Weekly issue

Week 7, 2025

Feb 10–16, 2025

Week 7, 2025 includes 3 curated papers, centered on spectroscopy, obscured AGN, LRD.

2502.07875v1

Investigating photometric and spectroscopic variability in the multiply-imaged Little Red Dot A2744-QSO1

Lukas J. Furtak, Amy R. Secunda, Jenny E. Greene, Adi Zitrin, Ivo Labbé, Miriam Golubchik, Rachel Bezanson, Vasily Kokorev, Hakim Atek, Gabriel B. Brammer, Iryna Chemerynska, Sam E. Cutler, Pratika Dayal, Robert Feldmann, Seiji Fujimoto, Joel Leja, Yilun Ma, Jorryt Matthee, Rohan P. Naidu, Erica J. Nelson, Richard Pan, Sedona H. Price, Katherine A. Suess, Bingjie Wang, John R. Weaver, Katherine E. Whitaker

Theme match 4/5

Digest

Exploiting the three lensed images of the z=7.045 LRD A2744-QSO1 with 22 yr (observer; 2.7 yr rest) delays, the authors test variability using two NIRSpec epochs and multi-epoch NIRCam. Magnification-insensitive EWs of broad Hα and Hβ vary by up to 18±3% and 22±8%, respectively, over 875 d (2.4 yr) in the rest frame, coherently across images. No significant broadband photometric variability is detected beyond ≈0.3 mag systematics, so the EW changes cannot yet be tied to line- versus continuum-driven variability. A DRW model for MBH≈4×10^7 M⊙ matches the sparse sampling, bolstering the AGN interpretation and motivating continued monitoring.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1: Compare the prism spectra of images A/B/C across the two NIRSpec epochs; note that the improved reductions now capture the full broad Hα profile, and the continuum-scaled zooms let you judge EW changes independent of magnification.
Figure 2: Track the rest-frame EW evolution of Hα and Hβ between images (especially C→A), quantifying the ≈18% (Hα) and ≈22% (Hβ) drops over the 875 d rest-frame interval and the consistency between the two Balmer lines.
Figure 3: Inspect the de-magnified, time-delay–corrected NIRCam light curves (with synthetic NIRSpec photometry) to see that scatter stays within ≈0.3 mag including systematics; also check the flagged lensing/contamination systematics, particularly for image B near a cluster galaxy.
Figure 4: Examine DRW simulations for MBH≈4×10^7 M⊙ sampled at the actual cadence; the histograms show low probability of >0.3 mag events in F115W/F356W, explaining the nondetection of significant photometric variability.

An X-ray view of the Cataclysmic Variable V902 Mon: Discovery of an X-ray eclipse

Nazma Islam, Koji Mukai

Theme match 2/5

Digest

NuSTAR timing of the eclipsing IP V902 Mon reveals a clear X‑ray eclipse in energy‑resolved lightcurves, phase‑coincident with AAVSO/CV optical minima. Joint NuSTAR+XMM‑Newton spectroscopy requires heavy local absorption (N_H ~1e23 cm^-2) and a strong 6.4 keV Fe Kα line with EW ≈0.7 keV. The authors favor an accretion‑disk‑corona–like, very high‑inclination geometry in which the direct accretion‑column emission is blocked at all phases and we see only scattered/reprocessed X‑rays. This positions V902 Mon as a reflection‑dominated IP where eclipse timing can localize the extended pre‑shock region a few WD radii above the plane.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1: Inspect the NuSTAR 3–25, 3–10, and 10–25 keV lightcurves (binned at the 2208 s spin period) to see repeated eclipses aligned with the predicted ephemeris and to gauge any energy dependence of eclipse depth and the absence/presence of coherent spin pulses.
Figure 2: Compare phase‑folded AAVSO/CV, NuSTAR (3–10, 10–25 keV), and XMM/PN (0.3–10 keV) profiles to confirm co‑phasing of the X‑ray and optical minima, measure the eclipse width/asymmetry, and test whether harder photons are less deeply eclipsed (scattering vs absorption).
Figure 3: From the joint spectral fit, read off the required local N_H ~1e23 cm^-2 and the Fe Kα EW ≈0.7 keV; check residuals around 6–7 keV and the overall faint, reflection/scattering‑dominated continuum compared to typical IPs.
Figure 4: Use the schematic to internalize the ADC‑like geometry—WD and primary column hidden by the thick disk at all phases, with scattered/reprocessed emission from a pre‑shock region a few WD radii above the orbital plane being eclipsed by the secondary.

The Rich JWST Spectrum of the Western Nucleus of Arp 220: Shocked Hot Core Chemistry Dominates the Inner Disk

Victorine Buiten, Paul van der Werf, Serena Viti, Daniel Dicken, Almudena Alonso Herrero, Gillian Wright, Torsten Böker, Bernhard Brandl, Luis Colina, Macarena García Maríin, Thomas Greve, Pierre Guillard, Olivia Jones, Laura Hermosa Muñoz, Álvaro Labiano, Göran Östlin, Lara Pantoni, Martin Ward, Michele Perna, Ewine van Dishoeck, Thomas Henning, Manuel Güdel, Thomas Ray

Theme match 2/5

Digest

JWST MIRI/MRS and NIRSpec/IFU 3–28 μm spectroscopy isolates the western nucleus of Arp 220 and reveals a forest of rovibrational absorptions, enabling column densities and rotational temperatures for 10 species, with optically thick C2H2, HCN, and HNC and columns ≈10× higher than Spitzer. A warm HCN component with Trot ≈ 330 K points to radiative excitation by a hot, ~20 pc inner core veiled by cooler dust. The chemistry resembles hot cores with added shocks, placing the absorbing gas in the inner starburst disk directly encasing the core. No X-ray–driven chemistry or extreme excitation is found, arguing against an energetically dominant buried AGN in this band.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1: Use the MIRI false-colour map and 0.435″ apertures to verify clean separation of the western vs. eastern nucleus and how the MRS channel fields cover the WN region used for spectral extraction.
Figure 2: Scan the combined 3–28 μm spectrum to see the breadth and depth of the molecular bands; note the saturated C2H2/HCN/HNC absorption and where the strongest rovibrational branches fall across the IFU coverage.
Figure 3: Inspect the C2H2+HCN modeling with two HCN components (plus N2H+ and CO2) to understand why a warm HCN component is required—watch the asymmetric HCN Q-branch fit and the optically thick regime implied by the residuals.
Figure 4: Examine the H2O band fit and line identifications to gauge the water excitation and column, and check the residuals/fit window to assess robustness and possible contamination by nearby C2H features.

Week 7, 2025

Investigating photometric and spectroscopic variability in the multiply-imaged Little Red Dot A2744-QSO1

Digest

Key figures to inspect

Tags

An X-ray view of the Cataclysmic Variable V902 Mon: Discovery of an X-ray eclipse

Digest

Key figures to inspect

Tags

The Rich JWST Spectrum of the Western Nucleus of Arp 220: Shocked Hot Core Chemistry Dominates the Inner Disk

Digest

Key figures to inspect

Tags