• Source: NY Virginis

      • NY Virginis is a binary star about 1,940 light-years away. The primary belongs to the rare class of subdwarf B stars, being former red giants with their hydrogen envelope completely stripped by a stellar companion. The companion is a red dwarf star. The binary nature of NY Virginis was first identified in 1998, and the extremely short orbital period of 0.101016 d, together with brightness variability on the timescale of 200 seconds was noticed, resulting in the identification of the primary star as a B-type subdwarf in 2003. Under a proposed classification scheme for hot subdwarfs it would be class sdB1VII:He1. This non-standard system indicates that it is a "normal" luminosity for a hot subdwarf and that the spectrum is dominated by hydrogen rather than helium.


      Planetary system


      In 2011, variations in the timing of the binary star's eclipses were used to infer the presence of a superjovian planet, NY Virginis (AB) b, on a wide orbit, with a second planet being suspected. A study in 2014 found that a two-planet model was preferred. The orbits of these two planets are near or at a 3:10 mutual orbital resonance. Another two-planet model with significant orbital eccentricity, updated to account for changes in eclipse timing not predicted by previous models, was published in 2019.
      Studies in 2022 have noted that since planetary models generally fail to predict subsequent changes in eclipse timing, and the most recent two-planet model as of 2021 results in orbits that are unstable on an astronomically-short timescale.
      However, in 2023 another model with circular orbits was proposed, which gives stability to the system. The same team also find that it is valid that there are exoplanets in the system creating the eclipe timing variations, and that the moderate eccentricites of the previous model likely caused the orbital instability.


      References

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