Astronomy:HD 18391
| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Cassiopeia[1] |
| Right ascension | Template:Ra[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[2] mas/yr Dec.: −1.376[2] mas/yr |
| Parallax (π) | 0.4084 ± 0.0219[2] mas |
| 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 | |
| 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]
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
- ↑ Anderson, E.; Francis, Ch. (2012-05-01). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331–346. doi:10.1134/S1063773712050015. ISSN 1063-7737. Bibcode: 2012AstL...38..331A.
- ↑ 2.0 2.1 2.2 2.3 2.4 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940 Gaia DR3 record for this source at VizieR.
- ↑ 3.0 3.1 "NSV 15616". https://www.aavso.org/vsx/index.php?view=detail.top&oid=54051.
- ↑ 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. doi:10.1086/191373. Bibcode: 1989ApJS...71..245K.
- ↑ 5.00 5.01 5.02 5.03 5.04 5.05 5.06 5.07 5.08 5.09 5.10 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. doi:10.1002/asna.200911238. Bibcode: 2009AN....330..807T.
- ↑ "HD 18391". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+18391.
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