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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.

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
2025-06-17 Isobel
2025-06-24 Last
2025-07-01 Summer
---------- ---------
2025-09-02 First

Minutes

2025-06-10: Tom

Discussed: RUBIES: A Spectroscopic Census of Little Red Dots (Hviding et al., 06-2025)

  • JWST study of sample of 80 broad-lines sources selected from a detailed study of ~1500 AGN from the RUBIES NIRCAM/NIRSPEC/PRISM survey, z>3.1. A significant number (36) have the LRD-blue+red continuum, a point source at the core and broad emission lines.
  • They find that all point sources with (spectroscopic) v-shaped continua exhibit broad Balmer lines where the data quality permits detection, suggesting these properties are directly linked.

XRISM Reveals a Remnant Torus in the Low-Luminosity AGN M81* (Miller et al., 05-2025) X-ray reflection spectroscopy with improved calculations of the emission angle (Huang et al., 06-2025)

Spins of Black Holes in X-ray Binaries and the Tension with the Gravitational Wave Measurements (Zdziarski et al., 05-2025)

Presented: The Onset of Feedback in Abell 1885: Evidence for Large-Scale Quenching Despite a Young Central AGN (White et al., 06-2025)

  • TL;DR - An interesting paper that looks at a young AGN's core and extended environment ICM to suggest a lack of synchronisation between feeding and feedback timescales and suggests instead that heating effects can 'linger' possibly with turbulent mixing.
  • Due to time constarints it will be discussed further on 2025-06-24

2025-06-03: Gloria

Discussed: NASA's President's proposed Budget Reflection Spectra of Accretion Disks Illuminated by an Off-Axis Corona (Feng et al., 06-2025)

Presented Papers:

2025-05-27: Fergus

Discusses Papers: Distinguishing the origin of eccentric black-hole mergers with gravitational-wave spin measurements (Stegmann et al., 05-2025)

  • Constraining origins of binary black holes using the spins of the eccentric sub-population with current and future GW detectors

Presented Paper: A rapid black hole spin or emission from the plunging region? (Mummery et al., 05-2025)

2025-05-20: Darius

Discussed papers: Electromagnetism as a purely geometric theory (Jussi Lindgren et al., 2025)

  • Doesn't need scalers terms, they vanish by themselves
  • Interesting interpretation of geometrical approaches to other forces beyond gravity
  • Can solve some difficult to solve eqns.
  • Direct explanation of QM waves

Possibility of Multi-Messenger Observations of Quasi-Periodic Eruptions with X-rays and Gravitational Waves (Suzuguchi et al., 05-2025)

  • Predicts only one joint X-ray and GW QPE detection during LISA's expected lifetime due to a small overlap in frequency detection.
  • Sub-mHz GW detection would enhance these detections significantly.

S241125n: Binary Black Hole Merger Produces Short GRB in AGN Disk (Zhang et al., 05-2025)

  • A binary BH merger in an AGN with merger remnants accreting at hyper-Eddington rates.
  • The observed GRB has a soft photon index is consistent with a jet inetracting with a dense AGN disk.
  • A hard X-ray afterglow indicates strong absorption

Black holes as gravitational mirrors (Santos et al., 05-2025)

  • Interesting paper for a concept of retrolensing
  • They show it is possible for photons to return to the same emission point after boomeranging around a BH
  • They suggest the possibility of looking at planets using retrolensing

Radiation and Magnetic Pressure Support in Accretion Disks around Supermassive Black Holes and The Physical Origin of the Extreme Ultraviolet to Soft X-ray Spectrum (Jiang et al., 05-2025)

Presented paper: NuSTAR Detection of an Absorption Feature in ESP 39607: Evidence for an Ultra-fast Inflow? (Peca et al., 03-2025)

  • Strong(?) evidence for real absorption feature and UF inflow
  • Confidence is >4$$\sigma$$ (individually between $$2\sigma-3\sigma$$) for absorption considering it is found in two separate observations
  • Inflow is ~$$0.125c$$ but data shows it could be either Fe-XXV or Fe-XXVI or a combination of both
  • Not in 2010 observation so supports UF-inflow assumption
  • Alternative is material launched outward without sufficient escape velocity. Or a failed-wind with a similar situation
  • Look at possible not being an ultra-fast inflow (e.g. warm-hot IGM accretion) but seem to think this is unlikely.
  • Possible outflow of $$0.75c$$ of lighter materials (e.g. Calcium) but unlikely due to lower abundance.
  • Conclude: best fit is UF-inflow.
  • In agreement with other UFI studies
  • Limitations of not having lower energies to fully test WHIM

2025-05-13: Jiachen

MeerKAT discovers a jet-driven bow shock near GRS 1915+105: How an invisible large-scale jet sculpts a microquasar's environment (Motta et al., 04-2025)

  • Deepest ever radio L-band obervations (15hrs)
  • Stellar mass BH jet energy dissipation is comparable to accretion energy through jet-ISM interactions and linked to SMBH
  • Compressed material behind bow shock observed - reminiscent with Cyg X-1
  • SF activity completely(?) unrelated. Old enough that previous jet activity could have triggered the SF.
  • Jet induced feedback not just SMBH but also their stellar mass counter parts. Lots of energy can be released back into the environment

Presented Paper(s) Quasi-periodic X-ray eruptions years after a nearby tidal disruption event (Nicholl et al., 10-2024)

2025-05-06: Arxiv

Identifying intermediate mass binary black hole mergers in AGN disks using LISA (Dutta Roy et al., 03-2025):

  • Binary with GW signature from merger
  • GW effected by star cluster & gas, almost insignificant contribution but could be detectable when imbedded in disk of significantly high density
  • Therefore they should be detectable with LISA (but needs to be relatively near by ~few Mpc)
  • Question: Do these objects exist (in the detectable universe)?
  • LISA expected to detect order of 100s on 10yr timescale, many of which will be archival.
  • Mass explained through BH mergers and and accretion within an AGN disk.

Testing X-ray Reprocessing and Mapping the Soft Excess of NGC 7469 with NICER (Partington et al., 04-2025):

  • Looking at a light curve between different wavebands for an AGN
  • Thermal re-processing model for X-ray heating disk to give UV emission seen
  • X-rays lead UV by less than a day
  • Soft excess from reflection rather than warm corona? No lag between X-ray power law and soft excess
  • Different results for long term (bins averaged over 20 days) variation compared to short term

2025-04-29: Andy

Mentioned Papers:

Discussed Papers:

Disk winds spectral energy distribution and the variability timescale of AGN (Netzer, 04-2025)

  • This paper may be of interest to some.
  • Using a recent Mrk 817 observation, a model with a radial and time-dependant mass outflow rate has been observed.
  • SED changes are more significant in X-rays than Optical.
  • Overall link between time-dependent disk wings, SED, thermal timescale and Optical-UV variability

A Sandwich Model for Changing-Look AGNs (Ma, 04-2025)

  • A multi-disk accretion disk to model CLAGNs. An optical thick disk in the centre, sandwiched between two optically thin disks.
  • The central disk can have increased velocity and thus lower accretion timescales.
  • The system (specifically thin disk) can resemble a warm corona when dominated by the magnetic pressure and produce the soft excess, and when this isn't the case, it can resemble a hot corona and show a shorter accretion timescale.

OGLE-2011-BLG-0462: An Isolated Stellar-mass Black Hole Confirmed Using New HST Astrometry and Updated Photometry (Sahu et al., 04-2025)

  • A set of observations over roghly 11 years for a microlensing event
  • A ~7 $$M_\odot$$ isolated BH ~1.5 kpc away moving at ~50 km $$\text{s}^{-1}$$ relative to background stars.
  • Possible that the velocity is due to a natal kick from its SNe

Presented Paper:

A consistent radio to sub-mm pc-scale study of the Nucleus of NGC 1068 (Mutie, 03-2025)

  • From observations over ~10 years (and much older VLA data) an SED of the central (~pc) region of NGC 1068 been found to fit a model with synchrotron, free-free, dust and coronal components.
  • The sub-mm excess suggests synchrotron emission from a compact and optically thick corona with $$R_c \approx 70 R_g$$, $$\sim 10%$$ of energy density in non-thermal electrons and $$B\approx148$$ G.
  • There is also a possible clumpy gas absorber to explain the curvy SED.

2025-04-22: Arxiv & Discussion

Jet properties of FR0 radio galaxies: need for VLBI data (Baldi et al., 01-2025)

  • Looks at FR0
  • Mildly relativistic jet bulk speed, lower compared to FRIs and FRIIs
  • Negligible relativistic beaming
  • SMBH Spin keping jets compact

Question on trapped photon orbits:

  • Geodesic photon rings - possible closed orbits do not necessarily take into affect the wave nature of photons
  • Possible expectation of processing and unstable closed orbits
  • No spin requriement to be able to generate a closed/null orbit

An interstellar mission to test astrophysical black holes (Bambi, 04-2025)

  • Possiblity of inetrstellar mission to send a probe to the nearest BH
  • Seems generally far-fetched with some back-of-the-envolope calculations but nevertheless an interesting paper on something that is not impossible.

2025-04-15: Belinda

Discussed Papers Elias Kamu et al. Lags behind X-ray explained by reverbaration

Recent view in the universe

Reviews on disk winds

Presented Paper:

ASKAP Discoveries of Giant Radio Galaxies in the Sculptor field (Koribalski, 04-2025)

  • Low resolution (~13")
  • ASKAP - Australian Square Kilometer Array Pathfinder at 700 MHz to 1.8 GHz
  • Over half have relatively young central sources
  • Once jets are off, there are a wide variety of shapes
  • Catalogue of 232 radio galaxies: 164 FRII 29 FRI
  • 15 GRGs with projected largest linear size >1 Mpc (3.8 Mpc is the biggest)
  • J0044-2317 very small Southern FRII jet lobe and a large sweeping FRI northern lobe
  • J0050-2135 diffuse emission beyond the jets with sharp bends, source located between two clusters
  • J0102-2154 Close pair at the core, northern lobes are partially covered by a foreground merging galaxies within a cluster. Possible annular shocks from ring-like Southern lobe structure.
  • J0107-2347 largest (3.79 Mpc) remained very straight, interesting background cluster
  • J0055-262 Head-tail source with jets that appear to merge
  • The slides are available here: GRG_from_ASKAP_Apr2025.pptx

2025-04-08: Gloria

Discussed Paper:

Euclid Quick Data Release (Q1). Extending the quest for little red dots to z<4 (Bisigello et al., 03-2025)

Presented Paper:

A New Hope for Obscured AGN: The PRIMA-NewAthena Alliance (Barchiesi et al., 03-2025) Slides for the presented paper are available here: Gloria_Raharimbolamena_Journal_Club_08_Apr_25.pdf

2025-04-01: Tom

Discussed Papers: Euclid Papers:

Latent Stochastic Differential Equations for Modeling Quasar Variability and Inferring Black Hole Properties (Fagin et al., 04-2024)

The very high X-ray polarisation of accreting black hole IGRJ17091-3624 in the hard state (Ewing et al., 03-2025)

Supermassive Black Holes in X-rays: From Standard Accretion to Extreme Transients (Kara & García, 03-2025)

Presented Paper:

Probing the Formation of Megaparsec-scale Giant Radio Galaxies (I): Dynamical Insights from MHD Simulations (Giri et al., 11-2024) Slides for the presentationa are available here: GRGs_simulation_paper-2.pdf

2025-03-25: Fergus

Presented Papers: Large and complex X-ray time lags from black hole accretion discs with compact inner coronae (Uttley & Malzac, 11-2024)

  • lag model that incorporates propagating fluctuations, coronal heating, and reverberation lags all in one go

2025-03-18: Darius

Discussed Papers:

The high energy Universe at ultra-high resolution: the power and promise of X-ray interferometry (Uttley et al., 06-2021)

Presented Papers:

On the Extremely X-ray Variable Active Galactic Nuclei in the XMM-LSS Field (Zhang et al., 02-2025)

2025-03-11: Jiachen

Discussed Papers:

A decade of sub-arcsecond imaging with the International LOFAR Telescope (Morabito et al., 02-2025)

  • A good paper that discusses the International LOFAR Telescope and its subarcsecond imaging

Unveiling AGN Outflows: [O iii] Outflow Detection Rates and Correlation with Low-Frequency Radio Emission (Escott et al., 12-2024)

  • Connections between LOFAR and [OIII]emissions in AGN outflows.
  • Majority of their selected AGN do not have powerful jets
  • Radio-detected AGN have higher outflow rates than the non-radio detected AGN
  • Indication of spatial relationship between outflows and radio emission.

Presented Papers:

The bulk motion of gas in the core of the Centaurus galaxy cluster (XRISM Collaboration, 02-2025) & An Hα–X-ray surface-brightness correlation for filaments in cooling-flow clusters (Olivares et al., 01-2025)

  • Two Nature papers on the Centaurus cluster and others (ft. XRISM, Chandra).

JWST Imaging of Edge-on Protoplanetary Disks. IV. Mid-infrared Dust Scattering in the HH 30 Disk (Tazaki et al., 02-2025)

  • An amazing disk, outflow, jet image of a protoplanetary disk w/ surprising similarity to BH disks, but we X-ray astronomers will never dream of (ft. JWST)

A confirmed deficit of hot and cold dust emission in the most luminous Little Red Dots (Setton et al., 03-2025)

  • rest frame IR SEDs of LRDs (trendy work with some big names on the paper)

Characterization of a Peculiar Einstein Probe Transient EP240408a: An Exotic Gamma-Ray Burst or an Abnormal Jetted Tidal Disruption Event? (O'Connor et al., 01-2025)

  • A possible new type of X-ray transient (ft. EP)

The THESEUS space mission: science goals, requirements and mission concept (Amati et al., 04-2021)

  • Which ESA mission will be there after Integral, which was shut recently (ft. THESEUS)

Overionized plasma in the supernova remnant Sagittarius A East anchored by XRISM observations (XRISM Collaboration, 12-2024)

  • Over-ionisation in a SNR near Sgr A* (ft. XRISM)

Populations of neutron star ultraluminous X-ray sources (Kovlakas et al., 01-2025)

  • Eddington luminosity w/ strong magnetic fields (ft. a lot of equations)

The Non-Uniform Expansion of the Crab Nebula (Martin et al., 02-2025)

  • I didn't know the Crab Pulsar is spinning down slower than it is supposed to be (ft. CFHT image)

2025-03-04: Andy

Discussed Paper:

The nature of an imaginary quasi-periodic oscillation in the soft-to-hard transition of MAXI J1820+070 (Bellavita et al., 02-2025)

  • Imaginary lags and QPOs?
  • Something to look into

JWST + ALMA ubiquitously discover companion systems within ≲18kpc around four z≈3.5 luminous radio-loud AGN (Wang et al., 02-2025)

  • Interesting paper looking at companion systems around AGN

Jet properties of FR0 radio galaxies: need for VLBI data (Baldi et al., 01-2025)

  • A very brief conference preceding that looks at FR0 parsec-scale jets, slower than those of FRI and FRII jets. Potential explanation from a SMBH low prograde spin or low magnetic fields limiting structure.

On the Extremely X-ray Variable Active Galactic Nuclei in the XMM-LSS Field (Zhang et al., 03-2025)

  • Looks at variable AGNs in the XMM-LSS field.
  • They have some very nice SEDs and observations from Chandra (ACIS-S), XMM (pn, M1 and M2,), eROSITA and optical/IR.
  • It looks like they only find 1 changing look and a few general variability AGNs with changing obscuration the leading contender to explain it.

Presented Paper: Temperature Profiles of Accretion Disks in Luminous Active Galactic Nuclei derived from Ultraviolet Spectroscopic Variability (Son et al., 02-2025)

  • Using optical/UV variability data to constrain accretion disk model
  • SDSS data to fit optical/UV light to accretion disk
  • In the $$\tau \propto L^a \lambda_{RF}^b$$, they find $$b$$ much lower than expected - consisten with some other studies.
  • Time lags for different wavelengths are a proxy for disk size
  • AD well fit by broken power law, variability amplitude increases with timescale and flattens above characterisitic timescale, $$\tau$$.
  • $$\tau$$ corresponds to thermal timescale.
  • SDSS- reverbaration model project. Broadline photomoetry improved with spectroscopic monitoring.
  • Compute a structure function from time lag and variability
  • In order to fit $$\tau \propto L^a \lambda_{RF}^b$$ (generated from Shakura & Sunyaev model) they assume SF follows universal function when in units of $\tau$
  • Slim disk and radially inefficient accretion flows have no significant impact
  • Balmer continuum isn't origin of colour profile
  • SF well fit but disagreement with Shakura & Sunyaev model
  • spectroscopic data more robust than just photometric data
  • Overall a bit of a mystery still.
  • Structure function model in Modelling the Multiwavelength Variability of Mrk 335 using Gaussian Processes (Griffiths et al., 07-2021) with gaussian processes.
  • time scale variability in Eleven years of monitoring the Seyfert 1 Mrk 335 with Swift: Characterizing the X-ray and UV/optical variability (Gallo et al., 05-2018)

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 $$&gt;2\mu \text{m}$$
  • 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)

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 $$\Gamma&gt;3$$ 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 $$&lt;10r_g$$. 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 $$&gt;Gyr$$
  • Binary SMBH
  • Potential causes for X-shaped emission: AGN re-orientation, overpressurised coccoon or faded starburst.

2025-01-21: Fergus

Discussed Papers:

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:

2025-01-07: Jiachen

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

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:

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

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:

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:

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:

2024-11-12: No Presentation

Discussed Papers:

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:

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.

2024-10-29: Tom

Discussed the following papers:

Also discussed was the EHT blog on the recent (independent) re-analysis of the Sgr A* EHT image from 2017 by Miyoshi, et al., 2024.

Presented:

2024-10-22: Darius

Discussed the following papers:

  • Modelling absorption and emission profiles from accretion disc winds with WINE Luminari, et al., 2024
  • Bridging Scales: Coupling the galactic nucleus to the larger cosmic environment Su, et al., 2024
  • MAXI J1820+070 with NuSTAR I. An increase in variability frequency but a stable reflection spectrum: coronal properties and implications for the inner disc in black hole binaries Buisson, et al., 2019 (Discussed from presented paper)

Presented:

  • Are the shape and flux of X-ray reflection spectra in hard state consistent with an accretion disk reaching close to the black hole? Datta et al. 2024

2024-10-25: Jiachen

Discussed the following papers:

Presented:

2024-10-08: Gloria

Discussed the following papers:

  • X-Ray Weak AGNs from Super-Eddington Accretion onto Infant Black Holes Madau & Haardt, 2024
  • The Case for Super-Eddington Accretion: Connecting Weak X-ray and UV Line Emission in JWST Broad-Line AGN During the First Gyr of Cosmic Time Lambrides, et al., 2024

Presented:

  • The size of accretion disks from self-consistent X-ray spectra + UV/optical/NIR photometry fitting: applications to ASASSN-14li and HLX-1 Guolo & Mummery, 2024.

2024-10-01: Fergus

Discussed the following papers:

  • The effects of instrumental deadtime on NICER timing products Webbe & Young, 2024
  • Self-Consistent Disk-Reflection Analysis of the Black-Hole Candidate X-ray Binary MAXI J1813-095 with NICER, Swift, Chandra, and NuSTAR Ubach et al., 2024
  • Magnetic flux inversion in a peculiar changing look AGN Scepi et al., 2020 (in reference to 1ES 1927+654)

Presented:

  • A New Broadband Spectral State in the Ultraluminous X-ray Source Holmberg IX X-1 Walton et al., 2024, compared to NGC 1313 X-1 and 1ES 1927+654

2024-09-24: Rhys

Discussed the followings papers:

  • Not-so-little Red Dots: Two Massive and Dusty Starbursts at z ∼ 5–7 Pushing the Limits of Star Formation Discovered by JWST in the COSMOS-Web Survey Gentile et al., 2024
  • Black Hole Accretion is all about Sub-Keplerian Flows Chakrabarti 2024
  • Close encounters of the primordial kind: A new observable for primordial black holes as dark matter Tung et al., 2024

Presented:

2024-09-17: Andy

Discussed the followings papers:

  • "Next Generation Accretion Disk Reflection Model: High-Density Plasma Effects" Ding et al., 2024
  • FORGE’D IN FIRE III: THE IMF IN QUASAR ACCRETION DISKS FROM STARFORGE Hopkins et al., 2024
  • Supermassive Black Holes from AU to Megaparsec YouTube
  • Mapping the circumnuclear regions of the Circinus galaxy with the Imaging X-ray Polarimetry Explorer Ursini et al., 2023

Presented:

  • "Multi-Phase Thermal Structure & The Origin of the Broad-Line Region, Torus, and Corona in Magnetically-Dominated Accretion Disks" Hopkins 2024

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