Search Publications
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…
A photospheric and chromospheric activity analysis of the quiescent retrograde-planet host ν Octantis A
Cantalloube, F.; Reffert, S.; Robertson, P. +4 more
The single-lined spectroscopic binary ν Octantis provided evidence of the first conjectured circumstellar planet demanding an orbit retrograde to the stellar orbits. The planet-like behaviour is now based on 1437 radial velocities (RVs) acquired from 2001 to 2013. ν Oct's semimajor axis is only 2.6 au with the candidate planet orbiting $\nu ~{\rm …
An extreme case of galaxy and cluster co-evolution at z = 0.7
Smail, I.; Koekemoer, A. M.; Richard, J. +3 more
We report the discovery of eMACS J0252.4-2100 (eMACS J0252), a massive and highly evolved galaxy cluster at z = 0.703. Our analysis of Hubble Space Telescope imaging and VLT/MUSE and Keck/DEIMOS spectroscopy of the system finds a high-velocity dispersion of 1020$^{+180}_{-190}$ km s-1 and a high (if tentative) X-ray luminosity of (1.2 ±…
The Hα line emission of the Be star β Psc: the last 40 yr
Diaz, Marcos P.; Amôres, Eduardo B.; Levenhagen, Ronaldo S. +1 more
A study on the photosphere and disc of the Be star β Psc is presented. We recover almost 40 yr of high-resolution spectroscopic observations and additional data gathered from the BeSS data base. We evaluate the photospheric parameters from the spectral energy distribution (SED) and fittings of state-of-the-art non-LTE model atmospheres to observed…
Searching for chemical abundance variations in young star clusters in the Magellanic Clouds: NGC 411, NGC 1718, and NGC 2213
Zucker, Daniel B.; de Grijs, Richard; Kapse, Shalmalee
The conventional picture of coeval, chemically homogeneous, populous star clusters - known as 'simple' stellar populations (SSPs) - is a view of the past. Photometric and spectroscopic studies reveal that almost all ancient globular clusters in the Milky Way and our neighbouring galaxies exhibit star-to-star light-element abundance variations, typ…
A search for pulsar companions around low-mass white dwarfs
Kramer, Michael; Athanasiadis, Tilemachos M.; Berezina, Marina +4 more
We report on a search for pulsars at the positions of eight low-mass white dwarfs and one higher mass white dwarf with the 100-m Effelsberg Radio Telescope. These systems have orbital parameters suggesting that their unseen companions are either massive white dwarfs or neutron stars (NSs). Our observations were performed at 1.36 GHz, reaching sens…
Blending and obscuration in weak-lensing magnification
Gaztanaga, E.; Schmidt, S. J.; Tyson, J. A. +1 more
We test the impact of some systematic errors in weak-lensing (WL) magnification measurements with the COSMOS 30-band photo-z Survey flux limited to Iauto < 25.0 using correlations of both source galaxy counts and magnitudes. Systematic obscuration effects are measured by comparing counts and magnification correlations. We use the Adv…
Pair lines of sight observations of multiphase gas bearing O VI in a galaxy environment
Beckett, Alexander; Morris, Simon L.; Muzahid, Sowgat +2 more
Using HST/COS spectra of the twin quasar lines of sight Q 0107-025A & Q 0107-025B, we report on the physical properties, chemical abundances, and transverse sizes of a multiphase medium in a galaxy field at z = 0.399. The angular separation between the quasars corresponds to a physical separation of 520 kpc at the absorber redshift. The absorb…
Spectroscopic and photometric analysis of the eclipsing binary HIP 7666 with δ Scuti pulsations
Esamdin, Ali; Wang, Liang; Cang, Tianqi +14 more
New multicolour photometric observations were carried out on 22 nights in three observation missions between 2015 October and 2016 February for eclipsing binary HIP 7666. High- and low-resolution spectroscopic observations were also carried out in the winters of 2015, 2016, and 2019, respectively. The fully phase-covered light curves and radial ve…
Radio/X-ray correlations and variability in the X-ray binary LS I +61°303
Kraus, A.; Chernyakova, M.; Malyshev, D. +6 more
The high-mass X-ray binary LS I +61°303 exhibits variability in its radio and X-ray emissions, ranging from minute to hour time-scales. At such short time-scales, not much is known about the possible correlations between these two emissions from this source, which might offer hints to their origin. Here, we study the relationship between these emi…