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Phase-resolved gamma-ray spectroscopy of the Crab pulsar observed by POLAR
Wu, Xin; Ge, Ming-Yu; Zhang, Shuang-Nan +14 more
The POLAR detector is a space based Gamma-Ray Burst (GRB) polarimeter sensitive in the 15-500 keV energy range. Apart from its main scientific goal as a Gamma-Ray Burst polarimeter it is also able to detect photons from pulsars in orbit. By using the six-months in-orbit observation data, significant pulsation from the PSR B0531+21 (Crab pulsar) wa…
H I Spectroscopy of Reverberation-mapped Active Galactic Nuclei
Bentz, Misty C.; Courtois, Hélène M.; Johnson, Megan C. +2 more
We present H I 21 cm spectroscopy from the Robert C. Byrd Green Bank Telescope for the host galaxies of 31 nearby active galactic nuclei with direct M BH measurements from reverberation mapping. These are the first published H I detections for 12 galaxies, and the spectral quality is generally an improvement over archival data for the…
A massive nebula around the luminous blue variable star RMC 143 revealed by ALMA
Paladini, R.; Umana, G.; Mehner, A. +11 more
The luminous blue variable (LBV) RMC 143 is located in the outskirts of the 30 Doradus complex, a region rich with interstellar material and hot luminous stars. We report the 3σ sub-millimetre detection of its circumstellar nebula with ALMA. The observed morphology in the sub-millimetre is different than previously observed with HST and ATCA in th…
A supragalactic conundrum: the globular clusters colour pattern in Virgo galaxies
Forte, Juan C.; Vega, E. Irene; Geisler, Douglas +8 more
The presence of systematic modulations in the colour distributions in composite samples of globular clusters (GCs) associated with galaxies in the Virgo and Fornax clusters has been reported in a previous work. In this paper, we focus on the 27 brightest galaxies in Virgo, and in particular on NGC 4486, the dominant system in terms of GC populatio…
Ultraviolet Extinction Properties of the 30 Dor Nebula and Interpreting Observations of Starburst Clusters
Panagia, Nino; De Marchi, Guido
Recent investigations of the extinction law in 30 Dor and the Tarantula Nebula, at optical and near-infrared wavelengths, have revealed a ratio of total to selective extinction R V = A V /E(B - V) of about 4.5. This indicates a larger fraction of big grains than in the Galactic diffuse interstellar medium (ISM). Possible o…
VVV-WIT-07: another Boyajian's star or a Mamajek's object?
Minniti, D.; Saito, R. K.; Baptista, R. +6 more
We report the discovery of VVV-WIT-07, a unique and intriguing variable source presenting a sequence of recurrent dips with a likely deep eclipse in 2012 July. The object was found serendipitously in the near-IR data obtained by the VISTA Variables in the Vía Láctea (VVV) ESO public survey. Our analysis is based on VVV variability, multicolour, an…
An Ultraviolet-Optical Color-Metallicity Relation for Red Clump Stars Using GALEX and Gaia
Hogg, David W.; Hawkins, Keith; Schiminovich, David +3 more
Although core helium-burning red clump (RC) stars are faint at ultraviolet wavelengths, their ultraviolet (UV)-optical color is a unique and accessible probe of their physical properties. Using data from the Galaxy Evolution Explorer All Sky Imaging Survey, Gaia Data Release 2, and the Sloan Digital Sky Survey Apache Point Observatory Galactic Evo…
Stellar Parameters for Pulsating B-star Candidates in the Kepler Field
McSwain, M. Virginia; Hanes, Richard J.; Waskie, Steven +3 more
The field of asteroseismology has enjoyed a large swath of data coming from recent missions (e.g., CoRoT, Kepler, K2). This wealth of new data has allowed the field to expand beyond the previous limitation of a few extremely bright and evolved stars. Asteroseismology relies on accurate surface measurements for boundary conditions, but the predicte…
Not so different after all: properties and spatial structure of column density peaks in the pipe and Orion A clouds
Lombardi, Marco; Palau, Aina; Alfaro, Emilio +4 more
We present a comparative study of the physical properties and the spatial distribution of column density peaks in two giant molecular clouds (GMCs), the Pipe Nebula and Orion A, which exemplify opposite cases of star cluster formation stages. The density peaks were extracted from dust extinction maps constructed from Herschel/SPIRE far-infrared im…
Gaia DR2 white dwarfs in the Hercules stream
Rebassa-Mansergas, Alberto; Althaus, Leandro G.; Torres, Santiago +5 more
Aims: We analyzed the velocity space of the thin- and thick-disk Gaia white dwarf population within 100 pc by searching for signatures of the Hercules stellar stream. We aimed to identify objects belonging to the Hercules stream, and by taking advantage of white dwarf stars as reliable cosmochronometers, to derive a first age distribution.