Search Publications
A broad-band look of the accreting millisecond X-ray pulsar SAX J1748.9-2021 using AstroSat and XMM-Newton
Beri, Aru; Sanna, Andrea; Dutta, Anjan +1 more
SAX J1748.9-2021 is a transient accretion powered millisecond X-ray pulsar located in the globular cluster NGC 6440. We report on the spectral and timing analysis of SAX J1748.9-2021 performed on AstroSat data taken during its faint and short outburst of 2017. We derived the best-fitting orbital solution for the 2017 outburst and obtained an avera…
Radial variation of the stellar mass functions in the globular clusters M15 and M30: clues of a non-standard IMF?
Dalessandro, E.; Monaco, L.; Beccari, G. +5 more
We exploit a combination of high-resolution Hubble Space Telescope and wide-field ESO-VLT observations to study the slope of the global mass function (αG) and its radial variation (α(r)) in the two dense, massive and post core-collapse globular clusters M15 and M30. The available data set samples the clusters' main sequence down to ∼0.2…
Rest-frame UV properties of luminous strong gravitationally lensed Lyα emitters from the BELLS GALLERY Survey
Pérez-Fournon, I.; Poidevin, F.; Shirley, R. +15 more
We present deep rest-frame UV spectroscopic observations using the Gran Telescopio Canarias of six gravitationally lensed Lyα emitters (LAEs) at 2.36 < z < 2.82 selected from the BELLS GALLERY survey. By taking the magnifications into account, we show that LAEs can be as luminous as LLyα ≃ 30 × 1042 erg s-1 a…
Discarding the disc in a changing-state AGN: the UV/X-ray relation in NGC 4151
Done, Chris; Mahmoud, Ra'ad D.
Recent monitoring campaigns designed to map the accretion regime in active galactic nuclei (AGN) show major discrepancies with models where the optical/ultraviolet (UV) is produced by X-ray-illuminated, optically thick disc material within a few hundred gravitational radii. However, these campaigns only monitored X-rays below 10 keV, whereas the b…
Young stars as tracers of a barred-spiral Milky Way
Ragan, Sarah E.; Pettitt, Alex R.; Smith, Martin C.
Identifying the structure of our Galaxy has always been fraught with difficulties, and while modern surveys continue to make progress building a map of the Milky Way, there is still much to understand. The arm and bar features are important drivers in shaping the interstellar medium (ISM), but their exact nature and influence still require attenti…
Photometric and kinematic study of the three intermediate age open clusters NGC 381, NGC 2360, and Berkeley 68
Joshi, Y. C.; Maurya, Jayanand
We present UBVRcIc photometric study of three intermediate age open star clusters NGC 381, NGC 2360, and Berkeley 68 (Be 68). We examine the cluster membership of stars using recently released Gaia DR2 proper motions and obtain a total of 116, 332, and 264 member stars in these three clusters. The mean reddening of E(B - V) =…
Is the gap in the DS Tau disc hiding a planet?
Herczeg, Gregory J.; Long, Feng; Pinte, Christophe +6 more
Recent millimetre-wavelength surveys performed with the Atacama Large Millimeter Array (ALMA) have revealed protoplanetary discs characterized by rings and gaps. A possible explanation for the origin of such rings is the tidal interaction with an unseen planetary companion. The protoplanetary disc around DS Tau shows a wide gap in the ALMA observa…
Extinction-free Census of AGNs in the AKARI/IRC North Ecliptic Pole Field from 23-band infrared photometry from Space Telescopes
Hashimoto, Tetsuya; Goto, Tomotsugu; Kim, Seong Jin +21 more
In order to understand the interaction between the central black hole and the whole galaxy or their co-evolution history along with cosmic time, a complete census of active galactic nucleus (AGN) is crucial. However, AGNs are often missed in optical, UV, and soft X-ray observations since they could be obscured by gas and dust. A mid-infrared (MIR)…
Optical polarization properties of AGNs with significant VLBI-Gaia offsets
Blinov, D.; Kovalev, Y. Y.; Zobnina, D. I. +1 more
Significant positional offsets of the value from 1 mas to more than 10 mas were found previously between radio (VLBI) and optical (Gaia) positions of active galactic nuclei (AGNs). They happen preferentially parallel to the parsec-scale jet direction. AGNs with VLBI-to-Gaia offsets pointed downstream the jet are found to have favourably higher opt…
Ultra-luminous quasars at redshift z > 4.5 from SkyMapper
Wolf, Christian; Schmidt, Brian P.; Bian, Fuyan +6 more
The most luminous quasars at high-redshift harbour the fastest growing and most massive black holes in the early Universe. They are exceedingly rare and hard to find. Here, we present our search for the most luminous quasars in the redshift range from z = 4.5 to 5 using data from SkyMapper, Gaia, and WISE. We use colours to select likely high-reds…