Search Publications
A catalogue of unusually long thermonuclear bursts on neutron stars
Degenaar, N.; in't Zand, J. J. M.; Kuulkers, E. +10 more
Rare, energetic (long) thermonuclear (Type I) X-ray bursts are classified either as intermediate-duration or 'supern' bursts, based on their duration. Intermediate-duration bursts lasting a few to tens of minutes are thought to arise from the thermonuclear runaway of a relatively thick (≈1010 g cm-2) helium layer, while super…
The false widow link between neutron star X-ray binaries and spider pulsars
Ingram, Adam; Middleton, Matthew; Rhodes, Lauren +3 more
The discovery of transitional millisecond pulsars (tMSPs) provided conclusive proof that neutron star (NS) low-mass X-ray binaries (LMXBs) comprise part of the evolutionary pathway towards binary millisecond pulsars (MSPs). Redback and black widow 'spider' pulsars are a subcategory of binary MSPs that 'devour' their companions through ablation - t…
The spectra of IceCube Neutrino (SIN) candidate sources - IV. Spectral energy distributions and multiwavelength variability
Giommi, Paolo; Padovani, Paolo; Karl, Martina
We present hybrid spectral energy distributions, combining photon, and neutrino fluxes, for a sample of blazars, which are candidate IceCube neutrino sources. We furthermore check for differences in our sources' variability in the near-infrared, optical, X-ray, and γ-ray bands compared to a sample of non-neutrino source candidate blazars, and inve…
A helium nova in the Large Magellanic Cloud - the faint supersoft X-ray source [HP99]159
Kato, Mariko; Hachisu, Izumi; Saio, Hideyuki
We propose a helium nova model for the Large Magellanic Cloud (LMC) supersoft X-ray source (SSS) [HP99]159. This object has long been detected as a faint and persistent SSS for about 30 yr, and recently been interpreted to be a source of steady helium-shell burning, because no hydrogen lines are observed. We find that the object can also be interp…
The 2021 outburst of the recurrent nova RS Ophiuchi observed in X-rays by the Neil Gehrels Swift Observatory: a comparative study
Ness, J. -U.; Munari, U.; Orio, M. +12 more
On 2021 August 8, the recurrent nova RS Ophiuchi (RS Oph) erupted again, after an interval of 15.5 yr. Regular monitoring by the Neil Gehrels Swift Observatory began promptly, on August 9.9 (0.37 d after the optical peak), and continued until the source passed behind the Sun at the start of November, 86 d later. Observations then restarted on day …
Model-independent redshift estimation of BL Lac objects through very-high-energy observations
Bhatt, Nilay; Malik, Zahoor; Sahayanathan, Sunder +3 more
The very-high-energy (VHE) gamma-ray spectral indices of blazars show a strong correlation with the source redshift. The absence of any such correlation in low-energy gamma-rays and X-rays indicates the presence of extragalactic background light (EBL)-induced absorption of VHE gamma-rays. By employing a linear regression analysis, this observation…
Detection of nearly periodic spin period reversals in Vela X-1 on long time-scales: inkling of solar-like cycle in the donor star?
Roy, Jayashree; Agrawal, P. C.; Choudhury, Manojendu +1 more
We explore the long-term evolution of the spin period of the high-mass X-ray binary pulsar Vela X-1 over a period of 46 yr. Our analysis indicates nearly periodic variations in the spin period of the pulsar on time-scales of about 5.9 yr. There is suggestion of an overall spin-down behaviour of the pulsar though it is noticed that the source appea…
Three discoveries of γ Cas analogues from dedicated XMM-Newton observations of Be stars
Smith, Myron A.; Nazé, Yaël; Torrejón, José M. +5 more
In the last years, a peculiarity of some Be stars - their association with unusually hard and intense X-ray emission - was shown to extend beyond a mere few cases. In this paper, we continue our search for new cases by performing a limited survey of 18 Be stars using XMM-Newton. The targets were selected either on the basis of a previous X-ray det…
Evidence for a TDE origin of the radio transient Cygnus A-2
Reynolds, C. S.; Rowlinson, A.; Siemiginowska, A. +3 more
In 2015, a radio transient named Cygnus A-2 was discovered in Cygnus A with the Very Large Array. Because of its radio brightness (νFν ≈ 6 × 1039 erg s-1), this transient likely represents a secondary black hole in orbit around the active galactic nucleus. Using Chandra ACIS observations from 2015 to 2017, we have …
Spectral energy distribution variations of nearby Seyfert galaxies during AGN watch monitoring programs
Vestergaard, M.; Kilerci Eser, Ece
We present and analyse quasi-simultaneous multi-epoch spectral energy distributions (SEDs) of seven reverberation-mapped active galactic nuclei (AGNs) for which accurate black hole mass measurements and suitable archival data are available from the `AGN Watch' monitoring programs. We explore the potential of optical-UV and X-ray data, obtained wit…