Planetary line-to-accretion luminosity scaling relations: Extrapolating to higher-order hydrogen lines

Abstract

Aoyama et al. (2021, ApJL) provided scaling relations between hydrogen-line luminosities and the accretion luminosity for planetary-mass objects. These fits should be an improvement over blind extrapolations of stellar relations. The fits go up only to the n = 8 electron energy level, but higher-n Balmer lines have been observed in the near-UV at Delorme 1 (AB)b with UVES (Ringqvist et al. 2023). We extend the scaling relations to higher-n levels for the Balmer and other series by fitting the fit coefficients (a, b) themselves and extrapolating them. Within the assumption of an accretion shock as the source of line emission, these fits should be robust for accreting planetary-mass objects.

3 pages, 1 four-panel figure. Published on December 9th, 2022. v1: updated links to published papers, added thanks. Fits of scaling relations available in Tomas Stolker's "species" toolkit (https://species.readthedocs.io). v2: corrected the accidental shuffle of the author names (!)

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