Search Publications
An investigation of the causal relationship between sunspot groups and coronal mass ejections by determining source active regions
Wang, Haimin; Wang, Jason T. L.; Cavus, Huseyin +3 more
Although the source active regions of some coronal mass ejections (CMEs) were identified in CME catalogues, vast majority of CMEs do not have an identified source active region. We propose a method that uses a filtration process and machine learning to identify the sunspot groups associated with a large fraction of CMEs and compare the physical pa…
High-resolution imaging follow-up of doubly imaged quasars
Treu, Tommaso; Wisotzki, Lutz; Fassnacht, Christopher D. +8 more
We report upon 3 years of follow-up and confirmation of doubly imaged quasar lenses through imaging campaigns from 2016 to 2018 with the Near-Infrared Camera2 (NIRC2) on the W. M. Keck Observatory. A sample of 57 quasar lens candidates are imaged in adaptive-optics-assisted or seeing-limited K'-band observations. Out of these 57 candida…
Red Be stars in the Magellanic Clouds?
Vieira, Katherine; Hernández, Jesús; García-Varela, Alejandro +2 more
We revisit the subject of Be candidate stars towards the Magellanic Clouds, previously studied by the authors using SPM4 proper motions. We obtain Gaia DR2 parallaxes and proper motions for 2357 and 994 LMC and SMC Be candidates, respectively. Parallaxes and proper motions versus colour V - I easily reveal the presence of the redder galactic conta…
Convex X-ray spectra of PKS 2155-304 and constraints on the minimum electron energy
Ravikumar, C. D.; Jagan, Sitha K.; Sahayanathan, S. +1 more
The convex (concave upward) high-energy X-ray spectra of the blazar PKS 2155-304, observed by XMM-Newton, is interpreted as the signature of subdominant inverse-Compton emission. The spectra can be well fitted by a superposition of two power-law contributions which imitate the emission due to synchrotron and inverse-Compton processes. The methodol…
Detailed studies of IPHAS sources - II. Sab 19, a true planetary nebula and its mimic crossing the Perseus Arm
Guerrero, M. A.; Ramos-Larios, G.; Sabin, L. +2 more
The INT Photometric Hα Survey (IPHAS) has provided us with a number of new emission-line sources, among which planetary nebulae (PNe) constitute an important fraction. Here we present a detailed analysis of the IPHAS nebula Sab 19 (IPHASX J055242.8+262116) based on radio, infrared, and optical images and intermediate- and high-dispersion long-slit…
A source of gamma rays coincident with the shell of the supernova remnant CTB 80
Araya, M.; Herrera, C.
CTB 80 (G69.0+2.7) is a relatively old (50-80 kyr) supernova remnant (SNR) with a complex radio morphology showing three extended radio arms and a radio and X-ray nebula near the location of the pulsar PSR B1951+32. We report on a study of the GeV emission in the region of CTB 80 with Fermi-Large Area Telescope data. An extended source with a size…
The cold dust content of the nearby galaxies IC 5325, NGC 7496, NGC 7590, and NGC 7599
Crawford, T. M.; Vieira, J. D.; Ashby, M. L. N. +6 more
Star-forming galaxies are rich reservoirs of dust, both warm and cold. But the cold dust emission is faint alongside the relatively bright and ubiquitous warm dust emission. Recently, evidence for a very cold dust (VCD) component has also been revealed via millimetre/submillimetre (mm/sub-mm) photometry of some galaxies. This component, despite be…
The flare-activity of 2MASS J16111534-1757214 in the upper Scorpius association
Guenther, E. W.; Chaturvedi, P.; Muheki, P. +3 more
Flares are known to play an important role for the evolution of the atmospheres of young planets. In order to understand the evolution of planets, it is thus important to study the flare-activity of young stars. This is particularly the case for young M‑stars, because they are very active. We study photometrically and spectroscopically the highly …
Feedback factory: multiple faint radio jets detected in a cluster at z = 2
Daddi, Emanuele; Finoguenov, Alexis; Elbaz, David +8 more
We report the detection of multiple faint radio sources, that we identify as active galactic nucleus (AGN) jets, within CLJ1449+0856 at z = 2 using 3 GHz Very Large Array observations. We study the effects of radio-jet-based kinetic feedback at high redshifts, which has been found to be crucial in low-redshift clusters to explain the observed ther…
Spatial statistics in star-forming regions: is star formation driven by column density alone?
Naylor, T.; Hatchell, J.; Retter, B.
Star formation is known to occur more readily where more raw materials are available. This is often expressed by a 'Kennicutt-Schmidt' relation where the surface density of young stellar objects (YSOs) is proportional to column density to some power, µ. The aim of this work was to determine if column density alone is sufficient to explain th…