Search Publications
Spectroscopic analysis of BPS CS 22940-0009: connecting evolved helium stars
Jeffery, C. S.; Woolf, V. M.; Snowdon, E. J. +1 more
BPS CS 22940-0009 is a helium-rich B-star that shares characteristics with both helium-rich B subdwarfs and extreme helium stars. The optical spectrum of BPS CS 22940-0009 has been analysed from SALT observations. The atmospheric parameters were found to be $T_{\rm eff} = 34\, 970 \pm 370$ K, $\log g/{\rm cm\, s^{-2}} = 4.79 \pm 0.17$, nH
Improved binary solution for the gamma-ray binary 1FGL J1018.6-5856
Monageng, I. M.; van Soelen, B.; Chernyakova, M. +4 more
The gamma-ray binary 1FGL J1018.6-5856 consists of an O6V((f)) type star and an unknown compact object, and shows orbitally modulated emission from radio to very high energy gamma rays. The X-ray light curve shows a maximum around the same phase as the GeV emission, but also a secondary maximum between phases ϕ = 0.2 and 0.6. A clear solution to t…
Tracing Milky Way substructure with an RR Lyrae hierarchical clustering forest
Mahabal, Ashish A.; Rebbapragada, Umaa; Cook, Brian T. +6 more
RR Lyrae variable stars have long been reliable standard candles used to discern structure in the Local Group. With this in mind, we present a routine to identify groupings containing a statistically significant number of RR Lyrae variables in the Milky Way environment. RR Lyrae variable groupings, or substructures, with potential Galactic archaeo…
Orbital solution and dynamical masses for the nearby binary system GJ 67 AB
Torres, Guillermo
We report spectroscopic observations of the nearby, 19.5-yr binary system GJ 67AB spanning more than 35 yr. We carry out a global orbital solution combining our radial-velocity measurements with others from the literature going back more than a century, and with all other available astrometric observations. The latter include measurements of the r…
Mass assembly history of dark matter haloes in the light of H0 tension
Kameli, Hamed; Baghram, Shant
The Hubble tension may introduce a new course of action to revise the standard Lambda cold dark matter (ΛCDM) model to unravel dark energy and dark matter physics. The Hubble parameter can be reconstructed by late-time observations of the background evolution model independently. We relate the reconstructed Hubble parameter to the structure format…
Understanding the physical state of hot plasma formed through stellar wind collision in WR140 using high-resolution X-ray spectroscopy
Hamaguchi, Kenji; Miyamoto, Asca; Sugawara, Yasuharu +5 more
We analyse a series of XMM-Newton RGS data of the binary Wolf-Rayet star WR140 that encompasses one entire orbit. We find that the RGS detects X-rays from optically thin thermal plasma only during orbital phases when the companion O star is on the near side of the WR star. Although such X-rays are believed to be emitted from the shock cone formed …
Searching for giant planets in the outer Solar system with far-infrared all-sky surveys
Serjeant, Stephen; Sedgwick, Chris
We have explored a method for finding giant planets in the outer Solar system by detecting their thermal emission and proper motion between two far-infrared all-sky surveys separated by 23.4 yr, taken with the InfraRed Astronomical Satellite (IRAS) and the AKARI Space Telescope. An upper distance limit of about 8000 AU is given by both the sensiti…
SDSS-IV MaNGA: Identification and multiwavelength properties of Type-1 AGN in the DR15 sample
Negrete, C. A.; Hernández-Toledo, H. M.; Ibarra-Medel, H. +2 more
We present a method to identify type-1 active galactic nuclei (AGNs) in the central 3 arcsec integrated spectra of galaxies in the MaNGA DR15 sample. It is based on flux ratios estimates in spectral bands flanking the expected H α broad component H αBC. The high signal-to-noise ratio obtained (mean S/N = 84) permits the identification o…
The changing-look AGN NGC 1566 in quiescence with XMM-Newton: a nuclear starburst and an AGN competing in power?
Santos-Lleó, M.; Ballo, L.; Jiménez Bailón, E. +8 more
Star formation accretion on to the super massive black holes (SMBHs) and feedback processes link the evolution of galaxies with their SMBHs. X-ray observations in the imaging and spectral regime have revealed to be an important tool to study the connection between nuclear activity and circumnuclear star formation in nearby active galactic nuclei (…
Gamma-ray light curves and spectra of classical novae
Siegert, Thomas; Leung, Shing-Chi
The nucleosynthesis in classical novae, in particular that of radioactive isotopes, is directly measurable by its γ-ray signature. Despite decades of observations, MeV γ-rays from novae have never been detected - neither individually at the time of the explosion, nor as a result of radioactive decay, nor the diffuse Galactic emission from the nova…