VZ Piscium

VZ Piscium

A light curve for VZ Piscium plotted from TESS data[1]
Observation data
Epoch J2000      Equinox J2000
Constellation Pisces
Right ascension 23h 27m 48.388s[2]
Declination +04° 51′ 23.94″[2]
Apparent magnitude (V) 10.20 – 10.45[3]
Characteristics
Evolutionary stage Main sequence
Spectral type K2 + K5 + M9[4]
B−V color index 1.15[5]
Variable type Contact-type W UMa[3]
Astrometry
Radial velocity (Rv)−4.3±1.8[6] km/s
Proper motion (μ) RA: +437.182 mas/yr[2]
Dec.: +177.857 mas/yr[2]
Parallax (π)18.3420 ± 0.0166 mas[2]
Distance177.8 ± 0.2 ly
(54.52 ± 0.05 pc)
Absolute magnitude (MV)6.51[5]
Orbit[7]
Period (P)0.26125921 d
Semi-major axis (a)1.897763 R☉
Inclination (i)56.3±0.2°
Details[7]
Primary
Mass0.742 M☉
Radius0.798 R☉
Temperature4,908±8 K
Secondary
Mass0.5998 M☉
Radius0.648 R☉
Temperature4,011±42 K
Tertiary
Mass87.41±9.54[8] MJup
Radius1.06±0.04[8] RJup
Luminosity3.802+0.272
−0.254×10−4[8] L☉
Surface gravity (log g)5.31±0.08[8] cgs
Temperature2,468±50[8] K
Other designations
VZ Psc, BD+04°5012, HIP 115819, SAO 109778, G 29-37, LTT 16900[9]
Database references
SIMBADdata

VZ Piscium is a triple star system in the equatorial constellation of Pisces. it is located at a distance of 178 light years from the Sun based on parallax measurements,[2] and has an apparent visual magnitude of about 10.3.[3][10] This is an eclipsing binary system that undergoes shallow eclipses; the brightness decreases to magnitude 10.45 during the primary eclipse, then to magnitude 10.43 with the secondary eclipse, although as a contact binary the brightness varies continuously with no period of constant maximum brightness.[3] The system is drifting closer with a radial velocity of approximately −4 km/s,[6] and has a net heliocentric velocity of 144.1 km/s.[10]

S. C. Wolff and associates examined the spectrum of this star in 1965 and found very weak H and K lines with an emission component. Some of the lines are doubled, which suggested this is a contact binary. It was confirmed as a W Ursae Majoris (W UMa) variable using photometric observations made by J. Moorhead.[11] O. J. Eggen in 1967 found a period of just 6.26 hours and a high tangential space velocity of at least 100 km/s.[12] Most of the variability of the system was found to be ellipsoidal and a small O'Connell effect was detected. The combined stellar class of the system matches a K-type main-sequence star with a type of about K3. A mass ratio close to one indicates the two stars have similar mass.[13]

Due to physical contact, most W UMa-type variables show eclipse minima of almost equal depth, but that is not the case for VZ Psc.[14] The H and K line emission for this system suggests surface magnetic activity, and thus star spots. These darker features may explain the varying light curve of the system.[14] A variation in the orbital period of the system has been observed over a time frame of 25 years, which may be explained by a magnetic activity cycle of the lower mass component.[15] There is a temperature difference of about 900 K between the two components, which remains unexplained as direct contact would tend to even out the temperature. Both stars are highly distorted by the gravity of the other star. The more massive star is a third larger in the direction of the companion than pole-to-pole, and the less massive star is even more distorted.[7]

The outer (tertiary) companion, named HIP 115819 B, was detected as a member of this system in 2014 using data from the Pan-STARRS.[16] It is located at a projected separation of 1,825+180
−390 AU from the inner pair. It is a very low-mass star with 7.9–8.5% the mass of the Sun and a spectral type M9.[4] This star has a cool effective temperature of 2,468±50 K and 1.06 times the radius of Jupiter (~0.11 times the radius of the Sun).[8]

  1. ^ Cite error: The named reference MAST was invoked but never defined (see the help page).
  2. ^ a b c d e Cite error: The named reference GaiaEDR3 was invoked but never defined (see the help page).
  3. ^ a b c d Cite error: The named reference Samus_et_al_2017 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference Baron2015 was invoked but never defined (see the help page).
  5. ^ a b Cite error: The named reference mateo2017 was invoked but never defined (see the help page).
  6. ^ a b Cite error: The named reference Bilir_et_al_2005 was invoked but never defined (see the help page).
  7. ^ a b c Cite error: The named reference Yue_et_al_2019 was invoked but never defined (see the help page).
  8. ^ a b c d e f Cite error: The named reference sanghi was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  10. ^ a b Cite error: The named reference Anderson_Francis_2012 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference Wolff_et_al_1965 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Eggen1967 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference Milone_et_al_1985 was invoked but never defined (see the help page).
  14. ^ a b Cite error: The named reference Maceroni_et_al_1990 was invoked but never defined (see the help page).
  15. ^ Cite error: The named reference Qian_et_al_2004 was invoked but never defined (see the help page).
  16. ^ Cite error: The named reference Deacon2014 was invoked but never defined (see the help page).