Search Publications
An Analytical Diffusion-Expansion Model for Forbush Decreases Caused by Flux Ropes
Dumbović, Mateja; Temmer, Manuela; Vršnak, Bojan +2 more
We present an analytical diffusion-expansion Forbush decrease (FD) model ForbMod, which is based on the widely used approach of an initially empty, closed magnetic structure (i.e., flux rope) that fills up slowly with particles by perpendicular diffusion. The model is restricted to explaining only the depression caused by the magnetic structure of…
Lense-Thirring precession in ULXs as a possible means to constrain the neutron star equation of state
Gehrels, N.; Fabian, A. C.; Pinto, C. +11 more
The presence of neutron stars in at least three ultraluminous X-ray sources is now firmly established and offers an unambiguous view of super-critical accretion. All three systems show long-time-scale periods (60-80 d) in the X-rays and/or optical, two of which are known to be super-orbital in nature. Should the flow be classically super critical,…
An astrophysical interpretation of the remarkable g-mode frequency groups of the rapidly rotating γ Dor star, KIC 5608334
Li, Gang; Bedding, Timothy R.; Antoci, Victoria +5 more
The Fourier spectrum of the γ-Dor variable KIC 5608334 shows remarkable frequency groups at ∼3, ∼6, ∼9, and 11-12 d-1. We explain the four frequency groups as prograde sectoral g modes in a rapidly rotating star. Frequencies of intermediate-to-high radial order prograde sectoral g modes in a rapidly rotating star are proportional to |m|…
Discovery and Dynamical Analysis of an Extreme Trans-Neptunian Object with a High Orbital Inclination
Smith, M.; D'Andrea, C. B.; Abdalla, F. B. +63 more
We report the discovery and dynamical analysis of 2015 BP519, an extreme trans-Neptunian object (TNO) detected by the Dark Energy Survey at a heliocentric distance of 55 au, perihelion of ∼36 au, and absolute magnitude H r = 4.3. The current orbit, determined from a 1110 day observational arc, has a semimajor axis a ≈ 450 a…
KELT-19Ab: A P ∼ 4.6-day Hot Jupiter Transiting a Likely Am Star with a Distant Stellar Companion
Bieryla, Allyson; Latham, David W.; Quinn, Samuel N. +51 more
We present the discovery of the giant planet KELT-19Ab, which transits the moderately bright (V∼ 9.9) A8V star TYC 764-1494-1 with an orbital period of 4.61 days. We confirm the planetary nature of the companion via a combination of radial velocities, which limit the mass to ≲ 4.1 {M}{{J}} (3σ ), and a clear Doppler tomography signal, w…
The Spatially Resolved Dust-to-metals Ratio in M101
Sandstrom, Karin M.; Johnson, L. Clifton; Leroy, Adam K. +3 more
The dust-to-metals ratio describes the fraction of heavy elements contained in dust grains, and its variation provides key insights into the life cycle of dust. We measure the dust-to-metals ratio in M101, a nearby galaxy with a radial metallicity (Z) gradient spanning ∼1 dex. We fit the spectral energy distribution of dust from 100 to 500 µ…
Study of Titan's fall southern stratospheric polar cloud composition with Cassini/CIRS: Detection of benzene ice
de Kok, R.; Flasar, F. M.; Bézard, B. +5 more
We report the detection of a spectral signature observed at 682 cm-1 by the Cassini Composite Infrared Spectrometer (CIRS) in nadir and limb geometry observations of Titan's southern stratospheric polar region in the middle of southern fall, while stratospheric temperatures are the coldest since the beginning of the Cassini mission. In …
The Instruments and Capabilities of the Miniature X-Ray Solar Spectrometer (MinXSS) CubeSats
Chamberlin, Phillip C.; Woods, Thomas N.; Caspi, Amir +6 more
The Miniature X-ray Solar Spectrometer (MinXSS) CubeSat is the first solar science oriented CubeSat mission flown for the NASA Science Mission Directorate, with the main objective of measuring the solar soft X-ray (SXR) flux and a science goal of determining its influence on Earth's ionosphere and thermosphere. These observations can also be used …
The Changing-look Quasar Mrk 590 Is Awakening
Vestergaard, M.; Peterson, B. M.; Goad, M. +9 more
Mrk 590 was originally classified as a Seyfert 1 galaxy, but then it underwent dramatic changes: the nuclear luminosity dropped by over two orders of magnitude and the broad emission lines all but disappeared from the optical spectrum. Here we present follow-up observations to the original discovery and characterization of this “changing-look” act…
Experimental results from the ST7 mission on LISA Pathfinder
Mendes, L.; Anderson, J.; Cooper, M. +146 more
The Space Technology 7 Disturbance Reduction System (ST7-DRS) is a NASA technology demonstration payload that operated from January 2016 through July 2017 on the European Space Agency's (ESA) LISA Pathfinder spacecraft. The joint goal of the NASA and ESA missions was to validate key technologies for a future space-based gravitational wave observat…