Search Publications
The Extended Distribution of Baryons around Galaxies
Bregman, Joel N.; Anderson, Michael E.; Qu, Zhijie +5 more
We summarize and reanalyze observations bearing on missing galactic baryons, where we propose a consistent picture for halo gas in L ≳ L* galaxies. The hot X-ray-emitting halos are detected to 50-70 kpc, where typically M hot(<50 kpc) ∼ 5 × 109 M ⊙, and with density n ∝ r -3/2. When extrapolated to R …
Forecasting the Arrival Time of Coronal Mass Ejections: Analysis of the CCMC CME Scoreboard
Dumbović, Mateja; Temmer, Manuela; Feng, Xueshang +15 more
Accurate forecasting of the properties of coronal mass ejections (CMEs) as they approach Earth is now recognized as an important strategic objective for both NOAA and NASA. The time of arrival of such events is a key parameter, one that had been anticipated to be relatively straightforward to constrain. In this study, we analyze forecasts submitte…
The temporal evolution of neutron-capture elements in the Galactic discs
Dreizler, Stefan; Bedell, Megan; Meléndez, Jorge +8 more
Important insights into the formation and evolution of the Galactic disc(s) are contained in the chemical compositions of stars. We analysed high-resolution and high signal-to-noise HARPS spectra of 79 solar twin stars in order to obtain precise determinations of their atmospheric parameters, ages (σ ∼0.4 Gyr) and chemical abundances (σ <0.01 d…
An absolute sodium abundance for a cloud-free `hot Saturn' exoplanet
Fortney, J. J.; Helling, Ch.; Burgasser, A. J. +20 more
Broad absorption signatures from alkali metals, such as the sodium (Na i) and potassium (K i) resonance doublets, have long been predicted in the optical atmospheric spectra of cloud-free irradiated gas giant exoplanets1-3. However, observations have revealed only the narrow cores of these features rather than the full pressure-broadene…
The Stellar Membership of the Taurus Star-forming Region
Luhman, K. L.
The high-precision astrometry from the second data release of the Gaia mission has made it possible to greatly improve the census of members of nearby clusters and associations. I have applied the Gaia data to the Taurus star-forming region, refining the sample of known members and identifying candidates for undiscovered members. The resulting sam…
Alternative Explanations for Extreme Supersolar Iron Abundances Inferred from the Energy Spectrum of Cygnus X-1
Gandhi, Poshak; Yamaoka, Kazutaka; Fürst, Felix +11 more
Here we study a 1-200 keV energy spectrum of the black hole binary Cygnus X-1 taken with NuSTAR and Suzaku. This is the first report of a NuSTAR observation of Cyg X-1 in the intermediate state, and the observation was taken during the part of the binary orbit where absorption due to the companion’s stellar wind is minimal. The spectrum includes a…
A candidate super-Earth planet orbiting near the snow line of Barnard's star
Rebolo, R.; Amado, P. J.; Caballero, J. A. +60 more
Barnard's star is a red dwarf, and has the largest proper motion (apparent motion across the sky) of all known stars. At a distance of 1.8 parsecs1, it is the closest single star to the Sun; only the three stars in the α Centauri system are closer. Barnard's star is also among the least magnetically active red dwarfs known2,3…
Nearby Early-type Galactic Nuclei at High Resolution: Dynamical Black Hole and Nuclear Star Cluster Mass Measurements
Böker, Torsten; Pechetti, Renuka; Caldwell, Nelson +12 more
We present a detailed study of the nuclear star clusters (NSCs) and massive black holes (BHs) of four of the nearest low-mass early-type galaxies: M32, NGC 205, NGC 5102, and NGC 5206. We measure the dynamical masses of both the BHs and NSCs in these galaxies using Gemini/NIFS or VLT/SINFONI stellar kinematics, Hubble Space Telescope (HST) imaging…
The initial masses of the red supergiant progenitors to Type II supernovae
Beasor, Emma R.; Davies, Ben
There are a growing number of nearby supernovae (SNe) for which the progenitor star is detected in archival pre-explosion imaging. From these images it is possible to measure the progenitor's brightness a few years before explosion, and ultimately estimate its initial mass. Previous work has shown that II-P and II-L SNe have red supergiant (RSG) p…
The distribution of stars around the Milky Way's central black hole. II. Diffuse light from sub-giants and dwarfs
Nogueras-Lara, F.; Gallego-Calvente, A. T.; Dong, H. +4 more
Context. This is the second of three papers that search for the predicted stellar cusp around the Milky Way's central black hole, Sagittarius A*, with new data and methods.
Aims: We aim to infer the distribution of the faintest stellar population currently accessible through observations around Sagittarius A*.
Methods: We used adaptive o…