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Keck HIRES spectroscopy of SkyMapper commissioning survey candidate extremely metal-poor stars
Schmidt, B. P.; Da Costa, G. S.; Marino, A. F. +11 more
We present results from the analysis of high-resolution spectra obtained with the Keck HIRES spectrograph for a sample of 17 candidate extremely metal-poor (EMP) stars originally selected from commissioning data obtained with the SkyMapper telescope. Fourteen of the stars have not been observed previously at high dispersion. Three have [Fe/H] ≤ -3…
Anomalous behaviour of the UV-optical continuum bands in NGC 5548
Knigge, C.; Kriss, G. A.; Starkey, D. A. +8 more
During the 2014 HST/Swift and ground-based multiwavelength monitoring campaign of NGC 5548 [active galactic nucleus (AGN) STORM], the UV-optical broad emission lines exhibited anomalous, decorrelated behaviour relative to the far-UV continuum flux variability. Here, we use key diagnostic emission lines (Ly α and He II) for this campaign to infer a…
An all-sky search for R Coronae Borealis stars in ASAS-SN
Kochanek, C. S.; Stanek, K. Z.; Dong, Subo +6 more
We report the discovery of 19 new R Coronae Borealis (RCB) star and DY Per candidates with light curves from the All-Sky Automated Survey for Supernovae. We examined both an existing set of 1602 near/mid-infrared (IR) selected candidates and an additional 2615 candidates selected to have near/mid-IR spectral energy distributions consistent with th…
The morpho-kinematics of the circumstellar envelope around the AGB star EP Aqr
Winters, J. M.; Tuan-Anh, P.; Hoai, D. T. +6 more
ALMA observations of CO(1-0) and CO(2-1) emissions of the circumstellar envelope of EP Aqr, an oxygen-rich asymptotic giant branch star, are reported. A thorough analysis of their properties is presented using an original method based on the separation of the data cube into a low-velocity component associated with an equatorial outflow and a faste…
Modelling the abundance structure of isocyanic acid (HNCO) towards the low-mass solar type protostar IRAS 16293-2422
Menten, Karl M.; Loinard, Laurent; Wiesenfeld, Laurent +5 more
Isocyanic acid (HNCO), the most stable of the simplest molecules containing the four main elements essential for organic chemistry, has been observed in several astrophysical environments such as molecular clouds, star-forming regions, external galaxies, and comets. In this work, we model HNCO spectral line profiles towards the low-mass solar type…
Beyond the Minisolar Maximum of Solar Cycle 24: Declining Solar Magnetic Fields and the Response of the Terrestrial Magnetosphere
Janardhan, P.; Ingale, M.; Bisoi, S. K.
The present study examines the response of the terrestrial magnetosphere to the long-term steady declining trends observed in solar magnetic fields and solar wind microturbulence levels since mid-1990s that has been continuing beyond the minisolar maximum of cycle 24. A detailed analysis of the response of the terrestrial magnetosphere has been ca…
UV to X-Ray Comptonization Delay in Mrk 493
Dewangan, Gulab C.; Pal, Main; Pawar, Pramod +1 more
The broadband X-ray emission from type 1 active galactic nuclei, dominated by a power-law continuum, is thought to arise from repeated inverse Compton scattering of seed optical/UV photons by energetic electrons in a hot corona. The seed optical/UV photons are assumed to arise from an accretion disk, but direct observational evidence has remained …
Measuring the expansion and age of the nova shell IPHASX J210204.7 + 471015
Guerrero, M. A.; Toalá, J. A.; Santamaría, E. +4 more
The parallax expansion and kinematics of a nova shell can be used to assess its age and distance, and to investigate the interaction of the ejecta with the circumstellar medium. These are key to understand the expansion and dispersal of the nova ejecta in the Galaxy. Multi-epoch images and high-dispersion spectroscopic observations of the recently…
First Evidence of Enhanced Recombination in Astrophysical Environments and the Implications for Plasma Diagnostics
Dupree, A. K.; Raymond, J.; García-Rojas, J. +6 more
We report the first unambiguous observational evidence of Rydberg Enhanced Recombination (RER), a potentially important recombination mechanism that has hitherto been unexplored in low-temperature photoionized plasmas. RER shares similarities with dielectronic recombination, with the difference that the electron is captured into a highly excited s…
Migrating Scarps as a Significant Driver for Cometary Surface Evolution
Soderblom, J. M.; Davidsson, B.; Oklay, N. +10 more
Rosetta observations of 67P/Churyumov-Gerasimenko (67P) reveal that most changes occur in the fallback-generated smooth terrains, vast deposits of granular material blanketing the comet's northern hemisphere. These changes express themselves both morphologically and spectrally across the nucleus, yet we lack a model that describes their formation …