 Avisual bandlight curve for RZ Gruis. The main plot shows the long term variation, and the inset plot shows the short term variability. Adapted from Sicklandet al. (1984)[1] | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Grus |
| Right ascension | 22h 47m 12.007s[2] |
| Declination | −42° 44′ 38.72″[2] |
| Apparent magnitude (V) | 11.6 - 13.6[3] |
| Characteristics | |
| Variable type | UX Ursae Majoris[1] |
| Astrometry | |
| Proper motion (μ) | RA: +23.779±0.019[2]mas/yr Dec.: +0.095±0.017[2]mas/yr |
| Parallax (π) | 1.8421±0.0588 mas[2] |
| Distance | 1,770 ± 60 ly (540 ± 20 pc) |
| Details | |
| Other designations | |
| 2MASS J22471199-4244385,AAVSO 2241-43,Gaia DR2 6544371342567818496[4] | |
| Database references | |
| SIMBAD | data |
RZ Gruis is anova-likebinary system in theconstellationGrus composed of awhite dwarf and anF-typemain-sequencestar. It is generally ofapparent magnitude of 12.3 with occasional dimming to 13.4. Its components are thought toorbit each other roughly every 8.5 to 10 hours (much longer than most nova-like variables, which have periods of around 3 to 4 hours). It belongs to the UX Ursae Majoris subgroup ofcataclysmic variable star systems, where material from the donor star is drawn to the white dwarf where it forms anaccretion disc that remains bright and outshines the two component stars. The system is around 1,434light-years away fromEarth;[5] or as much as 1,770 light years based on aGaia parallax.[6]
Originally named and discovered to be variable in 1949, RZ Gruis was discovered to be a cataclysmic variable after its spectrum was investigated in 1980. Considered initially to be a hot, blueB-type star, it was found to haveBalmer emission lines of the hydrogen atom. If it were indeed a B-type main-sequence star (and hence lie at a remote 35,000 light-years' distance), it would lie well out of thegalactic plane. The investigators proposed that theemission lines have arisen from an accretion disc around a white dwarf rather than from the star itself.[7] The system is poorly known,[5] though the donor star has been calculated to be ofspectral type F5V.[1] These stars have spectra very similar to novae that have returned to quiescence after outbursts, yet they have not been observed to have erupted themselves. TheAmerican Association of Variable Star Observers recommends watching this class of star for future events such as possible nova eruptions.[8]
