Search Publications
Relativistic reflection spectra of super-spinning black holes
Tripathi, Ashutosh; Zhou, Biao; Abdikamalov, Askar B. +4 more
We construct a relativistic reflection model in a non-Kerr spacetime in which, depending on the value of the deformation parameter of the metric, there are black hole solutions with spin parameter | a∗|>1 . We apply our model to fit Suzaku data of four Seyfert galaxies (Ton S180, Ark 120, 1H0419-577, and Swift J0501.9-3239). These ga…
The nature of 500 micron risers I: SMA observations
Pérez-Fournon, I.; Clements, D. L.; Conley, A. +4 more
We present SMA observations at resolutions from 0.35 to 3 arcsec of a sample of 34 candidate high redshift dusty star forming galaxies (DSFGs). These sources were selected from the HerMES Herschel survey catalogues to have SEDs rising from 250 to 350 to 500 µm, a population termed 500-risers. We detect counterparts to 24 of these sources, wi…
Accurate mass estimates from the proper motions of dispersion-supported galaxies
Bullock, James S.; Lazar, Alexandres
We derive a new mass estimator that relies on internal proper motion measurements of dispersion-supported stellar systems, one that is distinct and complementary to existing estimators for line-of-sight velocities. Starting with the spherical Jeans equation, we show that there exists a radius where the mass enclosed depends only on the projected t…
MADX - a simple technique for source detection and measurement using multiband imaging from the Herschel-ATLAS survey
Dunne, L.; Maddox, S. J.
We describe the method used to detect sources for the Herschel-ATLAS (Herschel Astrophysical Terahertz Large Area Survey) survey. The method is to filter the individual bands using a matched filter, based on the point spread function (PSF) and confusion noise, and then form the inverse variance-weighted sum of the individual bands, including weigh…
Evolution of supersonic downflows in a sunspot
Mathioudakis, M.; Krishna Prasad, S.; Nelson, C. J.
Context. Supersonic downflows have been observed in transition region spectra above numerous sunspots, however, little research has been conducted to date into how persistent these signatures are within sunspots on timescales longer than a few hours.
Aims: We aim to analyse the lead sunspot of AR 12526 to infer the properties and evolution of…
The Demagnetization of the Venusian Ionosphere under Nearly Flow-aligned Interplanetary Magnetic Fields
Xu, Qi; Zhang, Tielong; Xu, Xiaojun +4 more
Previous studies suggested that the interplanetary magnetic field (IMF) has a significant influence on the Venusian-induced magnetosphere. We present observations by Venus Express under a nearly flow-aligned IMF condition to investigate the demagnetization of the Venusian ionosphere. Our results show that the magnetic barrier becomes weak and narr…
A survey for variable young stars with small telescopes: II - mapping a protoplanetary disc with stable structures at 0.15 au
Scholz, Aleks; Eislöffel, Jochen; Dvorak, Shawn +57 more
The HOYS citizen science project conducts long-term, multifilter, high-cadence monitoring of large YSO samples with a wide variety of professional and amateur telescopes. We present the analysis of the light curve of V1490 Cyg in the Pelican Nebula. We show that colour terms in the diverse photometric data can be calibrated out to achieve a median…
Seismic solar models from Ledoux discriminant inversions
Buldgen, G.; Eggenberger, P.; Christensen-Dalsgaard, J. +6 more
Context. The Sun constitutes an excellent laboratory of fundamental physics. With the advent of helioseismology, we were able to probe its internal layers with unprecendented precision and thoroughness. However, the current state of solar modelling is still stained by tedious issues. One of these central problems is related to the disagreement bet…
How faculae and network relate to sunspots, and the implications for solar and stellar brightness variations
Solanki, S. K.; Yeo, K. L.; Krivova, N. A.
Context. How global faculae and network coverage relates to that of sunspots is relevant to the brightness variations of the Sun and Sun-like stars.
Aims: We aim to extend and improve on earlier studies that established that the facular-to-sunspot-area ratio diminishes with total sunspot coverage.
Methods: Chromospheric indices and the t…
An eclipsing M-dwarf close to the hydrogen burning limit from NGTS
Wheatley, Peter J.; Bayliss, Daniel; Moyano, Maximiliano +20 more
We present the discovery of NGTS J0930-18, an extreme mass ratio eclipsing M-dwarf binary system with an early M-dwarf primary and a late M-dwarf secondary close to the hydrogen burning limit. Global modelling of photometry and radial velocities reveals that the secondary component (NGTS J0930-18 B) has a mass of M* = $0.0818 ^{+0.0040}…