PREPRINT

# The Luminosity Phase Space of Galactic and Extragalactic X-ray Transients Out to Intermediate Redshifts

Ava Polzin, Raffaella Margutti, Deanne Coppejans, Katie Auchettl, Kim L. Page, Georgios Vasilopoulos, Joe S. Bright, Paolo Esposito, Peter K. G. Williams, Koji Mukai, Edo Berger

Submitted on 2 November 2022

## Abstract

We present a detailed compilation and analysis of the X-ray phase space of low- to intermediate-redshift transients that consolidates observed light curves (and theory where necessary) for a large variety of classes of transient/variable phenomena in the 0.3--10 keV band including gamma-ray burst afterglows, supernovae, supernova shocks interacting with the environment, tidal disruption events and active galactic nuclei, fast blue optical transients, cataclysmic variables, magnetar flares/outbursts and fast radio bursts, cool stellar flares, X-ray binary outbursts, and ultraluminous X-ray sources. Our over-arching goal is to offer a comprehensive resource for the examination of these ephemeral events, extending the X-ray duration-luminosity phase space (DLPS) to show luminosity evolution. We use existing observations (both targeted and serendipitous) to characterize the behavior of various transient/variable populations. Contextualizing transient signals in the larger DLPS serves two primary purposes: to identify areas of interest (i.e., regions in the parameter space where one would expect detections, but in which observations have historically been lacking) and to provide initial qualitative guidance in classifying newly discovered transient signals. We find that while the most luminous (largely extragalactic) and least luminous (largely Galactic) part of the phase space is well-populated at $t>0.1$ days, intermediate luminosity phenomena (L${}_{x}={10}^{34}-{10}^{42}$ erg s${}^{-1}$) represent a gap in the phase space. We thus identify L${}_{x}={10}^{34}-{10}^{42}$ erg s${}^{-1}$ and $t={10}^{-4}-0.1$ days as a key discovery phase space in transient X-ray astronomy.

## Preprint

Comment: 11 figures, 12 tables; to be submitted to the AAS Journals in ~a week. Comments welcome!

Subject: Astrophysics - High Energy Astrophysical Phenomena