Search Publications
Astrometric Calibration of the Beijing-Arizona Sky Survey
Fan, Xiaohui; Jiang, Linhua; Dey, Arjun +13 more
We present the astrometric calibration of the Beijing-Arizona Sky Survey (BASS). The BASS astrometry was tied to the International Celestial Reference Frame via the Gaia Data Release 2 reference catalog. For effects that were stable throughout the BASS observations, including differential chromatic refraction and the low charge transfer efficiency…
Where is the base of the Transition Region? Evidence from TRACE, SDO, IRIS and ALMA observations
Alissandrakis, Costas E.
Classic solar atmospheric models put the Chromosphere-Corona Transition Region (CCTR) at ∼ 2 Mm above the τ5000 = 1 level, whereas radiative MHD (rMHD) models place the CCTR in a wider range of heights. However, observational verification is scarce. In this work we review and discuss recent results from various instruments and spectral …
Nonthermal X-Rays from Pulsation-driven Shocks in Cepheids
Drake, Jeremy J.; Evans, Nancy Remage; Fraschetti, Federico +1 more
Rapid X-ray phase-dependent flux enhancement in the archetype classical Cepheid star δ Cep was observed by XMM-Newton and Chandra. We jointly analyze thermal and nonthermal components of the time-resolved X-ray spectra prior to, during, and after the enhancement. A comparison of the timescales of shock particle acceleration and energy losses is co…
Serendipitous discovery of the magnetic cataclysmic variable SRGE J075818−612027
Brink, Jaco; Buckley, David A. H.; Schwope, Axel +5 more
We report the discovery of SRGE J075818−612027, a deep stream-eclipsing magnetic cataclysmic variable found serendipitously in SRG/eROSITA calibration and performance verification phase (CalPV) observations of the open cluster NGC 2516 as an unrelated X-ray source. An X-ray timing and spectral analysis of the eROSITA data is presented and suppleme…
Confirmation of two magnetic cataclysmic variables as polars: 1RXS J174320.1-042953 and YY Sex
Pandey, J. C.; Potter, Stephen B.; De Becker, Michaël +5 more
We present our analysis of new and archived observations of two candidate magnetic cataclysmic variables, namely 1RXS J174320.1-042953 and YY Sex. 1RXS J174320.1-042953 was observed in two distinctive high and low states where a phase shift was seen, which could be due to changes in the shape, size, and (or) location of the accretion region. We fi…
Investigations of Flaring Plasma Parameters during an M-class Flare Using the Differential Evolution Method and XSM/Chandrayaan-2 Observations
Awasthi, Arun Kumar; Sylwester, Barbara; Sylwester, Janusz +2 more
We employ the differential evolution (DE) method to analyze observations from the Solar X-Ray Monitor on board the Chandrayaan-2 spacecraft. DE belongs to the family of evolutionary algorithms that find solutions using mechanisms inspired by biological processes. This approach enables us to simultaneously calculate the distribution of the differen…
Speckle-interferometric Study of Close Visual Binary System HIP 11253 (HD 14874) using Gaia (DR2 and EDR3)
Taani, Ali; Aljboor, Hussam
We present a comprehensive set of physical and geometrical parameters for each of the components of the close visual binary system HIP 11253 (HD 14874). We present an analysis for the binary and multiple stellar systems with the aim to obtain a match between the overall observational spectral energy distribution of the system and the spectral synt…
The common fundamental plane of X-ray emissions from pulsars and magnetars in quiescence
Chang, Hsiang-Kuang; Chu, Che-Yen
Magnetars are a unique class of neutron stars characterized by their incredibly strong magnetic fields. Unlike normal pulsars whose X-ray emission was driven by rotational energy loss, magnetars exhibit distinct X-ray emissions thought to be driven by their strong magnetic fields. Here, we present the results of magnetar X-ray spectra analysis in …
Detecting and Characterizing Young Quasars. III. The Impact of Gravitational Lensing Magnification
Hennawi, Joseph F.; Belli, Sirio; Tacchella, Sandro +8 more
We test the impact of gravitational lensing on the lifetime estimates of seven high-redshift quasars at redshift z ≳ 6. The targeted quasars are identified by their small observed proximity zone sizes, which indicate extremely short quasar lifetimes (t Q ≲ 105yr). However, these estimates of quasar lifetimes rely on the ass…
Magellanic System Stars Identified in SMACS J0723.3-7327 James Webb Space Telescope Early Release Observations Images
Holwerda, Benne W.; Koekemoer, Anton M.; Pirzkal, Nor +23 more
We identify 71 distant stars in James Webb Space Telescope/NIRCam early release observations (ERO) images of the field of galaxy cluster SMACS J0723.3-7327 (SMACS 0723). Given the relatively small (~10°) angular separation between SMACS 0723 and the Large Magellanic Cloud (LMC), it is likely that these stars are associated with the LMC outskirts o…