FY Canis Majoris (FY CMa), also known as HD 58978, is a star about 1,800 light years from the Earth, in the constellation Canis Major (very near the border of Puppis). It is usually a 5th magnitude star, so it will be visible to the naked eye of an observer far from city lights. It is a Gamma Cassiopeiae variable star, whose brightness varies from magnitude 4.8 to 6.25.
  | |
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Canis Major |
| Right ascension | 07h 26m 59.48269s[1] |
| Declination | −23° 05′ 09.6897″[1] |
| Apparent magnitude (V) | 4.8 - 6.25[2] |
| Characteristics | |
| Spectral type | B0.5 IVe[3] |
| Variable type | γ Cas[2] |
| Astrometry | |
| Proper motion (μ) | RA: −6.692±0.038[1] mas/yr Dec.: +4.054±0.078[1] mas/yr |
| Parallax (π) | 1.7919 ± 0.0645 mas[1] |
| Distance | 1,820 ± 70 ly (560 ± 20 pc) |
| Absolute magnitude (MV) | −2.23[4] |
| Orbit[5] | |
| Primary | Be star |
| Companion | hot subdwarf |
| Period (P) | 37.257±0.003 d |
| Inclination (i) | >66[6]° |
| Periastron epoch (T) | 2448529.64±0.15 |
| Semi-amplitude (K1) (primary) | 14.4±0.9 km/s |
| Semi-amplitude (K2) (secondary) | 128.2±2.2 km/s |
| Details | |
| Be star | |
| Mass | 10-13[6] M☉ |
| Radius | 6.8[6] R☉ |
| Luminosity | 26,915[6] L☉ |
| Temperature | 27,500±3,000[5] K |
| Rotational velocity (v sin i) | 340±40[5] km/s |
| hot subdwarf | |
| Mass | 1.1-1.5[6] M☉ |
| Radius | 0.81[6] R☉ |
| Luminosity | 2,399[6] L☉ |
| Temperature | 45,000±5,000[5] K |
| Rotational velocity (v sin i) | 41±5[5] km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
In 1967, Alejandro Feinstein detected low amplitude (0.14 magnitude) variability in HD 58978's brightness, from photoelectric observations at La Plata Observatory.[10] The star was given the variable star designation FY Canis Majoris in 1973.[11] During an outburst in 2009, the star brightened to magnitude 4.8, its historical peak brightness.[2] TESS data show that FY CMa pulsates at many different frequencies, with periods ranging from 1.07 hours to 5.8 days.[12]
In 1905, Edward King noted that FY CMa has a peculiar spectrum with an unusually bright Hβ (and other) emission lines.[13] Paul Merrill et al. listed it as a Be star in 1925.[14] Spectra taken by various observers over several decades of the 20th century showed that the strength and relative intensities of the star's emission line are variable,[3] and could change on a timescale of just a few days.[15]
In 2008, Geraldine Peters et al. obtained high resolution spectra from the IUE and found that the Be star has hot, far less massive subdwarf companion star, with which it forms a spectroscopic binary.[5]
Hui-Lau Cao calculated that FY CMa is losing mass at a rate of about 6 × 10−8 M☉/year via a stellar wind with a terminal velocity of about 750 km/sec.[16]
References edit
- ^ a b c d e 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.
- ^ a b c "FY CMa". The International Variable Star Index. AAVSO. Retrieved 1 February 2023.
- ^ a b Slettebak, A. (September 1982). "Spectral types and rotational velocities of the brighter Be stars and A-F type shell stars". Astrophysical Journal Supplement Series. 50: 55–83. Bibcode:1982ApJS...50...55S. doi:10.1086/190820.
- ^ Anderson, E.; Francis, Ch. (May 2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331–346. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. eISSN 1562-6873. ISSN 1063-7737. S2CID 119257644.
- ^ a b c d e f Peters, Geraldine J.; Gies, Douglas R.; Grundstrom, Erika D.; McSwain, M. Virginia (October 2008). "Detection of a Hot Subdwarf Companion to the Be Star FY Canis Majoris". Astrophysical Journal. 686 (2): 1280–1291. arXiv:0806.3004. Bibcode:2008ApJ...686.1280P. doi:10.1086/591145.
- ^ a b c d e f g Nazé, Yaël; Rauw, Gregor; Smith, Myron A.; Motch, Christian (2022). "The X-ray emission of Be+stripped star binaries★". Monthly Notices of the Royal Astronomical Society. 516 (3): 3366. arXiv:2208.03990. Bibcode:2022MNRAS.516.3366N. doi:10.1093/mnras/stac2245.
- ^ "HD 58978 -- Be Star". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2023-02-01.
- ^ "ASAS All Star Catalogue". The All Sky Automated Survey. Retrieved 1 February 2023.
- ^ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 1 February 2023.
- ^ Feinstein, A. (1968). "A Survey of Southern Be Stars. II. Photometric data". Zeitschrift für Astrophysik. 68: 29–47. Bibcode:1968ZA.....68...29F.
- ^ Kukarkin, B. V.; Kholopov, P. N.; Kukarkina, N. P.; Perova, N. B. (October 1973). "59th Name-List of Variable Stars" (PDF). Information Bulletin on Variable Stars. 834 (1): 1. Bibcode:1973IBVS..834....1K. Retrieved 2 February 2023.
- ^ Balona, L. A.; Ozuyar, D. (April 2020). "TESS observations of Be stars: a new interpretation". Monthly Notices of the Royal Astronomical Society. 493 (2): 2528–2544. arXiv:1911.03068. Bibcode:2020MNRAS.493.2528B. doi:10.1093/mnras/staa389.
- ^ Pickering, Edward C.; Fleming, W. P. (July 1905). "Stars having peculiar spectra. Spectra of known variables". Astrophysical Journal. 22: 87–90. Bibcode:1905ApJ....22...87P. doi:10.1086/141242.
- ^ Merrill, P. W.; Humason, M. L.; Burwell, C. G. (June 1925). "Discovery and Observations of Stars of Class Be". Astrophysical Journal. 61: 389–417. Bibcode:1925ApJ....61..389M. doi:10.1086/142899.
- ^ Peters, G. J. (May 1987). "FY Canis Majoris". IAU Circ. 4391: 2. Bibcode:1987IAUC.4391....2P. Retrieved 1 February 2023.
- ^ Cao, Hui-Lai (December 2001). "Infall and Outflow Activities in the Be star FY CMa". Chinese Journal of Astronomy & Astrophysics. 1 (6): 514–524. Bibcode:2001ChJAA...1..514C. doi:10.1088/1009-9271/1/6/514.