Hintze Centre for Astrophysical Surveys

Abstract:

Cir X-1 is a neutron star X-ray binary characterized by strong variations in flux during its eccentric ∼16.6 day orbit. There are also strong variations in the spectral state, and it has historically shown both atoll and Z state properties. We observed the source with the Imaging X-ray Polarimetry Explorer during two orbital segments, 6 days apart, for a total of 263 ks. We find an X-ray polarization degree in these segments of 1.6% ± 0.3% and 1.4% ± 0.3% at polarization angles of 37° ± 5° and −12° ± 7°, respectively. Thus, we observed a rotation of the polarization angle by 49° ± 8° along the orbit. Because variations of accretion flow, and then of the hardness ratio, are expected during the orbit, we also studied the polarization binned in hardness ratio and found the polarization angle differing by 67° ± 11° between the lowest and highest values of the hardness ratio. We discuss possible interpretations of this result that could indicate a possible misalignment between the symmetry axes of the accretion disk and the Comptonizing region caused by the misalignment of the neutron star’s angular momentum with respect to the orbital one

Abstract:

This data set contains the two JWST NIRSpec spectra presented by Gillanders & Smartt (2025).

These spectra have been carefully extracted and flux-calibrated to contemporaneous photometry. For full details of the reduction, see Gillanders & Smartt (2025) (linked below).

If you utilise these spectra, you must cite Levan et al. (2024) in addition to Gillanders & Smartt (2025).

Link to articles:

Gillanders & Smartt (2025): https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/staf287/8019796

Levan et al., (2024): https://www.nature.com/articles/s41586-023-06759-1

Abstract:

<jats:title>ABSTRACT</jats:title> <jats:p>We use high-resolution data from the millimetre-Wave Interferometric Survey of Dark Object Masses (WISDOM) project to investigate the connection between circumnuclear gas reservoirs and nuclear activity in a sample of nearby galaxies. Our sample spans a wide range of nuclear activity types including radio galaxies, Seyfert galaxies, low-luminosity active galactic nuclei (AGN) and inactive galaxies. We use measurements of nuclear millimetre continuum emission along with other archival tracers of AGN accretion/activity to investigate previous claims that at, circumnuclear scales (&amp;lt;100 pc), these should correlate with the mass of the cold molecular gas. We find that the molecular gas mass does not correlate with any tracer of nuclear activity. This suggests the level of nuclear activity cannot solely be regulated by the amount of cold gas around the supermassive black hole (SMBH). This indicates that AGN fuelling, that drives gas from the large-scale galaxy to the nuclear regions, is not a ubiquitous process and may vary between AGN type, with time-scale variations likely to be very important. By studying the structure of the central molecular gas reservoirs, we find our galaxies have a range of nuclear molecular gas concentrations. This could indicate that some of our galaxies may have had their circumnuclear regions impacted by AGN feedback, even though they currently have low nuclear activity. Alternatively, the nuclear molecular gas concentrations in our galaxies could instead be set by secular processes.</jats:p>

Abstract:

ABSTRACT We present observational evidence of late-time interaction between the ejecta of the hydrogen-poor Type Ib supernova (SN) 2019yvr and hydrogen-rich circumstellar material (CSM), similar to the Type Ib SN 2014C. A narrow H α emission line appears simultaneously with a break in the light-curve decline rate at around 80–100 d after explosion. From the interaction delay and the ejecta velocity, under the assumption that the CSM is detached from the progenitor, we estimate the CSM inner radius to be located at ∼6.5–9.1 × 1015 cm. The H α emission line persists throughout the nebular phase at least up to +420 d post-explosion, with a full width at half maximum of ∼2000 km s−1. Assuming a steady mass-loss, the estimated mass-loss rate from the luminosity of the H α line is ∼3–7 × 10−5 M⊙ yr−1. From hydrodynamical modelling and analysis of the nebular spectra, we find a progenitor He-core mass of 3–4 M⊙, which would imply an initial mass of 13–15 M⊙. Our result supports the case of a relatively low-mass progenitor possibly in a binary system as opposed to a higher mass single star undergoing a luminous blue variable phase.