Search Publications
Primordial Black Holes as a Dark Matter Candidate Are Severely Constrained by the Galactic Center 511 keV γ -Ray Line
Laha, Ranjan
We derive the strongest constraint on the fraction of dark matter that can be composed of low mass primordial black holes by using the observation of the Galactic Center 511 keV γ -ray line. Primordial black holes of masses ≲1015 kg will evaporate to produce e± pairs. The positrons will lose energy in the Galactic Center, bec…
An Embedded X-Ray Source Shines through the Aspherical AT 2018cow: Revealing the Inner Workings of the Most Luminous Fast-evolving Optical Transients
Berger, E.; Hurley, K.; Götz, D. +42 more
We present the first extensive radio to γ-ray observations of a fast-rising blue optical transient, AT 2018cow, over its first ∼100 days. AT 2018cow rose over a few days to a peak luminosity L pk ∼ 4 × 1044 erg s-1, exceeding that of superluminous supernovae (SNe), before declining as L ∝ t -2. Initial s…
A Decade of Gamma-Ray Bursts Observed by Fermi-LAT: The Second GRB Catalog
Troja, E.; Caraveo, P. A.; Mirabal, N. +120 more
The Large Area Telescope (LAT) aboard the Fermi spacecraft routinely observes high-energy emission from gamma-ray bursts (GRBs). Here we present the second catalog of LAT-detected GRBs, covering the first 10 yr of operations, from 2008 to 2018 August 4. A total of 186 GRBs are found; of these, 91 show emission in the range 30-100 MeV (17 of which …
Cyclotron lines in highly magnetized neutron stars
Haberl, F.; Klochkov, D.; Santangelo, A. +10 more
Cyclotron lines, also called cyclotron resonant scattering features are spectral features, generally appearing in absorption, in the X-ray spectra of objects containing highly magnetized neutron stars, allowing the direct measurement of the magnetic field strength in these objects. Cyclotron features are thought to be due to resonant scattering of…
Clusters of Primordial Black Holes
Belotsky, Konstantin M.; Dokuchaev, Vyacheslav I.; Eroshenko, Yury N. +7 more
The Primordial Black Holes (PBHs) are a well-established probe for new physics in the very early Universe. We discuss here the possibility of PBH agglomeration into clusters that may have several prominent observable features. The clusters can form due to closed domain walls appearance in the natural and hybrid inflation models whose subsequent ev…
ALMA observations of molecular tori around massive black holes
Krips, M.; van der Werf, P.; Combes, F. +12 more
We report Atacama Large Millimeter/submillimeter Array (ALMA) observations of CO(3-2) emission in a sample of seven Seyfert/LINER galaxies at the unprecedented spatial resolution of 0.″1 = 4-8 pc. Our aim is to explore the close environment of active galactic nuclei (AGN), and the dynamical structures leading to their fueling…
Constraining Primordial Black Hole Abundance with the Galactic 511 keV Line
DeRocco, William; Graham, Peter W.
Models in which dark matter consists entirely of primordial black holes (PBHs) with masses around 1 017 g are currently unconstrained. However, if PBHs are a component of the Galactic dark matter density, they will inject a large flux of energetic particles into the Galaxy as they radiate. Positrons produced by these black holes will su…
Primordial black holes from inflation with nonminimal derivative coupling
Wu, Puxun; Yu, Hongwei; Fu, Chengjie
We propose a novel enhancement mechanism of the curvature perturbations in the nonminimal derivative coupling inflation model with a coupling parameter related to the inflaton field. By considering a special form of the coupling parameter as a function of the inflaton, a period of ultra-slow-roll inflation can be realized due to the gravitationall…
Reclassification of Cepheids in the Gaia Data Release 2. Period-luminosity and period-Wesenheit relations in the Gaia passbands
Ripepi, V.; Molinaro, R.; Eyer, L. +3 more
Context. Classical Cepheids are the most important primary indicators for the extragalactic distance scale. Establishing the precise zero points of their period-luminosity and period-Wesenheit (PL/PW) relations has profound consequences on the estimate of H0. Type II Cepheids are also important distance indicators and tracers of old ste…
A magnetar-powered X-ray transient as the aftermath of a binary neutron-star merger
Lehmer, B. D.; Bauer, F. E.; Brandt, W. N. +14 more
Mergers of neutron stars are known to be associated with short γ-ray bursts1-4. If the neutron-star equation of state is sufficiently stiff (that is, the pressure increases sharply as the density increases), at least some such mergers will leave behind a supramassive or even a stable neutron star that spins rapidly with a strong magneti…