Search Publications
Observing the Earliest Stages of Star Formation in Galaxies: 8 µm Cores in Three Edge-on Disks
Elmegreen, Bruce G.; Elmegreen, Debra Meloy
To study the vertical distribution of the earliest stages of star formation in galaxies, three edge-on spirals, NGC 891, NGC 3628, and IC 5052, observed by the Spitzer Space Telescope InfraRed Array Camera (IRAC) were examined for compact 8 µm cores using an unsharp mask technique; 173, 267, and 60 cores were distinguished, respectively. Col…
HST/COS Spectra of the Wind Lines of VFTS 102 and 285
Gies, Douglas R.; Lester, Kathryn V.; Wang, Luqian +5 more
Rapid rotation in massive stars imposes a latitudinal variation in the mass loss from radiatively driven winds that can lead to enhanced mass loss at the poles (with little angular momentum loss) and/or equator (with maximal angular momentum loss). Here we present an examination of the stellar wind lines of the two O-type stars with the fastest kn…
Modeling the IRIS Lines During a Flare. I. The Blue-wing Enhancement in the Mg II k Line
Ding, M. D.; Li, Ying; Hong, Jie +1 more
The Interface Region Imaging Spectrograph (IRIS) Mg II k line serves as a very good tool to diagnose the heating processes in solar flares. Recent studies have shown that apart from the usual red asymmetries that are interpreted as the result of condensation downflows, this line could also show a blue-wing enhancement. To investigate how such a bl…
A HaloSat Analysis of the Cygnus Superbubble
Kaaret, Philip; Kuntz, K. D.; Bluem, Jesse +5 more
The Cygnus Superbubble (CSB) is a region of soft X-ray emission approximately 13 degrees wide in the direction of the local spiral arm. Such a large region might be the result of strong stellar winds and supernovae from nearby stellar nurseries, or it could be the result of a single event—a hypernova. HaloSat observed four nonoverlapping 10 degree…
On the Effects of UV Photons/X-Rays on the Chemistry of the Sgr B2 Cloud
Martín-Pintado, J.; Requena-Torres, M. A.; Llerena, M. +7 more
The lines of HOC+, HCO, and CO+ are considered good tracers of photon-dominated regions (PDRs) and X-ray-dominated regions. We study these tracers toward regions of the Sgr B2 cloud selected to be affected by different heating mechanisms. We find the lowest values of the column density ratios of HCO+ versus HOC
Phase-resolved Analyses of Millihertz Quasi-periodic Oscillations in 4U 1636-53 using the Hilbert-Huang Transform
Chou, Yi; Hsieh, Hung-En
We present phase-resolved spectroscopy based on the Hilbert-Huang transform (HHT) for millihertz quasi-periodic oscillations (mHz QPOs) in 4U 1636-53. The ∼8 mHz QPO can be detected approximately several thousand seconds before a type-I X-ray burst. It has been interpreted as marginally stable burning on the neutron-star surface. In this study, we…
ALMA Observations of the Molecular Clouds in NGC 625
De Looze, Ilse; Cormier, Diane; Faesi, Christopher M. +1 more
We present the highest-resolution (1″) 12CO observations of molecular gas in the dwarf starburst galaxy NGC 625 to date, obtained with Atacama Large Millimeter/submillimeter Array. The molecular gas, which is distributed in discrete clouds within an area of 0.4 kpc2, does not have well-ordered large-scale motions. We measure …
Statistical Signatures of Nanoflare Activity. II. A Nanoflare Explanation for Periodic Brightenings in Flare Stars Observed by NGTS
Mathioudakis, M.; Wheatley, P. J.; Goad, M. R. +9 more
Several studies have documented periodic and quasi-periodic signals from the time series of dMe flare stars and other stellar sources. Such periodic signals, observed within quiescent phases (i.e., devoid of larger-scale microflare or flare activity), range in a period from 1 to 1000 s and hence have been tentatively linked to ubiquitous p-mode os…
Local Starburst Conditions and Formation of GRB 980425/SN 1998bw within a Collisional Ring
Pian, E.; Bournaud, F.; Cormier, D. +9 more
We present the first spatially resolved study of molecular gas in the vicinity of a gamma-ray burst (GRB), using CO(2-1) emission-line observations with the Atacama Large Millimetre Array at ∼50 pc scales. The host galaxy of GRB 980425 contains a ring of high column density H I gas, which is likely to have formed due to a collision between the GRB…
Characterizing the Evolved Stellar Population in the Galactic Foreground. I. Bolometric Magnitudes, Spatial Distribution and Period-Luminosity Relations
Brown, Anthony G. A.; Rich, R. Michael; Stroh, Michael C. +6 more
Radio campaigns using maser stellar beacons have provided crucial information to characterize Galactic stellar populations. Currently, the Bulge Asymmetries and Dynamical Evolution (BAaDE) project is surveying infrared (IR) color-selected targets for SiO masers. This provides a sample of evolved stars that can be used to study the inner, optically…