SIMBAD references

Excess levels of ¹⁵N isotopes which have been detected in primitive solar system materials are explained as a remnant of interstellar chemistry which took place in regions of the protosolar nebula. Chemical models of nitrogen fractionation in cold clouds predict an enhancement in the gas-phase abundance of ¹⁵N-bearing molecules, thus we have searched for ¹⁵N variants of the N₂H⁺ ion in L1544, which is one of the best candidate sources for detection owing to its low central core temperature and high CO depletion. With the IRAM 30m telescope we have obtained deep integrations of the N¹⁵NH⁺(1-0) line at 91.2GHz. The N¹⁵NH⁺(1-0) line has been detected toward the dust emission peak of L1544. The ¹⁴N/¹⁵N abundance ratio in N¹⁵NH⁺ resulted 446±71, very close to the protosolar value of ∼450, higher than the terrestrial ratio of ∼270, and significantly lower than the lower limit in L1544 found by Gerin et al. (2002ApJ...570L.101B) in the same object using ammonia isotopologues.