Search Publications
A novel approach to detect line emission under high background in high-resolution X-ray spectra
Karovska, Margarita; Zhang, Xiangyu; Kashyap, Vinay +1 more
We develop a novel statistical approach to identify emission features or set upper limits in high-resolution spectra in the presence of high background. The method relies on detecting differences from the background using smooth tests and using classical likelihood ratio tests to characterize known shapes like emission lines. We perform signal det…
A different view of wind in X-ray binaries: the accretion disc corona source 2S 0921-630
Done, Chris; Tanimoto, Atsushi; Odaka, Hirokazu +1 more
Accretion disc coronae (ADC) sources are very high inclination neutron star or black hole binaries, where the outer accretion flow blocks a direct view of the central source. The weak observed X-ray emission is instead produced mainly by scattering of the intrinsic radiation from highly ionized gas surrounding the source, the ADC. However, the ori…
Probing the jet size of two black hole X-ray binaries in the hard state
Miller-Jones, J. C. A.; Tingay, S. J.; Strader, J. +5 more
Using multifrequency very long baseline interferometry (VLBI) observations, we probe the jet size in the optically thick hard state jets of two black hole X-ray binary (BHXRB) systems, MAXI J1820+070 and V404 Cygni. Because of optical depth effects, the phase-referenced VLBI core positions move along the jet axis of the BHXRB in a frequency-depend…
Low-density star cluster formation: discovery of a young faint fuzzy on the outskirts of the low-mass spiral galaxy NGC 247
Janz, Joachim; van Dokkum, Pieter G.; Forbes, Duncan A. +21 more
The classical globular clusters found in all galaxy types have half-light radii of rh ~ 2-4 pc, which have been tied to formation in the dense cores of giant molecular clouds. Some old star clusters have larger sizes, and it is unclear if these represent a fundamentally different mode of low-density star cluster formation. We report the…
Looking for nebular He II emission south of the multiple-massive star system, HD 5980
Sander, A. A. C.; Wofford, A.; Peimbert, A. +1 more
The nebular He II λ1640 emission line is observed in star-forming galaxies out to large distances and can be used to constrain the properties of sources of He+-ionizing photons. For this purpose, it is crucial to understand which are the main stellar sources of these photons. In some nearby metal-poor starburst galaxies, nebular He II λ…
Origins of B-type stars at high Galactic latitudes based on abundances and kinematics
Zhao, Gang; Liu, Chao; Liu, Zhicun +3 more
The spectral analysis and kinematic studies of faint blue stars of O and B types above the mid-plane of the Milky Way can lead to a better understanding of their populations and origins. In this paper, we present an analysis of the chemical composition and kinematics of 17 B-type stars. Our sample includes 13 B-type stars with |Z| > 0.5 kpc and…
A large sample of newly identified carbon-deficient red giants from APOGEE
Zhao, Gang; Campbell, Simon W.; Reddy, Bacham E. +2 more
Based on the Apache Point Observatory Galactic Evolution Experiment survey we conducted a search for carbon-deficient red giants (CDGs). We found 103 new CDGs, increasing the number in the literature by more than a factor of 3. CDGs are very rare, representing 0.03 per cent of giants. They appear as an extended tail off the normal carbon distribut…
Exploring the short-term variability of H α and H β emissions in a sample of M dwarfs
Queiroz, A. B. A.; Fernández-Trincado, José G.; Kumar, Vipin +2 more
The time-scales of variability in active M dwarfs can be related to their various physical parameters. Thus, it is important to understand such variability to decipher the physics of these objects. In this study, we have performed the low resolution (~5.7 Å) spectroscopic monitoring of 83 M dwarfs (M0-M6.5) to study the variability of H α/H β emis…
The spectra of IceCube Neutrino (SIN) candidate sources - IV. Spectral energy distributions and multiwavelength variability
Giommi, Paolo; Padovani, Paolo; Karl, Martina
We present hybrid spectral energy distributions, combining photon, and neutrino fluxes, for a sample of blazars, which are candidate IceCube neutrino sources. We furthermore check for differences in our sources' variability in the near-infrared, optical, X-ray, and γ-ray bands compared to a sample of non-neutrino source candidate blazars, and inve…
A search for Kuiper belt occultations using the Weizmann Fast Astronomical Survey Telescope
Ofek, Eran O.; Polishook, David; Nir, Guy +2 more
Measuring the size distribution of small (kilometre-scale) Kuiper belt objects (KBOs) can help constrain models of Solar system formation and planetary migration. Such small, distant bodies are hard to detect with current or planned telescopes, but can be identified as sub-second occultations of background stars. We present the analysis of data fr…