Novae: I. The maximum magnitude relation with decline time (MMRD) and distance [HEAP]

The origin and calibration of the maximum absolute magnitude relation with decline time (MMRD) for novae, first derived by Zwicky (1936) empirically validated by McLaughlin (1940) and widely used to estimate distances to classical novae and the near-constancy of the absolute magnitude of novae, 15 days after optical maximum, suggested by Buscombe and de Vaucouleurs (1955) are revisited in this paper and found to be valid. The main results presented in the paper are: (1) A physical derivation of the MMRD based on instantaneous injection of energy to the nova system. (2) A significantly better-constrained MMRD: M_{V,0} = 2.16(+-0.16)log_{10}t_2 – 10.804(+-0.117) using a two step calibration procedure. (3) It is shown that the MMRD is one of the best distance estimators to novae available to us and that accuracy of the distances is predominantly limited by an underestimated peak apparent brightness. (4) It is shown that the same MMRD calibration is applicable to novae of all speed class and to both Galactic and extragalactic novae. (5) It is shown that the absolute magnitudes of novae with 2.4 < t_2 < 86$days have a smaller scatter on day 12 (M_{V,12} = -6.616 +-0.043) compared to day 15 following optical maximum.
We reiterate the need for homogenised high fidelity spectrophotometric data in optical bands on classical and recurrent novae in outburst to effectively utilise the potential of the MMRD and M_{V,12} in determining their luminosities and distances.

Read this paper on arXiv…

N. Kantharia
Tue, 14 Mar 17

Comments: 25 pages