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Breaking Be: a sterile neutrino solution to the cosmological lithium problem
Lattanzi, M.; Melchiorri, A.; Pagano, L. +2 more
The possibility that the so-called ``lithium problem'', i.e., the disagreement between the theoretical abundance predicted for primordial 7Li assuming standard nucleosynthesis and the value inferred from astrophysical measurements, can be solved through a non-thermal Big Bang Nucleosynthesis (BBN) mechanism has been investigated by seve…
The Extreme Ultraviolet Variability of Quasars
O'Dea, Christopher P.; Zhang, Shaohua; Muzahid, Sowgat +2 more
We study the extreme ultraviolet (EUV) variability (rest frame wavelengths 500-920 Å) of high-luminosity quasars using Hubble Space Telescope (HST) (low to intermediate redshift sample) and Sloan Digital sky Survey (SDSS) (high redshift sample) archives. The combined HST and SDSS data indicates a much more pronounced variability when the sampling …
The apparent synchronization of V1500 Cygni
Harrison, Thomas E.; Campbell, Ryan K.
We have used XMM-Newton and ground-based optical/near-infrared photometry to explore the old classical nova, and asynchronous polar V1500 Cyg. The X-ray light curve shows a single bright phase once per orbit, associated with the main accretion region. Analysis of the X-ray light curve indicates that the white dwarf spin period is now similar to th…
Variation of Jupiter's aurora observed by Hisaki/EXCEED: 1. Observed characteristics of the auroral electron energies compared with observations performed using HST/STIS
Tsuchiya, Fuminori; André, Nicolas; Fujimoto, Masaki +9 more
Temporal variation of Jupiter's northern aurora is detected using the Extreme Ultraviolet Spectroscope for Exospheric Dynamics (EXCEED) on board JAXA's Earth-orbiting planetary space telescope Hisaki. The wavelength coverage of EXCEED includes the H2 Lyman and Werner bands at 80-148 nm from the entire northern polar region. The prominen…
Detailed study of the microwave emission of the supernova remnant 3C 396
de Bernardis, P.; Masi, S.; Piacentini, F. +8 more
We have observed the supernova remnant 3C 396 in the microwave region using the Parkes 64-m telescope. Observations have been made at 8.4, 13.5, and 18.6 GHz and in polarization at 21.5 GHz. We have used data from several other observatories, including previously unpublished observations performed by the Green Bank Telescope at 31.2 GHz, to invest…
First Observational Signature of Rotational Deceleration in a Massive, Intermediate-age Star Cluster in the Magellanic Clouds
Deng, Licai; de Grijs, Richard; Li, Chengyuan +1 more
While the extended main-sequence turnoffs (eMSTOs) found in almost all 1-2 Gyr old star clusters in the Magellanic Clouds are often explained by postulating extended star formation histories (SFHs), the tight subgiant branches (SGBs) seen in some clusters challenge this popular scenario. Puzzlingly, the SGB of the eMSTO cluster NGC 419 is signific…
The X-Ray Luminosity Function of M37 and the Evolution of Coronal Activity in Low-mass Stars
Agüeros, Marcel A.; Núñez, Alejandro
We use a 440.5 ks Chandra observation of the ≈500 Myr old open cluster M37 to derive the X-ray luminosity functions of its ≤1.2 {M}⊙ stars. Combining detections of 162 M37 members with upper limits for 160 non-detections, we find that its G, K, and M stars have a similar median (0.5-7 keV) X-ray luminosity {L}{{X}}={10}…
Validation of the Coronal Thick Target Source Model
Xu, Yan; Fleishman, Gregory D.; Gary, Dale E. +1 more
We present detailed 3D modeling of a dense, coronal thick-target X-ray flare using the GX Simulator tool, photospheric magnetic measurements, and microwave imaging and spectroscopy data. The developed model offers a remarkable agreement between the synthesized and observed spectra and images in both X-ray and microwave domains, which validates the…
Gravity field and solar component of the precession rate and nutation coefficients of Comet 67P/Churyumov-Gerasimenko
Souchay, J.; Lhotka, C.; Reimond, S. +1 more
The aim of this study is first to determine the gravity field of the comet 67P/Churyumov-Gerasimenko and second to derive the solar component of the precession rate and nutation coefficients of the spin-axis of the comet nucleus, I.e. without the direct, usually larger, effect of outgassing. The gravity field and related moments of inertia are obt…
The nuclear dust lane of Circinus: collimation without a torus
Tristram, K. R. W.; Prieto, M. A.; Fernández-Ontiveros, J. A. +1 more
In some AGN, nuclear dust lanes connected to kpc-scale dust structures provide all the extinction required to obscure the nucleus, challenging the role of the dusty torus proposed by the Unified Model. In this letter, we show the pc-scale dust and ionized gas maps of Circinus constructed using sub-arcsec-accuracy registration of infrared VLT AO im…