Abstract
Abstract There is a long-standing discrepancy between the observed Galactic classical nova rate of ∼10 yr−1 and the predicted rate from Galactic models of ∼30–50 yr−1. One explanation for this discrepancy is that many novae are hidden by interstellar extinction, but the degree to which dust can obscure novae is poorly constrained. We use newly available all-sky three-dimensional dust maps to compare the brightness and spatial distribution of known novae to that predicted from relatively simple models in which novae trace Galactic stellar mass. We find that only half (53%) of the novae are expected to be easily detectable (g ≲ 15) with current all-sky optical surveys such as the All-Sky Automated Survey for Supernovae (ASAS-SN). This fraction is much lower than previously estimated, showing that dust does substantially affect nova detection in the optical. By comparing complementary survey results from the ASAS-SN, OGLE-IV, and Palomar Gattini IR surveys using our modeling, we find a tentative Galactic nova rate of ∼30 yr−1, though this could be as high as ∼40 yr−1, depending on the assumed distribution of novae within the Galaxy. These preliminary estimates will be improved in future work through more sophisticated modeling of nova detection in ASAS-SN and other surveys.
Highlights
A classical nova occurs in an interacting binary system with a white dwarf primary, referred to as cataclysmic variable (CV; see Warner 1995)
We find that only half (53%) of the novae are expected to be detectable (g 15) with current all-sky optical surveys such as the All-Sky Automated Survey for Supernovae (ASAS-SN)
By comparing complementary survey results from the ASAS-SN, OGLE-IV, and Palomar Gattini IR surveys using our modeling, we find a tentative Galactic nova rate of ∼30 yr−1, though this could be as high as ∼40 yr−1, depending on the assumed distribution of novae within the Galaxy
Summary
A classical nova occurs in an interacting binary system with a white dwarf primary, referred to as cataclysmic variable (CV; see Warner 1995). This prospect is supported by the recently discovered sample of highly reddened and optically missed novae discovered by the Palomar Gattini IR (PGIR) survey (De et al 2020a, 2021). These results suggest that dust could cause a substantial fraction of Galactic nova events to go undetected by optical observations, but how many remains an open question. We discuss the components and assumptions that go into our Galactic nova model, the resulting Galactic apparent magnitude distribution of novae, and the spatial distribution of optically observable versus unobservable novae
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