SU Ursae Majoris

SU Ursae Majoris

A visual band light curve for the April 1989 superoutburst of SU Ursae Majoris, adapted from Udalski et al. (1990)[1]
Observation data
Epoch J2000      Equinox J2000
Constellation Ursa Major
Right ascension 08h 12m 28.26946s[2]
Declination +62° 36′ 22.4280″[2]
Apparent magnitude (V) 10.8–14.96[3]
Characteristics
Variable type SU UMa[3]
Astrometry
Radial velocity (Rv)+27.0[4] km/s
Proper motion (μ) RA: +6.582[2] mas/yr
Dec.: −24.538[2] mas/yr
Parallax (π)4.5347 ± 0.0286 mas[2]
Distance719 ± 5 ly
(221 ± 1 pc)
Absolute magnitude (MV)+5.1[5]
Orbit[6]
Period (P)0.076351±0.000043 d
Inclination (i)42[5]°
Periastron epoch (T)2,446,143.6672±0.0015 HJD
Semi-amplitude (K1)
(primary)		59±7 km s–1 km/s
Details
White dwarf
Mass0.8[7] M☉
Temperature28,000[7] K
Red dwarf
Mass0.105[8] M☉
Radius0.167[8] R☉
Other designations
AAVSO 0803+62, SU UMa, 2MASS J08122826+6236224[9]
Database references
SIMBADdata

SU Ursae Majoris, or SU UMa, is a close binary star in the northern circumpolar constellation of Ursa Major. It is a periodic cataclysmic variable that varies in magnitude from a peak of 10.8 down to a base of 14.96.[3] The distance to this system, as determined from its annual parallax shift of 4.53 mas,[2] is 719 light-years. It is moving further from the Earth with a heliocentric radial velocity of +27 km/s.[4]

The variable nature of this star was discovered at the Moscow Observatory by Lidiya Tseraskaya (L. Ceraski) in 1908.[10] It was classified as a U Geminorum-type variable, or dwarf nova.[11] Observation since 1926 showed that this variable undergoes two different types of eruptions: a short maxima lasting around two days that ranged in brightness between 11.6–12.9 magnitude, and a longer maxima extending for 13 days that ranged between 10.4–11.8 magnitude. The later event came to be referred to as 'supermaxima'.[12] Similar dwarf novae of this class have since been discovered, and SU UMa is now the prototype for this sub-category of variable stars.[13]

This is a single-lined spectroscopic binary with an orbital period of 1.83 hours.[6] It consists of a white dwarf star that is acquiring matter from its close companion via an accretion disk. This disk is unstable and undergoes periodic outbursts which increase the luminosity of the system.[14] For SU UMa, the accretion rate from the companion is 9.8×10−13 M☉·yr−1.[15] X-ray emission has been detected in the vicinity of the white dwarf, which drops by a factor of four during outbursts. This emission is theorized to come from the boundary layer between the white dwarf and its accretion disk.[14]

  1. ^ Cite error: The named reference Udalski was invoked but never defined (see the help page).
  2. ^ a b c d e f Cite error: The named reference GaiaDR2 was invoked but never defined (see the help page).
  3. ^ a b c Cite error: The named reference gcvs was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference Duflot1995 was invoked but never defined (see the help page).
  5. ^ a b Cite error: The named reference patterson was invoked but never defined (see the help page).
  6. ^ a b Cite error: The named reference Thorstensen1986 was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference urban was invoked but never defined (see the help page).
  8. ^ a b Cite error: The named reference knigge 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. ^ Cite error: The named reference Ceraski1908 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference Kraft1965 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Isles1974 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference vanParadijs1983 was invoked but never defined (see the help page).
  14. ^ a b Cite error: The named reference Collins2010 was invoked but never defined (see the help page).
  15. ^ Cite error: The named reference Zead2017 was invoked but never defined (see the help page).