Search Publications
Cosmology with AGN: can we use quasars as standard candles?
Lusso, E.; Risaliti, G.
The nonlinear relation between X-ray and UV luminosity in quasars can be used to estimate their distance. Recently, we have shown that, despite the large dispersion of the relation, a Hubble diagram made of large samples of quasars can provide unique constraints on cosmology at high redshift. Furthermore, the dispersion of the relation is heavily …
Rosetta measurements of lower hybrid frequency range electric field oscillations in the plasma environment of comet 67P
Nilsson, H.; André, M.; Karlsson, T. +6 more
Electric field measurements from cometary environments are very rare but can provide important information on how plasma waves help fashion the plasma environment. The long dwelling time of the Rosetta spacecraft close to comet 67P/Churyumov-Gerasimenko promises to improve this state. We here present the first electric field measurements from 67P,…
The aurorae of Uranus past equinox
Lamy, L.; Badman, S. V.; Cowley, S. W. H. +9 more
The aurorae of Uranus were recently detected in the far ultraviolet with the Hubble Space Telescope (HST) providing a new, so far unique, means to remotely study the asymmetric Uranian magnetosphere from Earth. We analyze here two new HST Uranus campaigns executed in September 2012 and November 2014 with different temporal coverage and under varia…
The Broadband Spectral Variability of Holmberg IX X-1
Harrison, F. A.; Ptak, A.; Stern, D. +9 more
We present results from four new broadband X-ray observations of the extreme ultraluminous X-ray source Holmberg IX X-1 ({L}{{X}}> {10}40 erg s-1), performed by Suzaku and NuSTAR in coordination. Combined with the archival data, we now have broadband observations of this remarkable source from six separate epoch…
How Much Flux Does a Flux Transfer Event Transfer?
Milan, S. E.; Fear, R. C.; Coxon, J. C. +1 more
Flux transfer events are bursts of reconnection at the dayside magnetopause, which give rise to characteristic signatures observed by a range of magnetospheric/ionospheric instrumentation. One outstanding problem is that there is a fundamental mismatch between space-based and ionospheric estimates of the flux that is opened by each flux transfer e…
Improved Point-source Detection in Crowded Fields Using Probabilistic Cataloging
Finkbeiner, Douglas P.; Daylan, Tansu; Portillo, Stephen K. N. +1 more
Cataloging is challenging in crowded fields because sources are extremely covariant with their neighbors and blending makes even the number of sources ambiguous. We present the first optical probabilistic catalog, cataloging a crowded (∼0.1 sources per pixel brighter than 22nd mag in F606W) Sloan Digital Sky Survey r-band image from M2. Probabilis…
The Lifetimes of Phases in High-mass Star-forming Regions
Battersby, Cara; Bally, John; Svoboda, Brian
High-mass stars form within star clusters from dense, molecular regions (DMRs), but is the process of cluster formation slow and hydrostatic or quick and dynamic? We link the physical properties of high-mass star-forming regions with their evolutionary stage in a systematic way, using Herschel and Spitzer data. In order to produce a robust estimat…
Belt(s) of debris resolved around the Sco-Cen star HIP 67497
Pinte, C.; Ménard, F.; van der Plas, G. +15 more
Aims: In 2015, we initiated a survey of Scorpius-Centaurus A-F stars that are predicted to host warm-inner and cold-outer belts of debris similar to the case of the system HR 8799. The survey aims to resolve the disks and detect planets responsible for the disk morphology. In this paper, we study the F-type star HIP 67497 and present a first-…
A gas density drop in the inner 6 AU of the transition disk around the Herbig Ae star HD 139614 . Further evidence for a giant planet inside the disk?
Pinte, C.; Kamp, I.; Thi, W. F. +16 more
Context. Quantifying the gas surface density inside the dust cavities and gaps of transition disks is important to establish their origin.
Aims: We seek to constrain the surface density of warm gas in the inner disk of HD 139614, an accreting 9 Myr Herbig Ae star with a (pre-)transition disk exhibiting a dust gap from 2.3 ± 0.1 to 5.3 ± 0.3 A…
Age Spreads and the Temperature Dependence of Age Estimates in Upper Sco
Herczeg, Gregory J.; Rizzuto, Aaron; Fang, Qiliang
Past estimates for the age of the Upper Sco Association are typically 11-13 Myr for intermediate-mass stars and 4-5 Myr for low-mass stars. In this study, we simulate populations of young stars to investigate whether this apparent dependence of estimated age on spectral type may be explained by the star formation history of the association. Solar …