ER Ursae Majoris

ER Ursae Majoris

A visual band light curve for ER Ursae Majoris. The main plot shows a normal outburst in 2004, with the estimated value for the unobserved maximum plotted in red. The inset plot shows superhump oscillations. Adapted from Zhao et al. (2006).[1]
Observation data
Epoch J2000      Equinox J2000
Constellation Ursa Major
Right ascension 09h 47m 11.941s[2]
Declination +51° 54′ 08.95″[2]
Apparent magnitude (V) 12.4 to 15.2[3]
Characteristics
Variable type Dwarf nova(?)[3]
Astrometry
Proper motion (μ) RA: 33.659 mas/yr[2]
Dec.: −6.209 mas/yr[2]
Parallax (π)2.8039 ± 0.0205 mas[2]
Distance1,163 ± 9 ly
(357 ± 3 pc)
Orbit[4]
Period (P)0.06366±0.00003 d
Eccentricity (e)0.00 (assumed)
Inclination (i)18–50[5]°
Periastron epoch (T)2,449,740.0637±0.0008 HJD
Argument of periastron (ω)
(secondary)		0.00 (assumed)°
Semi-amplitude (K1)
(primary)		48±4 km/s
Details
White dwarf
Mass1.0±0.2[5] M☉
Temperature32,000[5] K
Donor star
Mass0.10[5] M☉
Other designations
PG 0943+521, ER UMa, GSC 03439-00550, 2MASS J09471193+5154089[6]
Database references
SIMBADdata

ER Ursae Majoris is a variable star in the northern circumpolar constellation of Ursa Major, abbreviated ER UMa. It is a prototype system for a subclass of SU Ursae Majoris dwarf novae.[5] The system ranges in brightness from a peak apparent visual magnitude of 12.4 down to 15.2,[3] which is too faint to be visible to the naked eye. The distance to this system, based on parallax measurements, is approximately 1,163 light years.[2]

This system was identified as an ultraviolet excess object as part of the Palomar-Green (PG) survey by R. F. Green and associate in 1986. It was given the catalog identifier PG 0943+521, and was confirmed to be cataclysmic variable. In 1992, it was determined this is a dwarf nova that ranges in brightness from magnitude 12.3 down to 15.2. F. A. Ringwald in 1993 found a candidate orbital period of 0.1997 days based on radial velocity variation, but with some uncertainty.[7]

In 1995, T. Kato and C. Kunjaya confirmed this is a SU Ursae Majoris-type dwarf nova, and noted the unusual nature of this system, finding it has a long superoutburst lasting about 20 days and the supercycle (the time between superoutbursts) is very short at around 43 days.[8] Large amplitude superhumps were found to occur near the start of a superoutburst, with a brightness increase of around 0.35 magnitude.[9] The properties of the system suggest a high mass transfer rate and the white dwarf component is hotter than in other typical dwarf novae. During periods of quiescence, the accretion rate is 7.3×10−11 M☉·yr−1.[5]

  1. ^ Cite error: The named reference ZhaoPASJ was invoked but never defined (see the help page).
  2. ^ a b c d e Cite error: The named reference GaiaEDR3 was invoked but never defined (see the help page).
  3. ^ a b c Cite error: The named reference Samus_et_al_2017 was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference Thorstensen_et_al_1997 was invoked but never defined (see the help page).
  5. ^ a b c d e f Cite error: The named reference Guzman_et_al_2019 was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference Green_et_al_1982 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference Kato_Kunjaya_1995 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference Kato_et_al_1996 was invoked but never defined (see the help page).