Pulsars, transients and relativistic astrophysics

Abstract:

Context. Composite galaxies that contain both Seyfert and starburst components may produce very high-energy (VHE; > 100 GeV) γ -ray emission at a wide range of spatial scales, from a few Schwarzschild radii of a supermassive black hole (SMBH; R S = 10 −6 pc for M SMBH = 10 7 M ⊙ ) to dimensions of kiloparsec-size jet-driven outflows. In addition to supernova remnants, various sources have been suggested to explain data collected on composite galaxies, including multi-messenger neutrino and ultra-high-energy cosmic-ray data. Aims. The closest composite Seyfert–starburst galaxies (NGC 1068, the Circinus galaxy, and NGC 4945) are observed with the High Energy Stereoscopic System (H.E.S.S.) to provide constraints on cosmic-ray populations in these systems. Methods. Data obtained in H.E.S.S. observations have been analyzed to search for VHE γ -ray counterparts to the GeV γ -ray signals detected with Fermi -LAT and for potential spectral components in the VHE range. Results. No significant signals have been found in these H.E.S.S. data. Upper limits on the VHE γ -ray fluxes were applied to constrain theoretical models involving different spectral components.

Abstract:

Relativistic jets from supermassive black holes in active galactic nuclei are amongst the most powerful phenomena in the universe. Similar jets from stellar-mass black holes offer a chance to study the phenomena on accessible observation time scales. However, such comparative studies across black hole masses and time scales remain hampered by the long-standing perception that stellar-mass black hole jets are in a less relativistic regime. Here, we show the detection of two distinct, relativistic jet ejections from the Galactic black hole X-ray binary 4U 1543-47 during a single outburst, with radio interferometry monitoring observations. Our measurements reveal a likely Lorentz factor of approximately 8 and a minimum of 4.6 at launch with 95% confidence, demonstrating that stellar-mass black holes in X-ray binaries can launch jets as relativistic as those seen in active galactic nuclei.

Abstract:

Abstract Disc winds from active galactic nuclei (AGN) can be launched by radiation pressure acting on spectral lines. However, launching a line-driven wind in the X-ray rich environment of AGN is challenging, as the wind easily gets over-ionized. Previous simulations suggested that X-ray self-shielding could enable line driving, though it remained unclear whether this relied on simplified treatments of radiation and ionization. Here, we revisit the X-ray shielding scenario using the first multi-frequency, multi-directional Monte-Carlo radiative photo-ionization hydrodynamical simulations of AGN line-driven winds. We find that sustaining a steady wind with mass-loss rates of ≈20% of the accretion rate requires an unrealistically weak X-ray flux (αOX < −3). For stronger X-ray emission (−3 < αOX < −1), self-shielding is only transient, leading to episodic ejections with mass-loss rates approaching the accretion rate. Our steady winds naturally produce FeLoBAL, HiBAL, and broad emission line signatures, depending on the disc spectral energy distribution and the observer’s inclination. At moderate X-ray luminosities (αOX ∼ −3), transient winds can generate short-lived BAL and ultra-fast outflow (UFO) features. At the highest X-ray luminosities (αOX ∼ −1), the winds are too ionized to form BALs, but still produce UFOs. These results imply that additional physics is required to explain BAL outflows at realistic X-ray levels and to drive winds strong enough for AGN feedback. Nonetheless, our simulations provide a new framework for interpreting the observed diversity of AGN outflow signatures with fully coupled radiation and dynamics.

Abstract:

Abstract A central question regarding neutron star mergers is whether they are able to produce all the r-process elements, from first to third peak. We here study theoretical infrared signatures of first-peak elements with spectral synthesis modelling. By combining state-of-the-art NLTE physics with new radiative and collisional data for these elements, we identify several promising diagnostic lines from Ge, As, Se, Br, Kr and Zr. The models give self-consistent line luminosities and indicate specific features that probe emission volumes at early phases (∼10d), the product of ion mass and electron density in late phases (≳75d), and in some cases direct ionic masses at intermediate phases. Emission by [Se I] 5.03 μm + [Se III] 4.55 μm is the only one from the first r-process peak that could explain the Spitzer photometry of AT2017gfo. However, the models show consistently that with a Kr/Te and Se/Te ratio following the solar r-process pattern, Kr + Se emission is dominant over Te for the blend at 2.1 μm observed in both AT2017gfo and AT2023vfi. The somewhat better line profile fit with [Te III] may suggest that both AT2017gfo and AT2023vfi had a strongly sub-solar production of the light r-process elements. An alternative scenario could be that Kr + Se in an asymmetric morphological distribution generates the feature. Further JWST spectral observations holds promise to determine the light r-process production of kilonovae, and in particular whether the light elements are made in a slow disk wind or in a fast proto-NS wind. We identify specific needs for further atomic data for Z = 31 − 40 elements.

Abstract:

We present improved cosmological constraints from a re-analysis of the Dark Energy Survey (DES) 5-year sample of Type Ia supernovae (DES-SN5YR). This re-analysis includes an improved photometric cross-calibration, recent white dwarf observations to cross-calibrate between DES and low-redshift surveys, retraining the salt3 light-curve model and fixing a numerical approximation in the host-galaxy colour law. Our fully recalibrated sample, which we call DES-Dovekie, comprises 1600 likely Type Ia SNe from DES and 200 low-redshift SNe from other surveys. With DES-Dovekie, we obtain in flat Lambda-cold dark matter (CDM) which changes by compared to DES-SN5YR. Combining DES-Dovekie with cosmic microwave background data from Planck, Atacama Cosmology Telescope, and South Pole Telescope and the DESI DR2 measurements in a flat CDM cosmology, we find and . Our results hold a significance of , reduced from for DES-SN5YR, to reject the null hypothesis that the data are compatible with the cosmological constant. This significance is equivalent to a Bayesian model preference odds of approximately 5:1 in favour of the flat CDM model. Using generally accepted thresholds for model preference, our updated data exhibits only a weak preference for evolving dark energy.