FY Canis Majoris

FY Canis Majoris
Location of FY Canis Majoris (circled)
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]
Distance1,820 ± 70 ly
(560 ± 20 pc)
Absolute magnitude (MV)−2.23[4]
Orbit[5]
PrimaryBe star
Companionhot 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
Mass10-13[6] M☉
Radius6.8[6] R☉
Luminosity26,915[6] L☉
Temperature27,500±3,000[5] K
Rotational velocity (v sin i)340±40[5] km/s
hot subdwarf
Mass1.1-1.5[6] M☉
Radius0.81[6] R☉
Luminosity2,399[6] L☉
Temperature45,000±5,000[5] K
Rotational velocity (v sin i)41±5[5] km/s
Other designations
HD  58978, HIP 36168, HR 2855, SAO 173752, BD−22 1874[7]
Database references
SIMBADdata

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.

Light curves for FY CMa. The upper panel, showing the long-timescale variability, is plotted from ASAS data,[8] and the lower panels, showing short-timescale variability, is plotted from TESS data.[9]

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]

  1. ^ a b c d e Cite error: The named reference dr3 was invoked but never defined (see the help page).
  2. ^ a b c Cite error: The named reference IVSI was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference Slettebak1982 was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference xhip was invoked but never defined (see the help page).
  5. ^ a b c d e f Cite error: The named reference Peters2008 was invoked but never defined (see the help page).
  6. ^ a b c d e f g Cite error: The named reference naze2022 was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference ASASServer was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference MAST was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference Feinstein1968 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference Kukarkin1973 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Balona2020 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference Pickering1905 was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference Merrill1925 was invoked but never defined (see the help page).
  15. ^ Cite error: The named reference Peters1987 was invoked but never defined (see the help page).
  16. ^ Cite error: The named reference Cao2001 was invoked but never defined (see the help page).