Search Publications
Photometry and colour index of Comet 67P/Churyumov-Gerasimenko on 2015 December 12
Lasue, J.; Sen, A. K.; Gupta, R. +3 more
Comet 67P/Churyumov-Gerasimenko (hereafter, 67P) was observed on 2015 December 12, from 2 m Himalayan Chandra Telescope in India in photometry to study its dust properties, using Bessell R and I filters. We study the photometric images to highlight coma structures and jets. The radial decrease in intensity in the different coma structures is compa…
Infrared imaging of high-mass young stellar objects: evidence of multiple shocks and of a new protostar/star eclipsing system
Tapia, Mauricio; Persi, Paolo
We present deep near- and mid-infrared images of six high-mass young stellar objects (YSOs) in order to help understand the physical mechanisms of their formation. We have searched for shocked H2 emission around such massive protostars. All but one of these regions exhibit series of molecular hydrogen emission knots, either in perfect a…
AT 2017fvz: a nova in the dwarf irregular galaxy NGC 6822
Zheng, W.; Filippenko, A. V.; Henze, M. +7 more
A transient in the Local Group dwarf irregular galaxy NGC 6822 (Barnard's Galaxy) was discovered on 2017 August 2 and is only the second classical nova discovered in that galaxy. We conducted optical, near-ultraviolet, and X-ray follow-up observations of the eruption, the results of which we present here. This `very fast' nova had a peak V-band ma…
Ionization state of the accretion disc in the neutron star low-mass X-ray binary 4U 1728-34
Méndez, Mariano; Xiang, Fu-Yuan; Lyu, Ming +1 more
We analysed an XMM-Newton plus a simultaneous Rossi X-ray Timing Explorer observation and a separate Suzaku observation of the neutron star low-mass X-ray binary 4U 1728-34. We fitted the X-ray spectra with the self-consistent reflection model RELXILL. We found that the inclination angle of 4U 1728-34 is 49 ± 5 degree, consistent with the upper li…
Swift, NuStar, and XMM-Newton observations of the NLS1 galaxy RX J2317.8-4422 in an extreme X-ray low flux state
Fabian, Andrew C.; Komossa, S.; Miniutti, Giovanni +6 more
We report the discovery of RX J2317.8-4422 in an extremely low X-ray flux state by the Neil Gehrels Swift observatory in 2014 April/May. In total, the low-energy X-ray emission dropped by a factor of 100. We have carried out multiwavelength follow-up observations of this narrow-line Seyfert 1 galaxy. Here we present observations with Swift, XMM-Ne…
Multiwavelength survey of X-ray sources in the Sculptor Dwarf Spheroidal Galaxy
Barmby, P.; Maccarone, T. J.; Bahramian, A. +2 more
We present an unprecedented, deep study of the primordial low-mass X-ray binary population in an isolated, lower metallicity environment. We perform follow-up observations of previously identified X-ray binary candidates in the Sculptor Dwarf Galaxy by combining a second Chandra observation with Spitzer and Gemini photometry, as well as Gemini spe…
Characteristics of solar wind rotation
Li, K. J.; Feng, W.
Over 54 yr of hourly mean value of solar wind velocity from 1963 November 27 to 2017 December 31 are used to investigate characteristics of the rotation period of solar wind through autocorrelation analysis. Solar wind of high velocity is found to rotate faster than low-velocity wind, while its rotation rate increases with increasing velocity, but…
The evolving X-ray spectrum of active galactic nuclei: Evidence for an increasing reflection fraction with redshift
Ballantyne, D. R.; Avirett-Mackenzie, M. S.
The cosmic X-ray background (XRB) spectrum and active galaxy number counts encode essential information about the spectral evolution of active galactic nuclei (AGNs) and have been successfully modelled by XRB synthesis models for many years. Recent measurements of the 8-24 keV AGN number counts by NuSTAR and Swift-BAT are unable to be simultaneous…
Explaining the asymmetric line profile in Cepheus X-4 with spectral variation across pulse phase
Fürst, Felix; Pottschmidt, Katja; Ballhausen, Ralf +4 more
The high mass X-ray binary Cepheus X-4, during its 2014 outburst, showed evidence for an asymmetric cyclotron line in its hard X-ray spectrum. The 2014 spectrum provides one of the clearest cases of an asymmetric line profile among all studied sources with Cyclotron Resonance Scattering Features (CRSF). We present a phase-resolved analysis of NuST…
Erratum: MHD simulation of the solar wind flow around the coma of comet Churyumov-Gerasimenko during Rosetta's flyby
Baranov, V. B.; Alexashov, D. B.; Lebedev, M. G.