HD 142990, also known as HR 5942 and V913 Scorpii, is a star about 470
light years from the Earth, in the constellation
Scorpius.[2] It is a 5th
magnitude star, so it will be faintly visible to the
naked eye of an observer far from
city lights.[2] It is a variable star, whose brightness varies slightly from 5.40 to 5.47 during its 23.5 hour rotation period.[11][3] It is a member of the Upper Scorpius Region of the
Scorpius–Centaurus association.[12]
The variability of HD 142990 was discovered in 1977 by
Holger Pedersen and Bjarne Thomsen, during a
spectroscopic and
photometric study of helium weak and helium strong stars.[14] In 1978 the star was given the
variable star designation V913 Scorpii.[15] Far more extensive photometric data were provided by the
Kepler K2 program, which sampled the light curve well, and allowed Dominic Bowman et al. to measure the star's 0.978832±0.000002 day rotation period.[7]
The rotation period of HD 142990 appears to be decreasing at a rate of about 0.6 seconds per year. This might mean the star is still contracting towards the
zero-age main sequence, though other explanations involving
magnetohydrodynamics have been proposed.[16]
In 1989, Jeffrey Linsky et al. reported the detection of 6 cm radio emission from HD 142990, which appeared to be variable on a time scale of 5 minutes.[17] In 2018, Emil Lenc et al. found that the radio emission from the star is circularly polarized.[18] In 2019, Barnali Das et al. reported that HD 142990 exhibits
coherent electron cyclotron
maser emission at 200 MHz, making it, at that time, only the fourth hot magnetic star known to emit by this mechanism .[6]
^Houk, N.; Smith-Moore, M. (1988). Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars. Volume 4, Declinations -26°.0 to -12°. Department of Astronomy, University of Michigan.