Although there are extensive observations of Li in field stars of all types and in both open and ( recently ) globular cluster stars , there are relatively few observations of Be .
Because Be is not destroyed as easily as Li , the abundances of Li and Be together can tell us more about the internal physical processes in stars than either element can alone .
We have obtained high-resolution ( 45,000 ) and high signal-to-noise ( typically 90 per pixel ) spectra of the Be II resonance lines in 34 Hyades F and G dwarfs with the Keck I telescope and HIRES .
In addition we took a spectrum of the daytime sky to use as a surrogate for the solar spectrum so we could determine the value for Be in the sun - analyzed in the same manner as that for the stars .
We have adopted the stellar temperatures and some of the Li abundances for these stars from the literature .
For most of the F dwarfs we have rederived Li abundances .
The Be abundances have been derived with the spectrum synthesis method .
We find that Be is depleted , but detected , in the Li gap in the F stars reaching down to values of A ( Be ) = 0.60 , or a factor of nearly seven below the meteoritic Be abundance ( a factor of 3.5 below the solar value of Chmielewski et al . ) .
There is little or no depletion of Be in stars cooler than 6000 K , in spite of the large depletions ( 0.5 - 2.5 dex ) in Li .
The mean value of A ( Be ) for the ten coolest stars is 1.33 \pm 0.06 , not far from the meteoritic value of 1.42 .
The pattern in the Be abundances – a Be dip and undepleted Be in the cool stars – is well matched by the predictions of slow mixing due to stellar rotation .
We have interpolated the calculations of Deliyannis and Pinsonneault for Be depletion due to rotational mixing to the age of the Hyades ; we find excellent agreement of the predictions with the observed Be abundances but less good agreement with the observed Li abundances .
Some of our Hyades stars have photometrically-determined rotation periods , but there is no relation between Be and rotation period .
( Generally , the lower mass stars have lower Li and longer periods which may indicate greater spin-down and thus more Li depletion relative to Be . )
The Li and Be abundances are correlated for stars in the temperature range of 5850 - 6680 K , similar to results from earlier work on Li and Be in F and G field stars .
This indicates that the depletions are not just correlated - as is the only thing that can be claimed for the field stars - but are probably occurring together during main-sequence evolution .
The Hyades G dwarfs have more Be than the sun ; their initial Be may have been larger or they may not be old enough to have depleted much Be .
For those Hyades stars which appear to have little or no depletion of Li or Be , the Li/Be ratio is found to be 75 \pm 30 ; the meteoritic ratio Li/Be is 78 .
The Hyades ratio is a representative value for the initial ratio in the material out of which the Hyades cluster was formed .