Search Publications
Quiet-Sun and Coronal Hole in Mg II k Line as Observed by IRIS
Solanki, Sami K.; Peter, Hardi; Kayshap, Pradeep +1 more
Coronal hole (CH) regions are dark in comparison to the quiet Sun (QS) at coronal temperatures. However, at chromospheric and transition region temperatures, the QS and CHs are hardly distinguishable. In this study, we have used the Mg II 2796.35 Å spectral line recorded by the Interface Region Imaging Spectrometer (IRIS) to understand the similar…
Hubble Space Telescope Trigonometric Parallax of Polaris B, Companion of the Nearest Cepheid
Schaefer, Gail H.; Nelan, Edmund P.; Bond, Howard E. +2 more
Polaris, the nearest and brightest Cepheid, is a potential anchor point for the Leavitt period-luminosity relation. However, its distance is a matter of contention, with recent advocacy for a parallax of ∼10 mas, in contrast with the Hipparcos measurement of 7.54 ± 0.11 mas. We report an independent trigonometric parallax determination, using the …
High-frequency Spicule Oscillations Generated via Mode Conversion
Yokoyama, Takaaki; Shoda, Munehito
Spicule oscillations involve high-frequency components with a typical period approximately corresponding to 40-50 s. The typical timescale of the photospheric oscillation is a few minutes, and thus, the origin of this high-frequency component is not trivial. In this study, a one-dimensional numerical simulation is performed to demonstrate that the…
Large-scale three-dimensional Gaussian process extinction mapping
Sale, S. E.; Magorrian, J.
Gaussian processes (GPs) are the ideal tool for modelling the Galactic interstellar medium, combining statistical flexibility with a good match to the underlying physics. In an earlier paper, we outlined how they can be employed to construct three-dimensional maps of dust extinction from stellar surveys. GPs scale poorly to large data sets though,…
A New, Long-lived, Jupiter Mesoscale Wave Observed at Visible Wavelengths
de Pater, Imke; Wong, Michael H.; Fletcher, Leigh N. +12 more
Small-scale waves were observed along the boundary between Jupiter’s North Equatorial Belt (NEB) and North Tropical Zone, ∼16.°5 N planetographic latitude in Hubble Space Telescope data in 2012 and throughout 2015-2018, observable at all wavelengths from the UV to the near-IR. At peak visibility, the waves have sufficient contrast (∼10%) to be obs…
Improved estimation of Mars ionosphere total electron content
Sánchez-Cano, B.; Witasse, O.; Cantini, F. +5 more
We describe an improved method to estimate the Total Electron Content (TEC) of the Mars ionosphere from the echoes recorded by the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) (Picardi et al., 2005; Orosei et al., 2015) onboard Mars Express in its subsurface sounding mode. In particular, we demonstrate that this method solve…
SMBH accretion properties of radio-selected AGN out to z ∼ 4
Bondi, M.; Smolčić, V.; Alexander, D. M. +8 more
Exploring how radio-emitting active galactic nuclei (AGNs) behave and evolve with time is critical for understanding how AGN feedback impacts galaxy evolution. In this work, we investigate the relationship between 1.4 GHz radio continuum AGN luminosity (L^AGN_1.4), specific black hole accretion rate (s-BHAR, defined as the accretion luminosity rel…
Spatially Offset Active Galactic Nuclei. III. Discovery of Late-stage Galaxy Mergers with the Hubble Space Telescope
Greene, Jenny E.; Comerford, Julia M.; Barrows, R. Scott
Galaxy pairs with separations of only a few kiloparsecs represent important stages in the merger-driven growth of supermassive black holes (SMBHs). However, such mergers are difficult to identify observationally due to the correspondingly small angular scales. In Paper I we presented a method of finding candidate kiloparsec-scale galaxy mergers th…
LQAC-4: Fourth release of the Large Quasar Astrometric Catalogue. Compilation of 443 725 objects including cross-identifications with Gaia DR1
Barache, C.; Souchay, J.; Taris, F. +3 more
Context. From an astrometric point of view, quasars constitute the best and almost ideal reference objects in the celestial sphere, with a priori no significant proper motion. Since the third release of the Large Quasar Astrometric Catalogue (LQAC-3), a large number of quasars have been discovered, in particular those coming from the DR12Q release…
Chemical abundance analysis of red giant branch stars in the globular cluster E3
Monaco, L.; Mucciarelli, A.; Villanova, S. +2 more
Context. Globular clusters are known to host multiple stellar populations, which are a signature of their formation process. The globular cluster E3 is one of the few low-mass globulars that is thought not to host multiple populations.
Aims: We investigate red giant branch stars in E3 with the aim of providing a first detailed chemical invent…