s):  
D.H. Morgan ◽  
D. Hatzidimitriou
Keyword(s):  
Spatial Distribution ◽  
Horizontal Branch ◽  
Carbon Stars ◽  
Schmidt Telescope ◽  
Horizontal Branch Stars ◽  
Objective Prism

More than 1000 new carbon stars have been identified in a ∼200 deg2 area of the SMC during a survey of UK Schmidt Telescope objective-prism plates. Their spatial distribution is like that of the red horizontal branch stars.

scholarly journals The EC14026 Stars - Pulsating Hot Subdwarfs

1998 ◽  
Vol 185 ◽  
pp. 361-366
Author(s):  
C. Koen ◽  
D. O'Donoghue ◽  
D. Kilkenny ◽  
R.S. Stobie
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Plane ◽  
Cataclysmic Variables ◽  
Galactic Nuclei ◽  
Horizontal Branch ◽  
Stellar Objects ◽  
B Stars ◽  
Horizontal Branch Stars ◽  
Blue Object ◽  
Hot Subdwarfs

The Edinburgh-Cape Blue Object Survey (Stobie et al. 1997a) is a southern hemisphere survey to discover hot, blue stellar objects brighter than B=18 at galactic latitudes more than 30° from the galactic plane. The main categories of object detected are hot subdwarfs, white dwarfs, blue horizontal branch stars, apparently normal B stars, cataclysmic variables and (stellar-like) active galactic nuclei. Over 50% of the EC Survey comprises hot subdwarfs.

scholarly journals Mode identification in three pulsating hot subdwarfs observed with TESS satellite

2020 ◽  
Vol 495 (3) ◽  
pp. 2844-2857
Author(s):  
S K Sahoo ◽  
A S Baran ◽  
U Heber ◽  
J Ostrowski ◽  
S Sanjayan ◽  
...  
Keyword(s):  
Spectral Energy ◽  
Data Sets ◽  
B Stars ◽  
Mode Identification ◽  
Subdwarf B Stars ◽  
Stellar Oscillations ◽  
Horizontal Branch Stars ◽  
Trigonometric Parallaxes ◽  
Hot Subdwarfs ◽  
Stellar Masses

ABSTRACT We report on the detection of pulsations of three pulsating subdwarf B stars observed by the Transiting Exoplanet Survey Satellite (TESS) satellite and our results of mode identification in these stars based on an asymptotic period relation. SB 459 (TIC 067584818), SB 815 (TIC 169285097), and PG 0342 + 026 (TIC 457168745) have been monitored during single sectors resulting in 27 d coverage. These data sets allowed for detecting, in each star, a few tens of frequencies that we interpreted as stellar oscillations. We found no multiplets, though we partially constrained mode geometry by means of period spacing, which recently became a key tool in analyses of pulsating subdwarf B stars. Standard routine that we have used allowed us to select candidates for trapped modes that surely bear signatures of non-uniform chemical profile inside the stars. We have also done statistical analysis using collected spectroscopic and asteroseismic data of previously known subdwarf B stars along with our three stars. Making use of high precision trigonometric parallaxes from the Gaia mission and spectral energy distributions we converted atmospheric parameters to stellar ones. Radii, masses, and luminosities are close to their canonical values for extreme horizontal branch stars. In particular, the stellar masses are close to the canonical one of 0.47 M⊙ for all three stars but uncertainties on the mass are large. The results of the analyses presented here will provide important constrains for asteroseismic modelling.

scholarly journals Why do hot subdwarf stars pulsate?

2015 ◽  
Vol 11 (A29B) ◽  
pp. 521-524
Author(s):  
Stephan Geier
Keyword(s):  
Red Giants ◽  
Horizontal Branch ◽  
B Stars ◽  
Subdwarf B Stars ◽  
Long Period ◽  
Sdb Stars ◽  
Short Period ◽  
Instability Regions

AbstractHot subdwarf B stars (sdBs) are the stripped cores of red giants located at the bluest extension of the horizontal branch. Several different kinds of pulsators are found among those stars. The mechanism that drives those pulsations is well known and the theoretically predicted instability regions for both the short-period p-mode and the long-period g-mode pulsators match the observed distributions fairly well. However, it remains unclear why only a fraction of the sdB stars pulsate, while stars with otherwise very similar parameters do not show pulsations. From an observers perspective I review possible candidates for the missing parameter that makes sdB stars pulsate or not.

scholarly journals The Scale Height of Blue Halo subdwarf B Stars

1995 ◽  
Vol 164 ◽  
pp. 403-403
Author(s):  
K.S. De Boer ◽  
A. Theissen ◽  
U. Heber ◽  
S. Moehler
Keyword(s):  
Spatial Distribution ◽  
Scale Height ◽  
Horizontal Branch ◽  
B Stars ◽  
Subdwarf B Stars ◽  
Sdb Stars ◽  
The Past ◽  
Halo Stars ◽  
Red Giant ◽  
Branch Type

Numerous blue halo stars have been discovered during the past decade (e.g. the Palomar-Green Survey). Many are horizontal branch type, being HBA, HBB, sdB, or sdO star. The sdB stars (Teff between ≈ 18 000 and ≈ 30 000 K) are the endproducts of evolution in the red-giant phase. This means that the spatial distribution of the sdB stars can be used to get insight in the population nature and in their spatial origin.

A SEARCH FOR FIELD HORIZONTAL-BRANCH STARS NEAR THE SOUTH GALACTIC POLE

2010 ◽  
Vol 139 (3) ◽  
pp. 1031-1044 ◽  
Author(s):  
R. Ortiz ◽  
R. Wilhelm ◽  
R. D. D. Costa ◽  
S. Rossi ◽  
T. C. Beers
Keyword(s):  
Horizontal Branch ◽  
The South ◽  
Horizontal Branch Stars
Sign in / Sign up

Export Citation Format

Share Document