Search Publications
Fluorine Abundances in the Galactic Nuclear Star Cluster
Cunha, Katia; Smith, Verne V.; Daflon, Simone +4 more
Abundances of fluorine (19F), as well as isotopic ratios of 16O/17O, are derived in a sample of luminous young (~107-108 yr) red giants in the Galactic center (with galactocentric distances ranging from 0.6-30 pc), using high-resolution infrared spectra and vibration-rotation lines of H19…
Hubble Space Telescope Proper Motion (HSTPROMO) Catalogs of Galactic Globular Clusters. VII. Energy Equipartition
Anderson, Jay; van der Marel, Roeland P.; Alfaro-Cuello, Mayte +3 more
We examine the degree of energy equipartition in nine Galactic globular clusters using proper motions measured with the Hubble Space Telescope. For most clusters in the sample, this is the first energy equipartition study ever performed. This study is also the largest of its kind, albeit with only nine clusters. We begin by rigorously cleaning the…
Massive Black Hole Formation in Dense Stellar Environments: Enhanced X-Ray Detection Rates in High-velocity Dispersion Nuclear Star Clusters
Stone, Nicholas C.; Ostriker, Jeremiah P.; Baldassare, Vivienne F. +2 more
We analyze Chandra X-ray Observatory imaging of 108 galaxies hosting nuclear star clusters (NSCs) to search for signatures of massive black holes (BHs). NSCs are extremely dense stellar environments with conditions that can theoretically facilitate massive BH formation. Recent work by Stone et al. finds that sufficiently dense NSCs should be unsta…
Investigating the Low-flux States in Six Intermediate Polars
Littlefield, Colin; Heinke, Craig O.; Mukai, Koji +30 more
We present optical photometry of six intermediate polars that exhibit transitions to a low-flux state. For four of these systems, DW Cnc, V515 And, V1223 Sgr, and RX J2133.7+5107, we are able to perform timing analysis in and out of the low states. We find that, for DW Cnc and V515 And, the dominant periodicities in the light curves change as the …
The Physical Parameters of Four WC-type Wolf-Rayet Stars in the Large Magellanic Cloud: Evidence of Evolution
Aadland, Erin; Massey, Philip; Hillier, D. John +1 more
We present a spectral analysis of four Large Magellanic Cloud (LMC) WC-type Wolf-Rayet (WR) stars (BAT99-8, BAT99-9, BAT99-11, and BAT99-52) to shed light on two evolutionary questions surrounding massive stars. The first is: are WO-type WR stars more oxygen enriched than WC-type stars, indicating further chemical evolution, or are the strong high…
[C II] Map of the Molecular Ring and Arms of the Spiral Galaxy NGC 7331
Fadda, Dario; Sutter, Jessica
We present the [C II] 157.7 µm map of galaxy NGC 7331 obtained with the Field-Imaging Far-Infrared Line Spectrometer on board the Stratospheric Observatory for Infrared Astronomy (SOFIA). This map extends an existent Herschel/Photodetector Array Camera and Spectrometer observation of the central strip of the galaxy to encompass the entire mo…
Joint Survey Processing. I. Compact Oddballs in the COSMOS Field-Low-luminosity Quasars at z > 6?
Koekemoer, Anton M.; Brammer, Gabriel; Miyatake, Hironao +8 more
The faint-end slope of the quasar luminosity function at z ~ 6 and its implication on the role of quasars in reionizing the intergalactic medium at early times has been an outstanding problem for some time. The identification of faint high-redshift quasars with luminosities of <1044.5 erg s-1 is challenging. They are rare …
Observations of Instability-driven Nanojets in Coronal Loops
Antolin, Patrick; McLaughlin, James A.; Sukarmadji, A. Ramada C.
The recent discovery of nanojets by Antolin et al. represents magnetic reconnection in a braided field, thus clearly identifying reconnection-driven nanoflares. Due to their small scale (500 km in width, 1500 km in length) and short timescales (<15 s), it is unclear how pervasive nanojets are in the solar corona. In this paper, we present Inter…
Long-term Photometric and Low-resolution Spectroscopic Analysis of Five Contact Binaries
Joshi, Y. C.; Panchal, A.; De Cat, Peter +1 more
A photometric and spectroscopic investigation is performed on five W Ursae Majoris eclipsing binaries J015818.6+260247 (hereinafter as J0158b), J073248.4+405538 (hereinafter as J0732), J101330.8+494846 (hereinafter as J1013), J132439.8+130747 (hereinafter as J1324), and J152450.7+245943 (hereinafter as J1524). The photometric data are collected wi…
Multiwavelength Observations of the Obscuring Wind in the Radio-quiet Quasar MR 2251-178
Kaastra, J. S.; Djorgovski, S. G.; Stern, D. +11 more
Obscuring winds driven away from active supermassive black holes are rarely seen due to their transient nature. They have been observed with multiwavelength observations in a few Seyfert 1 galaxies and one broad absorption line radio-quiet quasar so far. An X-ray obscuration event in MR 2251-178 was caught in late-2020, which triggered multiwavele…