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

Abstract

An isolated compact object retains the point-source resolving power of the space-based slitless spectrograph. The baseline wavelength range is 0.2--1.5 $\mu$m. The planning baseline uses $R\simeq 1000$ for broad and faint transient spectra and reserves selectable bands at $R\simeq 5000$ for accretion-disk profiles, velocity structure, and precision line ratios. Broad features can be measured after binning the native $R\simeq 5000$ data to lower resolution. Rapid-response spectroscopy follows gravitational-wave counterparts and kilonovae from hours to days. Repeated spectra of dwarf novae and compact binaries trace accretion state and orbital phase, while uninterrupted imaging of white dwarfs measures pulsation frequencies. The program combines mission-based monitoring with external alerts, including KGMT transient detections. The instrument study must preserve calibrated throughput to 2.70 $\mu$m and evaluate a 3.0 $\mu$m operational band edge, with 2.5 $\mu$m retained as the formal engineering off-ramp. Mid-infrared imaging is not part of the adopted compact-object baseline.

Revised to focus the compact-object program on repeated optical/NIR spectroscopy, R~5000 line-profile measurements, and white-dwarf pulsations, with clearer roles for external alerts and complementary data