Search Publications
Carbon-deficient Red Giants
Bond, Howard E.
Carbon-deficient red giants (CDRGs) are a rare class of peculiar red giants, also called “weak G-band” or “weak CH” stars. Their atmospheric compositions show depleted carbon, a low {}12{{C}}{/}13{{C}} isotopic ratio, and an overabundance of nitrogen, indicating that the material at the surface has undergone CN-cycle hydrogen…
On Geometrical Invariants of the Magnetic Field Gradient Tensor in Turbulent Space Plasmas: Scale Variability in the Inertial Range
Marcucci, Maria Federica; Consolini, Giuseppe; Materassi, Massimo +1 more
In a recent paper, Consolini et al. investigated the statistics of geometrical invariants of the coarse-grained gradient tensor of plasma velocity for a case study of space plasma turbulence. They showed how, at spatial scales near the proton inertial length, there is evidence for the occurrence of dissipation structures along the Vieillefosse’s t…
Asymmetric Distribution of Weak Photospheric Magnetic Field Values
Mursula, Kalevi; Virtanen, Ilpo; Getachew, Tibebu
We use the synoptic maps of the photospheric magnetic field observed at Wilcox Solar Observatory, Mount Wilson Observatory, Kitt Peak, SOHO/MDI, SOLIS/VSM, and SDO/HMI to study the distribution of weak photospheric magnetic field values in 1974-2018. We fit the histogram distribution of weak field values for each synoptic map of the six data sets …
Measuring the Obscuring Column of a Disk Megamaser AGN in a Nearby Merger
Comastri, A.; Brusa, M.; Civano, F. +5 more
Active galactic nuclei (AGNs) hosting disk water megamasers are well known to be obscured by large amounts of gas, likely due to the presence along the line of sight of an almost edge-on disky structure orbiting the supermassive black hole. Correcting for the high obscuration is crucial to infer parameters intrinsic to the source, like its luminos…
Discovery of a Damped Lyα System in a Low-z Galaxy Group: Possible Evidence for Gas Inflow and Nuclear Star Formation
Heckman, Timothy M.; Tumlinson, Jason; Momjian, Emmanuel +3 more
We present a low-redshift (z = 0.029) damped Lyα (DLA) system in the spectrum of a background quasi-stellar object (QSO). The DLA is associated with an interacting galaxy pair within a galaxy group. We detected weak Lyα emission centered at the absorption trough of the DLA. The emission was likely tracing the neutral H I reservoir around the galax…
Catalog of High Protostellar Surface Density Regions in Nearby Embedded Clusters
Li, Juan; Myers, Philip C.; Kirk, Helen +3 more
We analyze high-quality stellar catalogs for 24 young and nearby (within 1 kpc) embedded clusters and present a catalog of 32 groups which have a high concentration of protostars. The median effective radius of these groups is 0.17 pc. The median protostellar and pre-main-sequence star surface densities are 46 M ⊙ pc-2 and 11…
T CrB: Radio Observations during the 2016-2017 “Super-active” State
Chomiuk, Laura; Sokoloski, Jennifer L.; Mukai, Koji +6 more
We obtained radio observations of the symbiotic binary and known recurrent nova T Coronae Borealis following a period of increased activity in the optical and X-ray bands. A comparison of our observations with those made prior to 2015 indicates that the system is in a state of higher emission in the radio as well. The spectral energy distributions…
HSC-XD 52: An X-Ray Detected AGN in a Low-mass Galaxy at z ∼ 0.56
Johnson, Sean D.; Sawicki, Marcin; Gwyn, Stephen +8 more
The properties of low-mass galaxies hosting central black holes provide clues about the formation and evolution of the progenitors of supermassive black holes. In this Letter, we present HSC-XD 52, a spectroscopically confirmed low-mass active galactic nucleus (AGN) at an intermediate redshift of z ∼ 0.56. We detect this object as a very luminous …
The Nature of the Broadband X-Ray Variability in the Dwarf Seyfert Galaxy NGC 4395
Kaastra, J. S.; Stern, D.; Brandt, W. N. +14 more
We present a flux-resolved X-ray analysis of the dwarf Seyfert 1.8 galaxy NGC 4395, based on three archival XMM-Newton and one archival NuSTAR observations. The source is known to harbor a low-mass black hole (∼ {10}4{--}{{a}} {few} × {10}5 {M}⊙ ) and shows strong variability in the full X-ray range during these ob…
Probing Clumpy Wind Accretion in IGR J18027-2016 with XMM-Newton
Paul, Biswajit; Ferrigno, Carlo; Pradhan, Pragati +2 more
Supergiant X-ray binaries usually comprise a neutron star accreting from the wind of an OB supergiant companion. They are classified as classical systems and supergiant fast X-ray transients (SFXTs). The different behavior of these subclasses of sources in X-rays, with SFXTs displaying much more pronounced variability, is usually (at least) partly…