Search Publications
Magnetic field-gas density relation and observational implications revisited
Panopoulou, G. V.; Pavlidou, V.; Tassis, K. +2 more
We revisit the relation between magnetic-field strength (B) and gas density (ρ) for contracting interstellar clouds and fragments (or, cores), which is central in observationally determining the dynamical importance of magnetic fields in cloud evolution and star formation. Recently, it has been claimed that a relation B ∝ ρ2/3 is statis…
Improved limits on sterile neutrino dark matter using full-sky Fermi Gamma-ray Burst Monitor data
Ng, Kenny C. Y.; Horiuchi, Shunsaku; Gaskins, Jennifer M. +2 more
A sterile neutrino of ∼keV mass is a well-motivated dark matter candidate. Its decay generates an x-ray line that offers a unique target for x-ray telescopes. For the first time, we use the Gamma-ray Burst Monitor (GBM) onboard the Fermi Gamma-Ray Space Telescope to search for sterile neutrino decay lines; our analysis covers the energy range 10-2…
Gone without a bang: an archival HST survey for disappearing massive stars
Gilmore, Gerard; Reynolds, Thomas M.; Fraser, Morgan
It has been argued that a substantial fraction of massive stars may end their lives without an optically bright supernova (SN), but rather collapse to form a black hole. Such an event would not be detected by current SN surveys, which are focused on finding bright transients. Kochanek et al. proposed a novel survey for such events, using repeated …
Electron acceleration in the dipolarization front driven by magnetic reconnection
Wang, Shui; Huang, Can; Lu, Quanming +2 more
A large-scale two-dimensional (2-D) particle-in-cell simulation is performed in this paper to investigate electron acceleration in the dipolarization front (DF) region during magnetic reconnection. It is found that the DF is mainly driven by an ion outflow which also generates a positive potential region behind the DF. The DF propagates with an al…
On the Origin of Mid-latitude Fast Wind: Challenging the Two-state Solar Wind Paradigm
Landi, Enrico; Zurbuchen, Thomas H.; Lepri, Susan T. +2 more
The bimodal paradigm of solar wind describes a slow solar wind situated near the heliospheric current sheet while a fast wind overexpands from the poles to fill in the remainder of the heliosphere. In this paper, we challenge this paradigm and focus here on mid-latitude wind using three fast-latitude passes completed by the Ulysses spacecraft. Bas…
Mass without radiation: Heavily obscured AGNs, the X-ray background, and the black hole mass density
Marconi, A.; Gilli, R.; Comastri, A. +2 more
A recent revision of black hole scaling relations indicate that the local mass density in black holes should be five times higher than previously determined values. The local black hole mass density is connected to the mean radiative efficiency of accretion through the time integral of the Active Galactic Nuclei (AGN) volume density and a signific…
Distribution of water around the nucleus of comet 67P/Churyumov-Gerasimenko at 3.4 AU from the Sun as seen by the MIRO instrument on Rosetta
Hartogh, P.; Lellouch, E.; Crovisier, J. +13 more
The Microwave Instrument on the Rosetta Orbiter (MIRO) has been observing the coma of comet 67P/Churyumov-Gerasimenko almost continuously since June 2014 at wavelengths near 0.53 mm. We present here a map of the water column density in the inner coma (within 3 km from nucleus center) when the comet was at 3.4 AU from the Sun. Based on the analysis…
Sizes and shapes of young star cluster light profiles in M83
Larsen, S.; Bastian, N.; Gallagher, J. S. +6 more
We measure the radii and two-dimensional light profiles of a large sample of young, massive star clusters in M83 using archival HST/Wide Field Camera 3 (WFC3) imaging of seven adjacent fields. We use GALFIT to fit the two-dimensional light profiles of the clusters, from which we find effective (half-light) radii, core radii, and slopes of the powe…
How clustering dark energy affects matter perturbations
Mehrabi, A.; Basilakos, S.; Pace, F.
The rate of structure formation in the Universe is different in homogeneous and clustered dark energy models. The degree of dark energy clustering depends on the magnitude of its effective sound speed c2_eff and for c2_eff=0 dark energy clusters in a similar fashion to dark matter while for c2_eff=1 it stays (appro…
A forecasting model of the magnetosphere driven by an optimal solar wind coupling function
Tsyganenko, N. A.; Andreeva, V. A.
A new empirical magnetospheric magnetic field model is described, driven by interplanetary parameters including a coupling function by Newell et al. (2007), termed henceforth as "N index." The model uses data from Polar, Geotail, Cluster, and Time History of Events and Macroscale Interactions during Substorms satellites, obtained in 1995-2013 at d…