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The molecular H2 and stellar discs in the nuclear region of NGC 4258
Steiner, J. E.; Menezes, R. B.; da Silva, Patrícia
NGC 4258 is an SABbc Seyfert galaxy, located at a distance of 7.2 ± 0.3 Mpc. This object is well known by its nearly edge-on molecular nuclear disc, located between 0.16 and 0.28 pc from the nucleus, whose H2O maser emission allows a very precise measurement of the central supermassive black hole mass (M•(maser) = 3.78 ± 0.01…
Searching for new young stars in the Northern hemisphere: the Pisces moving group
Jeffries, R. D.; Binks, A. S.; Ward, J. L.
Using the kinematically unbiased technique described in Binks, Jeffries & Maxted (2015), we present optical spectra for a further 122 rapidly rotating (rotation periods <6 d), X-ray active FGK stars, selected from the SuperWASP survey. We identify 17 new examples of young, probably single stars with ages of <200 Myr and provide additiona…
The photocentre-AGN displacement: is M87 actually harbouring a displaced supermassive black hole?
Prieto, M. A.; López-Navas, E.
M87 has been identified as a displaced supermassive black hole (SMBH) candidate. We investigated this possibility by a temporal analysis of 12 adaptive-optics assisted VLT and HST images spanning 20 yr. We found that the centre of the isophotal fitting to the nuclear region of M87 - assumed to mark the centre of mass of the galaxy - changes locati…
Blue straggler stars beyond the Milky Way: a non-segregated population in the Large Magellanic Cloud cluster NGC 2213
Hong, Jongsuk; Li, Chengyuan
Using the high-resolution observations obtained by the Hubble Space Telescope, we analysed the blue straggler stars (BSSs) in the Large Magellanic Cloud cluster NGC 2213. We found that the radial distribution of BSSs is consistent with that of the normal giant stars in NGC 2213, showing no evidence of mass segregation. However, an analytic calcula…
The nature of the Stingray nebula from radio observations
De Marco, Orsola; Cunningham, Maria; Harvey-Smith, Lisa +5 more
We have analysed the full suite of Australia Telescope Compact Array data for the Stingray planetary nebula. Data were taken in the 4-23 GHz range of radio frequencies between 1991 and 2016. The radio flux density of the nebula generally declined during that period, but between 2013 and 2016 it shows signs of halting that decline. We produced the …
Bulk Comptonization: new hints from the luminous blazar 4C+25.05
Ghisellini, G.; Behar, E.; Nardini, E. +3 more
Blazars are often characterized by a spectral break at soft X-rays, whose origin is still debated. While most sources show a flattening, some exhibit a blackbody-like soft excess with temperatures of the order of ∼0.1 keV, similar to low-luminosity, non-jetted Seyferts. Here, we present the analysis of the simultaneous XMM-Newton and NuSTAR observ…
A 149 min periodicity underlies the X-ray flaring of Sgr A*
Leibowitz, Elia
In a paper in 2017, I have shown that 39 large X-ray flares of Sgr A* that were recorded by Chandra observatory in the year 2012 are concentrated preferably around tick marks of an equi-distance grid on the time axis. The period of this grid as found in that paper is 0.1033 d. In this work I show that the effect can be found among all the large X-…
Cosmic happenstance: 24-µm selected, multicomponent Herschel sources are line-of-sight projections
Oliver, Seb; Wang, Lingyu; Wardlow, Julie L. +3 more
In this paper, we investigate the physical associations between blended far-infrared (FIR)-emitting galaxies, in order to identify the level of line-of-sight projection contamination in the single-dish Herschel data. Building on previous work, and as part of the Herschel Extragalactic Legacy Project, we identify a sample of galaxies in the COSMOS …
Pulsations and period variations of the δ Scuti star AN Lyncis in a possible three-body system
Li, Gang; Su, Jie; Fu, Jianning +5 more
Observations for the δ Scuti star AN Lyn have been made between 2008 and 2016 with the 85-cm telescope at Xinglong station of National Astronomical Observatories of China, the 84-cm telescope at SPM Observatory of Mexico and the Nanshan One metre Wide field Telescope of Xinjiang Observatory of China. Data in V in 50 nights and in R in 34 nights ar…
An ultraviolet study of B[e] stars: evidence for pulsations, luminous blue variable type variations and processes in envelopes
Krtička, J.; Krtičková, I.
Stars that exhibit a B[e] phenomenon comprise a very diverse group of objects in a different evolutionary status. These objects show common spectral characteristics, including the presence of Balmer lines in emission, forbidden lines and strong infrared excess due to dust. Observations of emission lines indicate illumination by an ultraviolet ioni…