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DM Ursae Majoris
	; Visual band light curves for DM Ursae Majoris, adapted from Mohin et al. (1985)
Observation data; Epoch J2000 Equinox J2000
Constellation	Ursa Major
Right ascension	10h 55m 43.544s
Declination	+60° 28′ 09.72″
Apparent magnitude (V)	9.29
Characteristics
Spectral type	K0III-IV (K0IV + K5V)
B−V color index	1.014±0.026
Variable type	RS CVn
Astrometry
Radial velocity (Rv)	−6.9±1.2 km/s
Proper motion (μ)	RA: −37.912 mas/yr ; Dec.: −7.566 mas/yr
Parallax (π)	5.3862 ± 0.0157 mas
Distance	606 ± 2 ly ; (185.7 ± 0.5 pc)
Absolute magnitude (MV)	3.65
Orbit
Period (P)	7.4920±0.0009 d
Eccentricity (e)	0.0 (assumed)
Inclination (i)	40°
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 M☉
Radius	6.00 R☉
Luminosity	4.24 L☉
Temperature	4,500 K
Secondary
Mass	~0.7 M☉
Other designations
	2A 1052+606, DM UMa, BD+61°1211, HIP 53425, SAO 15338, PPM 17646
Database references
SIMBAD	data

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]

References

^ Mohin, S.; Raveendran, A. V.; Mekkaden, M. V.; Hall, D. S.; Henry, G. W.; Lines, R. D.; Fried, R. E.; Louth, H.; Stelzer, H. J. (October 1985). "Evolution of Starspot Regions in DM UMa". Astrophysics and Space Science. 115 (2): 353–368. Bibcode:1985Ap&SS.115..353M. doi:10.1007/BF00653812. S2CID 119914476. Retrieved 6 October 2022.
^ ^a ^b ^c ^d ^e Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
^ ^a ^b ^c ^d ^e Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
^ ^a ^b ^c ^d Strassmeier, Klaus G. (September 2009), "Starspots", The Astronomy and Astrophysics Review, 17 (3): 251–308, Bibcode:2009A&ARv..17..251S, doi:10.1007/s00159-009-0020-6.
^ ^a ^b ^c ^d ^e ^f Kimble, R. A.; et al. (December 1981), "Discovery of a large-amplitude photometric wave in the RS CVn binary BD +61 1211 (=DM UMA) and constraints on starspot models for the observed variation", Astrophysical Journal, 251: 585–590, Bibcode:1981ApJ...251..585K, doi:10.1086/159502.
^ Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
^ ^a ^b ^c ^d ^e Crampton, D.; et al. (December 1979), "The RS CVn system BD +61 1211 = 2A 1052+60.6", Astrophysical Journal, 234: 993–996, Bibcode:1979ApJ...234..993C, doi:10.1086/157583, S2CID 120565755.
^ Hatzes, Artie P. (January 1995), "Spot and Chromospheric Activity on the RS CVN Star DM Ursae Majoris", Astronomical Journal, 109: 350, Bibcode:1995AJ....109..350H, doi:10.1086/117280.
^ "DM UMa". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2022-10-01.
^ Cooke, B. A.; et al. (February 1978), "The Ariel V (SSI) catalogue of high galactic latitude (|b| > 10°) X-ray sources", Monthly Notices of the Royal Astronomical Society, 182 (3): 489–515, Bibcode:1978MNRAS.182..489C, doi:10.1093/mnras/182.3.489.
^ Liller, W.; et al. (February 1978), Marsden, B. G. (ed.), "2A 1052+606 = SAO 015338?", IAU Circular, 3176: 2, Bibcode:1978IAUC.3176....2L.
^ ^a ^b ^c Rosario, M. J.; et al. (April 2009), "Spot activity in the RS CVn binary DM Ursae Majoris", Monthly Notices of the Royal Astronomical Society, 394 (2): 872–881, Bibcode:2009MNRAS.394..872R, doi:10.1111/j.1365-2966.2008.14372.x, S2CID 123218100.
^ Charles, P.; et al. (December 1979), "X-ray and optical variability in 2A1052+606-a new RS CVn-type system", Nature, 282 (5740): 691–692, Bibcode:1979Natur.282..691C, doi:10.1038/282691a0, S2CID 4315279.

Zhang, LiYun; et al. (June 2016), "Chromospheric activity on late-type star DM UMa using high-resolution spectroscopic observations", Monthly Notices of the Royal Astronomical Society, 459 (1): 854–862, arXiv:1611.07395, Bibcode:2016MNRAS.459..854Z, doi:10.1093/mnras/stw668.
Taş, G.; Evren, S. (2012), "A New Approach to the Long-Term Activity Behavior of DM UMa", Baltic Astronomy, 21 (4): 435–446, Bibcode:2012BaltA..21..435T, doi:10.1515/astro-2017-0401, S2CID 46781397.
Mohin, S.; Raveendran, A. V. (June 1994), "Near simultaneous BV photometry and Hα spectroscopy of the RS Canum Venaticorum binary DM Ursae Majoris", Astronomy and Astrophysics, 286: 824–828, Bibcode:1994A&A...286..824M.
Mohin, S.; Raveendran, A. V. (March 1992), "Photometric study of the RS CVn binary DM Ursa Majoris", Astronomy and Astrophysics, 256: 487–494, Bibcode:1992A&A...256..487M.
Heckert, P. A. (March 1990), "1988 and 1989 UBV Photometry of BD +61 1211", Information Bulletin on Variable Stars, 3446: 1, Bibcode:1990IBVS.3446....1H.
Heckert, P. A.; et al. (December 1988), "UBV Photometry of BD +61 1211 during 1986 and 1987", Information Bulletin on Variable Stars, 3274: 1, Bibcode:1988IBVS.3274....1H.
Heckert, P. A.; et al. (March 1988), "UBV Photometry of BD + 611211 and HD 80715 During 1986 and 1987", Bulletin of the American Astronomical Society, 20: 674, Bibcode:1988BAAS...20..674H.
Nations, Harold L.; Ramsey, Lawrence W. (December 1986), "Hα observations of RS Canum Venaticorum stars. II. 1981 observations for UX Arietis, HR 1099, and BD +61°1211", Astronomical Journal, 92: 1403–1408, Bibcode:1986AJ.....92.1403N, doi:10.1086/114274.
Nations, H. L.; Ramsey, L. W. (June 1985), "Hα Observations of RS CVn Stars: 1981 Spectra of UX Ari, HR 1099, BD +61 1211 and HD 155638", Bulletin of the American Astronomical Society, 17: 754, Bibcode:1985BAAS...17..754N.
Tan, Huisong; Liu, Xuefu (February 1985), "Halpha Emission in RS CVn Stars: BD +61 1211 and HD 37847", Information Bulletin on Variable Stars, 2669: 1, Bibcode:1979ApJ...234..993C, doi:10.1086/157583, S2CID 120565755.