Search Publications
Evidence against Anomalous Compositions for Giants in the Galactic Nuclear Star Cluster
Schultheis, M.; Ryde, N.; Rich, R. M. +5 more
Very strong Sc I lines have recently been found in cool M giants in the Nuclear Star Cluster (NSC) in the Galactic center. Interpreting these as anomalously high scandium abundances in the Galactic center would imply a unique enhancement signature and chemical evolution history for NSCs, and a potential test for models of chemical enrichment in th…
H2CO Ortho-to-para Ratio in the Protoplanetary Disk HD 163296
Öberg, K. I.; Carpenter, J.; Qi, C. +3 more
Ortho-to-para (o/p) ratios of species like water, ammonia, and formaldehyde ({{{H}}}2{CO}) are believed to encode information about the formation history of the molecule. Measurements of o/p ratios in protoplanetary disks could thus be used to constrain their physical and chemical histories. We present the first measurement of the {{{H}…
Balmer-dominated Shocks Exclude Hot Progenitors for Many Type Ia Supernovae
Badenes, C.; Gilfanov, M.; Woods, T. E. +1 more
The evolutionary mechanism underlying Type Ia supernova explosions remains unknown. However, recent efforts to constrain progenitor models based on the influence that their high energy emission would have on the interstellar medium within galaxies have proven successful. For individual remnants, Balmer-dominated shocks reveal the ionization state …
The Progenitor Age and Mass of the Black Hole Formation Candidate N6946-BH1
Dolphin, Andrew E.; Díaz-Rodríguez, Mariangelly; Murphy, Jeremiah W. +3 more
The failed supernova N6946-BH1 likely formed a black hole (BH); we age-date the surrounding population and infer an age and initial mass for the progenitor of this BH formation candidate. First, we use archival Hubble Space Telescope imaging to extract broadband photometry of the resolved stellar populations surrounding this event. Using this phot…
Constraining Gravity at Large Scales with the 2MASS Photometric Redshift Catalog and Planck Lensing
Reichardt, Christian L.; Bianchini, Federico
We present a new measurement of structure growth at z ≃ 0.08 obtained by correlating the cosmic microwave background (CMB) lensing potential map from the Planck satellite with the angular distribution of the 2MASS Photometric Redshift galaxies. After testing for, and finding no evidence for systematic effects, we calculate the angular auto- and cr…
Dynamics of Intense Currents in the Solar Wind
Zelenyi, Lev M.; Angelopoulos, Vassilis; Artemyev, Anton V. +3 more
Transient currents in the solar wind are carried by various magnetic field discontinuities that contribute significantly to the magnetic field fluctuation spectrum. Internal instabilities and dynamics of these discontinuities are believed to be responsible for magnetic field energy dissipation and corresponding charged particle acceleration and he…
Understanding the HMI Pseudocontinuum in White-light Solar Flares
Kleint, Lucia; Kašparová, Jana; Jurčák, Jan +1 more
We analyze observations of the X9.3 solar flare (SOL2017-09-06T11:53) observed by SDO/HMI and Hinode/Solar Optical Telescope. Our aim is to learn about the nature of the HMI pseudocontinuum I c used as a proxy for the white-light continuum. From model atmospheres retrieved by an inversion code applied to the Stokes profiles observed by …
In Search of Recent Disruption of (3200) Phaethon: Model Implication and Hubble Space Telescope Search
Ye, Quanzhi; Hui, Man-To; Wiegert, Paul A.
Near-Earth asteroid (3200) Phaethon is notable for its association with a strong annual meteor shower, the Geminids, indicative of one or more episodes of mass ejection in the past. The mechanism of Phaethon’s past activity is not yet understood. Here, we present a Hubble Space Telescope (HST) search of meter-sized fragments in the vicinity of Pha…
Connections between Star Cluster Populations and Their Host Galaxy Nuclear Rings
Ho, Luis C.; de Grijs, Richard; Ma, Chao
Nuclear rings are excellent laboratories for probing diverse phenomena such as the formation and evolution of young massive star clusters and nuclear starbursts, as well as the secular evolution and dynamics of their host galaxies. We have compiled a sample of 17 galaxies with nuclear rings, which are well resolved by high-resolution Hubble and Sp…
Spitzer Infrared Spectrograph Observations of the Galactic Center: Quantifying the Extreme Ultraviolet/Soft X-ray Fluxes
Simpson, Janet P.
It has long been shown that the extreme ultraviolet spectrum of the ionizing stars of H II regions can be estimated by comparing the observed line emission to detailed models. In the Galactic Center (GC), however, previous observations have shown that the ionizing spectral energy distribution (SED) of the local photon field is strange, producing b…