Astronomy:17 Comae Berenices

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Short description: Multiple star system in the constellation Coma Berenices
17 Comae Berenices
Coma Berenices IAU.svg
Red circle.svg
Location of 17 Com (circled)
Observation data
{{#ifeq:J2000.0|J2000.0 (ICRS)|Epoch J2000.0      Equinox J2000.0 (ICRS)| Epoch J2000.0      [[Astronomy:Equinox (celestial coordinates)|Equinox J2000.0}}
Constellation Coma Berenices
17 Com A
Right ascension  12h 28m 54.703s[1]
Declination +25° 54′ 46.27″[1]
Apparent magnitude (V) 5.242±0.004[2]
17 Com BC
Right ascension  12h 28m 44.565s[3]
Declination +25° 53′ 57.56″[3]
Apparent magnitude (V) 6.635[4]
Characteristics
17 Com A
Spectral type A0p[5]
A0 SrCrEu[2]
B−V color index −0.056±0.009[6]
Variable type α2 CVn + δ Sct(?)[7]
17 Com BC
Spectral type kA2hA9VmF0[8]
U−B color index 0.084[4]
B−V color index 0.216[4]
Astrometry
17 Com A
Radial velocity (Rv)−1.4±0.5[9] km/s
Proper motion (μ) RA: −23.539[1] mas/yr
Dec.: −15.620[1] mas/yr
Parallax (π)13.5382 ± 0.2245[1] mas
Distance241 ± 4 ly
(74 ± 1 pc)
Absolute magnitude (MV)0.98[6]
17 Com BC
Radial velocity (Rv)−1.8±0.1[10] km/s
Proper motion (μ) RA: −22.296 mas/yr
Dec.: −17.071 mas/yr
Parallax (π)13.6383 ± 0.0913[3] mas
Distance239 ± 2 ly
(73.3 ± 0.5 pc)
Absolute magnitude (MV)2.46[6]
Orbit[11]
Primary17 Com B
Companion17 Com C
Period (P)68.290±0.012 d
Eccentricity (e)0.296±0.008
Periastron epoch (T)2,448,313.4±0.4 JD
Argument of periastron (ω)
(secondary)		260.7±2.2°
Semi-amplitude (K1)
(primary)		14.0±0.2 km/s
Details
17 Com A
Mass2.38 M☉[2]
2.61 M☉[12]
2.75±0.3[13] M☉
Radius2.09[5] R☉
Luminosity42.7[5] L☉
Surface gravity (log g)4.27 cgs[12]
3.70±0.20[13] cgs
Temperature10,212 K[5]
9,309±250[13] K
Rotational velocity (v sin i)20.4±0.4[5] km/s
Age101[12] Myr
17 Com BC
Mass1.74±0.6[14] M☉
Surface gravity (log g)4.29±0.20[14] cgs
Temperature8,068±200[14] K
Rotational velocity (v sin i)22[4] km/s
Other designations
BU 1080, 17 Com, ADS 8568, WDS J12289+2555[15][16]
17 Com A: AI Com, BD+26°2354, GC 17012, HD 108662, HIP 60904, HR 4752, SAO 82330[15]
17 Com B: BD+26°2353, GC 17007, HD 108651, HIP 60891, HR 4751, SAO 82328[16]
Database references
17 Com A
SIMBADdata
17 Com B
SIMBADdata

17 Comae Berenices (17 Com) is a multiple star system in the northern constellation of Coma Berenices. The brighter component, 17 Com A, is a naked eye star with an apparent visual magnitude of 5.2.[2] It has a faint companion of magnitude 6.6,[6] 17 Com B, positioned at an angular separation of 146.4″ along a position angle of 251°, as of 2018.[17] They are located at a distance of approximately 240 light years from the Sun based on parallax measurements.[1]

The double nature of this system was documented by F. G. W. Struve in 1836.[17] The pair share a common proper motion through space[13] and thus may be associated. Component B is itself a binary star system, although only the brighter component is visible in the spectrum.[11] The Washington Double Star Catalogue lists the companion as component C, with a magnitude of 13.7 and a separation of 1.4″.[17] 17 Com has been recognized as members of the Coma Star Cluster,[18] but this is disputed.[19]

The star 17 Com A was classified as chemically peculiar by A. J. Cannon prior to 1918.[20] W. W. Morgan in 1932 found the star's spectral lines varied in strength and appearance,[21] and detected lines of the element europium.[22] H. W. Babcock and T. G. Cowling measured the Zeeman effect in this star, demonstrating in 1953 that it has a magnetic field.[23] In 1967, E. P. J. van den Heuvel noted the blue excess of this star, suggesting it is a blue straggler.[24] G. W. Preston and associates in 1969 found that the luminosity and magnetic field of this star varied in strength with a time scale of around five days.[25]

A light curve for AI Comae Berenices, plotted from TESS data[26]

17 Com A is a magnetic chemically peculiar Ap star with a stellar classification of A0p[5] or A0 SrCrEu,[2] with the latter indicating the spectrum shows abundance anomalies of the elements strontium, chromium, and europium. The level of silicon in the atmosphere is also enhanced[27] and it shows a significant helium deficiency.[5] It has the variable star designation of AI Com, and is classified as an Alpha2 Canum Venaticorum variable and a suspected Delta Scuti variable.[7] It has been identified as a suspected blue straggler.[13]

The primary has an estimated age of 101[12] million years and is spinning with a projected rotational velocity of 20 km/s.[5] It has more than double the mass and twice the radius of the Sun.[2][5] The magnetic field strength is 3,300±150 G.[5] It is radiating 43[5] times the luminosity of the Sun from its photosphere at an effective temperature of around 10,000 K.[5][13]

The co-moving companion, component B, is a single-lined spectroscopic binary with an orbital period of 68.3 days and an eccentricity (ovalness) of 0.3.[11] The visible member of this binary pair is a strong Am star[4] with a class of kA2hA9VmF0,[8] indicating it has the Calcium K-lines of an A0 star, the hydrogen lines of an A9 star, and the metallic lines of an F0 star.[28]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 Brown, A. G. A. (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics 649: A1. doi:10.1051/0004-6361/202039657. Bibcode: 2021A&A...649A...1G.  Gaia EDR3 record for this source at VizieR.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 Paunzen, E. et al. (July 2021), "Magnetic chemically peculiar stars investigated by the Solar Mass Ejection Imager", Monthly Notices of the Royal Astronomical Society 504 (3): 3758–3772, doi:10.1093/mnras/stab1100, Bibcode: 2021MNRAS.504.3758P. 
  3. ↑ 3.0 3.1 3.2 Brown, A. G. A. (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics 649: A1. doi:10.1051/0004-6361/202039657. Bibcode: 2021A&A...649A...1G.  Gaia EDR3 record for this source at VizieR.
  4. ↑ 4.0 4.1 4.2 4.3 4.4 Iliev, I. Kh. et al. (August 2006), "Abundance analysis of Am binaries and search for tidally driven abundance anomalies - II. HD861, HD18778, HD20320, HD29479, HD96528 and HD108651", Monthly Notices of the Royal Astronomical Society 370 (2): 819–827, doi:10.1111/j.1365-2966.2006.10513.x, Bibcode: 2006MNRAS.370..819I. 
  5. ↑ 5.00 5.01 5.02 5.03 5.04 5.05 5.06 5.07 5.08 5.09 5.10 5.11 Romanovskaya, A. M. et al. (September 2020), "Fundamental parameters of Ap-star HD 108662", INASAN Science Reports 5 (4): 219–223, doi:10.26087/INASAN.2020.5.4.010, Bibcode: 2020INASR...5..219R. 
  6. ↑ 6.0 6.1 6.2 6.3 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A. 
  7. ↑ 7.0 7.1 Samus, N. N. et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1 61 (1): 80–88, doi:10.1134/S1063772917010085, Bibcode: 2017ARep...61...80S. 
  8. ↑ 8.0 8.1 Abt, H. A.; Cardona, O. (1984), "The nature of the visual companions of AP and AM stars", The Astrophysical Journal 276: 266, doi:10.1086/161610, Bibcode: 1984ApJ...276..266A. 
  9. ↑ Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35495 Hipparcos stars in a common system", Astronomy Letters 32 (11): 759–771, doi:10.1134/S1063773706110065, Bibcode: 2006AstL...32..759G. 
  10. ↑ de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics 546: 14, doi:10.1051/0004-6361/201219219, A61, Bibcode: 2012A&A...546A..61D. 
  11. ↑ 11.0 11.1 11.2 Abt, Helmut A.; Willmarth, Daryl W. (August 1999), "Binaries in the Praesepe and Coma Star Clusters and Their Implications for Binary Evolution", The Astrophysical Journal 521 (2): 682–690, doi:10.1086/307569, Bibcode: 1999ApJ...521..682A. 
  12. ↑ 12.0 12.1 12.2 12.3 David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal 804 (2): 146, doi:10.1088/0004-637X/804/2/146, Bibcode: 2015ApJ...804..146D. 
  13. ↑ 13.0 13.1 13.2 13.3 13.4 13.5 Monier, Richard; Deal, Morgan (July 2020), "The Evolutionary Status of 17 Com, The Hottest Member of Coma Berenices", Research Notes of the AAS 4 (7): 104, doi:10.3847/2515-5172/aba35a, 104, Bibcode: 2020RNAAS...4..104M. 
  14. ↑ 14.0 14.1 14.2 Deal, Morgan; Monier, Richard (August 2020), "The Surface Abundances of 17 Com B: A Test for Self-consistent Evolutionary Models", Research Notes of the AAS 4 (8): 144, doi:10.3847/2515-5172/abb01f, 144, Bibcode: 2020RNAAS...4..144D. 
  15. ↑ 15.0 15.1 "HD 108662". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+108662. 
  16. ↑ 16.0 16.1 "HD 108651". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+108651. 
  17. ↑ 17.0 17.1 17.2 Mason, B. D. et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal 122 (6): 3466–3471, doi:10.1086/323920, Bibcode: 2001AJ....122.3466M. 
  18. ↑ Casewell, S. L. et al. (January 2006), "New stellar members of the Coma Berenices open star cluster", Monthly Notices of the Royal Astronomical Society 365 (2): 447–453, doi:10.1111/j.1365-2966.2005.09689.x, Bibcode: 2006MNRAS.365..447C. 
  19. ↑ Silaj, J.; Landstreet, J. D. (June 2014), "Accurate age determinations of several nearby open clusters containing magnetic Ap stars", Astronomy & Astrophysics 566: 18, doi:10.1051/0004-6361/201321468, A132, Bibcode: 2014A&A...566A.132S. 
  20. ↑ Perrine, C. D. (June 1918), "On the cause underlying the spectral differences of the stars", Astrophysical Journal 47: 289–323, doi:10.1086/142406, Bibcode: 1918ApJ....47..289P. 
  21. ↑ Morgan, W. W. (September 1932), "A Study of the Composite Spectrum of the A-Type Star 14 Comae", Astrophysical Journal 76: 144, doi:10.1086/143410, Bibcode: 1932ApJ....76..144M. 
  22. ↑ Morgan, W. W. (January 1932), "Studies in Peculiar Stellar Spectra. III. on the Occurrence of Europium in A-Type Stars", Astrophysical Journal 75: 46, doi:10.1086/143354, Bibcode: 1932ApJ....75...46M. 
  23. ↑ Babcock, H. W.; Cowling, T. G. (1953), "General magnetic fields in the Sun and stars (Report on progress of astronomy)", Monthly Notices of the Royal Astronomical Society 113: 357–381, doi:10.1093/mnras/113.3.357, Bibcode: 1953MNRAS.113..357B. 
  24. ↑ van den Heuvel, E. P. J. (April 1967), "The origin of blue stragglers and peculiar and metallic-line stars", The Observatory 87: 68–72, Bibcode: 1967Obs....87...68V. 
  25. ↑ Preston, G. W. et al. (May 1969), "The magnetic field and light variations of 17 COM and kap Cnc", Astrophysical Journal 156: 653, doi:10.1086/149995, Bibcode: 1969ApJ...156..653P. 
  26. ↑ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html. 
  27. ↑ Savanov, I. S. et al. (November 1996), "A study of the atmospheres of the SrCrEu stars 17 Com A and 21 Com in the Coma Cluster", Astronomy Letters 22 (6): 815–821, Bibcode: 1996AstL...22..815S. 
  28. ↑ Gray, Richard O.; Corbally, J. (2009), Stellar Spectral Classification, Princeton University Press, pp. 176–183, ISBN 978-0691125114 

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