 Artist's impression of BX Trianguli. The planet is not represented here. | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Triangulum |
| Right ascension | 02h 20m 50.85419s[1] |
| Declination | +33° 20′ 47.4683″[1] |
| Apparent magnitude (V) | 13.366±0.006[2] |
| Characteristics | |
| Evolutionary stage | Red dwarf |
| Spectral type | M2[3] |
| Variable type | Eclipsing binary[4] +Flare star[5] |
| Astrometry | |
| Proper motion (μ) | RA: +144.250mas/yr[1] Dec.: –111.210mas/yr[1] |
| Parallax (π) | 18.9896±0.0259 mas[1] |
| Distance | 171.8 ± 0.2 ly (52.66 ± 0.07 pc)[1] |
| Orbit[4] | |
| Primary | A |
| Companion | B |
| Period (P) | 0.1926 days (4.62 hours) |
| Semi-major axis (a) | 1.33±0.03 R☉ |
| Inclination (i) | 66.89±0.45° |
| Details[4] | |
| A | |
| Mass | 0.578±0.04 M☉ |
| Radius | 0.59±0.01 R☉ |
| Luminosity | 0.053[6] L☉ |
| Temperature | 3,735 K |
| B | |
| Mass | 0.28±0.02 M☉ |
| Radius | 0.27±0.01 R☉ |
| Luminosity | 0.007[6] L☉ |
| Temperature | 3,359±28 K |
| Other designations | |
| BX Tri,LSPM J0220+3320,GSC 02314-00530,2MASS J02205082+3320479, NSVS 6550671 | |
| Database references | |
| SIMBAD | data |
BX Trianguli is a binary system made up of two red dwarfs, in the constellationTriangulum. Both stars eclipse each other and have an orbital period of four hours and 40 minutes. They are located at around 170 light-years from Earth based uponparallax measurements.
This is aneclipsing binary variable, first identified by theNorthern Sky Variability Survey survey in 2004[4] and given itsvariable-star designation BX Trianguli in 2010. Both stars in the system eclipse each other as seen from Earth, causing the brightness of the system to drop from amagnitude of 12.35 to 12.6/12.7 on the secondary/primary ecplise respectively.[7]
The system has also been identified as aflare star.[4][5] Six flares were recorded between 2014 and 2017, the strongest being identified in November 2014, four times stronger than a typicalsuperflare.[5] The large occurrence of flares on BX Trianguli is the highest among eclipsing binaries afterCastor C (YY Geminorum)[8] and might be related to rapid mass transfer between the components. These flares likely occur on BX Trianguli B.[5]
BX Trianguli also has strongmagnetic activity, manifested asstarspots on the primary's surface andHα emission.[6][8]
This system is composed of twored dwarfs, which have an ultra-short period of just 4.6 hours and a separation of 1.33solar radii, or two and a half times thedistance to the Moon.[4] This orbit is one of the shortest known amongmain sequence stars.[8] The primary star, named BX Trianguli A, has a mass equivalent to 58% thesolar mass and a radius equivalent to 60% of thesolar radius, while the secondary BX Trianguli B is smaller, at 28% and 27% of the solar mass and radius respectively.[4] BX Trianguli has asemi-detached configuration, with the "A" component being distorted due to gravitational interactions with its partner.[6]
There is a star that could be bound to this system, called USNO-B1 1233−0046425, at roughly 3500astronomical units of distance.[6]
A circumbinary planet was discovered after analysis ofeclipse timing variations by a high school student and his teacher. After ruling out alternative expanations for the eclipse timing variations, the two discoverers found that they are caused by a seven-Jupiter-mass planet at a separation of 4.5astronomical units (670,000,000 km), with anorbital eccentricity of 0.4. The findings were published in 2024 at theAmerican Association of Variable Star Observers's 113th Annual Meeting.[9]
| Companion (in order from star) | Mass | Semimajor axis (AU) | Orbital period (days) | Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | 7.5 MJ | 4.5 | — | 0.4 | — | — |
