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Abstract:

We report on the detection of optical/near-infrared (O-IR) quasi-periodic oscillations (QPOs) from the black hole (BH) X-ray transient Swift J1727.8–1613. We obtained three X-ray and O-IR high-time-resolution observations of the source during its intermediate state (2023 September 9, 15, and 17) using NICER, HAWK-I@VLT, HIPERCAM@GTC, and ULTRACAM@NTT. We clearly detected a QPO in the X-ray and O-IR bands during all three epochs. The QPO evolved, drifting from 1.4 Hz in the first epoch, up to 2.2 Hz in the second, and finally reaching 4.2 Hz in the third epoch. These are among the highest O-IR QPO frequencies detected for a BH X-ray transient. During the first two epochs, the X-ray and O-IR emission are correlated, with an optical lag (compared to the X-rays) varying from +70 to 0 ms. Finally, during the third epoch, we measured, for the first time, a lag of the band with respect to the band at the QPO frequency ( +10 ms). By estimating the variable O-IR SED we find that the emission is most likely non-thermal. Current state-of-the-art models can explain some of these properties, but neither the jet nor the hot flow model can easily explain the observed evolution of the QPOs. While this allowed us to put tight constraints on these components, more frequent coverage of the state transition with fast multiwavelength observations is still needed to fully understand the evolution of the disc/jet properties in BH low-mass X-ray binaries.

Abstract:

ABSTRACT Models of sub-Chandrasekhar mass double detonations for Type Ia supernovae (SNe Ia) suggest a distinguishing property of this scenario is unburnt helium in the outer ejecta. However, modern explosion simulations suggest there may be significant variations in its mass and velocity distribution. We recently presented a NLTE (non local thermodynamic equilibrium) radiative transfer simulation for one realization of the double detonation scenario with a modest He mass (0.018 $\mathrm{M}_\odot$) present in the ejecta at relatively high velocities (${\sim }18\,000\, \mathrm{km}\, \mathrm{s}^{-1}$). That simulation predicted a He i 10 830 Å feature blueward of Mg ii 10 927 Å consistent with near-infrared observations of ‘transitional’ SNe Ia. To demonstrate the expected diversity in the helium signature, here we present a calculation for a double detonation model with a higher He mass (${\sim }$0.04 $\mathrm{M}_\odot$) ejected at lower velocities (${\sim }13\,000\, \mathrm{km}\, \mathrm{s}^{-1}$). Despite our simulation predicting no clear optical or 2 $\mu$m helium features, a strong and persistent He i 10 830 Å absorption is present. The feature appears at wavelengths consistent with the extended blue wing of the Mg ii 10 927 Å feature sometimes present in observations, suggesting this is a helium spectral signature (although for this particular model it is too strong and persistent to be consistent with normal SNe Ia). The significant differences in He i 10 830 Å predicted by the two simulations suggest helium spectral signatures likely show significant variation throughout the SNe Ia population. This motivates further work to use this observable signature to test the parameter space for double detonation models.

Abstract:

The impact of active galactic nuclei (AGNs) on the evolution of galaxies explains the steep decrease in the number density of the most massive galaxies in the Universe. However, the fuelling of the AGN and the efficiency of this feedback largely depend on their environment. We use data from the Low Frequency Array Two-metre Sky Survey Data Release 2 (DR2), the Dark Energy Spectroscopic Instrument Legacy Imaging Surveys, and the Sloan Digital Sky Survey DR12 to make the first study of the orientations of radio jets and their optical counterpart in relation to the cosmic web environment. We find that close to filaments (), galaxies tend to have their optical major axes aligned with the nearest filaments. On the other hand, radio jets, which are generally aligned perpendicularly to the optical major axis of the host galaxy, show more randomized orientations with respect to host galaxies within of filaments. These results support the scenario that massive galaxies in cosmic filaments grow by numerous mergers directed along the orientation of the filaments while experiencing chaotic accretion of gas on to the central black hole. The AGN-driven jets consequently have a strong impact preferentially along the minor axes of dark matter haloes within filaments. We discuss the implications of these results for large-scale radio jet alignments, intrinsic alignments between galaxies, and the azimuthal anisotropy of the distribution of circumgalactic medium and anisotropic quenching.

Abstract:

We present an expanded template library for the supernova identification (SNID) software, along with updated source files that make it easy to merge our templates—and other major SNID libraries—into the base code. This expansion, dubbed “Super-SNID,” increases the number of spectra for under-represented supernova classes (e.g., SNe Ia-02cx, Ibn) and adds new classes (e.g., SLSNe, TDEs, LFBOTs). Super-SNID includes 841 spectral templates for 161 objects, primarily from the Public ESO Spectroscopic Survey of Transient Objects Data Releases 1–4. The library is available on GitHub with simple installation instructions.