DM Ursae Majoris

DM Ursae Majoris

Visual band light curves for DM Ursae Majoris, adapted from Mohin et al. (1985)[1]
Observation data
Epoch J2000      Equinox J2000
Constellation Ursa Major
Right ascension 10h 55m 43.544s[2]
Declination +60° 28′ 09.72″[2]
Apparent magnitude (V) 9.29[3]
Characteristics
Spectral type K0III-IV[4] (K0IV + K5V)[5]
B−V color index 1.014±0.026[3]
Variable type RS CVn[6]
Astrometry
Radial velocity (Rv)−6.9±1.2[7] km/s
Proper motion (μ) RA: −37.912 mas/yr[2]
Dec.: −7.566 mas/yr[2]
Parallax (π)5.3862 ± 0.0157 mas[2]
Distance606 ± 2 ly
(185.7 ± 0.5 pc)
Absolute magnitude (MV)3.65[3]
Orbit[7]
Period (P)7.4920±0.0009 d
Eccentricity (e)0.0 (assumed)
Inclination (i)40[8]°
Periastron epoch (T)2,443,881.4±0.1 JD
Argument of periastron (ω)
(secondary)		0.0 (assumed)°
Semi-amplitude (K1)
(primary)		27.6 km/s
Details
Primary
Mass~1.2[5] M☉
Radius6.00[4] R☉
Luminosity4.24[3] L☉
Temperature4,500[4] K
Secondary
Mass~0.7[5] M☉
Other designations
2A 1052+606, DM UMa, BD+61°1211, HIP 53425, SAO 15338, PPM 17646[9]
Database references
SIMBADdata

DM Ursae Majoris is a binary star system in the northern circumpolar constellation of Ursa Major, abbreviated DM UMa. It is sometimes identified by the Bonner Durchmusterung catalogue designation BD +61 1211; DM UMa is the variable star designation. The system has a combined apparent visual magnitude of 9.29,[3] which is too faint to be visible to the naked eye. Based on parallax measurements, the system is located at a distance of approximately 606 light years from the Sun,[2] but it is drifting closer with a heliocentric radial velocity of −7 km/s.[7]

In 1978, the X-ray source designated 2A 1052+606 was initially included in the 2A catalogue of observations by the Ariel 5 satellite.[10] The approximate position of this source was determined using the HEAO-1 satellite, then W. Liller matched it with the candidate star SAO 015338 (later DM UMa). He determined the spectra matches a K-type star with strong H-alpha emission lines.[11] In 1979, this object was shown to be an RS Canum Venaticorum variable (RS CVn) by D. Crampton and associates, which indicated this is a close binary star system where one of the components has an active chromosphere with star spots.[7] DM UMa was the first RS CVn variable to be so classified based on its X-ray emission.[12]

Radial velocity measurements demonstrated an orbital period of about 7.5 days. A mass function of 0.016 M☉ suggested the system is being viewed from a low inclination, close to pole-on.[7] The system showed variations in emission lines on a time scale of a day.[13] A photometric light curve was generated by R. A. Kimble and associates in 1981, showing strong variability within each orbital period.[5] A model fit to the light curve indicated the star has an extensive distribution of star spots, with regions of enhanced spot activity toward and away from the companion. It is one of the few variables of this class that show a continual emission of H-alpha, although this varies by a factor of three over the course of an orbit.[12]

This is a single-lined spectroscopic binary[5] with the spectra matching a stellar classification of K0III-IV.[4] The secondary is at least 1.5 magnitudes fainter than the primary, so the contribution of the former to the luminosity is no more than 20%.[12] The observed properties of the system can be modeled by a combination of a subgiant primary of class K0IV with a K5V main sequence secondary.[5]

  1. ^ Cite error: The named reference MohinASSV115 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 d e Cite error: The named reference Anderson_Francis_2012 was invoked but never defined (see the help page).
  4. ^ a b c d Cite error: The named reference Strassmeier_2009 was invoked but never defined (see the help page).
  5. ^ a b c d e f Cite error: The named reference Kimble_et_al_1981 was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference Samus_et_al_2017 was invoked but never defined (see the help page).
  7. ^ a b c d e Cite error: The named reference Crampton_et_al_1979 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference Hatzes_1995 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 Cooke_et_al_1978 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference Liller_et_al_1978 was invoked but never defined (see the help page).
  12. ^ a b c Cite error: The named reference Rosario_et_al_2009 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference Charles_et_al_1979 was invoked but never defined (see the help page).