Photography of the Near Infra-Red Region of Stellar Spectra

This paper describes the chief features shown by a photographic reconnaissance of stellar spectra in the region XX 7000-9000 A, made with a plane-grating spectrograph attached to the 100-inch telescope. Most of the spectrograms are of dispersion 33 A/mm and show the region XX 83 20-8900, which is free from serious interference by terrestrial lines and includes a number of stellar lines of special interest. Results-Radial velocities from infra-red lines (Table VII) agree well with each other and with previous determinations from lines in the blue-violet region. The chief lines in the infra-red spectrum of a Cygni (Table II) are due to H, N i, o i, Mg ii, Ca u. The Paschen series of hydrogen lines is conspicuous in A-type spec- tra, especially those having the "c" characteristic, e.g., a Cygni, j3 Orionis. The lines of Ca ii XX 8498, 8542, 8662 are prominent in types A-M and may have an interesting relationship to absolute magnitude. They were found to be bright in the spectrum of R Hydrae. The 0 ilines XX 7772, 7774, 7775, and 8z~6 are important in types A and F. They appear very sensitive to absolute magnitude, being more intense in the brighter stars. Lines of neutral Ca, Ti, and Fe dominate spectra of classes K and M in the region XX 8320-8840. Many band heads were measured in spectra of class M. Most of them, especially in the X 7000 region, are due to TiO. A comparison of N-type spectra with furnace spectra taken by King shows that a large part of the complex structure between X 6910 and X 8780 is due to absorption by cyanogen