RS Telescopii

RS Telescopii, abbreviated RS Tel, is a variable star in the southern constellation of Telescopium. It is a dim star with an apparent visual magnitude of 10.67,^[3] which is much too faint to be visible without a telescope. The variability of this star was discovered by Evelyn F. Leland and announced by Edward C. Pickering in 1910.^[9] It was first studied by Cecilia H. Payne in 1928 at the Harvard College Observatory.^[10][11]

RS Telescopii

A visual band light curve for RS Telescopii, plotted from AAVSO data[1]
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Telescopium
Right ascension	18h 18m 51.2224s[2]
Declination	−46° 32′ 53.427″[2]
Apparent magnitude (V)	10.67[3]
Characteristics
Spectral type	R0
B−V color index	2.100±0.510[3]
Variable type	R CrB[4]
Astrometry
Radial velocity (Rv)	−3.0[3] km/s
Proper motion (μ)	RA: −2.730[2] mas/yr Dec.: −6.670[2] mas/yr
Parallax (π)	0.1732±0.0166 mas[2]
Distance	19,000 ± 2,000 ly (5,800 ± 600 pc)
Details
Radius	73[5] R☉
Luminosity	288 (at max)[6] L☉
Surface gravity (log g)	1.0[7] cgs
Temperature	5,800[6] K
Other designations
RS Tel, CD−46°12279, HIP 89739[8]
Database references
SIMBAD	data

This is an R-type carbon star with a class of R0.^[12] RS Tel is a typical R Coronae Borealis variable^[10]—an extremely hydrogen-deficient supergiant thought to have arisen as the result of the merger of two white dwarfs; fewer than 100 have been discovered as of 2012.^[4] It has under 55%^[13] the mass of the Sun and an effective temperature of around 5,800 K.^[6] The spectrum of the star shows anomalously weak lines of hydrogen, with strong lines of C₂, CN, and neutral carbon.^[14]

RS Tel has a maximum magnitude of 9.6 and a minimum magnitude 16.5.^[15] The star undergoes large, random variations in brightness on a time scale of thousands of days with no apparent periodicity.^[16] The star is surrounded by a circumstellar shell of dust which radiating an infrared excess.^[16]