HD 74180

Last updated
b Velorum
Vela constellation map.svg
Red circle.svg
Location of b Vel (circled)
Observation data
Epoch J2000       Equinox J2000
Constellation Vela
Right ascension 08h 40m 37.57017s [1]
Declination 46° 38 55.4770 [1]
Apparent magnitude  (V)3.81 [2]
Characteristics
Evolutionary stage Yellow supergiant or yellow hypergiant
Spectral type F8 Ib, [3] F0Ia+ [4] or F0Ia [5]
U−B color index +0.34 [2]
B−V color index +0.67 [6]
Variable type suspected α Cyg [4]
Astrometry
Radial velocity (Rv)−25.3 [7]  km/s
Proper motion (μ)RA: 6.124 [8]   mas/yr
Dec.: 4.473 [8]   mas/yr
Parallax (π)0.431 ± 0.101  mas [9]
Distance 3,230 8,250 [lower-alpha 1]   ly
(990 [3] [lower-alpha 2]  2,532 [9] [lower-alpha 3]   pc)
Absolute magnitude  (MV)6.50 [3]
Details
Mass 12.63 [3] 21.4±2.3 [10]   M
Radius 186 [3] [lower-alpha 4]   R
Luminosity 34,040 [3] [lower-alpha 5]   L
Surface gravity (log g)1.38 [3]   cgs
Temperature 5,750 [3]  7,839 [11]   K
Metallicity [Fe/H]0.56 [11]   dex
Rotational velocity (v sin i)21.7±6 [6]  km/s
Age 7.4±0.8 [10] [lower-alpha 6]   Myr
Other designations
b  Velorum, HR  3445, HD  74180, CD 46°4438, FK5 1226, HIP  42570, SAO  220265
Database references
SIMBAD data

HD 74180 is a single [12] star in the constellation Vela. It is a yellow-white F-type supergiant with a mean apparent magnitude of +3.81 and a spectral classification F8Ib. Estimates of its distance to Earth vary between 3,200 and 8,300 light-years.

Contents

A light curve for HD 74180, adapted from van Leeuwen et al. (1998) HD74180LightCurve.png
A light curve for HD 74180, adapted from van Leeuwen et al. (1998)

b Velorum has been classified as a suspected α Cygni variable star which varies by only 0.06 magnitude. There are possible periods near 53, 80, and 160 days, but the variation is largely irregular. [4] It lies less than a degree from the small open cluster NGC 2645, but is not a member. [3]

Several studies have considered b Velorum to be a highly luminous supergiant or hypergiant with an early F spectral type, for example F2 Ia+, [4] F0 Ia, [5] and F4 I. [13] There were corresponding luminosity estimates of several hundred thousand  L. A 2015 study used the Barbier-Chalonge-Divan (BCD) system to derive a luminosity of 34,000 L and a cooler less luminous F8 Ib spectral type. [3]

Distance and size

Multiple papers give different distances for b Velorum. Bailer-Jones et al. (2021) give a distance of about 2,530  pc (8,300  ly ). [9] The Hipparcos spacecraft give a parallax of 0.67±0.16  mas , translating into a distance of 1,492.5 pc (4,868 ly). [1] Aidelman et al. (2015) give a distance of 990 pc (3,200 ly). [3] At the Hipparcos distance, b Velorum has its apparent brightness diminished by 1.11  magnitudes due to interstellar extinction. [11]

b Velorum has an angular diameter estimated at 1.824  mas . [14] The physical size depends on the star's distance, and could be 190 R assuming the distance of Aidelman et al., 290 R assuming the Hipparcos distance, or even 500 R assuming the Bailer-Jones et al. distance. [15]

In chinese astronomy

In Chinese, 天社 (Tiān Shè), meaning Celestial Earth God's Temple , refers to an asterism consisting of Kappa Velorum, Gamma2 Velorum, b Velorum and Delta Velorum. [16] Consequently, Kappa Velorum itself is known as 天社五 (Tiān Shè wǔ), "the Fifth Star of Celestial Earth God's Temple". [17]

Notes

    1. Margin of error of +1960
      1290
      for the second value
    2. This distance applies is b Velorum has spectral type F8Ib.
    3. Margin of error of +600
      397
      for the second value
    4. Applying the Stefan–Boltzmann law with a nominal solar effective temperature of 5,772  K :
    5. From L = 10(0.4*(4.74(Mbol)), where L is the luminosity and Mbol the bolometric magnitude
    6. Assuming 21.4 M as the mass

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    References

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