Search Publications
New Parallaxes of Galactic Cepheids from Spatially Scanning the Hubble Space Telescope: Implications for the Hubble Constant
Casertano, Stefano; Anderson, Jay; Filippenko, Alexei V. +8 more
We present new measurements of the parallax of seven long-period (≥10 days) Milky Way (MW) Cepheid variables (SS CMa, XY Car, VY Car, VX Per, WZ Sgr, X Pup, and S Vul) using one-dimensional astrometric measurements from spatial scanning of Wide-Field Camera 3 on the Hubble Space Telescope (HST). The observations were obtained at ∼6 month intervals…
The 105-Month Swift-BAT All-sky Hard X-Ray Survey
Cenko, S. Bradley; Schawinski, Kevin; Koss, Michael +10 more
We present a catalog of hard X-ray sources detected in the first 105 months of observations with the Burst Alert Telescope (BAT) coded-mask imager on board the Swift observatory. The 105-month Swift-BAT survey is a uniform hard X-ray all-sky survey with a sensitivity of 8.40× {10}-12 {erg} {{{s}}}-1 {cm}}-2 over 90…
A physical model of the broad-band continuum of AGN and its implications for the UV/X relation and optical variability
Done, Chris; Kubota, Aya
We develop a new spectral model for the broad-band spectral energy distribution (SED) of active galactic nuclei (AGN). This includes an outer standard disc, an inner warm Comptonizing region to produce the soft X-ray excess and a hot corona. We tie these together energetically by assuming Novikov-Thorne emissivity, and use this to define a size sc…
A peculiar low-luminosity short gamma-ray burst from a double neutron star merger progenitor
Li, Y.; Shao, L.; Zhang, S. +15 more
Double neutron star (DNS) merger events are promising candidates of short gamma-ray burst (sGRB) progenitors as well as high-frequency gravitational wave (GW) emitters. On August 17, 2017, such a coinciding event was detected by both the LIGO-Virgo gravitational wave detector network as GW170817 and Gamma-Ray Monitor on board NASA's Fermi Space Te…
GRB 170817A Associated with GW170817: Multi-frequency Observations and Modeling of Prompt Gamma-Ray Emission
Lyutikov, M.; Minaev, P. Yu.; Pozanenko, A. S. +7 more
We present our observations of electromagnetic transients associated with GW170817/GRB 170817A using optical telescopes of Chilescope observatory and Big Scanning Antenna (BSA) of Pushchino Radio Astronomy Observatory at 110 MHz. The Chilescope observatory detected an optical transient of ∼19m on the third day in the outskirts of the ga…
Gamma-Ray Burst Jet Breaks Revisited
Zhang, Bing; Lin, Da-Bin; Li, Jing +4 more
Gamma-ray Burst (GRB) collimation has been inferred with the observations of achromatic steepening in GRB light curves, known as jet breaks. Identifying a jet break from a GRB afterglow light curve allows a measurement of the jet opening angle and true energetics of GRBs. In this paper, we re-investigate this problem using a large sample of GRBs t…
Imprints of cosmic rays in multifrequency observations of the interstellar emission
Orlando, E.
Ever since the discovery of cosmic rays (CRs), significant advancements have been made in modelling their propagation in the Galaxy and in the Heliosphere. However, propagation models suffer from degeneracy of many parameters. To complicate the picture, the precision of recent data have started challenging existing models. To tackle these issues, …
Accretion Disks and Coronae in the X-Ray Flashlight
Maccarone, Thomas J.; Li, Jian; Kretschmar, Peter +10 more
Plasma accreted onto the surface of a neutron star can ignite due to unstable thermonuclear burning and produce a bright flash of X-ray emission called a Type-I X-ray burst. Such events are very common; thousands have been observed to date from over a hundred accreting neutron stars. The intense, often Eddington-limited, radiation generated in the…
Luminosities and mass-loss rates of Local Group AGB stars and red supergiants
Groenewegen, M. A. T.; Sloan, G. C.
Context. Mass loss is one of the fundamental properties of asymptotic giant branch (AGB) stars, and through the enrichment of the interstellar medium, AGB stars are key players in the life cycle of dust and gas in the universe. However, a quantitative understanding of the mass-loss process is still largely lacking.
Aims: We aim to investigate…
Characteristics of Late-phase >100 MeV Gamma-Ray Emission in Solar Eruptive Events
White, S. M.; Dennis, B. R.; Murphy, R. J. +5 more
We characterize and catalog 30 solar eruptive events observed by the Fermi Large Area Telescope (LAT) having late-phase >100 MeV γ-ray emission (LPGRE), identified 30 yr ago in what were called long-duration gamma-ray flares. We show that LPGRE is temporally and spectrally distinct from impulsive phase emission in these events. The spectra are …