We have constrained the age of the globular cluster S312 in the Andromeda galaxy ( M31 ) by comparing its multicolor photometry with theoretical stellar population synthesis models .
This is both a check on the age of this globular cluster , as well a check on our methodology .
Main-sequence photometry has been the most direct method for determining the age of a star cluster .
S312 was observed as part of the Beijing-Arizona-Taiwan-Connecticut ( BATC ) Multicolor Sky Survey from 1995 February to 2003 December .
The photometry of BATC images for S312 was taken with 9 intermediate-band filters covering 5000 - 10000 Å .
Combined with photometry in the near-ultraviolet ( NUV ) of GALEX , broad-band UBVR and infrared JHK _ { s } of 2MASS , we obtained the accurate spectral energy distributions ( SEDs ) of S312 from 2267 - 20000 Å .
A quantitative comparison to simple stellar population models yields an age of 9.5 _ { -0.99 } ^ { +1.15 } Gyr , which is in very good agreement with the previous determination by main-sequence photometry .
S312 has a mass of 9.8 \pm { 1.85 } \times 10 ^ { 5 } M _ { \odot } , and is a medium-mass globular cluster in M31 .
By analysis of errors of ages determined based on the SED fitting method of this paper , secure age constraints are derived with errors of < 3 Gyr for ages younger than 9 Gyr .
In fact , the theoretical SEDs are not sensitive to the variation of age for ages greater than \sim 10 Gyr .
Therefore , for globular clusters as old as the majority of the Galactic GCs , our method do not distinguish them accurately .
We emphasize that our results show that even with multiband photometry spanning NUV to K _ { s } , our age constraints from SED fitting are distressingly uncertain , which has implications for age derivations in extragalactic globular cluster systems .