Red stars near chi Cyg

American Association of Variable Star Observers (AAVSO)
Sun, 02/12/2023 - 17:58

     While browsing through the GAIA3 spectra, I had a look in the area around chi Cyg.  In the early literature, Father Secchi found that the 'zones' (molecular bands mainly due to TiO) were weak in this star, and only the band near 5200A (attributed to magnesium at the time) was strong.  Fellow visual spectroscopist N. C. Duner suggested that perhaps Secchi had observed the wrong star, since the spectrum of  chi Cyg is so strongly broken up by the absorption bands.

     Is there another somewhat red star in the area that Secchi picked up, assuming chi Cyg was too faint for him at the time?  I compared the POSS-I blue and POSS-II far-red plate-scans to look for relatively bright stars that stood out on the far-red plate, and examined the GAIA3 spectra.  The rough list includes:

Name   V mag  MK type   remarks

HD 331350   10.4   K5III   HDE type K5

TYC 2673-3771-1   12.1   M3III

AG+32 1842   12.0   M2III

2MASS JJ19504002+3252373   13.9   M5/6III   ZTF var

HD 331363   10.6   K2III   HDE type K2

GSC 2673-3573   13.2   M4III   ASAS-SN var

The brightest red star is the first one, about 5' NW of chi Cyg, which would have the weakly-banded appearance described by Secchi, and is perhaps what he observed.  Annie Cannon's types for the two HDE stars are exactly right.  What about the GAIA3 spectrum of chi Cyg itself?  I estimate M5?SIII, where the TiO type is quite uncertain, but the bands due to ZrO characteristic of S-type stars seem to be present.