Boombox on the MMT and Magellan Telescopes: expanding spectroscopic capacity for the time-domain era

Abstract

While the Rubin Observatory is poised to discover over 1 million transients per year, fewer than 0.05% will be spectroscopically classified with current resources. Boombox is an upcoming set of spectrographs on the MMT and Magellan Telescopes designed to address this challenge, with broad optical coverage (355–1010 nm), moderate resolution (R∼1000), and high throughput to depths of r ≈ 23.5 magnitudes. The instrument is part of the Via survey, a large-scale fiber-fed survey with 600 robotically positioned fibers over 1 deg2, with 36 fibers feeding directly into Boombox. As part of this large survey, Boombox is on sky for over 100 nights per year, driving the survey for 10% of the observing time and conducting science simultaneously with its partner instrument, Viaspec, the remaining 90% of survey time. This configuration enables both rapid target-of-opportunity interrupts for newly discovered transients and large-scale spectroscopic campaigns. Boombox’s broad wavelength coverage and high sensitivity on 6.5-m telescopes will expand transient classification capabilities and enable a broad range of science studies, including studies of ultra-cool dwarfs, cosmology with fast radio burst host galaxies, kilonovae, and other rare transients. We present the instrument’s design, including optics, mechanics, and software, along with an updated status from the build, with commissioning expected in 2027.