Search Publications
Rapid Buildup of a Magnetic Flux Rope during a Confined X2.2 Class Flare in NOAA AR 12673
Wang, Yuming; Liu, Lijuan; Cui, Jun +3 more
Magnetic flux ropes (MFRs) are believed to be the core structure in solar eruptions; nevertheless, their formation remains intensely debated. Here we report a rapid buildup process of an MFR system during a confined X2.2 class flare occurred on 2017 September 6 in NOAA active region (AR) 12673, three hours after which the structure erupted to a ma…
CLUMP-3D: Testing ΛCDM with Galaxy Cluster Shapes
Zitrin, Adi; Umetsu, Keiichi; Meneghetti, Massimo +5 more
The ΛCDM model of structure formation makes strong predictions on the concentration and shape of dark matter (DM) halos, which are determined by mass accretion processes. Comparison between predicted shapes and observations provides a geometric test of the ΛCDM model. Accurate and precise measurements needs a full three-dimensional (3D) analysis o…
The r-process Pattern of a Bright, Highly r-process-enhanced Metal-poor Halo Star at [Fe/H] ∼ -2
Beers, Timothy C.; Placco, Vinicius M.; Venn, Kim A. +9 more
A high-resolution spectroscopic analysis is presented for a new highly r-process-enhanced ([Eu/Fe] = 1.27, [Ba/Eu] = -0.65), very metal-poor ([Fe/H] = -2.09), retrograde halo star, RAVE J153830.9-180424, discovered as part of the R-Process Alliance survey. At V = 10.86, this is the brightest and most metal-rich r-II star known in the Milky Way hal…
Infrared Variability of Two Dusty White Dwarfs
Dufour, Patrick; Xu, Siyi; Gänsicke, Boris T. +11 more
The most heavily polluted white dwarfs often show excess infrared radiation from circumstellar dust disks, which are modeled as a result of tidal disruption of extrasolar minor planets. Interaction of dust, gas, and disintegrating objects can all contribute to the dynamical evolution of these dust disks. Here, we report two infrared variable dusty…
One Thousand Days of SN2015bn: HST Imaging Shows a Light Curve Flattening Consistent with Magnetar Predictions
Berger, Edo; Chornock, Ryan; Alexander, Kate D. +9 more
We present the first observations of a Type I superluminous supernova (SLSN) at ≳1000 days after maximum light. We observed SN 2015bn using the Hubble Space Telescope (HST) Advanced Camera for Surveys in the F475W, F625W and F775W filters at 721 days and 1068 days. SN 2015bn is clearly detected and resolved from its compact host, allowing reliable…
A Machine-learning-based Investigation of the Open Cluster M67
Gao, Xinhua
In this paper, we use a machine-learning method, random forest (RF), to identify reliable members of the old (4 Gyr) open cluster M67 based on the high-precision astrometry and photometry taken from the second Gaia data release (Gaia-DR2). The RF method is used to calculate membership probabilities of 71,117 stars within 2.°5 of the cluster center…
Onset of the Magnetic Explosion in Solar Polar Coronal X-Ray Jets
Panesar, Navdeep K.; Moore, Ronald L.; Sterling, Alphonse C.
We follow up on the Sterling et al. discovery that nearly all polar coronal X-ray jets are made by an explosive eruption of a closed magnetic field carrying a miniature filament in its core. In the same X-ray and EUV movies used by Sterling et al., we examine the onset and growth of the driving magnetic explosion in 15 of the 20 jets that they stu…
The Magellan Evolution of Galaxies Spectroscopic and Ultraviolet Reference Atlas (MegaSaura). II. Stacked Spectra
Dahle, H.; Rigby, J. R.; Bayliss, M. B. +8 more
We stack the rest-frame ultraviolet spectra of N = 14 highly magnified gravitationally lensed galaxies at redshifts 1.6< z< 3.6. The resulting new composite spans 900< {λ }{rest}< 3000 Å, with a peak signal-to-noise ratio (S/N) of 103 per spectral resolution element (∼100 km s-1). It is the highest S/N, highest sp…
Two Transient X-Ray Quasi-periodic Oscillations Separated by an Intermediate State in 1H 0707-495
Zhang, Peng; Zhang, Peng-fei; Yan, Jing-zhi +3 more
In the narrow-line Seyfert 1 galaxy 1H 0707-495, recently a transient quasi-periodic oscillation (QPO) signal with a frequency of ∼ 2.6× {10}-4 Hz has been detected at a high statistical significance. Here, we reanalyze the same set of XMM-Newton data observed on 2008 February 4 with the weighted-wavelet Z-transform method. In addition …
An X-Ray Imaging Survey of Quasar Jets: The Complete Survey
Birkinshaw, M.; Worrall, D. M.; Schwartz, D. A. +8 more
We present Chandra X-ray imaging of a flux-limited sample of flat spectrum radio-emitting quasars with jet-like structure. X-rays are detected from 59% of 56 jets. No counter-jets were detected. The core spectra are fitted by power-law spectra with a photon index Γ x , whose distribution is consistent with a normal distribution, with a …