15 Cancri

15 Cancri

A light curve for BM Cancri, plotted from TESS data[1]
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cancer
Right ascension 08h 13m 08.87009s[2]
Declination +29° 39′ 23.5777″[2]
Apparent magnitude (V) 5.53 - 5.65[3]
Characteristics
Spectral type A0:V:spSiSr[4]
B−V color index −0.073±0.002[5]
Variable type α2 CVn[3]
Astrometry
Radial velocity (Rv)25.0±0.8[6] km/s
Proper motion (μ) RA: −12.959[2] mas/yr
Dec.: −22.232[2] mas/yr
Parallax (π)3.3279 ± 0.2458 mas[2]
Distance980 ± 70 ly
(300 ± 20 pc)
Absolute magnitude (MV)−0.97[5]
Orbit[6]
Primary15 Cancri A
Companion15 Cancri B
Period (P)635.73±0.53 days[note 1]
Eccentricity (e)0.55±0.08
Periastron epoch (T)2422045±18
Argument of periastron (ω)
(primary)		196±13°
Semi-amplitude (K1)
(primary)		9.6±1.1 km/s
Details
15 Cnc A
Luminosity327.24[5] L☉
Surface gravity (log g)3.22±0.2[7] cgs
Temperature10,080±200[7] K
Rotational velocity (v sin i)25[4] km/s
Other designations
15 Cnc, BM Cnc, BD+30°1664, HD 68351, HIP 40240, HR 3215, GSC 01939-01462[8]
Database references
SIMBADdata

15 Cancri is an α2 CVn-type variable star in the zodiac constellation of Cancer, located around 980[2] light years away. It has the variable star designation BM Cancri (BM Cnc); 15 Cancri (15 Cnc) is the Flamsteed designation. This system is visible to the naked eye as a faint, white-hued star with an apparent visual magnitude of about 5.6. It is moving away from the Earth with a heliocentric radial velocity of 25 km/s.[6]

Radial velocity measurements taken at the Dominion Astrophysical Observatory in Victoria, British Columbia Canada in 1918 and 1919 led to the determination that 15 Cancri is a single-lined spectroscopic binary system.[9] The first orbit was calculated in 1973 by Helmut Abt and Michael Snowden with a period of 585 days[10] however later measurements showed that the orbital period was 635 days.[6][note 1]

15 Cancri A, the visible component, is an Ap star, a chemically peculiar star with an over-abundance of iron peak elements, particularly silicon, chromium, and strontium, in its spectrum.[11][4]

Like all Ap stars, 15 Cancri has a strong magnetic field. This magnetic field varies as it rotates and in 1968 the visual brightness of the star was shown to vary regularly over about four days.[12] 15 Cancri was given the variable star designation BM Cancri in 1972 as a member of the α2 CVn class of variable stars.[13] The period has since been measured more accurately at 3.3095 d, believed to be the rotational period of the star.[14]

  1. ^ Cite error: The named reference MAST was invoked but never defined (see the help page).
  2. ^ a b c d e f Cite error: The named reference GaiaDR2 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference gcvs was invoked but never defined (see the help page).
  4. ^ a b c Cite error: The named reference abt was invoked but never defined (see the help page).
  5. ^ a b c Cite error: The named reference Anderson2012 was invoked but never defined (see the help page).
  6. ^ a b c d Cite error: The named reference Stickland1984 was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference Khalack2015 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference Plaskett1919 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference Abt1973 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference renson was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference stepien was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference ibvs was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference wraight was invoked but never defined (see the help page).


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