Engineering topics

Pilachowski, Catherine

Publications and source records attributed to Pilachowski, Catherine.

2 records

NASA NTRS1986

Lithium in M67

Echelle spectra recorded at the Li I 6707-A line are reported for seven main-sequence members and one cool subgiant in M67. The spectral types of the seven dwarfs studied range from about F8 at the turnoff point to about G5. The principal result is that the average lithium abundance in the three hottest main-sequence stars is 0.45 x 10 to the -9th. Any enrichment of lithium in the gas of the Galactic disk in the last 5 Gyr therefore has not exceeded a factor of about two and probably is entirely negligible, when the corresponding results for NGC 752 and the Hyades are taken into account.

Hobbs, L. M.↗

NASA NTRS1986

Lithium in NGC 752

Echelle spectra recorded at the Li I 6707 A line are reported for 19 main sequence members of NGC 752, an open cluster about 2.5 times older than the Hyades. A sharp decline of the lithium abundance toward cooler temperatures is found which is more pronounced than in the Hyades, as expected. The initial cluster lithium abundance is estimated at roughly 1 x 10 to the -9th. No significant increase of the lithium fraction in the gas of the Galactic disk apparently has occurred in at least the last 1.7 Gyr. Four stars in a very narrow temperature range centered near 6600 K show a deficiency of atmospheric lithium which ranges up to a factor of more than 30 compared to slightly hotter or cooler stars.

Hobbs, L. M.↗