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MOCA
MOCA (Meeting OAS–CtAo) is a bi-monthly event that brings together researchers and students from the Bologna area (OAS / IRA / DIFA / CTA HQ) working in the field of very-high-energy astrophysics. Meetings are held on Wednesdays, in Room 409, on the second floor of the OAS Institute, via Gobetti 101, Area della Ricerca CNR (Bologna).
Image credits: CTA/M-A. Besel/IAC (G.P. Diaz)/ESO
21 October 2026, 11 AM
Cristina Nanci (INAF-OAS Bologna)
IGMF Constraints from CTAO Pair-Halo Simulations
The intergalactic magnetic field (IGMF) remains one of the least constrained components of the large-scale structure of the Universe. Very-high-energy gamma rays emitted by blazars interact with the extragalactic background light, initiating electromagnetic cascades whose charged particles are deflected by the IGMF. The resulting secondary gamma-ray emission is expected to produce an extended halo around the source, providing an indirect probe of the IGMF strength.
In this work, we investigate the potential of the Cherenkov Telescope Array Observatory (CTAO) to detect gamma-ray pair halos and constrain the IGMF strength through dedicated simulations. We generate cascade templates for different magnetic field strengths, adopting the extreme BL Lac object 1ES 0229+200 as a reference source. These templates are then combined with the point-like source emission and instrumental background to simulate CTAO Northern Array observations.
Our analysis follows a two-step approach. First, we investigate the detectability of extended emission by comparing point-source and point-source-plus-extended emission models. Second, we perform a likelihood-based scan over a grid of cascade templates, varying the IGMF strength and the intrinsic source spectral parameters, to assess whether the injected magnetic field can be recovered and constrained. We present the analysis framework and preliminary results.
7 October 2026, 11 AM
Gabriele Panebianco (INAF-OAS Bologna)
Intra-day variability of the gamma-ray/optical emission of 3C 454.3: the complexity beyond the long-term correlation
We investigate the gamma-ray/optical correlation and intra-day variability of blazar 3C 454.3 over more than 17 years of observations, combining AGILE and Fermi-LAT gamma-ray data with WEBT optical photometry. We focus on timescales of less than 24 hours and analyse both the long-term behaviour and 14 individual flaring epochs.
We confirm the long-term gamma-ray/optical correlation, but find a large intrinsic dispersion and a correlation slope of η ≃ 1.6–1.7, which cannot be explained by a single canonical one-zone emission scenario. On intra-day timescales, the source shows a much more diverse behaviour: individual flares can be weakly or strongly correlated, with correlation slopes ranging from η ≃ 0.4 to 2.0, orphan flares in both bands, different flare profiles, and strongly variable Compton dominance, reaching values as high as ~120. The shortest variability timescales, below about 3 hours, further indicate that compact, localized emission regions are required.
These results suggest that the long-term gamma-ray/optical correlation does not arise from a single emission regime. Instead, it emerges from the superposition of different physical states that dominate at different epochs. Intra-day, multi-epoch studies provide crucial information for disentangling the physical processes governing the emission of bright FSRQs.
6 May 2026, 11 AM
Gabriele Panebianco (INAF-OAS Bologna)
AGILE detection of transient emission from the region of the supergiant fast X-ray transient IGR J17354−3255
On April 14, 2009, the AGILE satellite detected a gamma-ray flare from an unknown transient source. Follow-up observations with Swift and INTEGRAL identified the Supergiant Fast X-ray Transient (SFXT) IGR J17354−3255 as the best candidate counterpart, based on positional coincidence and a similar temporal behaviour. SFXTs, a subclass of High Mass X-ray Binaries with OB supergiant companions that show extreme X-ray variability. To date, no SFXT has been firmly detected at high energies, and whether they can emit MeV-TeV photons in short flares (hours to days) with low duty cycles remains an open question.
In this work, we analyse archival AGILE data to search for gamma-ray flares consistent with IGR J17354−3255 and evaluate their possible physical origin. We identified a transient source, AGL J1736-3250, that emitted 19 gamma-ray flares and is positionally consistent with IGR J17354−3255. Most flares, detected on a 1 d timescale, concentrate most of their emission on 2-, 4- or 6-hour timescales, resembling those observed in the X-ray band from IGR J17354-3255. Orbital phase analysis revealed that approximately half of the gamma-ray activity occurs around the apastron passage of the compact object hosted in the binary system.
Our results support a possible physical association between IGR J17354-3255 and AGL J1736-3250, providing evidence that SFXTs may constitute a new class of Galactic high-energy transient emitters.
15 April 2026, 11 AM
Ivan Ezequiel Lopez (INAF-OAS Bologna)
Shock-driven feedback in low-luminosity AGN
Supermassive black holes spend up to 95% of their lifetimes in low-accretion states, yet the nature and cumulative impact of their feedback remain poorly constrained. Recent JWST observations of M58, a nearby low-luminosity AGN (LLAGN), reveal more than 44 molecular hydrogen emission lines excited by low-velocity, low-density shocks. The shocked warm molecular gas extends to kiloparsec scales without exhibiting strong large-scale kinematic disturbances. However, within the central ~200 pc, the gas shows enhanced turbulence consistent with low-velocity outflows. A simple expanding-bubble model indicates a strong coupling between the shock energy and the warm molecular phase. Comparable H₂ excitation signatures observed in other nearby LLAGN suggest that this subtle, yet measurable, mode of feedback may be more widespread than previously recognised.
11 March 2026, 11 AM
*exceptionally in the IRA Meeting Room (4^ floor/CNR)
Ettore Bronzini (INAF-OAS/DIFA Bologna)
Exploring TeV-Emitting Radio Galaxies with CTAO.
Insights into the Physics of Relativistic Jets
PhD defense rehearsal
4 February 2026, 11 AM
Giulia Brunelli (INAF-OAS/DIFA Bologna)
Finding new PeVatrons in the Galactic Center: the case of PWN G0.9+0.1
One of the major open questions in high-energy astrophysics is identifying the sources capable of accelerating electrons and positrons in our Galaxy above 1 PeV. These sources are commonly referred to as “PeVatrons”. The Galactic Center is a crowded region hosting many PeVatron candidates, including binaries, stellar clusters and pulsar wind nebulae. PWN G0.9+0.1, located at a small offset from SgrA*, is a young pulsar wind nebula that has been detected up to tens of TeV, which suggests its likely PeVatron nature. We conducted a broadband X-ray study on the source, including new NuSTAR observations. Using these new results, we performed a multiwavelength SED analysis with two different models, to constrain the system parameters. The results of the two models are consistent with each other and indicate that the maximum energy of the pulsar wind nebula is ~2 PeV, supporting the hypothesis that PNW G0.9+0.1 is a new PeVatron candidate in the Galactic Center region.
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