We use imaging and spectroscopy from the Hubble Space Telescope ( HST ) to examine the properties of a bright planetary nebula ( PN ) projected within M31 ’ s young open cluster B477-D075 .
We show that the probability of a chance superposition of the PN on the cluster is small , { \lesssim } 2 \% .
Moreover , the radial velocity of the PN is the same as that of the cluster within the measurement error of \sim 10 km s ^ { -1 } .
Given the expected \sim 70 km s ^ { -1 } velocity dispersion in this region , { \sim } 8 kpc from M31 ’ s nucleus , the velocity data again make it extremely likely that the PN belongs to the cluster .
Applying isochrone fitting to archival color-magnitude photometric data from the HST Advanced Camera for Surveys , we determine the cluster age and metallicity to be 290 Myr and Z = 0.0071 , respectively , implying an initial mass of 3.38 ^ { +0.03 } _ { -0.02 } M _ { \odot } for any PN produced by the cluster .
From HST ’ s Space Telescope Imaging Spectrograph observations and C LOUDY photoionization modeling , we find that the PN is likely a Type I planetary , with a nitrogen abundance that is enhanced by { \sim } 5–6 times over the solar value scaled to the cluster metallicity .
If the PN is indeed a cluster member , these data present strong empirical evidence that hot-bottom burning occurs in AGB stars with initial masses as low as 3.4 M _ { \odot } .