36 Serpentis
Star in the constellation Serpens
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36 Serpentis is a triple star[9] system in the equatorial constellation of Serpens. It has the Bayer designation b Serpentis, while 36 Serpentis is the Flamsteed designation.[12] The system is visible to the naked eye as a dim, white-hued point of light with a combined apparent visual magnitude of 5.09.[2] It is located 162 light years away from the Sun based on parallax,[1] and is moving closer with a radial velocity of −8 km/s.[8]
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Serpens |
| Right ascension | 15h 51m 15.59418s[1] |
| Declination | −03° 05′ 25.7938″[1] |
| Apparent magnitude (V) | 5.09[2] (5.2 + 7.8)[3] |
| Characteristics | |
| Spectral type | A3Vn[4] or A2IV-Vn[5] (A7 + G0)[6] |
| U−B color index | +0.07[7] |
| B−V color index | +0.12[7] |
| Astrometry | |
| Radial velocity (Rv) | −8[8] km/s |
| Proper motion (μ) | RA: −91.09[1] mas/yr Dec.: −28.21[1] mas/yr |
| Parallax (π) | 20.10±0.33 mas[1] |
| Distance | 162 ± 3 ly (49.8 ± 0.8 pc) |
| Absolute magnitude (MV) | 1.61[2] |
| Orbit[9] | |
| Primary | 36 Ser A |
| Name | 36 Ser B |
| Period (P) | 1,073 days |
| Eccentricity (e) | 0.7 |
| Semi-amplitude (K1) (primary) | 6 km/s |
| Orbit[6] | |
| Primary | 36 Ser AB |
| Name | 36 Ser C |
| Period (P) | 50.6±1.5 yr |
| Semi-major axis (a) | 0.400±0.006″ |
| Eccentricity (e) | 0.8323±0.0047 |
| Inclination (i) | 98.08±0.31° |
| Longitude of the node (Ω) | 74.00±0.31° |
| Periastron epoch (T) | 2002.78±0.17 |
| Argument of periastron (ω) (secondary) | 72.84±0.91° |
| Details | |
| 36 Ser A | |
| Mass | 1.97[9] M☉ |
| Radius | 2.25[9] R☉ |
| Luminosity | 19.13[2] L☉ |
| Surface gravity (log g) | 3.89[10] cgs |
| Temperature | 8,213[9] K |
| Metallicity [Fe/H] | −2.00[10] dex |
| Rotational velocity (v sin i) | 229[11] km/s |
| Age | 710[9] Myr |
| 36 Ser B | |
| Mass | ≥0.37 and ≤0.50[9] M☉ |
| 36 Ser C | |
| Mass | 1.27[9] M☉ |
| Radius | 1.26[9] R☉ |
| Temperature | 6,255[9] K |
| Age | 710[9] Myr |
| Other designations | |
| b Ser, 36 Ser, BD−02°4058, FK5 2249, GC 4210, HD 141851, HIP 77660, HR 5895, SAO 140801, WDS J15513-0305[12] | |
| Database references | |
| SIMBAD | data |
Characteristics
The system consists of two spectroscopic binaries. The inner pair contains components A and B, while the outer pair contains components AB and C. The age of the whole system is estimated at 710 million years.[9]
The components AB and C orbit each other over a long orbital period of 52.8 years and a high eccentricity of 0.83.[6] Gray et al. (2017) found a merged stellar classification of A2IV-Vn for this system,[5] while Cowley et al. matched it with a class of A3Vn,[4] where the 'n' indicates "nebulous" lines caused by rapid rotation.
The primary component, 36 Serpentis A, is an A7-class[6] main sequence star of visual magnitude 5.2.[3] It is spinning rapidly, showing a projected rotational velocity of 229 km/s.[11] It was once thought to be a Lambda Boötis star[13] but this is now disputed.[9] The star is 710 million years old with 1.97 times the mass of the Sun and 2.25 times the Sun's radius.[9] It is radiating 19 times the Sun's luminosity from its photosphere[2] at an effective temperature of 8,213 K.[9]
The secondary, 36 Serpentis B, has been detected only by spectroscopy. It has an orbital period of 1,073 days (2.94 years) and a high eccentricity of 0.7. Interferometric observations have failed to detect this star, implying a luminosity-derived mass less than 0.50 M☉. The radial velocity data suggest a mass of at least 0.37 solar masses. It may be a faint red dwarf or a white dwarf. 36 Ser B is likely the source for the X-ray emission that has been detected coming from this system.[9]
The tertiary, 36 Serpentis C, is a G0 star[6] with a visual magnitude of 7.8.[3] It has 1.27 times the Sun's mass, 1.26 times the Sun's radius, and an effective temperature of 6,555 K.[9]