Search Publications
Chemically Peculiar A and F Stars with Enhanced s-process and Iron-peak Elements: Stellar Radiative Acceleration at Work
Ting, Yuan-Sen; Rix, Hans-Walter; Zhang, Meng +6 more
We present ≳15,000 metal-rich ([Fe/H] > -0.2 dex) A and F stars whose surface abundances deviate strongly from solar abundance ratios and cannot plausibly reflect their birth material composition. These stars are identified by their high [Ba/Fe] abundance ratios ([Ba/Fe] > 1.0 dex) in the LAMOST DR5 spectra analyzed by Xiang et al. They are …
A Catalog of Bipolar Active Regions Violating the Hale Polarity Law, 1989 - 2018
Zhukova, Anastasiya; Sokoloff, Dmitry; Abramenko, Valentina +1 more
There is no list of bipolar active regions (ARs) with reverse polarity (anti-Hale regions), although statistical investigations of such ARs (bearing the imprint of deep subphotospheric processes) are important for understanding solar-cycle mechanisms. We studied 8606 ARs from 1 January 1989 to 31 December 2018 to detect anti-Hale regions and to co…
Chandra Monitoring of the J1809-1917 Pulsar Wind Nebula and Its Field
Pavlov, George G.; Kargaltsev, Oleg; Klingler, Noel +3 more
PSR J1809-1917 is a young (τ = 51 kyr) and energetic ( $\dot{E}=1.8\times {10}^{36}$ erg s-1) radio pulsar powering an X-ray pulsar wind nebula (PWN) that exhibits morphological variability. We report on the results of a new monitoring campaign by the Chandra X-ray Observatory (Chandra), carried out across six epochs with a ∼7 week cade…
A Rapidly Varying Red Supergiant X-Ray Binary in the Galactic Center
Gottlieb, Amy M.; Ackley, Kendall; DeWitt, Curtis +2 more
We analyzed multiwavelength observations of the previously identified Galactic center X-ray binary CXO 174528.79-290942.8 (XID 6592) and determine that the near-infrared counterpart is a red supergiant based on its spectrum and luminosity. Scutum X-1 is the only previously known X-ray binary with a red supergiant donor star and closely resembles X…
The Detection of Dust Gap-ring Structure in the Outer Region of the CR Cha Protoplanetary Disk
Dong, Ruobing; Kataoka, Akimasa; Sitko, Michael +13 more
We observe the dust continuum at 225 GHz and CO isotopologue (12CO, 13CO, and C18O) J = 2-1 emission lines toward the CR Cha protoplanetary disk using the Atacama Large Millimeter/submillimeter Array. The dust continuum image shows a dust gap-ring structure in the outer region of the dust disk. A faint dust ring is…
Placing limits on long-term variations in quiet-Sun irradiance and their contribution to total solar irradiance and solar radiative forcing of climate
Lockwood, Mike; Ball, William T.
Recent reconstructions of total solar irradiance (TSI) postulate that quiet-Sun variations could give significant changes to the solar power input to Earth's climate (radiative climate forcings of 0.7-1.1 W m-2 over 1700-2019) arising from changes in quiet-Sun magnetic fields that have not, as yet, been observed. Reconstructions without…
Influence of Collisions with Hydrogen on Titanium Abundance Determinations in Cool Stars
Sitnova, T. M.; Yakovleva, S. A.; Belyaev, A. K. +1 more
The possibility of solving the problem of a discrepancy in the non-LTE abundances from Ti I and Ti II lines in metal-poor stars is investigated by applying accurate data to take into account the collisions with hydrogen atoms. For this purpose, we have calculated for the first time the rate coefficients for bound-bound transitions in inelastic col…
The long-term enhanced brightness of the magnetar 1E 1547.0-5408
Enoto, Teruaki; Esposito, Paolo; Rea, Nanda +6 more
We present the evolution of the X-ray emission properties of the magnetar 1E 1547.0-5408 since February 2004 over a time period covering three outbursts. We analyzed new and archival observations taken with the Swift, NuSTAR, Chandra, and XMM-Newton X-ray satellites. The source has been observed at a relatively steady soft X-ray flux of ≈10-1…
Phase-curve Pollution of Exoplanet Transit Depths
Lagage, Pierre-Olivier; Morello, Giuseppe; Cossou, Christophe +2 more
The next generation of space telescopes will enable transformative science to understand the nature and origin of exoplanets. In particular, transit spectroscopy will reveal the chemical composition of the exoplanet atmospheres with unprecedented detail thanks to precise measurements of the visible-to-infrared transit depths down to 10 parts per m…
Distance and mass of the M 104 (Sombrero) group
Anand, Gagandeep S.; Shaya, Edward J.; Karachentsev, Igor D. +3 more
Aims: Distances and radial velocities of galaxies in the vicinity of the luminous early-type galaxy M 104 (Sombrero) are used to derive its dark matter mass.
Methods: Two dwarf galaxies: UGCA 307 and KKSG 30 situated near M 104 were observed with the Advanced Camera for Surveys on the Hubble Space Telescope. The distances 9.03-0.51<…