Which is the best day of the week to submit to arXiv:astro-ph?

Abstract

We examine whether the citations received by refereed astronomy papers vary systematically with the day of the week of their arXiv preprint release. We use NASA ADS citation data for all refereed articles published in 2020--2023 in six journals (MNRAS, ApJ, ApJL, ApJS, A\&A and JCAP; 37,173 papers with astro-ph primary preprints), combined with version-1 submission timestamps from the arXiv API. We group papers both by submission weekday and by the day their announcement batch appears on arXiv, accounting for arXiv's weekday deadline and lack of weekend announcements. Given the heavy skew of citation distributions, our primary statistic is the median citations per group, with bootstrap confidence intervals. Papers submitted on weekends, all of which appear in the Monday listing, have median citations significantly lower than weekday submissions in five of the six journals, by 12--26 \%; the sixth (JCAP) shows the same direction, but not significantly, consistent with its small weekend sample. Median citations are indistinguishable across the five weekdays. These results extend the recently reported weekend citation disadvantage in particle and nuclear physics to astronomy. The link is correlational, consistent with either compositional variations in weekend submissions or reduced visibility in the enlarged Monday listings.