Search Publications
UOCS-IX. AstroSat/UVIT Study of the Open Cluster NGC 2818: Blue Stragglers, Yellow Stragglers, Planetary Nebula, and their Membership
Rao, N. Kameswara; Subramaniam, Annapurni; Rani, Sharmila +1 more
We present the first far-UV (FUV) imaging results of the intermediate-age Galactic open cluster NGC 2818 that has a planetary nebula (PN) within the field using images taken from the Ultra Violet Imaging Telescope (UVIT) aboard AstroSat. We identify cluster members by combining UVIT-detected sources with Gaia EDR3 data. We detect four bright and h…
What Do Halo CMEs Tell Us about Solar Cycle 25?
Gopalswamy, Nat; Akiyama, Sachiko; Yashiro, Seiji +3 more
It is known that the weak state of the heliosphere due to diminished solar activity in cycle 24 backreacted on coronal mass ejections (CMEs) to make them appear wider for a given speed. One of the consequences of the weak state of the heliosphere is that more CMEs appear as halo CMEs (HCMEs), and halos are formed at shorter heliocentric distances.…
Cool, Luminous, and Highly Variable Stars in the Magellanic Clouds. II. Spectroscopic and Environmental Analysis of Thorne-Żytkow Object and Super-AGB Star Candidates
Drout, Maria R.; O'Grady, Anna J. G.; Kochanek, C. S. +9 more
In previous work, we identified a population of 38 cool and luminous variable stars in the Magellanic Clouds and examined 11 in detail in order to classify them as either Thorne-Żytkow objects (TŻOs; red supergiants with a neutron star cores) or super-asymptotic giant branch (sAGB) stars (the most massive stars that will not undergo core collapse)…
The First Y Dwarf Data from JWST Show that Dynamic and Diabatic Processes Regulate Cold Brown Dwarf Atmospheres
Leggett, S. K.; Tremblin, Pascal
The James Webb Space Telescope (JWST) is now observing Y dwarfs, the coldest known brown dwarfs, with effective temperatures T eff ≲ 475 K. The first published observations provide important information: not only is the atmospheric chemistry out of equilibrium, as previously known, but the pressure-temperature profile is not in the stan…
The First Weak-lensing Analysis with the James Webb Space Telescope: SMACS J0723.3-7327
Faisst, Andreas; Chary, Ranga-Ram; Jee, M. James +1 more
Utilizing the James Webb Space Telescope Early Release NIRCam Observations, we perform a weak-lensing analysis of the massive galaxy cluster SMACS J0723.3-7327 (z = 0.39). We investigate the spatial variation of the point-spread function (PSF) from the stars in the mosaic image. Our measurements show that the PSF for both modules has very small sp…
Enhanced Size Uniformity for Near-resonant Planets
Dai, Fei; Wang, Songhu; Goyal, Armaan V.
Super-Earths within the same close-in, compact planetary system tend to exhibit a striking degree of uniformity in their radius, mass, and orbital spacing, and this "peas-in-a-pod" phenomenon itself serves to provide one of the strongest constrains on planet formation at large. While it has been recently demonstrated from independent samples that …
Effective Temperature Estimations from Line Depth Ratios in the H- and K-band Spectra of IGRINS
Jaffe, Daniel T.; Mace, Gregory N.; Afşar, Melike +5 more
Determining accurate effective temperatures of stars buried in the dust-obscured Galactic regions is extremely difficult from photometry. Fortunately, high-resolution infrared spectroscopy is a powerful tool for determining the temperatures of stars with no dependence on interstellar extinction. It has long been known that the depth ratios of temp…
An APEX Study of Molecular Outflows in FUor-type Stars
Henning, Thomas; Ábrahám, Péter; Kóspál, Ágnes +4 more
The FU Orionis-type objects (FUors) are low-mass pre-main-sequence objects that go through a short-lived phase (~100 yr) of increased mass accretion rate (from 10-8 to 10-4 M ⊙ yr-1). These eruptive young stars are in the early stages of stellar evolution and thus still deeply embedded in a massive envel…
The Spin-Orbit Misalignment of TOI-1842b: The First Measurement of the Rossiter-McLaughlin Effect for a Warm Sub-Saturn around a Massive Star
Rice, Malena; Wang, Songhu; Hixenbaugh, Kyle +1 more
The mechanisms responsible for generating spin-orbit misalignments in exoplanetary systems are still not fully understood. It is unclear whether these misalignments are related to the migration of hot Jupiters or are a consequence of general star and planet formation processes. One promising method to address this question is to constrain the dist…
As Simple as Possible but No Simpler: Optimizing the Performance of Neural Net Emulators for Galaxy SED Fitting
Johnson, Benjamin D.; Tacchella, Sandro; Suess, Katherine A. +7 more
Artificial neural network emulators have been demonstrated to be a very computationally efficient method to rapidly generate galaxy spectral energy distributions, for parameter inference or otherwise. Using a highly flexible and fast mathematical structure, they can learn the nontrivial relationship between input galaxy parameters and output obser…