Search Publications
The Timing Behavior of the Central Compact Object Pulsar 1E 1207.4-5209
Gotthelf, E. V.; Halpern, J. P.
We present 20 yr of timing observations for 1E 1207.4-5209, the central compact object in supernova remnant PKS 1209-51/52, to follow up on our detection of an unexpected timing glitch in its spin-down. Using new XMM-Newton and NICER observations of 1E 1207.4-5209, we now find that the phase ephemeris can be well modeled by either two small glitch…
Reflection Features in the X-Ray Spectrum of Fairall 9 and Implications for Tests of General Relativity
Abdikamalov, Askar B.; Ayzenberg, Dimitry; Bambi, Cosimo +2 more
X-ray reflection spectroscopy is potentially a powerful tool to probe the spacetime geometry around astrophysical black holes and test general relativity in the strong field regime. However, precision tests of general relativity are only possible if we employ the correct astrophysical model and if we can limit the systematic uncertainties. It is t…
PHAT XX. AGB Stars and Other Cool Giants in M31 Star Clusters
Dolphin, Andrew E.; Skillman, Evan D.; Williams, Benjamin F. +20 more
The presence of asymptotic giant branch (AGB) stars in clusters provides key constraints for stellar models, as has been demonstrated with historical data from the Magellanic Clouds. In this work, we look for candidate AGB stars in M31 star clusters from the Panchromatic Hubble Andromeda Treasury survey. Our photometric criteria selects stars brig…
Evidence for Resonance Scattering in the X-Ray Grating Spectrum of the Supernova Remnant N49
Gu, Liyi; Uchida, Hiroyuki; Tsuru, Takeshi Go +2 more
Resonance scattering (RS) is an important process in astronomical objects, because it affects measurements of elemental abundances and distorts surface brightness of the object. It is predicted that RS can occur in plasmas of supernova remnants (SNRs). Although several authors reported hints of RS in SNRs, no strong observational evidence has been…
Probing Axial Symmetry Breaking in the Galaxy with Gaia Data Release 2
Yanny, Brian; Gardner, Susan; Hinkel, Austin
We study a set of solar neighborhood (d < 3 kpc) stars from Gaia Data Release 2 to determine azimuthal star count differences, I.e., left and right of the line from the Galactic Center (GC) through the Sun - and compare these differences north and south. In this companion paper to Gardner et al., we delineate our procedures to remove false asym…
Suzaku Measurements of Hot Halo Emission at Outskirts for Two Poor Galaxy Groups: NGC 3402 and NGC 5129
Sun, Ming; Dai, Xinyu; Nugent, Jenna M.
We present Suzaku off-center observations of two poor galaxy groups, NGC 3402 and NGC 5129, with temperatures below 1 keV. Through spectral decomposition, we measured their surface brightnesses and temperatures out to 530 and 1430 times the critical density of the universe for NGC 3402 and NGC 5129, respectively. These quantities are consistent wi…
Fluid Theory of Coherent Magnetic Vortices in High-β Space Plasmas
Alexandrova, Olga; Maksimović, Milan; Jovanović, Dušan +1 more
In situ observations in Earth's and Saturn's magnetosheaths and in the solar wind reveal the presence of Alfvén vortices as intermittent structures in the range of scales from fluid lengths down to a few ion lengths. The density and the magnetic field associated with them appear to be compressible for higher plasma betas. Until now, only incompres…
Spectroscopic Monitoring of Rapidly Rotating Early-type Stars in the Pleiades Cluster
Torres, Guillermo
Radial velocities for the early-type stars in the Pleiades cluster have always been challenging to measure because of the significant rotational broadening of the spectral lines. The large scatter in published velocities has led to claims that many are spectroscopic binaries, and in several cases, preliminary orbital solutions have been proposed. …
Distortion of Magnetic Fields in the Dense Core CB81 (L1774, Pipe 42) in the Pipe Nebula
Kwon, Jungmi; Nagata, Tetsuya; Tamura, Motohide +9 more
The detailed magnetic field structure of the starless dense core CB81 (L1774, Pipe 42) in the Pipe Nebula was determined based on near-infrared polarimetric observations of background stars to measure dichroically polarized light produced by magnetically aligned dust grains in the core. The magnetic fields pervading CB81 were mapped using 147 star…
Effects of Solar Activity on Taylor Scale and Correlation Scale in Solar Wind Magnetic Fluctuations
Zhou, G.; Wan, W.; He, H. -Q.
The correlation scale and the Taylor scale are evaluated for interplanetary magnetic field fluctuations from two-point, single time correlation function using the Advanced Composition Explorer (ACE), Wind, and Cluster spacecraft data during the time period from 2001 to 2017, which covers over an entire solar cycle. The correlation scale and the Ta…