Search Publications
A Large Population of Obscured AGN in Disguise as Low-luminosity AGN in Chandra Deep Field South
Heckman, Timothy; Vito, Fabio; Chiaberge, Marco +3 more
Population synthesis models of actively accreting supermassive black holes (or active galactic nuclei (AGN)) predict a large fraction that must grow behind dense, obscuring screens of gas and dust. Deep X-ray surveys are thought to have provided the most complete and unbiased samples of AGN, but there is strong observational evidence that a portio…
Elemental Abundances in M31: A Comparative Analysis of Alpha and Iron Element Abundances in the the Outer Disk, Giant Stellar Stream, and Inner Halo of M31
Gilbert, Karoline M.; Wojno, Jennifer; Guhathakurta, Puragra +3 more
We measured [Fe/H] and [α/Fe] using spectral synthesis of low-resolution stellar spectroscopy for 70 individual red-giant-branch stars across four fields spanning the outer disk, Giant Stellar Stream (GSS), and inner halo of M31. Fields at M31-centric projected distances of 23 kpc in the halo, 12 kpc in the halo, 22 kpc in the GSS, and 26 kpc in t…
Intensity interferometry of P Cygni in the H α emission line: towards distance calibration of LBV supergiant stars
Domiciano de Souza, A.; Vakili, F.; Rivet, J. -P. +7 more
We present intensity interferometry of the luminous blue variable P Cyg in the light of its H α emission performed with 1 m-class telescopes. We compare the measured visibility points to synthesized interferometric data based on the CMFGEN physical modelling of a high-resolution spectrum of P Cyg recorded almost simultaneously with our interferome…
Evidence for variability time-scale-dependent UV/X-ray delay in Seyfert 1 AGN NGC 7469
Peterson, Bradley M.; Horne, Keith; Gültekin, Kayhan +5 more
Using a month-long X-ray light curve from RXTE/PCA and 1.5 month-long UV continuum light curves from IUE spectra in 1220-1970 Å, we performed a detailed time-lag study of the Seyfert 1 galaxy NGC 7469. Our cross-correlation analysis confirms previous results showing that the X-rays are delayed relative to the UV continuum at 1315 Šby 3.49 ± 0.22 d…
Exploring the Perturbed Milky Way Disk and the Substructures of the Outer Disk
Xu, Y.; Liu, C.; Tian, H. +7 more
The recent discovery of a spiral feature in the Z - VZ phase plane in the solar neighborhood implies that the galactic disk has been remarkably affected by a dwarf galaxy passing through it some hundreds of millions of years ago. Using 429,500 Large Sky Area Multi-Object Fibre Spectroscopic Telescope K giants stars, we show that the spi…
Probing the Galactic Halo with RR Lyrae Stars. I. The Catalog
Huang, Y.; Chen, B. -Q.; Wang, C. +9 more
We present a catalog of 5290 RR Lyrae stars (RRLs) with metallicities estimated from spectra of the LAMOST Experiment for Galactic Understanding and Exploration (LEGUE) and the Sloan Extension for Galactic Understanding and Exploration (SEGUE) surveys. Nearly 70% of them (3642 objects) also have systemic radial velocities measured. Given the pulsa…
A Comparison of the Stellar, CO, and Dust-continuum Emission from Three Star-forming HUDF Galaxies at z ∼ 2
Inami, Hanae; Smail, Ian; Neeleman, Marcel +17 more
We compare the extent of the dust, molecular gas, and stars in three star-forming galaxies, at z = 1.4, 1.6, and 2.7, selected from the Hubble Ultra Deep Field based on their bright carbon monoxide (CO) and dust-continuum emission as well as their large rest-frame optical sizes. The galaxies have high stellar masses, ${M}_{* }\gt {10}^{11}{M}_{\od…
The high-energy environment and atmospheric escape of the mini-Neptune K2-18 b
Udry, Stéphane; Pepe, Francesco; dos Santos, Leonardo A. +6 more
K2-18 b is a transiting mini-Neptune that orbits a nearby (38 pc), cool M3 dwarf and is located inside its region of temperate irradiation. We report on the search for hydrogen escape from the atmosphere K2-18 b using Lyman-α transit spectroscopy with the Space Telescope Imaging Spectrograph instrument installed on the Hubble Space Telescope. We a…
An ALMA Survey of λ Orionis Disks: From Supernovae to Planet Formation
Hacar, Alvaro; Ansdell, Megan; Facchini, Stefano +8 more
Protoplanetary disk surveys by the Atacama Large Millimeter/submillimeter Array (ALMA) are now probing a range of environmental conditions, from low-mass star-forming regions like Lupus to massive OB clusters like σ Orionis. Here we conduct an ALMA survey of protoplanetary disks in λ Orionis, an ∼5 Myr old OB cluster in Orion with dust mass sensit…
Asteroseismic Modeling of Gravity Modes in Slowly Rotating A/F Stars with Radiative Levitation
Dotter, Aaron; Aerts, Conny; Van Reeth, Timothy +3 more
It has been known for several decades that transport of chemical elements is induced by the process of microscopic atomic diffusion. Yet the effect of atomic diffusion, including radiative levitation, has hardly been studied in the context of gravity-mode pulsations of core hydrogen burning stars. In this paper we study the difference in the prope…