Search Publications
MIFAL: fully automated Multiple-Image Finder ALgorithm for strong-lens modelling - proof of concept
Zitrin, Adi; Carrasco, Mauricio; Seidel, Gregor
We outline a simple procedure designed for automatically finding sets of multiple images in strong lensing (SL) clusters. We show that by combining (a) an arc-finding (or source extracting) program, (b) photometric redshift measurements, and (c) a preliminary light-traces-mass lens model, multiple-image systems can be identified in a fully automat…
Polarimetry of the superluminous transient ASASSN-15lh
Sollerman, J.; Maund, J. R.; Patat, F. +3 more
ASASSN-15lh is the intrinsically brightest transient observed to date. Despite being the subject of concerted photometric and spectroscopic observing campaigns, there is still significant debate about the true nature of this transient and the mechanism responsible for its great luminosity. Here we report five epochs of imaging polarimetry and two …
Individual optical variability of active galactic nuclei from the MEXSAS2 sample
Paolillo, M.; Middei, R.; Vagnetti, F. +1 more
At present, most of the variability studies of active galactic nuclei (AGNs) are based on ensemble analyses. Nevertheless, it is interesting to provide estimates of the individual variability properties of each AGN, in order to relate them with intrinsic physical quantities. A useful data set is provided by the Catalina Surveys Data Release 2 (CSD…
Calibrating the BHB star distance scale and the halo kinematic distance to the Galactic Centre
Utkin, Nikita D.; Dambis, Andrei K.
We report the first determination of the distance to the Galactic Centre based on the kinematics of halo objects. We apply the statistical-parallax technique to the sample of ~2500 blue horizontal branch (BHB) stars compiled by Xue et al. to simultaneously constrain the correction factor to the photometric distances of BHB stars as reported by tho…
A search for the modern counterparts of the Far Eastern guest stars 369 CE, 386 CE and 393 CE
Hoffmann, Susanne M.; Vogt, Nikolaus
In this study, we apply our previously developed method to investigate ancient transient sightings in order to derive consequences for modern astrophysical problems. We present case studies of three observations of so-called guest stars in the fourth century CE, which lasted several months each. These three observations had been discussed and sugg…
A survey for variable young stars with small telescopes - III. Warm spots on the active star V1598 Cyg
Scholz, Aleks; Eislöffel, Jochen; Froebrich, Dirk +1 more
Magnetic spots on low-mass stars can be traced and characterized using multiband photometric light curves. Here, we analyse an extensive data set for one active star, V1598 Cyg, a known variable K dwarf which is either pre-main sequence and/or in a close binary system. Our light curve contains 2854 photometric data points, mostly in V, Rc
The corona of GJ 1151 in the context of star-planet interaction
Schmitt, J. H. M. M.; Poppenhaeger, K.; Alvarado-Gómez, J. D. +1 more
The low-mass star GJ 1151 has been reported to display variable low-frequency radio emission, which has been interpreted as a signpost of coronal star-planet interactions with an unseen exoplanet. Here we report the first X-ray detection of GJ 1151's corona based on the XMM-Newton data. We find that the star displays a small flare during the X-ray…
Evidence for non-smooth quenching in massive galaxies at z ∼ 1
Whitaker, Katherine; Guo, Yicheng; Nayyeri, Hooshang +3 more
We investigate a large sample of massive galaxies at z ∼ 1 with combined Hubble Space Telescope (HST) broad-band and grism observations to constrain the star formation histories (SFHs) of these systems as they transition from a star-forming state to quiescence. Among our sample of massive (M_*> 10^{10} M_{⊙}) galaxies at 0.7 < z < 1.2, du…
TESS photometry of helium-rich hot subdwarfs: r modes in BD+37°442 and BD+37°1977
Jeffery, C. Simon
Transiting Exoplanet Survey Satellite photometry of the extremely helium-rich hot subdwarfs BD+37°442 and BD+37°1977 demonstrates multiperiodic low-amplitude variability with principal periods of 0.56 and 1.14 d, respectively, and with both first and second harmonics present. The light curves are not perfectly regular, implying additional periodic…
Analysis of absorption lines in the high-resolution spectra of five hot post-AGB candidates
Herrero, A.; Simón-Díaz, S.; Hubrig, S. +3 more
From an analysis of absorption lines in the high-resolution spectra, we have derived the radial velocities, stellar parameters (Teff, log g, wind-strength parameter log Q, and projected rotational velocity), and abundances (C, N, O, and Si) of IRAS 17460-3114, IRAS 18131-3008, IRAS 19336-0400, LSE 45, and LSE 163. Abundances are found t…