CM Draconis

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CM Draconis
CMDraLightCurve.png
A red band light curve for CM Draconis, adapted from Kozhevnikova et al. (2009) [1]
Observation data
Epoch J2000.0        Equinox J2000.0 (ICRS)
Constellation Draco
Right ascension 16h 34m 20.33027s [2]
Declination +57° 09′ 44.3689″ [2]
Apparent magnitude  (V)12.87 [3]
Characteristics
Spectral type M4.5V / M4.5V [4] / DQ8 [5]
Variable type BY Draconis variable
Eclipsing binary
Flare star
Astrometry
Radial velocity (Rv)–118.24 [3]  km/s
Proper motion (μ)RA: –1113.797  mas/yr [2]
Dec.: 1180.977  mas/yr [2]
Parallax (π)67.2876 ± 0.0337  mas [2]
Distance 48.47 ± 0.02  ly
(14.862 ± 0.007  pc)
Absolute magnitude  (MV)12.1[ citation needed ]
Orbit [6]
Period (P)1.2683900573(17)  d
Semi-major axis (a)0.0173945(64)  AU
Eccentricity (e)0.00527(21)
Inclination (i)89.5514±0.0020°
Longitude of the node (Ω)15.79 [4] °
Argument of periastron (ω)
(secondary)		107.98±0.70°
Semi-amplitude (K1)
(primary)		72.23 [4] km/s
Semi-amplitude (K2)
(secondary)		77.95 [4] km/s
Details
A
Mass 0.22507(24) [6]   M☉
Radius 0.25113(16) [6]   R☉
Luminosity (bolometric)0.00552 [4]   L☉
Surface gravity (log g)4.994±0.007 [4]   cgs
Temperature 3130 ± 70 [4]   K
Metallicity [Fe/H]−0.30±0.12 [7]   dex
Age 4.1 ± 0.8 [4]   Gyr
B
Mass 0.21017(28) [6]   M☉
Radius 0.23732(14) [6]   R☉
Luminosity (bolometric)0.00486 [4]   L☉
Surface gravity (log g)5.009±0.006 [4]   cgs
Temperature 3120 ± 70 [4]   K
Metallicity [Fe/H]−0.30±0.12 [7]   dex
Age 4.1 ± 0.8 [4]   Gyr
Other designations
Eclipsing binary: CM Dra, GJ  630.1A, CCDM J16343+5710A, WDS J16345+5709A, LHS  421, LP  101-15, NLTT  43148, TIC  199574208 [3]
White dwarf: GJ  630.1B, CCDM J16343+5710B, WDS J16345+5709B, EG GR  258, LHS  422, LP  101-16, NLTT  43149, WD  1633+57, TIC  199574211 [5]
Database references
SIMBAD A
B
ARICNS A
B

CM Draconis (GJ 630.1A) is an eclipsing binary star system 48.5 light-years (14.9 parsecs ) away in the constellation of Draco (the Dragon). The system consists of two nearly identical red dwarf stars that orbit each other with a period of 1.268 days and a separation of 2.6 million kilometres (0.017 AU). [6] Along with two stars in the triple system KOI-126, the stars in CM Draconis are among the lightest stars with precisely measured masses and radii. Consequently, the system plays an important role in testing stellar structure models for very low mass stars. [4] These comparisons find that models underpredict the stellar radii by approximately 5%. This is attributed to consequences of the stars' strong magnetic activity. [4]

Contents

According to the system's entry in the Combined General Catalogue of Variable Stars, at least one of the components is a flare star and at least one is a BY Draconis variable. [8] The white dwarf star GJ 630.1B, located 25.7 arcseconds away shares the same proper motion as the CM Draconis stars and is thus a true companion star of the system. [9] Given the system's distance of 47 light years, [10] this corresponds to a separation of at least 370 astronomical units between CM Draconis and GJ 630.1B.

Search for planets

The system was the subject of a dedicated search for transiting extrasolar planets in orbit around the binary from 1994–1999. In the end, the existence of all of the transiting planet candidates suggested by the project was ruled out. [11] [12]

Based on variations in the timing of the system's eclipses, it has been suggested that there may be an object in a circumbinary orbit around the two red dwarf stars. In 2000, it was proposed that a Jovian planet is orbiting the system with a period of 750–1050 days. [13] A later analysis of timing variations did not confirm this proposed planet and instead suggested that there was a Jovian planet in an 18.5-year orbit, or a more massive object further out. [9] This analysis was itself not supported by a 2009 study that found the eclipse timings were indistinguishable from linear, though the binary stars do have a small eccentricity that may indicate that they are being perturbed by an orbiting body that prevents the orbit from being fully circularised by tidal effects. A massive planet or brown dwarf on an orbit of 50–200 days would fulfil the observational criteria: the requirement for dynamical stability, the constraints from the lack of observed timing variations and the requirement that the object can maintain the eccentricity of the binary stars. [4]

As of 2024, no planet has been found orbiting CM Draconis. [6]

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References

  1. ↑ Kozhevnikova, A. V.; Svechnikov, M. A.; Kozhevnikov, V. P. (October 2009). "V.P. Starspot and flare activity of the dwarf system CM Dra". Astrophysics. 52 (4): 512–522. Bibcode:2009Ap.....52..512K. doi:10.1007/s10511-009-9090-4. S2CID   121618264 . Retrieved 3 January 2022.
  2. 1 2 3 4 5 Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv: 2208.00211 . Bibcode:2023A&A...674A...1G. doi: 10.1051/0004-6361/202243940 . S2CID   244398875. Gaia DR3 record for this source at VizieR.
  3. 1 2 3 "V* CM Dra". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 7 May 2024.
  4. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Morales, Juan Carlos; Ribas, Ignasi; Jordi, Carme; Torres, Guillermo; Gallardo, José; Guinan, Edward F.; Charbonneau, David; Wolf, Marek; Latham, David W.; Anglada-Escudé, Guillem; Bradstreet, David H.; Everett, Mark E.; O'Donovan, Francis T.; Mandushev, Georgi; Mathieu, Robert D. (2009). "Absolute Properties of the Low-Mass Eclipsing Binary CM Draconis". The Astrophysical Journal. 691 (2): 1400–1411. arXiv: 0810.1541 . Bibcode:2009ApJ...691.1400M. doi:10.1088/0004-637X/691/2/1400. S2CID   3752277.
  5. 1 2 "EGGR 258". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 7 May 2024.
  6. 1 2 3 4 5 6 7 Martin, David V.; Sethi, Ritika; et al. (February 2024). "The benchmark M dwarf eclipsing binary CM Draconis with TESS: spots, flares, and ultra-precise parameters". Monthly Notices of the Royal Astronomical Society . 528 (1): 963–975. arXiv: 2301.10858 . Bibcode:2024MNRAS.528..963M. doi: 10.1093/mnras/stae015 .
  7. 1 2 Terrien, Ryan C.; Fleming, Scott W.; et al. (November 2012). "The Metallicity of the CM Draconis System". The Astrophysical Journal Letters . 760 (1): L9. arXiv: 1210.4736 . Bibcode:2012ApJ...760L...9T. doi:10.1088/2041-8205/760/1/L9.
  8. ↑ Samus (2004). "CM Dra". Combined General Catalogue of Variable Stars.
  9. 1 2 Deeg, H. J.; Ocaña, B.; Kozhevnikov, V. P.; Charbonneau, D.; O'Donovan, F. T.; Doyle, L. R. (2008). "Extrasolar planet detection by binary stellar eclipse timing: evidence for a third body around CM Draconis". Astronomy and Astrophysics. 480 (2): 563–571. arXiv: 0801.2186 . Bibcode:2008A&A...480..563D. doi:10.1051/0004-6361:20079000. S2CID   10252705.
  10. ↑ Gliese, W.; Jahreiß, H. (1991). "GJ 630.1A". Preliminary Version of the Third Catalogue of Nearby Stars. Retrieved 2008-10-12.
  11. ↑ "The TEP network".
  12. ↑ Doyle, Laurance R.; Deeg, Hans J.; Kozhevnikov, Valerij P.; Oetiker, Brian; Martín, Eduardo L.; Blue, J. Ellen; Rottler, Lee; Stone, Remington P. S.; Ninkov, Zoran; Jenkins, Jon M.; Schneider, Jean; Dunham, Edward W.; Doyle, Moira F.; Paleologou, Efthimious (2000). "Observational Limits on Terrestrial-sized Inner Planets around the CM Draconis System Using the Photometric Transit Method with a Matched-Filter Algorithm". The Astrophysical Journal. 535 (1): 338–349. arXiv: astro-ph/0001177 . Bibcode:2000ApJ...535..338D. doi:10.1086/308830. S2CID   18639250.
  13. ↑ Deeg, Hans J.; Doyle, Laurance R.; Kozhevnikov, Valerij P.; Blue, J. Ellen; Martín, Eduardo L.; Schneider, Jean (2000). "A search for Jovian-mass planets around CM Draconis using eclipse minima timing". Astronomy and Astrophysics. 358: L5–L8. arXiv: astro-ph/0003391 . Bibcode:2000A&A...358L...5D.
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