Search Publications
A Helium-flash-induced Mixing Event Can Explain the Lithium Abundances of Red Clump Stars
Schwab, Josiah
Observations demonstrate that the surface abundance of ${}^{7}\mathrm{Li}$ in low-mass stars changes dramatically between the tip of the red giant branch and the red clump. This naturally suggests an association with the helium core flash, which occurs between these two stages. Using stellar evolution models and a simple, ad hoc mixing prescriptio…
Magnetic Field Dependence of Bipolar Magnetic Region Tilts on the Sun: Indication of Tilt Quenching
Banerjee, Dipankar; Jha, Bibhuti Kumar; Karak, Bidya Binay +1 more
The tilt of the bipolar magnetic region (BMR) is crucial in the Babcock-Leighton process for the generation of the poloidal magnetic field in the Sun. Based on the thin flux-tube model of the BMR formation, the tilt is believed to be caused by the Coriolis force acting on the rising flux tube of the strong toroidal magnetic field from the base of …
Mapping the Galactic Disk with the LAMOST and Gaia Red Clump Sample. VI. Evidence for the Long-lived Nonsteady Warp of Nongravitational Scenarios
Wang, H. -F.; López-Corredoira, M.; Huang, Y. +6 more
By combining LAMOST DR4 and Gaia DR2 common red clump stars with age and proper motion, we analyze the amplitude evolution of the stellar warp independently of any assumption with a simple model. The greatest height of the warp disk increases with galactocentric distance in different populations and is dependent on age: the younger stellar populat…
The Mass-Size Relation and the Constancy of GMC Surface Densities in the Milky Way
Lada, Charles J.; Dame, T. M.
We use two existing molecular cloud catalogs derived from the same CO survey and two catalogs derived from local dust extinction surveys to investigate the nature of the giant molecular cloud (GMC) mass-size relation in the Galaxy. We find that the four surveys are well described by MGMC ∼ R2, implying a constant mean surface…
Searching for z > 6.5 Analogs Near the Peak of Cosmic Star Formation
Martin, Crystal L.; Chevallard, Jacopo; Shapley, Alice E. +5 more
Strong [O III]λλ4959,5007 + Hβ emission appears to be typical in star-forming galaxies at z > 6.5. As likely contributors to cosmic reionization, these galaxies and the physical conditions within them are of great interest. At z > 6.5, where Lyα is greatly attenuated by the intergalactic medium, rest-UV metal emission lines provide an altern…
Gamma-Ray Emission of 60Fe and 26Al Radioactivity in Our Galaxy
Greiner, J.; Wang, W.; Siegert, T. +7 more
The isotopes 60Fe and 26Al originate from massive stars and their supernovae, reflecting ongoing nucleosynthesis in the Galaxy. We studied the gamma-ray emission from these isotopes at characteristic energies 1173, 1332, and 1809 keV with over 15 yr of SPI data, finding a line flux in 60Fe combined lines of $(0.31\…
The Formation of a Stellar Association in the NGC 7000/IC 5070 Complex: Results from Kinematic Analysis of Stars and Gas
Hillenbrand, Lynne A.; Carpenter, John M.; Kuhn, Michael A. +1 more
We examine the clustering and kinematics of young stellar objects (YSOs) in the North America/Pelican Nebulae, as revealed by Gaia astrometry, in relation to the structure and motions of the molecular gas, as indicated in molecular-line maps. The Gaia parallaxes and proper motions allow us to significantly refine previously published lists of YSOs…
NGTS-11 b (TOI-1847 b): A Transiting Warm Saturn Recovered from a TESS Single-transit Event
Henning, Thomas; Jordán, Andrés; Espinoza, Néstor +38 more
We report the discovery of NGTS-11 b (=TOI-1847b), a transiting Saturn in a 35.46 day orbit around a mid K-type star ( ${T}_{\mathrm{eff}}$ = 5050 ± 80 K). We initially identified the system from a single-transit event in a TESS full-frame image light curve. Following 79 nights of photometric monitoring with an NGTS telescope, we observed a second…
Stellar Properties of z ≳ 8 Galaxies in the Reionization Lensing Cluster Survey
Ouchi, Masami; Mahler, Guillaume; Frye, Brenda L. +18 more
Measurements of stellar properties of galaxies when the universe was less than one billion years old yield some of the only observational constraints on the onset of star formation. We present here the inclusion of Spitzer/IRAC imaging in the fitting of the spectral energy distribution of the seven highest-redshift galaxy candidates selected from …
A Well-aligned Orbit for the 45 Myr-old Transiting Neptune DS Tuc Ab
Butler, R. P.; Crane, J. D.; Teske, J. K. +18 more
DS Tuc Ab is a Neptune-sized planet that orbits around a G star in the 45 Myr old Tucana-Horologium moving group. Here, we report the measurement of the sky-projected angle between the stellar spin axis and the planet's orbital axis, based on the observation of the Rossiter-McLaughlin effect during three separate planetary transits. The orbit appe…