Search Publications
Properties of the Obscuring Torus in NGC 1052 from Multiepoch Broadband X-Ray Spectroscopy
Brenneman, L.; Urry, C. M.; Baloković, M. +1 more
Obscuration of the innermost parts of active galactic nuclei (AGN) is observed in the majority of the population both in the nearby universe and at high redshift. However, the nature of the structures causing obscuration, especially in low-luminosity AGN, is poorly understood at present. We present a novel approach to multiepoch broadband X-ray sp…
On the Impact of Inclination-dependent Attenuation on Derived Star Formation Histories: Results from Disk Galaxies in the Great Observatories Origins Deep Survey Fields
Basu-Zych, Antara; Garofali, Kristen; Lehmer, Bret D. +4 more
We develop and implement an inclination-dependent attenuation prescription for spectral energy distribution (SED) fitting and study its impact on derived star formation histories. We apply our prescription within the SED fitting code Lightning to a clean sample of 82, z = 0.21-1.35 disk-dominated galaxies in the Great Observatories Origins Deep Su…
Census of R Coronae Borealis Stars. I. Infrared Light Curves from Palomar Gattini IR
Soria, Roberto; Tinyanont, Samaporn; De, Kishalay +16 more
We are undertaking the first systematic infrared (IR) census of R Coronae Borealis (RCB) stars in the Milky Way, beginning with IR light curves from the Palomar Gattini IR (PGIR) survey. The PGIR is a 30 cm J-band telescope with a 25 deg2 camera that is surveying 18,000 deg2 of the northern sky (δ > -28°) at a cadence of 2…
XMM-Newton Observes the Intrabinary Shock of PSR J1959+2048
An, Hongjun; Romani, Roger W.; Kandel, D.
In a multi-orbit (100 ks) XMM-Newton exposure of the original black widow pulsar, PSR J1959+2048, we measure the strong orbital modulation caused by intrabinary shock (IBS) emission. The IBS light curve peak appears asymmetric, which we attribute to sweep-back effects in the companion wind. We also see evidence for an X-ray eclipse by the companio…
Discovery of an Edge-on Circumstellar Debris Disk around BD+45° 598: A Newly Identified Member of the β Pictoris Moving Group
Mamajek, Eric; Hinkley, Sasha; Matthews, Brenda +25 more
We report the discovery of a circumstellar debris disk viewed nearly edge-on and associated with the young, K1 star BD+45° 598 using high-contrast imaging at 2.2 µm obtained at the W.M. Keck Observatory. We detect the disk in scattered light with a peak significance of ∼5σ over three epochs, and our best-fit model of the disk is an almost ed…
Multiple Sources of Solar High-energy Protons
Yu, Sijie; Vainio, Rami; Gary, Dale E. +6 more
During the 24th solar cycle, the Fermi Large Area Telescope (LAT) has observed a total of 27 solar flares possessing delayed γ-ray emission, including the exceptionally well-observed flare and coronal mass ejection (CME) on 2017 September 10. Based on the Fermi/LAT data, we plot, for the first time, maps of possible sources of the delayed >100 …
Is Flare Ribbon Fine Structure Related to Tearing in the Flare Current Sheet?
Wyper, P. F.; Pontin, D. I.
Observations of solar flare ribbons show significant fine structure in the form of breaking wavelike perturbations and spirals. The origin of this structure is not well understood, but one possibility is that it is related to the tearing instability in the flare current sheet. Here we study this connection by constructing an analytical 3D magnetic…
The RS CVn-type Star GT Mus Shows Most Energetic X-Ray Flares Throughout the 2010s
Hamaguchi, Kenji; Corcoran, Michael F.; Maeda, Yoshitomo +14 more
We report that the RS CVn-type star GT Mus (HR 4492, HD 101379+HD 101380) was the most active star in the X-ray sky in the last decade in terms of the scale of recurrent energetic flares. We detected 11 flares from GT Mus in 8 yr of observations with the Monitor of All-sky X-ray Image (MAXI) from 2009 August to 2017 August. The detected flare peak…
Unsupervised Machine Learning for the Identification of Preflare Spectroscopic Signatures
De Pontieu, Bart; Sainz Dalda, Alberto; Woods, Magnus M.
The study of the preflare environment is of great importance to understanding what drives solar flares. k-means clustering, an unsupervised machine-learning technique, has the ability to cluster large data set in a way that would be impractical or impossible for a human to do. In this paper we present a study using k-means clustering to identify p…
Exploring Mutual Information between IRIS Spectral Lines. II. Calculating the Most Probable Response in all Spectral Windows
Kleint, Lucia; Panos, Brandon
A three-dimensional picture of the solar atmosphere's thermodynamics can be obtained by jointly analyzing multiple spectral lines that span many formation heights. In Paper I, we found strong correlations between spectral shapes from a variety of different ions during solar flares in comparison to the quiet Sun. We extend these techniques to addre…