17 Comae Berenices

17 Comae Berenices
Location of 17 Com (circled)
Observation data
Epoch J2000.0      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 mas/yr[1]
Dec.: −15.620 mas/yr[1]
Parallax (π)13.5382 ± 0.2245 mas[1]
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[3]
Dec.: −17.071 mas/yr[3]
Parallax (π)13.6383 ± 0.0913 mas[3]
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]

  1. ^ a b c d e Cite error: The named reference GaiaEDR2_A was invoked but never defined (see the help page).
  2. ^ a b c d e f Cite error: The named reference Paunzen_et_al_2021 was invoked but never defined (see the help page).
  3. ^ a b c d Cite error: The named reference GaiaEDR2_B was invoked but never defined (see the help page).
  4. ^ a b c d e Cite error: The named reference Iliev_et_al_2006 was invoked but never defined (see the help page).
  5. ^ a b c d e f g h i j k l Cite error: The named reference Romanovskaya_et_al_2020 was invoked but never defined (see the help page).
  6. ^ a b c d Cite error: The named reference Anderson_Francis_2012 was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference Samus_et_al_2017 was invoked but never defined (see the help page).
  8. ^ a b Cite error: The named reference Abt_Cardona_1984 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference Gontcharov2006 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference de_Bruijne_Eilers_2012 was invoked but never defined (see the help page).
  11. ^ a b c Cite error: The named reference Abt_Willmarth_1999 was invoked but never defined (see the help page).
  12. ^ a b c d Cite error: The named reference David_Hillenbrand_2015 was invoked but never defined (see the help page).
  13. ^ a b c d e f Cite error: The named reference Minier_Deal_2020a was invoked but never defined (see the help page).
  14. ^ a b c Cite error: The named reference Minier_Deal_2020b was invoked but never defined (see the help page).
  15. ^ a b Cite error: The named reference SIMBAD_A was invoked but never defined (see the help page).
  16. ^ a b Cite error: The named reference SIMBAD_B was invoked but never defined (see the help page).
  17. ^ a b c Cite error: The named reference Mason_et_al_2014 was invoked but never defined (see the help page).
  18. ^ Cite error: The named reference Casewell_et_al_2006 was invoked but never defined (see the help page).
  19. ^ Cite error: The named reference Silaj_Landstreet_2014 was invoked but never defined (see the help page).
  20. ^ Cite error: The named reference Perrine1018 was invoked but never defined (see the help page).
  21. ^ Cite error: The named reference Morgan1932a was invoked but never defined (see the help page).
  22. ^ Cite error: The named reference Morgan1932b was invoked but never defined (see the help page).
  23. ^ Cite error: The named reference Babcock_Cowling_1953 was invoked but never defined (see the help page).
  24. ^ Cite error: The named reference van_den_Heuvel_1967 was invoked but never defined (see the help page).
  25. ^ Cite error: The named reference Preston_et_al_1969 was invoked but never defined (see the help page).
  26. ^ Cite error: The named reference MAST was invoked but never defined (see the help page).
  27. ^ Cite error: The named reference Savanov_et_al_1996 was invoked but never defined (see the help page).
  28. ^ Cite error: The named reference Gray_Corbally_2009 was invoked but never defined (see the help page).