Search Publications
Repeating behaviour of FRB 121102: periodicity, waiting times, and energy distribution
Kramer, M.; Seymour, A.; Scholz, P. +7 more
Detections from the repeating fast radio burst FRB 121102 are clustered in time, noticeable even in the earliest repeat bursts. Recently, it was argued that the source activity is periodic, suggesting that the clustering reflected a not-yet-identified periodicity. We performed an extensive multiwavelength campaign with the Effelsberg telescope, th…
A constraint on light primordial black holes from the interstellar medium temperature
Kim, Hyungjin
Primordial black holes are a viable dark matter candidate. They decay via Hawking evaporation. Energetic particles from the Hawking radiation interact with interstellar gas, depositing their energy as heat and ionization. For a sufficiently high Hawking temperature, fast electrons produced by black holes deposit a substantial fraction of energy as…
A new radio census of neutron star X-ray binaries
Maccarone, T. J.; Degenaar, N.; Wijnands, R. +16 more
We report new radio observations of a sample of 36 neutron star (NS) X-ray binaries, more than doubling the sample in the literature observed at current-day sensitivities. These sources include 13 weakly magnetized (B < 1010 G) and 23 strongly magnetized (B ≥ 1010 G) NSs. 16 of the latter category reside in high-mass X-ray…
A new lepto-hadronic model applied to the first simultaneous multiwavelength data set for Cygnus X-1
Bremer, M.; Wilms, J.; Uttley, P. +10 more
Cygnus X-1 is the first Galactic source confirmed to host an accreting black hole. It has been detected across the entire electromagnetic spectrum from radio to GeV gamma-rays. The source's radio through mid-infrared radiation is thought to originate from the relativistic jets. The observed high degree of linear polarization in the MeV X-rays sugg…
The Swift bulge survey: motivation, strategy, and first X-ray results
Maccarone, T. J.; Degenaar, N.; Wijnands, R. +12 more
Very faint X-ray transients (VFXTs) are X-ray transients with peak X-ray luminosities (LX) of L$_X \lesssim 10^{36}$ erg s-1, which are not well understood. We carried out a survey of 16 deg2 of the Galactic Bulge with the Swift Observatory, using short (60 s) exposures, and returning every 2 weeks for 19 epochs in…
NuSTAR measurement of the cosmic X-ray background in the 3-20 keV energy band
Krivonos, Roman; Sazonov, Sergey; Zoglauer, Andreas +5 more
We present measurements of the intensity of the cosmic X-ray background (CXB) with the Nuclear Spectroscopic Telescope Array (NuSTAR) telescope in the 3-20 keV energy range. Our method uses spatial modulation of the CXB signal on the NuSTAR detectors through the telescope's side aperture. Based on the NuSTAR observations of selected extragalactic …
Press-Schechter primordial black hole mass functions and their observational constraints
Padilla, Nelson D.; Magaña, Juan; Sureda, Joaquín +1 more
We present a modification of the Press-Schechter (PS) formalism to derive general mass functions for primordial black holes (PBHs), considering their formation as being associated with the amplitude of linear energy density fluctuations. To accommodate a wide range of physical relations between the linear and non-linear conditions for collapse, we…
The chemical composition of the accretion disc and donor star in ultra-compact X-ray binaries: A comprehensive X-ray analysis
Vasilopoulos, Georgios; Webb, Natalie; Koliopanos, Filippos +1 more
We have analysed the X-ray spectra of all known Ultra-Compact X-ray Binaries (UCXBs), with the purpose of constraining the chemical composition of their accretion disc and donor star. Our investigation was focused on the presence (or absence) of the Fe Kα emission line, which was used as the probe of chemical composition of the disc, based on prev…
Hard X-ray selected giant radio galaxies - III. The LOFAR view
Venturi, T.; Dallacasa, D.; Ubertini, P. +12 more
Giant radio galaxies (GRGs), with extended structures reaching hundreds of kpc, are among the most spectacular examples of ejection of relativistic plasma from supermassive black holes. In this work, third of a series, we present Low-Frequency Array (LOFAR) images at 144 MHz, collected in the framework of the LOFAR Two-metre Sky Survey Data Releas…
The Galactic neutron star population - I. An extragalactic view of the Milky Way and the implications for fast radio bursts
Lyman, J. D.; Groot, P. J.; Nelemans, G. +2 more
A key tool astronomers have to investigate the nature of extragalactic transients is their position on their host galaxies. Galactocentric offsets, enclosed fluxes, and the fraction of light statistic are widely used at different wavelengths to help infer the nature of transient progenitors. Motivated by the proposed link between magnetars and fas…