Search Publications
A long serendipitous XMM-Newton observation of the intermediate polar XY Ari1
Burwitz, V.; Balman, Ş.; Zengin Ćamurdan, D.
XY Ari is one of the few known eclipsing intermediate polars. We present results from a detailed analysis of an unpublished archival observation using XMM-Newton EPIC pn and MOS data in a quiescent state of XY Ari. The X-ray orbital modulation and spin-pulse variations were investigated for energy-dependent modulations in different energy bands. T…
A Chandra X-ray census of the interacting binaries in old open clusters - NGC 188
Wijnands, Rudy; van den Berg, Maureen; Vats, Smriti
We present a new X-ray study of NGC 188, one of the oldest open clusters known in our Galaxy (7 Gyr). Our observation with the Chandra X-ray Observatory is aimed at uncovering the population of close interacting binaries in NGC 188. We detect 84 sources down to a luminosity of LX ≈ 4 × 1029 erg s-1 (0.3-7 keV), of …
First speckle interferometric measurements at the Observatório do Pico dos Dias of the Laboratório Nacional de Astrofísica
Borges Fernandes, M.; Guerrero, C. A.; Souza, T. B. +2 more
In this paper we present the first speckle interferometric measurements of binary stars performed at the Observatório do Pico dos Dias of the Laboratório Nacional de Astrofísica in Brazil, using the 1.60 m Perkin-Elmer telescope. In order to carry out these observations, we had to perform an opto-mechanical modification to Camera 1 of the 1.60 m t…
Discovery of a radio nebula around PSR J0855-4644
Acero, F.; Maitra, C.; Roy, S. +1 more
We report the discovery of a diffuse radio emission around PSR J0855-4644 using an upgraded GMRT (uGMRT) observation at 1.35 GHz. The radio emission is spatially coincident with the diffuse X-ray pulsar wind nebula (PWN) seen with XMM-Newton but is much larger in extent compared to the compact axisymmetric PWN seen with Chandra. The morphology of …
Simulating radiative magnetohydrodynamical flows with ASTROBEAR: implementation and applications of non-equilibrium cooling
Raymond, J. C.; Hansen, E. C.; Hartigan, P. +2 more
Radiative cooling plays a crucial role in the dynamics of many astrophysical flows, and is particularly important in the dense shocked gas within Herbig-Haro (HH) objects and stellar jets. Simulating cooling processes accurately is necessary to compare numerical simulations with existing and planned observations of HH objects, such as those from t…
The Bursting Pulsar GRO J1744-28: the slowest transitional pulsar?
Court, J. M. C.; Altamirano, D.; Sanna, A.
GRO J1744-28 (the Bursting Pulsar) is a neutron star low-mass X-ray binary which shows highly structured X-ray variability near the end of its X-ray outbursts. In this letter we show that this variability is analogous to that seen in Transitional Millisecond Pulsars such as PSR J1023+0038: `missing link' systems consisting of a pulsar nearing the …
The first optical spectra of Wolf-Rayet stars in M101 revealed with Gemini/GMOS
Crowther, P. A.; Long, K. S.; Moffat, A. F. J. +4 more
Deep narrow-band Hubble Space Telescope (HST) imaging of the iconic spiral galaxy M101 has revealed over a thousand new Wolf-Rayet (WR) candidates. We report spectrographic confirmation of 10 He II-emission line sources hosting 15 WR stars. We find WR stars present at both sub- and super-solar metallicities with WC stars favouring more metal-rich …
The star-forming cores in the centre of the Trifid nebula (M 20): from Herschel to the near-infrared
Elia, D.; Giovannelli, F.; Persi, P. +3 more
A new detailed infrared (IR) study of eight star-forming dense condensations (TCs) in M 20, the Trifid nebula, is presented. The aim is to determine the physical properties of the dust in such globules and establish the presence and properties of their embedded protostellar and/or young stellar population. For this, we analysed new Herschel far-IR…
The failed state transition of the ATOLL source GRS 1724-308
Capitanio, F.; Tarana, A.; Cocchi, M.
The 2004-2012 X-ray time history of the NS LMXB GRS 1724-308 shows, along with the episodic brightenings associated with the low-high state transitions typical of the ATOLL sources, a peculiar, long lasting (∼300 d) flaring event, observed in 2008. This rare episode, characterized by a high-flux hard state, has never been observed before for GRS 1…
Exploring the nature and synchronicity of early cluster formation in the Large Magellanic Cloud - III. Horizontal branch morphology
Cohen, Roger E.; Wagner-Kaiser, R.; Sarajedini, Ata +5 more
We leverage new high-quality data from Hubble Space Telescope program GO-14164 to explore the variation in horizontal branch morphology among globular clusters in the Large Magellanic Cloud (LMC). Our new observations lead to photometry with a precision commensurate with that available for the Galactic globular cluster population. Our analysis ind…