Star in the constellation Aquila
! style="text-align: center; background-color: #FFFFC0;" colspan="2" | Observation dataEpoch J2000      Equinox J2000
! style="text-align:left" | Constellation
! style="text-align:left" | Right ascension
! style="text-align:left" | Declination
! style="text-align:left" | Apparent magnitude (V)
! style="background-color: #FFFFC0; text-align: center;" colspan="2"| Characteristics
! style="text-align:left" | Spectral type
! style="text-align:left" | B−V 
! style="text-align:left" | Variable type
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HD 175640 is a star in the equatorial constellation of Aquila. It has an apparent visual magnitude of 6.20, which is bright enough to be visible to the naked eye under suitable seeing conditions. The star is located at a distance of approximately 516 light years as determined through parallax measurements. At that distance, the star's color is modified by an extinction of 0.36 magnitude due to interstellar dust. It is drifting closer with a heliocentric radial velocity of roughly −26 km/s.
This is classified as a mercury-manganese star, which is a late B-type chemically peculiar star of type CP3. A distinctive feature of this class of stars is an apparent extreme overabundance of the elements mercury and manganese. It has a low longitudinal magnetic field strength of . This is a particularly stable star, showing no signs of pulsation. As with other HgMn stars, it is spinning slowly, showing a projected rotational velocity of 1.6 km/s.
In 2007, some evidence was found that this may be a single-lined spectroscopic binary star system. In particular, shifts in radial velocity were observed in the range of .
References.
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