New limit on magnetic monopole flux from catalysis of proton decay in white dwarfs.

We propose a question that why no late type M and much later type N white dwarfs (WDs) with surface temperatures less than 3000 K have ever been observed? On the basis of proton decay catalyzed by magnetic monopoles(MMs), we have presented four new energy-source models associated with MMs to discuss the cooling of WDs by some observations from seven red giant stars with LAMOST. It is found that the number of MMs captured by a WD can reach the maximum value of 9. 5 8 1 6 × 1 0 1 7 when the MMs flux ϕ = 9. 5 9 × 1 0 − 2 6 cm − 2 s − 1 sr − 1 . The good agreement of our luminosities calculated for WDs with the observations shows that our models are rational due to the Rubakov Callan (RC) effect by MMs. It is concluded that the energy source of WDs is the proton decay catalyzed by MMs. We obtain a new limit of the MMs flux of ϕ 〈 σ m v T 〉 − 2 8 ≤ 4. 2 2 4 2 × 1 0 − 1 3 cm − 2 s − 1 sr − 1 for WDs when the number density of nucleons n B c = 7. 9 9 × 1 0 3 3 cm − 3 and asteroseismic correction factor f △ ν = 1. 0 0 due to the RC effect by MMs. [ABSTRACT FROM AUTHOR]