Search Publications
Near-Gaussian distributions for modelling discrete stellar velocity data with heteroskedastic uncertainties
Evans, N. Wyn; Sanders, Jason L.
The velocity distributions of stellar tracers in general exhibit weak non-Gaussianity encoding information on the orbital composition of a galaxy and the underlying potential. The standard solution for measuring non-Gaussianity involves constructing a series expansion (e.g. the Gauss-Hermite series) that can produce regions of negative probability…
Rotational modulation and single g-mode pulsation in the B9pSi star HD 174356?
Ilyin, I.; Järvinen, S.; Niemczura, E. +19 more
Chemically peculiar (CP) stars of the upper main sequence are characterized by specific anomalies in the photospheric abundances of some chemical elements. The group of CP2 stars, which encompasses classical Ap and Bp stars, exhibits strictly periodic light, spectral, and spectropolarimetric variations that can be adequately explained by the model…
The ISM local to the runaway star WR16
Noriega-Crespo, A.; Reynoso, E. M.; Cichowolski, S. +3 more
Massive stars leave their imprint on the interstellar medium as they radiate their energy and undergo episodes of mass ejection throughout their lives. In this paper, we analyse the case of the Wolf-Rayet star WR16 combining archival multiwavelength data with new molecular observations obtained with the Atacama Submillimeter Telescope Experiment (…
Optical and X-ray studies of three polars: RX J0859.1+0537, RX J0749.1-0549, and RX J0649.8-0737
Raj, Ashish; Pandey, J. C.; Singh, K. P. +3 more
We present optical photometric and spectroscopic observations, and an analysis of archival X-ray data of three polars: RX J0859.1+0537, RX J0749.1-0549, and RX J0649.8-0737. Optical light curves of these three polars reveal eclipse-like features that are deep, total, and variable in shape. The optical and X-ray modulations of RX J0859.1+0537, RX J…
Solar-metallicity gas in the extended halo of a galaxy at z ∼ 0.12
Pradeep, Jayadev; Narayanan, Anand; Khaire, Vikram +4 more
We present the detection and analysis of a weak low-ionization absorber at z = 0.121 22 along the sightline of the blazar PG 1424+240, using spectroscopic data from both HST/COS and STIS. The absorber is a weak Mg II analogue, with an incidence of weak C II and Si II, along with multicomponent C IV and O VI. The low ions are tracing a dense (n
Electromagnetic counterparts to gravitational wave events from Gaia
Harrison, D. L.; Koposov, S. E.; Evans, D. W. +15 more
The recent discoveries of gravitational wave events and in one case also its electromagnetic (EM) counterpart allow us to study the Universe in a novel way. The increased sensitivity of the LIGO and Virgo detectors has opened the possibility for regular detections of EM transient events from mergers of stellar remnants. Gravitational wave sources …
Characterizing continuum variability in the radio-loud narrow-line Seyfert 1 galaxy IRAS 17020+4544
Fabian, A. C.; Gallo, L. C.; Alston, W. N. +4 more
We present results of temporal and spectral analyses on four XMM-Newton EPIC pn observations of IRAS 17020+4544, a narrow-line Seyfert 1 galaxy with evidence of a radio jet. Analysis of the light curves reveals that this radio-loud source does not behave like the bulk population of its radio-quiet counterparts. A trend of spectral hardening with i…
Multiwavelength classification of X-ray selected galaxy cluster candidates using convolutional neural networks
Kendrew, Sarah; Valtchanov, Ivan; Werner, Norbert +15 more
Galaxy clusters appear as extended sources in XMM-Newton images, but not all extended sources are clusters. So, their proper classification requires visual inspection with optical images, which is a slow process with biases that are almost impossible to model. We tackle this problem with a novel approach, using convolutional neural networks (CNNs)…
HD 93795: a late-B supergiant star with a square circumstellar nebula
Katkov, I. Y.; Gvaramadze, V. V.; Castro, N. +1 more
We report the discovery of a square axisymmetric circumstellar nebula around the emission-line star HD 93795 in the archival Spitzer Space Telescope 24 {µ m} data. We classify HD 93795 as a B9 Ia star using optical spectra obtained with the Southern African Large Telescope (SALT). A spectral analysis carried out with the stellar atmosphere c…
ALMA reveals the coherence of the magnetic field geometry in OH 231.8+4.2
Sahai, R.; Zijlstra, A. A.; Sabin, L. +7 more
In a continuing effort to investigate the role of magnetic fields in evolved low- and intermediate-mass stars (principally regarding the shaping of their envelopes), we present new Atacama Large Millimeter/submillimeter Array (ALMA) high-resolution polarization data obtained for the nebula OH 231.8+4.2. We found that the polarized emission likely …