TZ Mensae
Algol type binary in the constellation Mensa
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TZ Mensae is a binary star in the southern circumpolar constellation Mensa. The system has a combined maximum apparent magnitude of 6.19,[13] placing it near the limit for naked eye visibility. Parallax measurements place the system at a distance of 403 light years.[2] The radial velocity is small.[7]
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Mensa |
| Right ascension | 05h 30m 13.8827s[2] |
| Declination | −84° 47′ 06.366″[2] |
| Apparent magnitude (V) | 6.19 to 6.87[3] |
| Characteristics | |
| U−B color index | −0.11[4] |
| B−V color index | −0.02[4] |
| Variable type | Algol variable[5] |
| A | |
| Spectral type | A0 V[6] |
| B | |
| Spectral type | A8 V[6] |
| Astrometry | |
| Radial velocity (Rv) | −0.3±0.9[7] km/s |
| Proper motion (μ) | RA: −6.242 mas/yr[2] Dec.: +43.141 mas/yr[2] |
| Parallax (π) | 8.0907±0.0381 mas[2] |
| Distance | 403 ± 2 ly (123.6 ± 0.6 pc) |
| Absolute magnitude (MV) | +0.93[8] (combined) |
| Orbit[9] | |
| Primary | A |
| Name | B |
| Period (P) | 8.569 d |
| Semi-major axis (a) | 0.13 AU |
| Eccentricity (e) | 0.035±0.007 |
| Inclination (i) | 88.73° |
| Periastron epoch (T) | 2442403.7085 |
| Argument of periastron (ω) (secondary) | 295° |
| Semi-amplitude (K1) (primary) | 62.2 km/s |
| Semi-amplitude (K2) (secondary) | 102.8 km/s |
| Details[10] | |
| A | |
| Mass | 2.49±0.02 M☉ |
| Radius | 1.90±0.02 R☉ |
| Luminosity | 39.8+7 −6 L☉ |
| Surface gravity (log g) | 4.22±0.01[9] cgs |
| Temperature | 10,543+421 −405 K |
| Rotational velocity (v sin i) | 16±4[9] km/s |
| B | |
| Mass | 1.50±0.01 M☉ |
| Radius | 1.40±0.01 R☉ |
| Luminosity | 4.57+0.8 −0.7 L☉ |
| Surface gravity (log g) | 4.30±0.01[9] cgs |
| Temperature | 7178+303 −291 K |
| Rotational velocity (v sin i) | 12[9] km/s |
| Metallicity [Fe/H] | −0.12±0.05[6] dex |
| Age | 141±3[6] Myr |
| Other designations | |
| 31 G. Mensae[11], TZ Men, CD−84°63, CPD−84°75, FK5 1659, GC 7134, HD 39780, HIP 25776, HR 2059, SAO 258418[12] | |
| Database references | |
| SIMBAD | data |
The components of TZ Mensae have stellar classifications of A0 V and A8 V,[6] both indicating that they are ordinary A-type main-sequence stars. They have masses of 1.5 and 2.5 M☉, and radii of 1.4 and 1.9 R☉, respectively.[10] The primary has an effective temperature of 10,543 K and a luminosity 40 times that of the Sun (L☉).[10] As for the companion, it has a temperature of 7,178 K. and a luminosity less than five L☉[10] The rotation of both stars is apparently synchronous with the orbital period, with projected rotational velocities of 12 and 16 km/s respectively.[9] The system is estimated to be 141 million years old.[6]
The two components take about 8 days to revolve around each other in a relatively circular orbit.[9] Since the inclination is close to 90° (actually 88.7°),[9] the two stars periodically pass in front of one another and it has been classified as a eclipsing binary, specifically the Algol type.[5] If the brighter component is eclipsing the dimmer one, the brightness drops to 6.36.[5] If vice versa, it drops to 6.87,[3] which is below the limit for naked eye visibility.