Search Publications
Constraints on the dust extinction law of the Galaxy with Swift/UVOT, Gaia, and 2MASS
Cropper, Mark; Charlot, Stéphane; Kawata, Daisuke +6 more
We explore variations of the dust extinction law of the Milky Way by selecting stars from the Swift/UVOT Serendipitous Source Catalogue, cross-matched with Gaia DR2 and 2MASS to produce a sample of 10 452 stars out to ~4 kpc with photometry covering a wide spectral window. The near ultraviolet passbands optimally encompass the 2175 Å bump, so that…
Signature and escape of highly fractionated plasma in an active region
Brooks, David H.; Yardley, Stephanie L.
Accurate forecasting of space weather requires knowledge of the source regions where solar energetic particles (SEP) and eruptive events originate. Recent work has linked several major SEP events in 2014, January, to specific features in the host active region (AR 11944). In particular, plasma composition measurements in and around the footpoints …
Particle-in-cell simulations of the Cassini spacecraft's interaction with Saturn's ionosphere during the Grand Finale
Shebanits, Oleg; Zhang, Zeqi; Desai, Ravindra T. +2 more
A surprising and unexpected phenomenon observed during Cassini's Grand Finale was the spacecraft charging to positive potentials in Saturn's ionosphere. Here, the ionospheric plasma was depleted of free electrons with negatively charged ions and dust accumulating up to over 95 per cent of the negative charge density. To further understand the spac…
Automatic identification of outliers in Hubble Space Telescope galaxy images
Shamir, Lior
Rare extragalactic objects can carry substantial information about the past, present, and future universe. Given the size of astronomical data bases in the information era, it can be assumed that very many outlier galaxies are included in existing and future astronomical data bases. However, manual search for these objects is impractical due to th…
Low-radio frequency observations of seven nearby galaxies with GMRT
Roy, Subhashis; Manna, Souvik
We have observed seven nearby large-angular-sized galaxies at 0.33 GHz using Giant Metrewave Radio Telescope with an angular resolution of ~10 arcsec and sub-mJy sensitivity. Using archival higher frequency data at 1.4 or ~6 GHz, we have then determined their spatially resolved non-thermal spectrum. As a general trend, we find that the spectral in…
Identification of emission-line stars in transition phase from pre-main sequence to main sequence
Mathew, Blesson; Kartha, Sreeja S.; Paul, K. T. +3 more
Pre-main-sequence (PMS) stars evolve into main-sequence (MS) phase over a period of time. Interestingly, we found a scarcity of studies in existing literature that examine and attempt to better understand the stars in PMS to MS transition phase. The purpose of this study is to detect such rare stars, which we named as 'transition phase' (TP) candi…
Evidence for Fe Kα line and soft X-ray lag in NGC 7456 ultraluminous X-ray source-1
Markowitz, Alex; Mondal, Samaresh; De Marco, Barbara +1 more
We report the first detection of an Fe Kα line and soft X-ray lag in the ultraluminous X-ray (ULX) source NGC 7456 ULX-1. The XMM-Newton spectra show the presence of the 6.4 keV Fe line at 2.6σ confidence and an upper limit on the FWHM of 32900 km s-1. Assuming that the line arises by reflection from a Keplerian disk, it must…
First detection of VHE gamma-ray emission from TXS 1515-273, study of its X-ray variability and spectral energy distribution
Maraschi, L.; Covino, S.; Antonelli, L. A. +196 more
We report here on the first multiwavelength (MWL) campaign on the blazar TXS 1515-273, undertaken in 2019 and extending from radio to very-high-energy gamma-rays (VHE). Up until now, this blazar had not been the subject of any detailed MWL observations. It has a rather hard photon index at GeV energies and was considered a candidate extreme high-s…
Thermodynamic evolution of a sigmoidal active region with associated flares
Mulay, Sargam M.; Tripathi, Durgesh; Mason, Helen
Active regions often show S-shaped structures in the corona called sigmoids. These are highly sheared and twisted loops formed along the polarity inversion line. They are considered to be one of the best pre-eruption signatures for CMEs. Here, we investigate the thermodynamic evolution of an on-disc sigmoid observed during 2015 December 24-28. For…
The nearby spiral density-wave structure of the Galaxy: line-of-sight velocities of the Gaia DR2 OB stars
Gedalin, Michael; Jiang, Ing-Guey; Griv, Evgeny
Distances and line-of-sight velocities of 964 Gaia Data Release 2 (DR2) OB stars of Xu et al. within 3 kpc from the Sun and 500 pc from the Galactic mid-plane with accuracies of <50 per cent are selected. The data are used to find small systematic departures of velocities from the mean circular motion for the stars in the solar neighborhood due…