The electronic bands of CrD, CrH, MgD and MgH: application to the "deuterium test"

TL;DR

This paper calculates molecular opacities for CrD, CrH, MgD, and MgH to evaluate their effectiveness in the deuterium test for distinguishing brown dwarfs from planetary objects.

Contribution

It provides adjusted spectroscopic constants and synthetic spectra for CrD and MgD, assessing their potential for the deuterium test in astrophysics.

Findings

CrD shows promising spectral bands at 0.795 and 0.968 microns.

CrD may be more useful than MgD for the deuterium test.

Synthetic spectra support the potential application in astrophysical object classification.

Abstract

We compute opacities for the electronic molecular band systems A 6Sigma+ -- X 6Sigma+ of CrH and CrD, and A 2Pi -- X 2Sigma+ of MgH and MgD. The opacities are computed by making use of existing spectroscopic constants for MgH and CrH. These constants are adjusted for the different reduced masses of MgD and CrD. Frank-Condon factors are used to provide intensities for the individual vibronic bands. These results are used in the computation of synthetic spectra between Tef = 1800 and 1200 K with an emphasis on the realisation of ``deuterium test'', first proposed by Bejar et al. (1999) to distinguish brown dwarfs from planetary mass objects. We discuss the possible use of CrD and MgD electronic bands for the "deuterium test". We find CrD to be the more promising of the two deuterides, potentially, the most useful bands of CrH/CrD are the Delta v = +1 and Delta v = -1 at 0.795 and 0.968 micron.