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] |
Distance | 980 ± 70
ly (300 ± 20 pc) |
Absolute magnitude (MV) | −0.97 [5] |
Orbit [6] | |
Primary | 15 Cancri A |
Companion | 15 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 | |
Luminosity | 327.24 [5] L☉ |
Surface gravity (log g) | 3.22±0.2 [7] cgs |
Temperature | 10,080±200 [7] K |
Rotational velocity (v sin i) | 25 [4] km/s |
Other designations | |
Database references | |
SIMBAD | data |
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]