BL Bootis

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Stern
BL Bootis
AladinLite
Observation
dates equinox :  J2000.0 , epoch : J2000.0
Constellation Bear keeper
Right ascension 14 h 05 m 40.46 s
declination + 28 ° 29 ′ 12.3 ″
Apparent brightness 14.75 (14.45 to 15.1) mag
Typing
B − V color index (+0.35) 
Variable star type ACEP 
Astrometry
distance (55,000)  ly
Visual absolute brightness M vis (−1.27 ± 0.02) mag
Proper movement 
Rec. Share: (−5.50 ± 0.05)  mas / a
Dec. portion: (−0.71 ± 0.05)  mas / a
Physical Properties
Dimensions ~ 1.5  M ☉
radius ~ 10  R ☉
Luminosity

~ 300  L ☉

Effective temperature ~ 7000  K
Other names
and catalog entries
2MASS catalog 2MASS J14054048 + 2829123 [1]
Other names BL Bootis, NGC 5466 SAW V19

BL Bootis is a star in the Bear Keeper constellation . As a member of the globular cluster NGC 5466, it is located at a distance of about 55,000  light years . Today the star is counted among the unusual Cepheids .

Investigation history

In 1961 the star was recognized as a variable star . The Russian astronomer Kurotschkin initially thought it was an eclipsing star . Later studies by the astronomer Gryzunowa in the early 1970s indicated an RR Lyrae star with a period of brightness fluctuations of 0.82 days.

Robert Zinn confirmed BL Bootis' affiliation with NGC 5466, but found it too blue to be an RR Lyrae variable. He gave the star the name V19 in the globular cluster.

Today, BL Bootis is considered the prototype of the unusual Cepheids. These stars are similar to the classical Cepheids, but also to the RR Lyrae stars. The origin of these stars has not yet been clarified. For BL Bootis, with a certain mass, formation through merging of two stars is considered likely or as an alternative mass transfer in a binary star system . This is due to the fact that the globular cluster NGC 5466 and the star have a low metallicity and thus a great age. Since the star nevertheless has a higher mass than the sun , it would have to have evolved into a white dwarf long ago if it had had this mass from the start.

Individual evidence

  1. ↑ a b c d BL Boo. In: SIMBAD . Center de Données astronomiques de Strasbourg , accessed January 19, 2019 .
  2. ↑ a b BL Boo. In: VSX. AAVSO, accessed January 19, 2019 .
  3. ↑ a b c d e Robert Zinn, Christopher R. King: The mass of the anomalous cepheid in the globular cluster NGC 5466 . In: The Astrophysical Journal . 262, 1982, pp. 700-08. bibcode : 1982ApJ ... 262..700Z . doi : 10.1086 / 160462 .
  4. ^ A b Robert Zinn, Conard C. Dahn: Variable 19 in NGC 5466: an anomalous cepheid in a globular cluster . In: Astronomical Journal . 81, 1976, pp. 527-33, 565. bibcode : 1976AJ ..... 81..527Z . doi : 10.1086 / 111916 .
  5. ↑ LA Balona: Challenges in Stellar Pulsation . Bentham Science Publishers, 2010, ISBN 978-1-60805-185-4 , p. 135.
  6. ↑ Marcio Catelan, Horace A. Smith: Pulsating Stars . Wiley-VCH, 2015, ISBN 978-3-527-65520-5 .