Journal Club

"Observational constraints on the spin/anisotropy of the CCOs of Cassiopeia A, Vela Jr. and G347.3-0.5 and a single surviving continuous gravitational wave candidate"

Anirudh Nemmani (NCAC, Warsaw)

based on https://arxiv.org/abs/2512.15672 from Ming et al. (Dec 2025).

"HALO I: Photometric continuum reverberation mapping of Fairall 9"

Amit Kumar Mandal (NCAC, Warsaw)

based on https://arxiv.org/abs/2512.13296 from Madal et al. (Dec 2025). We have initiated a dedicated photometric AGN monitoring program, Hubble Constant Constraint through AGN Light-curve Observations (HALO), at the Obserwatorium Cerro Murphy (OCM) in Chile. The primary goal of HALO is to estimate the Hubble constant by modeling AGN continuum light curves using a physically motivated framework that combines a standard accretion disk, an optional inner hot flow, lamp-post irradiation, and a radiation-pressure-regulated broad-line region (BLR). By performing simultaneous lag-spectrum and spectral energy distribution (SED) fitting, with the accretion rate and luminosity distance treated as free parameters, this approach enables an independent determination of the Hubble constant. As part of HALO, we have completed observations and lag analysis for the first target in our sample, Fairall 9. In this journal club, I will present the construction of the continuum lag-spectrum and discuss the physical origins of the observed inter-band time delays. We find that the observed lag-spectrum of Fairall 9 significantly deviates from the predictions of a standard Shakura-Sunyaev disk, primarily due to the combined effects of BLR scattering, reprocessing, and dust emission at longer wavelengths. This measured lag-spectrum will serve as a key input for the forthcoming Hubble constant estimation in the next phase of the HALO program.

"Vanishing Massive Stars? The Curious Case of M31-2014-DS1"

Abbas Askar (NCAC, Warsaw)

Based on:
- https://arxiv.org/pdf/2601.05774
- https://arxiv.org/pdf/2601.05317
- https://arxiv.org/pdf/2410.14778

"Broad Iron Line as a Relativistic Reflection from Warm Corona in AGN"

Parikshit Biswas (NCAC, Warsaw)

based on https://arxiv.org/abs/2511.03575

"PeVs from Cyg X-3"

Andrzej Zdziarski (NCAC, Warsaw)

based on https://arxiv.org/abs/2512.16638

"Is the nitrogen-rich source PN K4-47 a true planetary nebula?"

Thomas Steinmetz (NCAC, Toruń)

Based on: https://arxiv.org/abs/2602.08959v1

"Hypersoft X-ray Sources: A New Class of Luminous Cosmic Emitters"

Krystian Iłkiewicz (NCAC, Warsaw)

based on https://arxiv.org/pdf/2602.06192 from Muhibullah et al. (Feb 2026)

"JWST Confirmation of a Runaway Supermassive Black Hole via Its Supersonic Bow Shock"

Gergely Hajdu (NCAC, Warsaw)

based on https://ui.adsabs.harvard.edu/abs/2026ApJ...998L..27V/abstract from van Dokkum et al. (Feb 2026).

"Radiation GRMHD Models of Accretion onto Stellar-mass Black Holes. I. Survey of Eddington Ratios"

Krzysztof Nalewajko (NCAC, Warsaw)

based on https://ui.adsabs.harvard.edu/abs/2025ApJ...995...26Z/abstract from Zhang et al. (2025)

"Can Transformers help us perform parameter estimation of overlapping signals in gravitational wave detectors?"

Valeria Maria Dinis Carvalho (NCAC, Warsaw)

based on https://arxiv.org/pdf/2505.02773 from Papalini et al. (May 2025).

"The mass distribution in and around the Local Group"

Paulina Karczmarek (NCAC, Warsaw)

Discussion paper link: https://www.nature.com/articles/s41550-025-02770-w

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TBA (NCAC, Warsaw)

"Gravitational self-lensing of Fast Radio Bursts in neutron star magnetospheres: II. Applications to strong repeaters and the CHIME population"

Debora Lancova (NCAC, Warsaw)

Link to the discussion paper: https://arxiv.org/abs/2603.12386