Search Publications
Discovery of a resolved white dwarf-brown dwarf binary with a small projected separation: SDSS J222551.65+001637.7AB
Debes, John H.; Manjavacas, Elena; Dupuy, Trent J. +4 more
We present the confirmation of SDSS J222551.65+001637.7AB as a closely separated, resolved, white dwarf-brown dwarf binary. We have obtained spectroscopy from GNIRS and seeing-limited Ks-band imaging from NIRI on Gemini North. The target is spatially resolved into its constituent components: a 10926 ± 246 K white dwarf, with log g = 8.2…
A critique of the Spite Plateau and the astration of primordial lithium
Yong, D.; Norris, J. E.; Frebel, A. +1 more
We investigate the distribution of the lithium abundances, A(Li), of metal-poor dwarf and subgiant stars within the limits 5500 K < Teff < 6700 K, -6.0 < [Fe/H] < -1.5, and log g ≳ 3.5 (a superset of parameters first adopted by Spite and Spite), using literature data for some 200 stars. We address the problem of the several …
A unified exploration of the chronology of the Galaxy
Stokholm, Amalie; Stello, Dennis; Hon, Marc +2 more
The Milky Way has distinct structural stellar components linked to its formation and subsequent evolution, but disentangling them is non-trivial. With the recent availability of high-quality data for a large numbers of stars in the Milky Way, it is a natural next step for research in the evolution of the Galaxy to perform automated explorations wi…
Analysis of the ionized interstellar medium and orbital dynamics of PSR J1909-3744 using scintillation arcs
Shannon, R. M.; Askew, J.; Reardon, D. J.
Long-term studies of binary millisecond pulsars (MSPs) provide precise tests of strong-field gravity, and can be used to measure neutron-star masses. PSR J1909-3744, a binary MSP has been the subject of several pulsar timing analyses. The edge-on orbit enables measurement of its mass using the Shapiro delay; however, there is degeneracy in the sen…
Propeller states in locally supercritical ULXs
Walton, D. J.; Middleton, M.; Gúrpide, A.
An expected signature of the presence of neutron stars in the population of ultraluminous X-ray sources (ULXs) are large scale changes in X-ray luminosity, as systems reach spin equilibrium and a propeller state ensues. We explore the predicted luminosity changes when the disc is locally supercritical, finding that a significant parameter space in…
Tentative detection of titanium oxide in the atmosphere of WASP-69 b with a 4m ground-based telescope
Zhao, Gang; Wang, Wei; Zhao, Fei +6 more
Transiting planets provide unique opportunities for the atmospheric characterization of exoplanets as they can reveal composition and the temperature structures at the day-night terminator regions in planetary atmospheres, and help understand the atmospheric process and formation environments of exoplanets. Here, we present the optical transmissio…
Robust clustering of the local Milky Way stellar kinematic substructures with Gaia eDR3
Frebel, Anna; Necib, Lina; Ou, Xiaowei
Understanding local stellar kinematic substructures in the solar neighbourhood helps build a complete picture of the formation of the Milky Way, as well as an empirical phase space distribution of dark matter that would inform detection experiments. We apply the clustering algorithm HDBSCAN on the Gaia early third data release to identify a list o…
Planetary nebulae and supernova remnants in NGC 4214 from the SIGNALS survey
Vicens-Mouret, Sébastien; Drissen, Laurent; Robert, Carmelle +3 more
Using datacubes from the imaging Fourier transform spectrometer SITELLE at the Canada-France-Hawaii Telescope as part of the star formation, ionized gas, and nebular abundances legacy survey, we identify 15 new planetary nebulae (PNe) as well as five new supernova remnants (SNRs) in the outer parts of the nearby dwarf starburst galaxy NGC 4214. Th…
An XMM-Newton study of six narrow-line Seyfert 1 galaxies at z = 0.35-0.92
Fabian, Andrew C.; Brandt, William N.; Reynolds, Christopher S. +5 more
We report a detailed analysis of the XMM-Newton spectra of six narrow-line Seyfert 1 (NLS1) galaxies at redshift z = 0.35-0.92. Compared with the NLS1s at lower redshift in the previously most-studied sample, these NLS1s have larger black hole (BH) masses ($\log \, M_\mathrm{BH}\gt 7.5$ ) with similar or even lower Eddington ratios. Our extended X…
Pulse frequency fluctuations of persistent accretion powered pulsars
Serim, M. M.; Baykal, A.; Serim, D.
In this study, we examine the long-term torque noise fluctuations of persistent X-ray binaries Her X-1, Vela X-1, GX 301-2, Cen X-3, 4U 1538-53, OAO 1657-415, and 4U 1626-67 using the historical pulse frequency measurements provided by CGRO/BATSE and Fermi/GBM. We find that known disc-fed sources exhibit a 1/ω2 red noise component in th…