Publications (60)
Optical line spectra of tidal disruption events from reprocessing in optically thick outflows
Edward J. Parkinson, Christian Knigge, James H. Matthews +4
A significant number of tidal disruption events (TDEs) radiate primarily at optical and ultraviolet (UV) wavelengths, with only weak soft X-ray components. One model for this optic…
Thermal and radiation driving can produce observable disk winds in hard-state X-ray binaries
Nick Higginbottom, Christian Knigge, Stuart A. Sim +5
X-ray signatures of outflowing gas have been detected in several accreting black-hole binaries, always in the soft state. A key question raised by these observations is whether the…
Models for Type Ia supernovae and related astrophysical transients
Friedrich K. Roepke, Stuart A. Sim
We give an overview of recent efforts to model Type Ia supernovae and related astrophysical transients resulting from thermonuclear explosions in white dwarfs. In particular we poi…
SIROCCO: A Publicly Available Monte Carlo Ionization and Radiative Transfer Code for Astrophysical Outflows
James H. Matthews, Knox S. Long, Christian Knigge +8
Outflows are critical components of many astrophysical systems, including accreting compact binaries and active galactic nuclei (AGN). These outflows can significantly affect a sys…
Collisional and Radiative Data for Tellurium ions in Kilonovae modelling and Laboratory Benchmarks
Leo Patrick Mulholland, Fiona McNeill, Stuart A. Sim +2
Tellurium is a primary candidate for the identification of the 2.1 m emission line in kilonovae (KNe) spectra AT2017gfo and GRB230307A. Despite this, there is currently an insu…
Modelling the H Lyman lines in evolved late-type stars
Stuart A. Sim
The importance of Partial Redistribution (PRD) in the modelling of the Lyman Alpha and Lyman Beta emission lines of hydrogen in stellar atmospheres is examined using simple atmosph…
The critical role of clumping in line-driven disc winds
Amin Mosallanezhad, Christian Knigge, Nicolas Scepi +4
Radiation pressure on spectral lines is a promising mechanism for powering disc winds from accreting white dwarfs (AWDs) and active galactic nuclei (AGN). However, in radiation-hyd…
Sub-luminous type Ia supernovae from the mergers of equal-mass white dwarfs with M~0.9 M_sun
Ruediger Pakmor, Markus Kromer, Friedrich K. Roepke +3
Type Ia supernovae (SNe Ia) are thought to result from thermonuclear explosions of carbon-oxygen white dwarf stars. Existing models generally explain the observed properties, with…
Double detonations: variations in Type Ia supernovae due to different core and He shell masses -- II: synthetic observables
Christine E. Collins, Sabrina Gronow, Stuart A. Sim +1
Double detonations of sub-Chandrasekhar mass white dwarfs are a promising explosion scenario for Type Ia supernovae, whereby a detonation in a surface helium shell triggers a secon…
No rungs attached: A distance-ladder free determination of the Hubble constant through type II supernova spectral modelling
Christian Vogl, Stefan Taubenberger, Géza Csörnyei +10
The ongoing discrepancy in the Hubble constant () estimates obtained through local distance ladder methods and early universe observations poses a significant challenge to the…
Three-dimensional simulations of gravitationally confined detonations compared to observations of SN 1991T
Ivo R. Seitenzahl, Markus Kromer, Sebastian T. Ohlmann +9
The gravitationally confined detonation (GCD) model has been proposed as a possible explosion mechanism for Type Ia supernovae in the single-degenerate evolution channel. Driven by…
A Diagnostic Kit for Optical Emission Lines Shaped by Accretion Disc Winds
Austen G. W. Wallis, Christian Knigge, James H. Matthews +2
Blueshifted absorption is the classic spectroscopic signature of an accretion disc wind in X-ray binaries and cataclysmic variables (CVs). However, outflows can also create pure em…
SNe Ia from double detonations: Impact of core-shell mixing on the carbon ignition mechanism
Sabrina Gronow, Christine Collins, Sebastian T. Ohlmann +5
Sub-Chandrasekhar mass white dwarfs accreting a helium shell on a carbon-oxygen core are potential progenitors of normal Type Ia supernovae. This work focuses on the details of the…
Testing Quasar Unification: Radiative Transfer in Clumpy Winds
James H. Matthews, Christian Knigge, Knox S. Long +3
Various unification schemes interpret the complex phenomenology of quasars and luminous active galactic nuclei (AGN) in terms of a simple picture involving a central black hole, an…
Accretion Disc Winds in Tidal Disruption Events: Ultraviolet Spectral Lines as Orientation Indicators
Edward J. Parkinson, Christian Knigge, Knox S. Long +4
Some tidal disruption events (TDEs) exhibit blueshifted broad absorption lines (BALs) in their rest-frame ultraviolet (UV) spectra, while others display broad emission lines (BELs)…
Radiation-hydrodynamic simulations of thermally-driven disc winds in X-ray binaries: A direct comparison to GRO J1655-40
Nick Higginbottom, Christian Knigge, Knox S. Long +3
Essentially all low-mass X-ray binaries (LMXBs) in the soft state appear to drive powerful equatorial disc winds. A simple mechanism for driving such outflows involves X-ray heatin…
Monte Carlo Radiative Transfer
Ulrich M. Noebauer, Stuart A. Sim
The theory and numerical modelling of radiation processes and radiative transfer play a key role in astrophysics: they provide the link between the physical properties of an object…
Metallicity-dependent nucleosynthetic yields of Type Ia supernovae originating from double detonations of sub-M white dwarfs
Sabrina Gronow, Benoit Cote, Florian Lach +4
Double detonations in sub-Chandrasekhar mass carbon-oxygen white dwarfs with helium shell are a potential explosion mechanism for a Type Ia supernova (SNe Ia). It comprises a shell…
Stratified disc wind models for the AGN broad-line region: ultraviolet, optical and X-ray properties
James H. Matthews, Christian Knigge, Nick Higginbottom +5
The origin, geometry and kinematics of the broad line region (BLR) gas in quasars and active galactic nuclei (AGN) are uncertain. We demonstrate that clumpy biconical disc winds il…
Helium as a signature of the double detonation in Type Ia supernovae
Christine E. Collins, Stuart A. Sim, Luke. J. Shingles +5
The double detonation is a widely discussed mechanism to explain Type Ia supernovae from explosions of sub-Chandrasekhar mass white dwarfs. In this scenario, a helium detonation is…
On the relativistic iron line and soft excess in the Seyfert 1 galaxy Markarian 335
Paul M. O'Neill, Kirpal Nandra, Massimo Cappi +2
We report on a 133 ks XMM-Newton observation of the Seyfert 1 galaxy Markarian 335. The 0.4-12 keV spectrum contains an underlying power law continuum, a soft excess below 2 keV, a…
The lowest of the low: discovery of SN 2019gsc and the nature of faint Iax supernovae
Shubham Srivastav, Stephen J. Smartt, Giorgos Leloudas +15
We present the discovery and optical follow-up of the faintest supernova-like transient known. The event (SN 2019gsc) was discovered in a star-forming host at 53\,Mpc by ATLAS. A d…
Line-driven Disk Winds in Active Galactic Nuclei: The Critical Importance of Ionization and Radiative Transfer
Nick Higginbottom, Daniel Proga, Christian Knigge +3
Accretion disk winds are thought to produce many of the characteristic features seen in the spectra of active galactic nuclei (AGN) and quasi-stellar objects (QSOs). These outflows…
Self-consistent 3D radiative transfer for kilonovae: directional spectra from merger simulations
Luke J. Shingles, Christine E. Collins, Vimal Vijayan +7
We present three-dimensional radiative transfer calculations for the ejecta from a neutron star merger that include line-by-line opacities for tens of millions of bound-bound trans…
Monte-Carlo radiation hydrodynamic simulations of line-driven disc winds: relaxing the isothermal approximation
Amin Mosallanezhad, Christian Knigge, Nicolas Scepi +4
Disc winds play a crucial role in many accreting astrophysical systems across all scales. In accreting white dwarfs (AWDs) and active galactic nuclei (AGN), radiation pressure on s…
Strontium and helium in the kilonova AT2017gfo: Origin of the 1μm feature constrained via NLTE calculations
Aayush Arya, Rasmus Damgaard, Albert Sneppen +4
Mergers of neutron stars are believed to be one of the primary sites for the synthesis of the universe's heavy elements via the rapid neutron capture process. AT2017gfo, the kilono…
The Geometry and Ionization Structure of the Wind in the Eclipsing Nova-like Variables RW Tri and UX UMa
Ulrich M. Noebauer, Knox S. Long, Stuart A. Sim +1
The UV spectra of nova-like variables are dominated by emission from the accretion disk, modified by scattering in a wind emanating from the disk. Here we model the spectra of RW T…
Paschen Jumps in Little Red Dots: Evidence for Nebular Continua
Albert Sneppen, James H. Matthews, Darach Watson +6
''Little Red Dots'' (LRDs) are broad-line sources at high redshift, initially identified by their compact morphologies, red colours and prominent Balmer breaks. The origin of their…
Double detonations of sub-Chandrasekhar mass CO white dwarfs: Can different core and He shell masses explain variations of Type Ia supernovae?
Sabrina Gronow, Christine E. Collins, Stuart A. Sim +1
Sub-Chandrasekhar mass carbon-oxygen white dwarfs (CO WDs) with a surface helium (He) shell have been proposed as progenitors of Type Ia supernovae (SNe Ia). If true, the resulting…
Modelling the ionisation state of Type Ia supernovae in the nebular-phase
Luke J. Shingles, Andreas Flörs, Stuart A. Sim +4
The nebular spectra of Type Ia supernovae ( 100 days after explosion) consist mainly of emission lines from singly- and doubly-ionised Fe-group nuclei. However, theoret…
The Impact of Accretion Disk Winds on the Optical Spectra of Cataclysmic Variables
James H. Matthews, Christian Knigge, Knox S. Long +2
Many high-state non-magnetic cataclysmic variables (CVs) exhibit blue-shifted absorption or P-Cygni profiles associated with ultraviolet (UV) resonance lines. These features imply…
Radiation-ionization hydrodynamic simulations of AGN line-driven winds lead to transient shielding and BAL/UFO signatures
Nicolas Scepi, Christian Knigge, Amin Mosallanezhad +4
Disc winds from active galactic nuclei (AGN) can be launched by radiation pressure acting on spectral lines. However, launching a line-driven wind in the X-ray rich environment of…
A spectral synthesis code for rapid modelling of supernovae
Wolfgang E. Kerzendorf, Stuart A. Sim
We present TARDIS - an open-source code for rapid spectral modelling of supernovae (SNe). Our goal is to develop a tool that is sufficiently fast to allow exploration of the comple…
Helium features are inconsistent with the spectral evolution of the kilonova AT2017gfo
Albert Sneppen, Rasmus Damgaard, Darach Watson +3
The spectral features observed in kilonovae (KNe) reveal the elemental composition and the velocity structures of matter ejected from neutron star mergers. In the spectra of the ki…
SN2018kzr: a rapidly declining transient from the destruction of a white dwarf
Owen R. McBrien, Stephen J. Smartt, Ting-Wan Chen +31
We present SN2018kzr, the fastest declining supernova-like transient, second only to the kilonova, AT2017gfo. SN2018kzr is characterized by a peak magnitude of , peak…
State-of-the-art simulations of line-driven accretion disc winds: realistic radiation-hydrodynamics leads to weaker outflows
Nick Higginbottom, Nicolas Scepi, Christian Knigge +3
Disc winds are a common feature in accreting astrophysical systems on all scales. In active galactic nuclei (AGN) and accreting white dwarfs (AWDs), specifically, radiation pressur…
StaNdaRT: A repository of standardized test models and outputs for supernova radiative transfer
Stéphane Blondin, Sergei Blinnikov, Fionntan P. Callan +26
We present the first results of a comprehensive supernova (SN) radiative-transfer (RT) code-comparison initiative (StaNdaRT), where the emission from the same set of standardized t…
Three-dimensional delayed-detonation models with nucleosynthesis for Type Ia supernovae
Ivo R. Seitenzahl, Franco Ciaraldi-Schoolmann, Friedrich K. Roepke +7
We present results for a suite of fourteen three-dimensional, high resolution hydrodynamical simulations of delayed-detonation modelsof Type Ia supernova (SN Ia) explosions. This m…
Observational signatures of thermonuclear electron-capture supernovae -- Ne II line strengthening and color evolution as traces of the explosion mechanism
Alexander Holas, Fionntan P. Callan, Samuel W. Jones +7
Thermonuclear electron-capture supernovae (tECSNe) are a potential fate of certain intermediate mass stars forming ONe cores at the end of their evolution. Simulations suggest that…
'Super-Chandrasekhar' Type Ia Supernovae at nebular epochs
Stefan Taubenberger, Markus Kromer, Stephan Hachinger +11
We present a first systematic comparison of superluminous Type Ia supernovae (SNe Ia) at late epochs, including previously unpublished photometric and spectroscopic observations of…
Type Iax SNe as a few-parameter family
Barnabas Barna, Tamas Szalai, Wolfgang E. Kerzendorf +4
We present direct spectroscopic modeling of five Type Iax supernovae (SNe) with the one dimensional Monte Carlo radiative transfer code TARDIS. The abundance tomography technique i…
Non-LTE radiative transfer simulations: Improved agreement of the double detonation with normal Type Ia supernovae
Christine E. Collins, Luke J. Shingles, Stuart A. Sim +6
The double detonation is a widely discussed explosion mechanism for Type Ia supernovae, whereby a helium shell detonation ignites a secondary detonation in the carbon/oxygen core o…
The asymmetry of white dwarf double detonations and the observed scatter around the Phillips relation
Alexander Holas, Friedrich K. Roepke, Rüdiger Pakmor +6
Recent Type Ia supernova (SN Ia) simulations featuring a double detonation scenario have managed to reproduce the overall trend of the Phillips relation reasonably well. However, m…
Quenching of X-ray emission in little red dots by both Compton-thick gas and high accretion rates
Albert Sneppen, Darach Watson, James H. Matthews +1
Little red dots (LRDs) are candidate high-redshift supermassive black holes accreting in dense gas. They remain undetected in X-rays. In previous work, we provided the first quanti…
Electron impact excitation of Te IV and V and Level Resolved R-matrix Photoionization of Te I - IV with application to modelling of AT2017gfo
Leo P. Mulholland, Catherine A. Ramsbottom, Connor P. Ballance +2
Spectral modelling of kilonovae (KNe) require large amounts of collisional excitation and photoionization atomic data for lowly ionised (neutral, singly and doubly ionised) species…
Helium in Double-Detonation Models of Type Ia Supernovae
Aoife Boyle, Stuart A. Sim, Stephan Hachinger +1
The double-detonation explosion model has been considered a candidate for explaining astrophysical transients with a wide range of luminosities. In this model, a carbon-oxygen whit…
The white dwarf's carbon fraction as a secondary parameter of Type Ia supernovae
Sebastian T. Ohlmann, Markus Kromer, Michael Fink +4
Binary stellar evolution calculations predict that Chandrasekhar-mass carbon/oxygen white dwarfs (WDs) show a radially varying profile for the composition with a carbon depleted co…
Towards inferring the geometry of kilonovae
Christine E. Collins, Luke J. Shingles, Andreas Bauswein +11
Recent analysis of the kilonova, AT2017gfo, has indicated that this event was highly spherical. This may challenge hydrodynamics simulations of binary neutron star mergers, which u…
Type Ia supernovae from exploding oxygen-neon white dwarfs
Kai S. Marquardt, Stuart A. Sim, Ashley J. Ruiter +5
The progenitor problem of Type Ia supernovae (SNe Ia) is still unsolved. Most of these events are thought to be explosions of carbon-oxygen (CO) white dwarfs (WDs), but for many of…
Synthetic Light Curves and Spectra for the Photospheric Phase of a 3D Stripped-Envelope Supernova Explosion Model
Thomas Maunder, Fionntan P. Callan, Stuart A. Sim +2
We present synthetic light curves and spectra from three-dimensional (3D) Monte Carlo radiative transfer simulations based on a 3D core-collapse supernova explosion model of an ult…
Exploring the diversity of kilonovae with 3D radiative transfer I. The polar direction
Christine E. Collins, Luke J. Shingles, Vimal Vijayan +7
We present 3D kilonova radiative transfer simulations for a series of binary neutron star merger models. The masses of the neutron stars are varied as well as the total mass of the…
On the use of the Axelrod formula for thermal electron collisions in Astrophysical Modelling
Leo P. Mulholland, Steven J. Bromley, Connor P. Ballance +2
The Axelrod approximation is widely used in astrophysical modelling codes to evaluate electron-impact excitation effective collision strengths for forbidden transitions. Approximat…
A theoretical color-velocity correlation for supernovae associated with gamma-ray bursts
Sharon Rapoport, Stuart A. Sim, Keiichi Maeda +4
We carry out the first multi-dimensional radiative transfer calculations to simultaneously compute synthetic spectra and light curves for models of supernovae driven by fast bipola…
Modelling the spectra of (BAL)QSOs
Nick Higginbottom, Knox S. Long, Christian Knigge +1
We have embarked upon a project to model the UV spectra of BALQSOs using a Monte Carlo radiative transfer code previously validated through modelling of the winds of cataclysmic va…
Helium as an Indicator of the Neutron-Star Merger Remnant Lifetime and its Potential for Equation of State Constraints
Albert Sneppen, Oliver Just, Andreas Bauswein +9
The time until black hole formation in a binary neutron-star (NS) merger contains invaluable information about the nuclear equation of state (EoS) but has thus far been difficult t…
3D radiative transfer kilonova modelling for binary neutron star merger simulations
Christine E. Collins, Andreas Bauswein, Stuart A. Sim +5
The detection of GW170817 and the accompanying electromagnetic counterpart, AT2017gfo, have provided an important set of observational constraints for theoretical models of neutron…
Locations of Peculiar Supernovae as a Diagnostic of Their Origins
Fang Yuan, Chiaki Kobayashi, Brian P. Schmidt +3
We put constraints on the properties of the progenitors of peculiar calcium-rich transients using the distribution of locations within their host galaxies. We confirm that this cla…
AT2018kzr: the merger of an oxygen-neon white dwarf and a neutron star or black hole
James H. Gillanders, Stuart A. Sim, Stephen J. Smartt
We present detailed spectroscopic analysis of the extraordinarily fast-evolving transient AT2018kzr. The transient's observed lightcurve showed a rapid decline rate, comparable to…
The effect of helium accretion efficiency on rates of Type Ia supernovae: double-detonations in accreting binaries
Ashley J. Ruiter, Krzysztof Belczynski, Stuart A. Sim +2
The double-detonation explosion scenario of Type Ia supernovae has gained increased support from the SN Ia community as a viable progenitor model, making it a promising candidate a…
SN2014J gamma-rays from the 56Ni decay chain
Roland Diehl, Thomas Siegert, Wolfgang Hillebrandt +7
The measurement of gamma-ray lines from the decay chain of 56Ni provides unique information about the explosion in supernovae. The 56Ni freshly-produced in the supernova powers the…