Search Publications
Gaia Data Release 2. The celestial reference frame (Gaia-CRF2)
Prusti, T.; Mazeh, T.; Zucker, S. +449 more
Context. The second release of Gaia data (Gaia DR2) contains the astrometric parameters for more than half a million quasars. This set defines a kinematically non-rotating reference frame in the optical domain. A subset of these quasars have accurate VLBI positions that allow the axes of the reference frame to be aligned with the International Cel…
Solar UV and X-ray spectral diagnostics
Del Zanna, Giulio; Mason, Helen E.
X-ray and ultraviolet (UV) observations of the outer solar atmosphere have been used for many decades to measure the fundamental parameters of the solar plasma. This review focuses on the optically thin emission from the solar atmosphere, mostly found at UV and X-ray (XUV) wavelengths, and discusses some of the diagnostic methods that have been us…
Hot axions and the H0 tension
Notari, Alessio; D'Eramo, Francesco; Ferreira, Ricardo Z. +1 more
Scattering and decay processes of thermal bath particles involving heavy leptons can dump hot axions in the primordial plasma around the QCD phase transition. We compute their relic density, parameterized by an effective number ΔNeff of additional neutrinos. For couplings allowed by current bounds, production via scattering yields ΔN
Reducing the H0 and σ8 tensions with dark matter-neutrino interactions
Di Valentino, Eleonora; Bœhm, Céline; Bouchet, François R. +1 more
The introduction of dark matter-neutrino interactions modifies the cosmic microwave background (CMB) angular power spectrum at all scales, thus affecting the reconstruction of the cosmological parameters. Such interactions can lead to a slight increase of the value of H0 and a slight decrease of S8≡σ8√{Ωm
Ghostly tributaries to the Milky Way: charting the halo's stellar streams with the Gaia DR2 catalogue
Malhan, Khyati; Ibata, Rodrigo A.; Martin, Nicolas F.
We present a panoramic map of the stellar streams of the Milky Way based upon astrometric and photometric measurements from the Gaia DR2 catalogue. In this first contribution, we concentrate on the halo at heliocentric distances beyond 5{ kpc}, and at Galactic latitudes |b| > 30°, using the STREAMFINDER algorithm to detect structures along plau…
Constraints on the ejecta of the GW170817 neutron star merger from its electromagnetic emission
Gal-Yam, Avishay; Waxman, Eli; Ofek, Eran O. +1 more
We present a simple analytic model that captures the key features of the emission of radiation from material ejected by the merger of neutron stars (NSs), and construct the multiband and bolometric luminosity light curves of the transient associated with GW170817, AT 2017gfo, using all available data. The ultraviolet to infrared (IR) emission is s…
Non-gravitational acceleration in the trajectory of 1I/2017 U1 ('Oumuamua)
Chambers, Kenneth C.; Wainscoat, Richard J.; Weaver, Harold A. +14 more
'Oumuamua (1I/2017 U1) is the first known object of interstellar origin to have entered the Solar System on an unbound and hyperbolic trajectory with respect to the Sun. Various physical observations collected during its visit to the Solar System showed that it has an unusually elongated shape and a tumbling rotation state and that the physical pr…
GeV-scale thermal WIMPs: Not even slightly ruled out
Slatyer, Tracy R.; Beacom, John F.; Ng, Kenny C. Y. +1 more
Weakly interacting massive particles (WIMPs) have long reigned as one of the leading classes of dark matter candidates. The observed dark matter abundance can be naturally obtained by freezeout of weak-scale dark matter annihilations in the early Universe. This "thermal WIMP" scenario makes direct predictions for the total annihilation cross secti…
TESS Discovery of a Transiting Super-Earth in the pi Mensae System
Deming, Drake; Pál, András; Torres, Guillermo +63 more
We report the detection of a transiting planet around π Men (HD 39091), using data from the Transiting Exoplanet Survey Satellite (TESS). The solar-type host star is unusually bright (V = 5.7) and was already known to host a Jovian planet on a highly eccentric, 5.7 yr orbit. The newly discovered planet has a size of 2.04 ± 0.05 R ⊕ and …
Implications of an extended dark energy cosmology with massive neutrinos for cosmological tensions
Kamionkowski, Marc; Boddy, Kimberly K.; Poulin, Vivian +1 more
We perform a comprehensive analysis of the most common early- and late-universe solutions to the H0 , Ly -α , and S8 discrepancies. When considered on their own, massive neutrinos provide a natural solution to the S8 discrepancy at the expense of increasing the H0 tension. If all extensions are considere…