Search Publications
An accreting white dwarf displaying fast transitional mode switching
Knigge, C.; de Martino, D.; Groot, P. J. +6 more
Accreting white dwarfs are often found in close binary systems with orbital periods ranging from tens of minutes to several hours. In most cases, the accretion process is relatively steady, with significant modulations only occurring on timescales of ~days or longer1,2. Here we report the discovery of abrupt drops in the optical luminos…
Clues to the Formation of Liller 1 from Modeling Its Complex Star Formation History
Pallanca, Cristina; Dalessandro, Emanuele; Ferraro, Francesco R. +7 more
Liller 1 and Terzan 5 are two massive systems in the Milky Way bulge hosting populations characterized by significantly different ages (Δt > 7-8 Gyr) and metallicities (Δ[Fe/H] ~ 1 dex). Their origin is still strongly debated in the literature and all formation scenarios proposed so far require some level of fine-tuning. The detailed star forma…
First direct dynamical detection of a dual supermassive black hole system at sub-kiloparsec separation
Pechetti, Renuka; Neumayer, Nadine; Seth, Anil C. +7 more
We investigated whether the two recently discovered nuclei in NGC 7727 both host a super-massive black hole (SMBH). We used the high spatial resolution mode of the integral-field spectrograph MUSE on the VLT in adaptive optics mode to resolve the stellar kinematics within the sphere of influence of both putative black holes. We combined the kinema…
Inferring the morphology of AGN torus using X-ray spectra: a reliability study
Markowitz, Alex G.; Buchner, Johannes; Saha, Tathagata
Numerous X-ray spectral models have been developed to model emission reprocessed by the torus of an active galactic nucleus (AGN), e.g. UXCLUMPY, CTORUS, and MYTORUS. They span a range of assumed torus geometries and morphologies - some posit smooth gas distributions, and others posit distributions of clouds. It is suspected that given the quality…
Jovian Auroral Electron Precipitation Budget—A Statistical Analysis of Diffuse, Mono-Energetic, and Broadband Auroral Electron Distributions
Saur, J.; Mauk, B. H.; Salveter, A. +1 more
Recent observations by the Juno spacecraft have shown that electrons contributing to Jupiter's main auroral emission appear to be frequently characterized by broadband electron distributions, but also less often mono-energetic electron distributions are observed as well. In this work, we quantitatively derive the occurrence rates of the various el…
High-precision star-formation efficiency measurements in nearby clouds
Gutermuth, Robert A.; Pokhrel, Riwaj; Hu, Zipeng +1 more
On average molecular clouds convert only a small fraction ϵff of their mass into stars per free-fall time, but different star-formation theories make contrasting claims for how this low mean efficiency is achieved. To test these theories, we need precise measurements of both the mean value and the scatter of ϵff, but high-pre…
LeMMINGs - IV. The X-ray properties of a statistically complete sample of the nuclei in active and inactive galaxies from the Palomar sample
Muxlow, T. W. B.; Argo, M. K.; Knapen, J. H. +22 more
All 280 of the statistically complete Palomar sample of nearby (<120 Mpc) galaxies δ > 20° have been observed at 1.5 GHz as part of the LeMMINGs e-MERLIN legacy survey. Here, we present Chandra X-ray observations of the nuclei of 213 of these galaxies, including a statistically complete sub-set of 113 galaxies in the declination range 40° &l…
Low Star Formation Activity and Low Gas Content of Quiescent Galaxies at z = 3.5-4.0 Constrained with ALMA
Papovich, Casey; Kacprzak, Glenn G.; Glazebrook, Karl +10 more
The discovery in deep near-infrared surveys of a population of massive quiescent galaxies at z > 3 has given rise to the question of how they came to be quenched so early in the history of the universe. Measuring their molecular gas properties can distinguish between physical processes where they stop forming stars due to a lack of fuel versus …
The Active Chromospheres of Lithium-rich Red Giant Stars
Dupree, Andrea K.; Mahadevan, Suvrath; Terrien, Ryan +17 more
We have gathered near-infrared zyJ-band high-resolution spectra of nearly 300 field red giant stars with known lithium abundances in order to survey their He I λ10830 absorption strengths. This transition is an indicator of chromospheric activity and/or mass loss in red giants. The majority of stars in our sample reside in the red clump or red hor…
Do radio active galactic nuclei reflect X-ray binary spectral states?
Guainazzi, Matteo; Moravec, Emily; Panessa, Francesca +5 more
Context. Over recent years there has been mounting evidence that accreting supermassive black holes in active galactic nuclei (AGNs) and stellar mass black holes have similar observational signatures: thermal emission from the accretion disk, X-ray coronas, and relativistic jets. Further, there have been investigations into whether or not AGNs hav…