44 bootis

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Double star
44 bootis
Observation
dates equinox :  J2000.0 , epoch : J2000.0
AladinLite
Constellation Bear keeper
Apparent brightness  4.76var (4.70-4.86) mag
Astrometry
Radial velocity −17.89 ± 0.40 km / s
parallax 78.39 ± 1.03 mas
distance  41.6 ± 0.6 ly
(12.8 ± 0.2 pc )
Proper movement :
Rec. Share: −436.24 ± 1.01 mas / a
Dec. portion: 18.94 ± 1.05 mas / a
orbit 
period 209.8 ± 3.3 a
Major semi-axis 3.666 ± 0.021 ″ (≙ 47 AU)
eccentricity 0.511 1 ± 0.006 5
Orbit inclination 83.55 ± 0.05 °
Argument of the node 57.14 ± 0.06 °
Epoch of the periastron 2012.04 ± 0.26
Argument of the periapsis 39.86 ± 0.68 °
Individual data
Names A; B.
Observation data:
Right ascension A. 15 h 03 m 47.30 s
B. 15 h 03 m 47.48 s
declination A. 2473914.6+ 47 ° 39 ′ 14.6 ″
B. 2473915.9+ 47 ° 39 ′ 15.9 ″
Apparent brightness A. 5.14 likes
B. 6.00var (5.8 - 6.4) mag
Typing:
Spectral class A. G1 V
B. K2 V
B − V color index A. 0.58 ± 0.02
B. 0.82 ± 0.02
Physical Properties:
Dimensions A. 1.04 ± 0.02 M ☉
B. 1.28 ± 0.02 M ☉
radius A. 1.05 ± 0.07 R ☉
B. ≈ 0.9 / ≈ 0.6 R ☉
Luminosity A. ≈ 1.2 L ☉
B. ≈ 0.6 / ≈ 0.3 L ☉
Effective temperature A. 5900 ± 65 K
B. ≈ 5,300 / ≈ 5 035 K.
Rotation time A.
B. 0.27 / 0.27 d
Other names
and catalog entries
Bayer name i Bootis
Flamsteed name 44 bootis
Bonn survey BD + 48 ° 2259
Bright Star Catalog HR 5618 [2]
Henry Draper Catalog HD 133640 [3]
Hipparcos catalog HIP 73695 [4]
Tycho catalog TYC 3484-1580-1 [5] TYC 3484-1580-2 [6]
WDS catalog WDS 15038 + 4739
Further designations: Σ1909; GJ 575; CCDM 15038 + 4739

Template: Infobox double star / maintenance / single coordinates

44 Bootis (short 44 Boo ) or i Bootis (short i Boo ; not to be confused with ι Bootis (Iota Bootis)) is a triple star system and variable star in the constellation Bear Guardian . 44 Bootis is 42 light years away from the Sun and appears to us as a fifth magnitude star in the night sky.

The star system

The system initially appears as a visual double star with an orbital period of 210 years and consists of the main star 44 Boo A ( V  = 5.1 mag) and its companion 44 Boo B ( V  = 5.8 - 6.4 mag), whereby the apparent distance is 0.4 ″ ( epoch 2018). In truth, the companion is itself a spectroscopic and photometric double star ( 44 Boo B and 44 Boo C ) with a very short orbital period of 0.2678 days (6.43 hours). Furthermore, the star of this spectroscopic / photometric system form a W Ursae Majoris Variable and thus a contact system (a tight double-star system whose components touching or eng in a common gas envelope (. Common envelope ) are wrapped). At a distance of 42 light years, it is the closest contact system to the sun.

Wilhelm Herschel discovered the double star nature of 44 Boo in 1781. In 1926 the Dutch-American astronomer Jan Schilt identified the companion as the W-Ursae-Majoris star.

Properties of the components

Boo 44 A is a solar analog having an effective temperature of about 5900 K . Different studies come in good agreement on the spectral type G1 (G0 - G2) and a mass of 1.0 - 1.1  M ⊙ .

44 Boo B (≙ 44 Boo BC) is a W-Ursae-Majoris star (subtype W) and one of the interacting binary stars , the quasi-circular orbit having a radius of 1.9  R ⊙ (1.3 million km). The single stars 44 Boo B and 44 Boo C fill their Roche limits almost exactly. The stellar masses and radii are:

  • according to Maceroni et al. (1981): i Boo B: 0.94 M ⊙ , R 0.84 ⊙ ; i Boo C: 0.47 M ⊙ , 0.59 R ⊙ ,
  • by Hill / Fisher / Holmgren (1989): i Boo B: 0.98 M ⊙ , R 0.87 ⊙ ; i Boo C: 0.55 M ⊙ , 0.66 R ⊙ .

According to a more recent determination of the mass based on the orbit around 44 Boo A, the mass seems to be somewhat lower (system mass M B  +  M C  = 1.28 ± 0.02 M ⊙ ). Due to the assumed bound rotation, the rotation of the components around their own axis takes the same time as the period of revolution. During the 6.43-hour orbit, there is mutual cover , which leads to a decrease in brightness. The catalog information on the V brightnesses in the maximum ( V max ), in the main minimum ( V minI ) and in the secondary minimum ( V minII ) are as follows:

  • for the whole system (i Boo A and B): V max = 4.70 mag, V minI = 4.86 mag, V minII = 4.84 mag,
  • only for i Boo B: V max = 5.80 mag, V minI = 6.39 mag, V minII = 6.29 mag.

The light curve profile can vary slightly, which is interpreted as a sequence of star spots . As long-term observations show, the period of the 44-Boo-B system is not perfectly uniform. On the one hand, this is due to the movement of 44 Boo A and B around their barycentre . As a result, the component slowly approaches or moves away from us and the light transit time changes. On the other hand, actual period changes also take place. Such intrinsic changes occurred in the late 1960s (−7  ppm compared to the previous period), 1974 (−9 ppm) and 1986 (−11 ppm). The specialist literature reports further period changes, several of which later turned out to be incorrect because the authors ignored the change in the time of flight. The intrinsic period changes are so far only poorly understood, but a process such as z. B. mass flow between the components in a contact system as here as the obvious cause. Like all W Ursae Majoris stars, 44 Boo B is an X-ray source and shows pronounced atmospheric and magnetic activities. The Chandra X-ray telescope detected an active region at one pole of the heavier star that generates at least half of the system's X-ray radiation. According to the general fate of W Ursae Majoris stars, it can be assumed that both stars will merge into a single star in a few hundred million years.

observation

The visual pair can already be resolved with amateur telescopes during the predominant orbit . At the moment this is difficult to do due to the small angular distance. The angular distance will reach its minimum of 0.2 ″ in 2021, after which it will increase again. For amateurs with small instruments ( opening ≈ 10 cm), 44 Boo can be separated more easily from the beginning of the 2030s. For the visual system, the following ephemeris can be calculated from the path elements in the info box on the right (distance ρ and position angle θ of 44 Boo B to A for the middle of the year):

  • Epoch 2010.5: ρ = 1.56 ″, θ = 61 °
  • Epoch 2015.5: ρ = 0.91 ″, θ = 69 °
  • Epoch 2020.5: ρ = 0.24 ″, θ = 129 °
  • Epoch 2025.5: ρ = 0.80 ″, θ = 219 °
  • Epoch 2030.5: ρ = 1.55 ″, θ = 228 °
  • Epoch 2035.5: ρ = 2.22 ″, θ = 232 °
  • Epoch 2040.5: ρ = 2.80 ″, θ = 233 °

Web links

Remarks

  1. ↑ The term "44i Bootis" can also be found in many publications.
  2. ↑ Unless explicitly referred to the single star, "44 Boo B" means the binary star system (components B and C).

Individual evidence

  1. ^ Dorrit Hoffleit, Wayne H. Warren Jr .: VizieR Online Data Catalog: Bright Star Catalog, 5th Revised Ed. (Hoffleit +, 1991) . In: VizieR On-line Data Catalog: V / 50. Originally published in: 1964BS .... C ...... 0H . 1995. bibcode : 1995yCat.5050 .... 0H . VizieR catalog entry .
  2. ↑ a b N. N. Samus, EV Kazarovets, OV Durlevich, NN Kireeva, EN Pastukhova: General catalog of variable stars: Version GCVS 5.1 . In: Astronomy Reports . Vol. 61, Issue 8, 2017, pp. 80-88. bibcode : 2017ARep ... 61 ... 80S , doi: 10.1134 / S1063772917010085 . GCVS catalog entry (version 12/2018) .
  3. ↑ a b c Wenxian Lu, Slavek M. Rucinski, Waldemar Ogłoza: Radial Velocity Studies of Close Binary Stars. IV . In: The Astronomical Journal . Vol. 122, Ed. 1, 2001, pp. 403-404. bibcode : 2001AJ .... 122..402L , doi: 10.1086 / 321131 , arxiv : astro-ph / 0104065 .
  4. ^ ESA : VizieR Online Data Catalog: The Hipparcos and Tycho Catalogs (ESA 1997) . In: VizieR On-line Data Catalog: I / 239. Originally published in: 1997HIP ... C ...... 0E . 1997. bibcode : 1997yCat.1239 .... 0E . VizieR catalog entry .
  5. ↑ Derived from parallax ( π = 78.39 ± 1.03 mas, ESA 1997).
  6. ^ A b c d e f Henry Zirm: The Rapid Convergence of 44 Boötis with Revised Orbit and Updated Ephemerides . In: Journal of Double Star Observations . Vol. 7, Issue 1, 2011, pp. 24-36. bibcode : 2011JDSO .... 7 ... 24Z .
  7. ↑ a b c d e Erik Høg et al. : VizieR Online Data Catalog: The Tycho-2 Catalog (Hog + 2000) . In: VizieR On-line Data Catalog: I / 259. Originally published in: 2000A & A ... 355L..27H . 2000. bibcode : 2000yCat.1259 .... 0H . VizieR catalog entry (44 Boo A) . VizieR catalog entry (44 Boo B) . V-brightnesses and color indices quoted from SIMBAD.
  8. ↑ a b c Information from the American Association of Variable Star Observers ( [1] ).
  9. ↑ a b c d e Carla Maceroni et al. : Determination of parameters of W UMa systems. I. AE Phe, AQ Tuc, 44 i Boo . In: Astronomy and Astrophysics Supplement Series . Vol. 45, 1981, p. 189. bibcode : 1981A & AS ... 45..187M .
  10. ^ A b c d e f g Graham Hill, Wes A. Fisher, David E. Holmgren: Studies of late-type binaries. I - The physical parameters of 44ι Bootis ABC . In: Astronomy and Astrophysics . Vol. 211, Ed. 1, 1989, pp. 81-98. bibcode : 1989A & A ... 211 ... 81H .
  11. ↑ Brian D. Mason et al. : VizieR Online Data Catalog: The Washington Visual Double Star Catalog (Mason + 2001-2014) . Vers. 2019-06-11. In: VizieR On-line Data Catalog: B / wds. Originally published in: 2001AJ .... 122.3466M . 2019. bibcode : 2019yCat .... 102026M . VizieR catalog entry .
  12. ^ Jan Schilt: Two new variables stars of the type of W Ursae Majoris . In: Astrophysical Journal . Vol. 64, 1926, p. 215. bibcode : 1926ApJ .... 64..215S , doi: 10.1086 / 143006 .
  13. ↑ Kosmas Gazeas, Kazimierz Stępień: Angular momentum and mass evolution of contact binaries . In: Monthly Notices of the Royal Astronomical Society . Vol. 390, Ausg. 4, 2008, p. 1578. bibcode : 2008MNRAS.390.1577G , doi: 10.1111 / j.1365-2966.2008.13844.x , arxiv : 0803.0212 .
  14. ↑ John M. Saxton: Recent observations of 44 Bootis . In: Variable Star Section Circular . No. 91, 1997, pp. 11-16. Ed .: The British Astronomical Association .
  15. ^ Nancy S. Brickhouse, Andrea K. Dupree, Peter R. Young: X-Ray Doppler Imaging of 44i Bootis with Chandra . In: The Astrophysical Journal . Vol. 562, Ed. 1, 2001, L75-L78. bibcode : 2001ApJ ... 562L..75B , doi: 10.1086 / 338121 , arxiv : astro-ph / 0110560 , press article (English) .
  16. ↑ Calculated with the Binary Star Calculator (Vers. 3) by Brian Workman based on the orbital elements of Zirm 2011.