HD 18391

Last updated
HD 18391
Observation data
Epoch J2000       Equinox J2000
Constellation Cassiopeia [1]
Right ascension 02h 59m 48.72255s [2]
Declination +57° 39′ 47.6735″ [2]
Apparent magnitude  (V)+6.89 –+6.98 [3]
Characteristics
Evolutionary stage yellow supergiant
Spectral type G5Ia-Ib [4]
Variable type SRd [3]
Astrometry
Radial velocity (Rv)−38.47±0.68 [2] km/s
Proper motion (μ)RA: +0.227 mas/yr [2]
Dec.: −1.376 mas/yr [2]
Parallax (π)0.4084±0.0219  mas [2]
Distance 8,000 ± 400  ly
(2,400 ± 100  pc)
Absolute magnitude  (MV)−7.8 [5]
Details
Mass 19 [5]   M☉
Radius 329 [5]   R☉
Luminosity 104,000 [5]   L☉
Surface gravity (log g)1.2 [5]   cgs
Temperature 5,775 [5]   K
Metallicity [Fe/H]+0.02 [5]   dex
Age 9±1 [5]   Myr
Other designations
NSV 15616, BD+57°672, HD 18391, HIP 13962 [6]
Database references
SIMBAD data

HD 18391 is a yellow supergiant star in the northern constellation Cassiopeia. Its brightness varies between apparent magnitudes 6.89 and 6.98 which makes it hard to be seen by the naked eye even from dark skies.

Parallax measurements by the Gaia spacecraft suggest a distance of around 8,000  light years, although an earlier analysis of nearby luminous main sequence stars forming a loose open cluster suggest a distance closer to 5,400 light years if HD 18391 is a member. [5]

A visual band light curve for HD 18391, plotted from data published by Turner et al. (2009) HD18391LightCurve.png
A visual band light curve for HD 18391, plotted from data published by Turner et al. (2009)

HD 18391 lies close to the instability strip, an area of the H-R Diagram where variable stars pulsate in a regular manner with periods related to their luminosity. It is slightly hotter and more luminous than classical Cepheid variable stars on the strip and its pulsations are somewhat less regular. The main pulsation period is 123 days, but with a secondary period of 178 days. The amplitude of the light variations is smaller than most Cepheid variables at less than 0.1 magnitudes. If the secondary period represents the fundamental mode, then it corresponds closely to the period expected for a Cepheid variable of similar luminosity. [5]

References

  1. ↑ Anderson, E.; Francis, Ch. (2012-05-01). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331–346. arXiv: 1108.4971 . Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. ISSN   1063-7737.
  2. 1 2 3 4 5 6 Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv: 2208.00211 . Bibcode:2023A&A...674A...1G. doi: 10.1051/0004-6361/202243940 . S2CID   244398875. Gaia DR3 record for this source at VizieR.
  3. 1 2 "NSV 15616". International Variable Star Index. Retrieved 2025-03-13.
  4. ↑ Keenan, Philip C.; McNeil, Raymond C. (1989). "The Perkins Catalog of Revised MK Types for the Cooler Stars". The Astrophysical Journal Supplement Series. 71: 245. Bibcode:1989ApJS...71..245K. doi:10.1086/191373.
  5. 1 2 3 4 5 6 7 8 9 10 11 Turner, D. G.; Kovtyukh, V. V.; Majaess, D. J.; Lane, D. J.; Moncrieff, K. E. (2009). "The Cepheid impostor HD 18391 and its anonymous parent cluster". Astronomische Nachrichten. 330 (8): 807. arXiv: 0907.2904 . Bibcode:2009AN....330..807T. doi:10.1002/asna.200911238.
  6. ↑ "HD 18391". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 2025-03-13.
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