Search Publications
Discovery of 40.5 ks Hard X-Ray Pulse-phase Modulations from SGR 1900+14
Suzuki, H.; Enoto, T.; Makishima, K. +4 more
X-ray timing properties of the magnetar SGR 1900+14 were studied, using the data taken with Suzaku in 2009 and NuSTAR in 2016, for a time lapse of 114 and 242 ks, respectively. On both occasions, the object exhibited the characteristic two-component spectrum. The soft component, dominant in energies below ~5 keV, showed a regular pulsation, with a…
The Pulsating White Dwarf G117-B15A: Still the Most Stable Optical Clock Known
Kepler, S. O.; Hermes, J. J.; Bell, Keaton J. +14 more
The pulsating hydrogen atmosphere white dwarf star G 117-B15A has been observed since 1974. Its main pulsation period at 215.19738823(63) s, observed in optical light curves, varies by only (5.12 ± 0.82) × 10-15 s s-1 and shows no glitches, as pulsars do. The observed rate of period change corresponds to a change of the pulsa…
The Black Hole Mass of NGC 4151 from Stellar Dynamical Modeling
Vasiliev, Eugene; Onken, Christopher A.; Bentz, Misty C. +2 more
The mass of a supermassive black hole (MBH) is a fundamental property that can be obtained through observational methods. Constraining MBH through multiple methods for an individual galaxy is important for verifying the accuracy of different techniques and for investigating the assumptions inherent in each method. However, th…
Correlated X-Ray and Optical Variability in the O-type Supergiant ζ Puppis
Moffat, Anthony F. J.; Richardson, Noel D.; Nichols, Joy S. +11 more
Analysis of the recent long exposure Chandra X-ray observation of the early-type O star ζ Pup shows clear variability with a period previously reported in optical photometric studies. These 813 ks of HETGS observations taken over a roughly one-year time span have two signals of periodic variability: (1) a high-significance period of 1.7820 ± 0.000…
A Comparison of Rest-frame Ultraviolet and Optical Emission-line Diagnostics in the Lensed Galaxy SDSS J1723+3411 at Redshift z = 1.3293
Rigby, J. R.; Momcheva, Ivelina; Brammer, Gabriel +13 more
For the extremely bright lensed galaxy SDSS J1723+3411 at z = 1.3293, we analyze spatially integrated MMT, Keck, and Hubble Space Telescope spectra that fully cover the rest-frame wavelength range of 1400-7200 Å. We also analyze near-IR spectra from Gemini that cover Hα for a portion of the lensed arc. We report fluxes for 42 detected emission lin…
A Characterization of the Circumstellar Gas of WD 1124-293 Using Cloudy
Dufour, Patrick; Steele, Amy; Debes, John +2 more
Between 30% and 50% of white dwarfs (WDs) show heavy elements in their atmospheres. This pollution is thought to arise from the accretion of planetesimals perturbed by outer planet(s) to within the WD's tidal disruption radius. A small fraction of these WDs show either emission or absorption from circumstellar (C-S) gas. The abundances of metals i…
Potential Black Hole Seeding of the Spiral Galaxy NGC 4424 via an Infalling Star Cluster
Soria, Roberto; Ciambur, Bogdan C.; Swartz, Douglas A. +2 more
Galaxies can grow through their mutual gravitational attraction and subsequent union. While orbiting a regular high-surface-brightness galaxy, the body of a low-mass galaxy can be stripped away. However, the stellar heart of the infalling galaxy, if represented by a tightly bound nuclear star cluster, is more resilient. From archival Hubble Space …
The Core Mass Function in the Orion Nebula Cluster Region: What Determines the Final Stellar Masses?
Sanhueza, Patricio; Mairs, Steve; Nakamura, Fumitaka +29 more
Applying dendrogram analysis to the CARMA-NRO C18O (J = 1-0) data having an angular resolution of ∼8″, we identified 692 dense cores in the Orion Nebula Cluster region. Using this core sample, we compare the core and initial stellar mass functions in the same area to quantify the step from cores to stars. About 22% of the identified cor…
Spatially Resolved RGS Analysis of Kepler's Supernova Remnant
Katsuda, Satoru; Sato, Toshiki; Hughes, John P. +4 more
The distribution and kinematics of the circumstellar medium (CSM) around a supernova remnant (SNR) tell us useful information about the explosion of its natal supernova (SN). Kepler's SNR, the remnant of SN 1604, is widely regarded to be of Type Ia origin. Its shock is moving through a dense, asymmetric CSM. The presence of this dense gas suggests…
TESS Observations of Be Stars: General Characteristics and the Impulsive Magnetic Rotator Model
Balona, Luis A.; Ozuyar, Dogus
Evidence of rotational light modulation in 30%-40% of normal B stars is presented, suggesting the presence of starspots and photospheric activity. On this basis, we propose that mass loss in Be stars is a result of magnetic reconnection coupled with rapid but not necessarily near-critical rotation. The ejected matter is trapped at two diametricall…