Search Publications
The Radiation Environments of Middle-aged F-type Stars
France, K.; Hinton, P. C.; Fleming, B. +5 more
Far-ultraviolet (FUV) emission lines from dwarf stars are important driving sources of photochemistry in planetary atmospheres. Properly interpreting spectral features of planetary atmospheres critically depends on the emission of its host star. While the spectral energy distributions (SEDs) of K- and M-type stars have been extensively characteriz…
Accretion Disk Wind of Hercules X-1 during the Short High State
Fabian, A. C.; Pinto, C.; Kara, E. +5 more
Hercules X-1 is a nearly edge-on X-ray binary with a warped, precessing accretion disk, which manifests through a 35-day cycle of alternating High and Low flux states. This disk precession introduces a changing line of sight toward the X-ray source, through an ionized accretion disk wind. The sightline variation allows us to uniquely determine how…
A Broad-line Quasar with Unexplained Extreme Velocity Offsets: Post-shock Outflow?
Schramm, Malte; Mobasher, Bahram; Steinhardt, Charles L. +4 more
The quasar SDSS 0956 + 5128 exhibits three distinct velocity components with large offsets in emission: the systemic velocity of [O II], [O III], and [Ne III] narrow lines have redshift z = 0.7142; the broad Mg II line is shifted by -1200 km s-1 with respect to the narrow lines; the broad Hα and Hβ lines are at -4100 km s-1. …
Strong Variability in AzV 493, an Extreme Oe-type Star in the SMC
Oey, M. S.; Renzo, M.; Castro, N. +11 more
We present 18 yr of OGLE photometry together with spectra obtained over 12 yr revealing that the early Oe star AzV 493 shows strong photometric (ΔI < 1.2 mag) and spectroscopic variability with a dominant, 14.6 yr pattern and ~40 day oscillations. We estimate the stellar parameters T eff = 42,000 K, $\mathrm{log}L/{L}_{\odot }=5.83\p…
A Search for X-Ray/UV Correlation in the Reflection-dominated Seyfert 1 Galaxy Markarian 1044
Jithesh, V.; Medhi, Biman J.; Misra, Ranjeev +3 more
Correlated variability between coronal X-rays and disk optical/UV photons provides a very useful diagnostic of the interplay between the different regions around an active galactic nucleus (AGN) and how they interact. AGNs that reveal strong X-ray reflection in their spectra should normally exhibit optical/UV to X-ray correlation consistent with r…
Atmospheric Pressure and Molecular Cloud Formation in Early-type Galaxies
McNamara, B. R.; Russell, H. R.; Edge, A. C. +3 more
A strong correlation between atmospheric pressure and molecular gas mass is found in central cluster galaxies and early-type galaxies. This trend and a similar trend with atmospheric gas density would naturally arise if the molecular clouds condensed from hot atmospheres. Limits on the ratio of molecular to atomic hydrogen in these systems exceed …
Transverse Vertical Oscillations During the Contraction and Expansion of Coronal Loops
Li, Qiao; Zhang, Qingmin; Li, Chuan +5 more
In this paper, we carry out a detailed analysis of the M1.6 class eruptive flare occurring in NOAA active region 13078 on 2022 August 19. The flare is associated with a fast coronal mass ejection (CME) propagating in the southwest direction with an apparent speed of ~926 km s-1. Meanwhile, a shock wave is driven by the CME at the flank.…
Angular Momentum Variation of the Milky Way Thick Disk: The Dependence of Chemical Abundance and Evidence of the Inside-out Formation Scenario
Li, Lu; Hu, Guozhen; Shao, Zhengyi
We investigate the angular momentum of mono-abundance populations (MAPs) of the Milky Way thick disk by using a sample of 26,076 giant stars taken from APOGEE Data Release (DR) 17 and Gaia early DR3. The vertical and perpendicular angular momentum components, L Z and L P , of the MAPs in narrow bins have significant variat…
Searching for the Role of Mergers in Fast and Early SMBH Growth: Morphological Decomposition of Quasars and Their Hosts at z 4.8
Trakhtenbrot, Benny; Simmons, Brooke D.; Netzer, Hagai +4 more
We present rest-frame ultraviolet images of six luminous quasars at z ~ 4.8 obtained with the Hubble Space Telescope (HST). These quasars exhibit a wide range of star formation rates (SFRs) and lie in a wide range of environments. We carefully model and subtract the point-like quasar emission and investigate the morphology of the underlying host g…
Gaia17bpp: A Giant Star with the Deepest and Longest Known Dimming Event
Davenport, James R. A.; Bellm, Eric C.; Tzanidakis, Anastasios +1 more
We report the serendipitous discovery of Gaia17bpp/2MASS J19372316+1759029, a binary star with a deep single large-amplitude dimming event of ~4.5 mag that lasted over 6.5 yr. Using the optical-to-IR spectral energy distribution (SED), we constrain the primary star to be a cool giant M0III star with effective temperature T eff = 3850 K …