Black Hole Journal Club

We meet every Tuesday at:

12:00 until 13:00 (UTC + 0)

The Zoom link has been emailed to the group.

NOTE: we will have a review of arxiv on the 10th december and there is no journal club on the 17th December. We will be restarting on 7th January.

Agenda

Presentation of chosen paper (~30 mins)
Discussion
Other papers from the week

Rota

To generate additional entries for the rota, use scripts/rota.py.

Date	Presenter
2025-03-04	Andy
2025-03-11	Jiachen
2025-03-18	Darius
2025-03-25	Fergus
2025-04-01	Tom
2025-04-08	Gloria
2025-04-15	Belinda
2025-04-22	Easter
2025-04-29	Andy
2025-05-06	Arxiv
2025-05-13	Jiachen

Minutes

2025-02-25: Belinda

Discussed Papers:

The X-ray Integral Field Unit at the end of the Athena reformulation phase (Peille et al., 02-2025)

Redesign of X-IFU, (one of the) primary science instrument on NewAthena
New 'simple' cooling system - Passive cooling to 50k.
Adiabetic cooling to ~ few mK at the focal plane.

Flip-flop QPO changes during state transitions: a case study of GX339-4 and theoretical discussion (Buisson et al., 02-2025)

Interesting QPO case of flipping types

Presented Paper:

The JWST View of Cygnus A: Jet-Driven Coronal Outflow with a Twist (Ogle et al., 02-2025)

Radio-jet Feedback & Galaxy Star Formation. Jet impact depends on age, power and geometry.
JWST and Keck observations
Chandra X-rays fill the apparent open cone.
AGN core in polarised light, X-rays highly obscured $$N_H \sim 10^{23} \text{cm}^{-2}$$.
Hot dust in inner torus produce continuum at $$>2\mu \text{m}$$
94 ionized emission lines - consistent with AGN photoionization
Radio jet clearing and emptying cone
Quickly-moving [Fe-II] clump in western cone
Outflow $$\sim 250\text{km s}^{-1}$$
Clump may be line of sight - high velocity absorption lines
High velocity could be due to radiation pressure in centre
[Fe-II] clump has $$\sim 40M_{\odot}\text{yr}^{-1}$$ and mass $$1.1\times10^8$$
Velocity field, spiral outflow models show rotating cone around radio axis.
Line splitting in model
Spiral Outflow: AGN/jet driven or residual roation from infalling gas
AGN/jet driven model needs a secondary driving force to maintain velocity - unlikely?
residual rotation requires puffed-up disk (e.g. Muhkerjee+2018). Disk velocity needs sub-keplerian but not observed.

2025-02-18: Arxiv

Discussed Papers: A New Interpretation for the Hot Corona in Active Galactic Nuclei (Zhao et al., 02-2025)

Magnetically reconnecting layer above accretion disk
Allows investigation betwen height of corona and X-ray luminosity
Very nice cartoon diagrams for magnetic reconnection
Implementations could be used in Gradus.jl
Similar to jet sheath model A relativistic outflow model of the X-ray polarization in Cyg X-1 (Dexter, Begelman, 08-2023)
Similar to hyperbolic corona Modeling fast X-ray variability around an accreting black hole (Zhan et al., 02-2025) Dust beyond the torus: Revealing the mid-infrared heart of local Seyfert ESO 428-G14 with JWST/MIRI (Haidar et al., 04-2024)
Seyfert II AGN & Compton Thick in X-rays
IR (warmer) dust emission from jet axis being heated by jet radiation
Radially driven dusty winds Is the Spin of the Black Hole in GX 339-4 Negative? (Zdziarski et al., 12-2024)
Potential selection bias from fits
Dramatically different results from similar selections Links to Fifty Years After the Discovery of the First Stellar-Mass Black Hole: A Review of Cyg X-1 (Jiang, 11-2024)
X-ray & GW binary detection spin discrepency
BH HMXBs unlikely to be GW binary BH

2025-02-11: Gloria

Discused Papers: Not enough time to go through them so they will be discussed briefly next week

Presented Paper: Multi-wavelength observations of a jet launch in real time from the post-changing-look Active Galaxy 1ES 1927+654 (Laha, et al., 01-2025) Slides available here: Gloria_Raharimbolamena_Preprint_04_Feb_25.pdf

Jet launch mechanism from a Changing-look AGN
Rapid accretion mode
1ES1927+654, QPO activity.
- Acts differently to other AGN. No optical-UV correlation from flares
- Object has 'true type II AGN pre-outburst'
Steep initial spectrum of $$\Gamma\sim2.4$$
Steepening power law during flaring (reaching $$\Gamma>3$$ during radio flaring)
Indications of sources other than UV accretion
Soft excess increasing in flux
Blackbody model best fits the soft excess
No significant Optical or UV variability
High colimation suggest Blanford-Zanjek (BZ) lauch mechanism (Using BH roational energy)
Outflow speeds suggest $$0.2c$$, a BP mechanism would need launch distance $$<10r_g$$. Low speed for BZ, could indicate inclination angle
Kinetic power of jet suggests near 100% efficiency of BZ.
Magnetic field well above equiparition
Origin of new soft excess is unique and not found in RQ-AGN. Possibly due to magnetic energy & jet emission
The (near-)concurance of QPO and jet signals shows similarities with BH binaries
Radio flare delay due to a screen of hot gas
This type of QPO acitivity never observed in AGN.

2025-01-28: Tom

Discussed Papers: No Papers discussed due to time constraints. Noted papers will be discussed at a later date

Presented: SAUNAS II: Discovery of Cross-shaped X-ray Emission and a Rotating Circumnuclear Disk in the Supermassive S0 Galaxy NGC 5084 (Borlaff et al., 08-2024)

Radio observations reveal low polarization degree but assumed from beam depolarization and therefore ignored in this study.
SNe feedback, AGN & Galactic winds to explain some soft excess
Reduction with SAUNAS pipeline (Borlaff et al., 05-2024) which includeds standard reduction, PSF modelling and deconvolution and low surface brightness estimations.
Included in SUNAS is bootstrapping and MC simulations for error estimation and Voronoi binning.
NGC 5085 is at $$z=$$ so $$20 kpc \sim 2.9"$$
$$5\sigma$$ detection of emission perpendicular to galaxy.
$$3\sigma$$ detection parallel to disk of galaxy
Highly inclinated circumnuclear disk
Jet changing orientation of $$\sim90\deg$$ possibly but unlikely? Would likely need external influence (mergers)
fig 8. shows nice cartoon of potential causes for a change of orientation
Outflow appears to have stopped. Stellar population should be young but blue emission not seen
Stellar age is $$>Gyr$$
Binary SMBH
Potential causes for X-shaped emission: AGN re-orientation, overpressurised coccoon or faded starburst.

2025-01-21: Fergus

Discussed Papers:

25 years of XMM-Newton observations of the Sgr A complex: 3D distribution and internal structure of the clouds (Stel et al., 01-2025)
- 3D mapping of Sgr A clouds to generate complex cloud compositions and models.
The properties of GSN 069 accretion disk from a joint X-ray and UV spectral analysis: stress-testing quasi-periodic eruption models (Guolo et al., 01-2025)
- Looks at TDE
X-ray Dips and Polarization Angle Swings in GX 13+1 (Di Marco et al., 01-2025)
- Polarisation angle is changing over time
Markarian 590: The AGN Awakens (Palit et al., 01-2025)
- A changing look AGN that is awakening to a type 1
- Soft X-ray jump of factor of about 10
- Complexes in optical spectra
Multi-wavelength observations of a jet launch in real time from the post-changing-look Active Galaxy 1ES 1927+654 (Laha et al., 01-2025)
- Jet swicth on and QPO

Presented Paper:

Continuum Reverberation in Active Galactic Nuclei Disks Only With Sufficient X-ray Luminosity and Low Albedo (Secunda et al., 01-2025)

Weakly correlated X-ray & UV light curves -> Problematic for the standard Reverberation Mapping models
Mechanisms could be instrinsic uv-optical variability in disk
Model turbulance & cross-sections
Line opacity can affect models
ATHENA++ code
Intensity set by lightcurve
Curve dominated by scattering opacity
Temperature dependant opacity
Closer PSD of X-ray irradiation to DWR, more X-ray supress UV emission
Decreasing X-ray flux leads to lower X-ray & UV correlations
Variability driven by AGN disk
Higher order models with different reprocessing ratios could be a better fit
Test 1 day time lag: reconstained 1 day lag from JAVILIN method
Need sophisticated opacity models for stronger correlations. Modelling the Multiwavelength Variability of Mrk 335 using Gaussian Processes (Griffiths et al., 07-2021)
- Time lags & reprocessed emission

2025-01-14: Darius

Discussed Papers:

The NewAthena mission concept in the context of the next decade of X-ray astronomy (Cruise et al., 08-2024)
- NewAthena Redefinition article on Nature Astronomy.
Insight into the Starburst Nature of Galaxy GN-z11 with JWST MIRI Spectroscopy (Álvarez-Márquez et al., 12-2024)
- See the closed issue for 14th January for relavane background papers.
AT2021aeuk: A Repeating Partial Tidal Disruption Event Candidate in a Narrow-line Seyfert 1 (Jingbo et al., 01-2025)
- A TDE in NLS1.
The size of accretion disks from self-consistent X-ray spectra and UV/optical/NIR photometry fitting: applications to ASASSN-14li and HLX-1 (Guolo & Mummery, 01-2025)
- Github code available here
X-ray Dips and Polarization Angle Swings in GX 13+1 (Di Marco at al., 01-2025)
- looks at the Polarisation in LMXRB GX13+1. Model proposed includes obscuration regions and steep inclination.
Astronomical X-ray Polarimetry as a diagnostic for questions of fundamental Physics. What we learned from the Imaging X-Ray Polarimetry Explorer (IXPE) (Soffitta & Costa, 12-2024)
RTFAST-Spectra: Emulation of X-ray reverberation mapping for active galactic nuclei (Ricketts et al., 12-2024)
Analytical ray-tracing of synchrotron emission around accreting black holes (Veledina & Pélissier, 12-2024) Presented Paper:
An Exceptionally Powerful, Radiatively Driven Ultrafast Outflow in the Rapidly Accreting AGN REJ1034+396 (Taylor et al., 12-2025)
- Approximately 1Ms of observatons on a rapidly accreting AGN with XMM.
- Modelled by steep emission from corona and relativisitic blurred reflection from the AD.
- Evidience of an UFO.
- The outflow could be capable of driving out most gas and dust.

2025-01-07: Jiachen

Discussed Papers: Not necessarily discussed in great detail but mentioned were:

Impact of radiative cooling on the magnetised geometrically thin accretion disk around Kerr black hole (Dihingia et al., 05-2023)
A simplified approach for reproducing fully relativistic spectra in X-ray binary systems: Application to Cygnus X-1 (Papavasileiou et al., 08-2024)

Presented: Fifty Years After the Discovery of the First Stellar-Mass Black Hole: A Review of Cyg X-1 (Jiang, 11-2024)

Cyg X-1 is 1st known Stellar Mass BH known and hosts $20 M_\odot$ BH with $40 M_\odot$ companion star. One of a few High Mass X-ray Binary (HMXB)
Review goes through physics beind measurements in useful detail.
BH-BH merger candiadate
First instance of HMXB using typical AGN models
3% probability to observe BH > $35 M_{\odot}$ and 0.6% of HMXB GW source within hubble time.
Harder X-ray for low luminosity states
Disk emissivity profile indicates compact corona (~5-7 $r_g$) but still unknown geometry.
Over-polarise, expected 1% but found 4%, this suggests a higher material speed and thus higher scattering cross-section. The jet may also help produce these observations.
polarisation aligns with radio jet over AU scales.
Corona geometries are source dependent and testing models should not rule out other models.
Polarisation angle changes at higher energies. Possibly higher polarisation degree for emission closer to BH, consistent with very high BH spin.
Fe lines seen in LMXB are not seen in Cyg X-1
Emmission above 511 keV constarined by pair-production and produces a peak, the annihilation line is always present in Cyg X-1 models. Doppler broadening allows for higher $e^-$ temperature.
Non-thermal emission from jet and corona
In the high density model, free-free absorption is important.

2024-12-10: Arxiv

Discussed papers: We very briefly mentioned some of the papers that were lightly discussed last week although not in great detail:

X-ray polarization from accretion disk winds (Nitindala et al., 11-2024)
Polarization of synchrotron radiation from blazar jets (Boris et al., 11-2024)
New Insights with XRISM & Cloudy: A novel Column Density Diagnostic (Gunasekera et al., 11-2024)

We discussed a few other papers in a little more detail.

Feedback from Intermediate Mass Black Holes on Dwarf Galaxy Morphology at z = 2 (Bi et al., 12-2024)
- Looking at IMBHs with AGN feedback influencing gas fraction, SF and galaxy structrue.
- Potential need for low-z diagnostics for high-z.
- Also looked at JWST pixelation effects.
Physical Pathways for JWST-Observed Supermassive Black Holes in the Early Universe (Jeon et al., 02-2024)
- Looking at masses of AGN compared to the stellar mass and different ratios.
- Investigates direct collapse black holes.
Lack of Rest-frame UV Variability in Little Red Dots Based on HST and JWST Observations (Tee et al., 12-2024)
- V-shaped SEDs appear less variable
- Possible heavy AGN obsuration
- No variability suggests stellar contributions
Probing orbits of stellar mass objects deep in galactic nuclei with quasi-periodic eruptions (Zhou et al., 05-2024)
- useful figures
- QPEs from TDE & stellar mass object collisions
- Looks at example GSN 069
A Comprehensive Hadronic Code Comparison for Active Galactic Nuclei (Cerruti et al,. 11-2024)
- SED comparisons with blazars
- comparing different models

2024-12-03: Gloria

Presented paper:

The Study of Jet Formation Mechanism in Fermi Blazars (Xie et al., 2024)
- Presentation slides are available here
- A study of 937 Blazars studied for jet formation mechanisms
- Jet power could come from the rotational energy of BH (BZ mdoel) or AD (BP model)
- Study finds no significant relationship between jet power and accretion rate. Possible week relationship for FSQR
- Adding BH mass gets stronger relationship (using F-test)
- BH more important in fueling jets than AD
- Neitehr BZ or BP fully explain jet-powering of blazars but $P_{jet}$ observations are difficult.
- FSRQ from BP (not BZ sufficient), BL Lacs could be BZ model
- BL Lacs ADAF dominated, for FSRQs standard disk dominates.
- BZ MAD disk model in BL Lacs

Other papers:

X-ray polarization from accretion disk winds (Nitindala et al., 2024)
- Scattering in winds reproduces polarization results
- Casts doubts on accretion disk geometries
A Short-lived Rejuvenation during the Decades-long Changing-look Transition in the Nucleus of Mrk 1018 (et al., 2024)
- Full cycle of transitions observed

2024-11-26: Fergus

Presented paper:

On the Morphology of Relativistically Broadened Line Emission from Axisymmetric Equatorial Accretion Disks (Gates et al., 2024)
- Uses geometrically thin, equatorial disk models & describes how to determine emission line morphologies from redshift and accretion disk patterns.
- Very interesting figures, Fig 1 maps different redshifted emission within in the disk to structure of emission line.
- Looks at an infinitely far outer disk radius (removing outer-outer and outer-inner paths) then at finite outer disk radius.
- Critical points dictating central regions
- Also compared different disk models: "Cunningham" model (with inter-ISCO contributions), and non-Keplerian (towards slim-disc) models, but keeping the same geometry. Overall effect of Cunningham model can be large depending on inclination, but for non-Keplerian is a stretching of the location of the critical values.
- Red-tail could overestimate very high BH spin if material is not inside the ISCO
- Changing keplarian factor by $5%$ can change line profile features, but more pronounced at blueshifted side.

Other papers:

Precession and Split of Tilted, Geometrically Thin Accretion Disk: an Analytical Study (Shen et al., 2024)
- This paper looks at cork-screw jet precessions in relation to the accretion disk.
Outgoing electromagnetic flux from rotating wormholes (Urtubey et al., 2024)
- On the predictions from Einstein's field equation
Changing Look AGN: An X-ray Look (Titarchuk et al., 2024)
- Looking at comptonization evolution of NGC 1566 X-ray sepctra

2024-11-19: Andy

Presented paper:

X-ray reverberation modelling of the continuum, optical/UV time-lags in quasars (Langis et al., 2024)
- Investigating variation that is wavelength dependent. UV/optical variations are well correlated
- Initial 191 AGN sample and using a G-band reference.
- Spread in time delay from BH mass.
- Model assumes thin disk & lamppost model with either spin 1 or spin 0.
- Skin of hot electrons compton scatter a blackbody.
- High source height for disk illumination (observation consistent?)
- Different BLR x-rays & Balmer jump at 4000 $\mathring{A}$
- Interesting $\chi^2$ values

Discussed papers:

Three similar papers on applying ray-tracing to image different types of black holes.
- Observational features of the rotating Bardeen black hole surrounded by perfect fluid dark matter (He et al., 2024)
- Shadow Images of Ghosh-Kumar Rotating Black Hole Illuminated By Spherical Light Sources and Thin Accretion Disks (Yang et al., 2024)
- Image of the Kerr–Newman Black Hole Surrounded by a Thin Accretion Disk (Guo et al., 2024)
Comparing indirect methods for black hole masses in AGN: the good, the bad, and the ugly (Gliozzi et al., 2023)
- Comparing different methods, such as the $M-\sigma_*$ relation with dynamical methods and have generated a correcting factor.
- Conducted on an 'unbiased', volume-limited and hard X-ray selected sample.

2024-11-12: No Presentation

Discussed Papers:

Effects of ultra-fast outflows on X-ray time lags in AGN (Xu et al., 2024)
- They observe 3 AGN with UFOs between $0.03-0.3$ c
- Disk fluctuations in cold (soft) and hot (hard) X-rays
- Low frequency hard-lags suppression in UFO states
- Magnetically Driven Accretion Disk Winds and Ultra-fast Outflows in PG 1211+143 (Keigo et al., 2015)
The XRISM/Resolve view of the Fe K region of Cyg X-3 (XRISM Collaboration, 2024)
- Wind-focused BH
- Orbital period ~5hrs
X-Ray View of Little Red Dots: Do They Host Supermassive Black Holes? (Ananna et al., 2024)
- Large uncertanties
- Compton thick
  - X-ray column density $n_H\gtrsim10^{25}$ $\text{cm}^{-2}$
  - JWST inconsistent with $n_H\sim10^{21}$ $\text{cm}^{-2}$
- AGN interpretation prefered in UNCOVER Spectroscopy Confirms the Surprising Ubiquity of Active Galactic Nuclei in Red Sources at z > 5 (Greene et al., 2024) but SF could fit.
- A small and vigorous black hole in the early Universe (Maiolino et al., 2024)
  - SMBH faster growth than stellar mass

Keeping up to date with papers:

Benty-fields: Uses ML to give papers heirachy
ADS emails: Sorts by key words - regular email updates

2024-11-05: Belinda

Discussed Papers:

The XRISM/Resolve view of the Fe K region of Cyg X-3 (XRISM Collaboration, 2024).
- Really nice detailed spectrum with a lot of Fe absorption and emission lines observed.
Little Red Dots: an abundant population of faint AGN at z∼5 revealed by the EIGER and FRESCO JWST surveys (Matthee, et al., 2024)
- A paper hinting towards the seeing early AGN feedback and early SMBH growth being highlt obscured.
Deep Chandra Observations of NGC 5728. III: Probing the High-Resolution X-ray Morphology and Multiphase ISM Interactions in the Circumnuclear Region (Falcao, et al., 2024)
- A paper looking at ISM interactions within a Seyfert 2 galaxy likely from X-ray binaries
Structural Decomposition of Merger-Free Galaxies Hosting Luminous AGNs (Fahey, et al., 2024)
- Investigates AGN evolution in merger-free galaxies. A weak correlations between bulge & SMBH masses, and for stellar & SMBH masses observed for disk-dominated galaxies.

Presented paper:

X-Ray View of Little Red Dots: Do They Host Supermassive Black Holes? (Ananna, et al., 2024)
- Unknown reason for JWST-observed 'little red dots', with flux either AGN dominated, young star formation dominated or both.
- Over 100 Chandra observations of lensing cluster Abell 2744 equating up to $\approx 2$ Ms or $\approx90$ Ms stacked.
- No significant detection until broad-line $H\alpha$ galaxies are stacked.
- Possibly Compton thick AGN to explain non-detections.
- Results from X-ray and NIR suggest scaling relations from virial relations may not be applicable at high redshift.
- LRDs likely either do not contain overmassive SMBHs or accrete at a low eddington rate.
Also discussed was UNCOVER Spectroscopy Confirms the Surprising Ubiquity of Active Galactic Nuclei in Red Sources at z > 5 (Greene, et al., 2024)
- Shows a absorbed component and either AGN scattering or star formation to contribute to the UV.