3.5-meter Segmented-Mirror Robotic Space Telescope Mission White Paper V. Key Scientific Mission: Compact-Object Time-Domain Science

This white paper defines the compact-object time-domain science case for a 3.5-meter segmented-mirror robotic space telescope. It notes that an isolated compact object retains the point-source resolving power of a space-based slitless spectrograph, and sets a baseline wavelength range of 0.2--1.5 micrometers.

The planning baseline uses R approximately 1000 for broad and faint transient spectra, while reserving selectable bands at R approximately 5000 for accretion-disk profiles, velocity structure, and precision line ratios; broad features can still be measured by binning the native R approximately 5000 data to lower resolution. Rapid-response spectroscopy will follow gravitational-wave counterparts and kilonovae from hours to days, repeated spectra of dwarf novae and compact binaries will trace accretion state and orbital phase, and uninterrupted imaging of white dwarfs will measure pulsation frequencies. The science program combines mission-based monitoring with external alerts, including KGMT transient detections.

The instrument study must preserve calibrated throughput to 2.70 micrometers and evaluate a 3.0 micrometer operational band edge, with 2.5 micrometers retained as the formal engineering off-ramp. Mid-infrared imaging is not part of the adopted compact-object baseline.