HD 170657

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HD 170657
Observation data
Epoch J2000      Equinox J2000
Constellation Sagittarius
Right ascension 18h 31m 18.9597s[1]
Declination –18° 54′ 31.722″[1]
Apparent magnitude (V) 6.82
Spectral type K2V[2]
U−B color index +0.56[3]
B−V color index +0.87[3]
Variable type Suspected[4]
Radial velocity (Rv) –35[5] km/s
Proper motion (μ) RA: –140.14[1] mas/yr
Dec.: –194.60[1] mas/yr
Parallax (π) 75.71 ± 0.89[1] mas
Distance 43.1 ± 0.5 ly
(13.2 ± 0.2 pc)
Mass 0.79 ± 0.11[6] M
Surface gravity (log g) 4.61[6] cgs
Temperature 5,156[6][7] K
Rotational velocity (v sin i) 1.5[6] km/s
Age 1.6–6.1[7] Gyr
Other designations
GJ 716, BD-18 4986, HD 170657, LTT 7358, SAO 161557, HIP 90790.[8]
Database references

HD 170657 is a star in the constellation Sagittarius. It is located at a distance of about 43 light years. It has 0.79 solar masses and is a suspected variable star that varies in apparent magnitude from 6.82−6.88.[4]

When observed with the Spitzer Space Telescope, this star did not display an excess emission of infrared radiation, which may otherwise indicate the presence of an orbiting debris disk.[7] The space velocity components of this star are (U, V, W) = (–41, –26, +6) km/s.[9]

Sources give contradictory measurements for the abundance of elements in this star. Lawler et al. (2009) lists an iron abundance of [Fe/H] = 0.27 dex,[7] while Valenti et al. (2005) has an iron abundance of [Fe/H] = –0.15.[6]


  1. ^ a b c d e Perryman, M. A. C.; et al. (April 1997). "The HIPPARCOS Catalogue". Astronomy & Astrophysics. 323: L49–L52. Bibcode:1997A&A...323L..49P. 
  2. ^ Gray, R. O.; et al. (July 2006). "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 pc-The Southern Sample". The Astronomical Journal. 132 (1): 161–170. arXiv:astro-ph/0603770Freely accessible. Bibcode:2006AJ....132..161G. doi:10.1086/504637. 
  3. ^ a b Corben, P. M.; Carter, B. S.; Banfield, R. M.; Harvey, G. M. (1972). "UBV Photometry of 500 Southern Stars [erratum: 1973MNSSA..32...48C]". Monthly Notes of the Astronomical Society of Southern Africa. 31: 7. Bibcode:1972MNSSA..31....7C. 
  4. ^ a b Kukarkin, B. V.; et al. (1981). Nachrichtenblatt der Vereinigung der Sternfreunde e.V. (Catalogue of suspected variable stars). Moscow: Academy of Sciences USSR Shternberg. Bibcode:1981NVS...C......0K. 
  5. ^ Evans, D. S. (June 20–24, 1966). "The Revision of the General Catalogue of Radial Velocities". In Batten, Alan Henry; Heard, John Frederick. Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30. University of Toronto: International Astronomical Union. Retrieved 2009-09-10. 
  6. ^ a b c d e Valenti, Jeff A.; Fischer, Debra A. (July 2005). "Spectroscopic Properties of Cool Stars (SPOCS). I. 1040 F, G, and K Dwarfs from Keck, Lick, and AAT Planet Search Programs". The Astrophysical Journal Supplement Series. 159 (1): 141–166. Bibcode:2005ApJS..159..141V. doi:10.1086/430500. 
  7. ^ a b c d Lawler, S. M.; et al. (November 2009). "Explorations Beyond the Snow Line: Spitzer/IRS Spectra of Debris Disks Around Solar-type Stars". The Astrophysical Journal. 705 (1): 89–111. arXiv:0909.0058Freely accessible. Bibcode:2009ApJ...705...89L. doi:10.1088/0004-637X/705/1/89. 
  8. ^ "HD 170657 -- Variable Star". Centre de Données astronomiques de Strasbourg. Retrieved 2010-07-21. 
  9. ^ Gliese, W. (1969). Catalogue of Nearby Stars. Heidelberg: Veröffentlichungen des Astronomischen Rechen-Instituts. Bibcode:1969VeARI..22....1G.