X Cancri
  | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cancer |
| Right ascension | 08h 55m 22.88246s[1] |
| Declination | +17° 13′ 52.5853″[1] |
| Apparent magnitude (V) | 6.28[2] |
| Characteristics | |
| Spectral type | C-N4.5 C25.5 MS3[3] |
| B−V color index | +2.975±0.039[2] |
| Variable type | SRb[4] |
| Astrometry | |
| Radial velocity (Rv) | −5.0±0.7[2] km/s |
| Proper motion (μ) | RA: −2.577[1] mas/yr Dec.: +6.303[1] mas/yr |
| Parallax (π) | 1.1129 ± 0.2875[1] mas |
| Distance | approx. 2,900 ly (approx. 900 pc) |
| Absolute magnitude (MV) | −4.96[5] |
| Details | |
| Radius | 208[6] R☉ |
| Luminosity | 4,646[6] L☉ |
| Surface gravity (log g) | −0.014[6] cgs |
| Temperature | 3,239[6] K |
| Metallicity [Fe/H] | −0.3[7] dex |
| Other designations | |
| Database references | |
| SIMBAD | data |
X Cancri is a variable star in the northern constellation of Cancer.[8] It has a red hue and is visible to the naked eye at peak magnitude, fluctuating around an apparent visual magnitude of 6.28.[2] The distance to this object is approximately 2,900 light years based on parallax measurements,[1] but is drifting closer with a radial velocity of −5 km/s.[2] It lies very close to the equinox and so is subject to lunar occultations.[9]
This object is carbon star – an aging red giant star on the asymptotic giant branch that has a higher abundance of carbon than oxygen in its atmosphere[5] – and is one of the brightest carbon stars in the sky.[10] It has a carbon star spectral classification of C-N4.5 C25.5 MS3.[3] The first C indicates that it is a carbon star, and the N5 that it is a fairly cool strongly red AGB star. The C2 index indicates the strength of the Swan bands on a scale of one to eight, which shows the relative abundance of carbon vs oxygen. The MS index, not to be confused with an MS spectral class, indicates the strength of the SiC2 bands on a scale of one to seven. These bands are thought to be very sensitive to temperature.[11]
This is a semiregular variable star of subtype SRb that ranges in brightness from visual magnitude 5.52 down to 7.5 with a period of 193 days.[4] Fourier analysis has shown that the star also pulsates with periods of 350 and 1,870 days.[12]
The angular diameter of X Cancri has been measured using both lunar occultations and very long baseline interferometry, both methods giving a diameter around 8 mas.[13]
References[edit]
- ^ a b c d e f Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
- ^ a b c d e Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015.
- ^ a b Barnbaum, Cecilia; et al. (1996), "A Moderate-Resolution Spectral Atlas of Carbon Stars: R, J, N, CH, and Barium Stars", Astrophysical Journal Supplement, 105: 419, Bibcode:1996ApJS..105..419B, doi:10.1086/192323.
- ^ a b Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085.
- ^ a b Guandalini, R.; Cristallo, S. (2013), "Luminosities of carbon-rich asymptotic giant branch stars in the Milky Way", Astronomy & Astrophysics, 555: 7, arXiv:1305.4203, Bibcode:2013A&A...555A.120G, doi:10.1051/0004-6361/201321225, A120.
- ^ a b c d McDonald, I.; Zijlstra, A. A.; Watson, R. A. (2017), "Fundamental parameters and infrared excesses of Tycho-Gaia stars", Monthly Notices of the Royal Astronomical Society, 471 (1): 770, arXiv:1706.02208, Bibcode:2017MNRAS.471..770M, doi:10.1093/mnras/stx1433.
- ^ Lambert, David L.; et al. (October 1986), "The Chemical Composition of Carbon Stars. I. Carbon, Nitrogen, and Oxygen in 30 Cool Carbon Stars in the Galactic Disk", Astrophysical Journal Supplement, 62: 373, Bibcode:1986ApJS...62..373L, doi:10.1086/191145.
- ^ a b "X Cnc". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-02-26.
- ^ Schmidtke, P. C.; Africano, J. L. (January 2011), "KPNO Lunar Occultation Summary. III", The Astronomical Journal, 141 (1): 7, Bibcode:2011AJ....141...10S, doi:10.1088/0004-6256/141/1/10, 10.
- ^ Upgren, A. R. (February 1973), "The Parallax and Proper Motion of the Carbon Star X CANCRI", Astrophysical Journal, 179: L121, Bibcode:1973ApJ...179L.121U, doi:10.1086/181130.
- ^ Keenan, Philip C. (1993), "Revised MK Spectral Classification of the Red Carbon Stars", Publications of the Astronomical Society of the Pacific, 105: 905, Bibcode:1993PASP..105..905K, doi:10.1086/133252.
- ^ Kiss, L. L.; Szatmáry, K.; Cadmus, R. R.; Mattei, J. A. (1999), "Multiperiodicity in semiregular variables. I. General properties", Astronomy and Astrophysics, 346: 542, arXiv:astro-ph/9904128, Bibcode:1999A&A...346..542K.
- ^ Richichi, A.; Percheron, I. (2002), "CHARM: A Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics, 386 (2): 492–503, Bibcode:2002A&A...386..492R, doi:10.1051/0004-6361:20020236.
