Time Evolving Photo Ionisation Device (TEPID): a novel code for out-of-equilibrium gas ionisation

Abstract

Photoionisation is one of the main mechanisms at work in the gaseous environment of bright astrophysical sources. Many information on the gas physics, chemistry and kinematics, as well as on the ionising source itself, can be gathered through optical to X-ray spectroscopy. While several public time equilibrium photoionisation codes are readily available and can be used to infer average gas properties at equilibrium, time-evolving photoionisation models have only very recently started to become available. They are needed when the ionising source varies faster than the typical gas equilibration timescale. Indeed, using equilibrium models to analyse spectra of non-equilibrium gas may lead to inaccurate results and prevents a solid assessment of the gas density, physics and geometry. We present our novel Time-Evolving PhotoIonisation Device (TEPID), which self-consistently solves time evolving photoionisation equations (thermal and ionisation balance) and follows the response of the gas to changes of the ionising source. The code can be applied to a variety of astrophysical scenarios and produces time-resolved gas absorption spectra to fit the data. To describe the main features of TEPID, we apply it to two dramatically different astrophysical scenarios: a typical ionised absorber observed in the X-ray spectra of Active Galactic Nuclei (e.g. Warm Absorbers and UFOs) and the circumburst environment of a Gamma-Ray Burst. In both cases, the gas energy and ionisation balances vary as a function of time, gas density and distance from the ionising source. Time evolving ionisation leads to unique ionisation patterns which cannot be reproduced by stationary codes when the gas is out of equilibrium. This demonstrates the need for codes such as TEPID in view of the up-coming high-resolution X-ray spectrometers onboard missions like XRISM or Athena.

Accepted for publication on Astronomy & Astrophysics. 23 pages, 25 figures

References in corpus (17)

• Array Programming with NumPy
• A nearby long gamma-ray burst from a merger of compact objects
• Radiative recombination data for modelling dynamic finite-density plasmas
• Ionized outflows from active galactic nuclei as the essential elements of feedback
• The response of relativistic outflowing gas to the inner accretion disk of a black hole
• The prompt, high resolution spectroscopic view of the "naked-eye" GRB080319B
• The NICER "Reverberation Machine": A Systematic Study of Time Lags in Black Hole X-Ray Binaries
• XMM-Newton View of the Multi-Phase Warm Absorber in Seyfert 1 Galaxy NGC985
• Speed limits for radiation driven SMBH winds
• TPHO: a time-dependent photoionisation model for AGN outflows
• Detection of a Multi-Phase Ultra-Fast Wind in the Narrow-Line Seyfert 1 Galaxy Mrk 1044
• Properties of High-Redshift GRBs
• Photoionization Models for High Density Gas
• Time Dependent Photoionization Modeling of Warm Absorbers in Active Galactic Nuclei
• Towards an understanding of long gamma-ray burst environments through circumstellar medium population synthesis predictions
• Spectral-timing of AGN ionized outflows with Athena
• X-ray absorbing column densities of a complete sample of short Gamma Ray Bursts

Cited by in corpus (4)

• A systematic study of the ultra-fast outflow responses to luminosity variations in active galactic nuclei
• Time-dependent photoionization spectroscopy of the Seyfert galaxy NGC 3783
• Dense gas linked to star-forming regions photoionised by embedded gamma-ray bursts
• Unveiling BLR Structure in AGN with High Resolution X-Ray Spectra: An Analytic Approach to Wind Emission Line Profiles