# Astro 2020 Science White Paper: Time Domain Studies of Neutron Star and Black Hole Populations: X-ray Identification of Compact Object Types

## TL;DR

This white paper emphasizes the importance of wide-field X-ray monitoring combined with deep surveys to identify and study neutron stars and black holes, advancing understanding of their formation, evolution, and demographics through time-domain analysis.

## Contribution

It proposes a new observational strategy using wide-field X-ray monitors and high-resolution telescopes to improve compact object classification and demographic studies.

## Key findings

- Time-domain measurements can revolutionize understanding of NS and BH populations.
- Synergy with multiwavelength data enhances source characterization.
- Proposed methods link source phenomena to galaxy parameters.

## Abstract

What are the most important conditions and processes governing the growth of stellar-origin compact objects? The identification of compact object type as either black hole (BH) or neutron star (NS) is fundamental to understanding their formation and evolution. To date, time-domain determination of compact object type remains a relatively untapped tool. Measurement of orbital periods, pulsations, and bursts will lead to a revolution in the study of the demographics of NS and BH populations, linking source phenomena to accretion and galaxy parameters (e.g., star formation, metallicity). To perform these measurements over sufficient parameter space, a combination of a wide-field (>5000 deg^2) transient X-ray monitor over a dynamic energy range (~1-100 keV) and an X-ray telescope for deep surveys with <5 arcsec PSF half-energy width (HEW) angular resolution are required. Synergy with multiwavelength data for characterizing the underlying stellar population will transform our understanding of the time domain properties of transient sources, helping to explain details of supernova explosions and gravitational wave event rates.