Search Publications
The Chameleon on the branches: spectral state transition and dips in NGC 247 ULX-1
Fabian, A. C.; Pinto, C.; D'Aì, A. +14 more
Soft Ultra-Luminous X-ray (ULXs) sources are a subclass of the ULXs that can switch from a supersoft spectral state, where most of the luminosity is emitted below 1 keV, to a soft spectral state with significant emission above 1 keV. In a few systems, dips have been observed. The mechanism behind this state transition and the dips nature are still…
Origin of metals in old Milky Way halo stars based on GALAH and Gaia
Kobayashi, Chiaki; Tominaga, Nozomu; Nomoto, Ken'ichi +6 more
Stellar and supernova nucleosynthesis in the first few billion years of the cosmic history have set the scene for early structure formation in the Universe, while little is known about their nature. Making use of stellar physical parameters measured by GALAH Data Release 3 with accurate astrometry from the Gaia EDR3, we have selected ~100 old main…
An enquiry on the origins of N-rich stars in the inner Galaxy based on APOGEE chemical compositions
Bizyaev, Dmitry; Brownstein, Joel R.; Pan, Kaike +10 more
Recent evidence based on APOGEE data for stars within a few kpc of the Galactic Centre suggests that dissolved globular clusters (GCs) contribute significantly to the stellar mass budget of the inner halo. In this paper, we enquire into the origins of tracers of GC dissolution, N-rich stars, that are located in the inner 4 kpc of the Milky Way. Fr…
A search for trends in spatially resolved debris discs at far-infrared wavelengths
Marshall, J. P.; Wang, L.; Kennedy, G. M. +2 more
Debris discs around main-sequence stars are belts of planetesimals - asteroids and comets - formed in the protoplanetary discs around young stars. Planetesimals comprise both the building blocks of planets around young stars and the source of dusty debris around older stars. Imaging observations of dust continuum emission and scattered light revea…
Creation/destruction of ultra-wide binaries in tidal streams
Peñarrubia, Jorge
This paper uses statistical and N-body methods to explore a new mechanism to form binary stars with extremely large separations ( ${\gtrsim}0.1\, {\rm pc}$ ), whose origin is poorly understood. Here, ultra-wide binaries arise via chance entrapment of unrelated stars in tidal streams of disrupting clusters. It is shown that (i) the formation of ult…
Multiband variability of the TeV blazar PG 1553+113 with XMM-Newton
Gupta, Alok C.; Wiita, Paul J.; Gaur, Haritma +1 more
We present variability analyses of twenty pointed XMM-Newton observations of the high energy peaked TeV blazar PG 1553+113 taken during 2010-2018. We found intraday variability in the total X-ray energy range (0.3-10 keV) in 16 out of 19 light curves or a duty cycle of ~84 per cent. A discrete correlation function analysis of the intraday light cu…
The X-ray evolution and geometry of the 2018 outburst of XTE J1810-197
Tiengo, A.; Götz, D.; Mereghetti, S. +17 more
After 15 yr, in late 2018, the magnetar XTE J1810-197 underwent a second recorded X-ray outburst event and reactivated as a radio pulsar. We initiated an X-ray monitoring campaign to follow the timing and spectral evolution of the magnetar as its flux decays using Swift, XMM-Newton, NuSTAR, and NICER observations. During the year-long campaign, th…
A deep learning approach to quasar continuum prediction
Liu, Bin; Bordoloi, Rongmon
We present a novel intelligent quasar continuum neural network (iQNet), predicting the intrinsic continuum of any quasar in the rest-frame wavelength range of $1020 \, {\mathring{\rm A}}\le \lambda _{\text{rest}} \le 1600 \, {\mathring{\rm A}}$ . We train this network using high-resolution Hubble Space Telescope/Cosmic Origin Spectrograph ultravio…
The Pristine survey - XIV. Chemical analysis of two ultra-metal-poor stars
Bonifacio, P.; Caffau, E.; Jablonka, P. +15 more
Elemental abundances of the most metal-poor stars reflect the conditions in the early Galaxy and the properties of the first stars. We present a spectroscopic follow-up of two ultra-metal-poor stars ([Fe/H] < -4.0) identified by the survey Pristine: Pristine 221.8781+9.7844 and Pristine 237.8588+12.5660 (hereafter Pr 221 and Pr 237, respectivel…
The symbiotic recurrent nova V3890 Sgr: binary parameters and pre-outburst activity
Udalski, A.; Mikołajewska, J.; Iłkiewicz, K. +4 more
We present and analyse optical photometry and high-resolution Southern African Large Telescope spectra of the symbiotic recurrent nova V3890 Sgr at quiescence. The orbital period, P = 747.6 d, has been derived from both photometric and spectroscopic data. Our double-line spectroscopic orbits indicate that the mass ratio is q = Mg/M…