Barbara Castanheira, Ph.D.
Assistant Professor Baylor University
Media
Biography
Areas of Expertise
Education
Universidade Federal do Rio Grande do Sul
Ph.D.,
Physics
2007
Universidade Federal do Rio Grande do Sul
M.Sc.
Astronomy
2003
Universidade Federal do Rio Grande do Sul
B.Sc.
Physics
2002
Media Appearances
Newly Discovered Asteroid 2024 PT5 Becomes Earth’s Temporary Mini-Moon
Baylor University online
2024-09-27
“This mini moon is particularly interesting for its size – it’s one of the largest ones. But it’s not a rare event,” said Barbara Castanheira Endl, Ph.D., assistant professor of physics at Baylor University.
'Some are counterfeit' | Your 2024 guide to buying total solar eclipse glasses
KCEN tv
2024-02-19
As far as when to keep your glasses on and when to take them off, Dr. Barbara Castanheira Endl with Baylor University says there are a few things you need to keep in mind.
"Put your glasses on and then you look to the sun and then you look away and you take them off," Endl said. "You only have the four minutes, or a little over four minutes depending on where you are, when the moon is fully eclipsing the sun that you can look, and you should, because if you look through your glasses, you won't be able to see the sun. That's the only thing that has to be done."
Rare “Ring of Fire” Eclipse Will Be Visible in Texas on Saturday, Oct. 14
Baylor University online
2023-10-02
Baylor University astrophysicist Barbara Castanheira Endl, Ph.D., assistant professor of physics, said the conditions must be perfect for this natural phenomenon to occur. The sun and the moon must be exactly in line with the Earth. As they cross paths, the moon will appear slightly smaller than the sun, producing the “Ring of Fire.”
‘The universe is fascinating’: Professor explores research on dwarf stars
Baylor Lariat print
2023-09-21
Dr. Barbara Castanheira Endl, assistant professor of physics, is preparing to publish the results of her research on white dwarf stars.
Her focus was to understand the structure and components of the stars. Due to their very small and faint appearance and being at the final stage of star evolution, studying them is often on the fringes of telescopic capabilities.
Articles
The Pulsating White Dwarf G117-B15A: Still the Most Stable Optical Clock Known
The Astrophysical Journal2020
The pulsating hydrogen atmosphere white dwarf star G 117-B15A has been observed since 1974. Its main pulsation period at 215.19738823(63) s, observed in optical light curves, varies by only (5.12 ± 0.82) × 10−15 ss−1 and shows no glitches, as pulsars do. The observed rate of period change corresponds to a change of the pulsation period by 1 sin 6.2 million yr. We demonstrate that this exceptional optical clock can continue to put stringent limits on fundamental physics, such as constraints on interaction from hypothetical dark matter particles, as well as to search for the presence of external substellar companions.
The Stars of the HETDEX Survey. I. Radial Velocities and Metal-poor Stars from Lowresolution Stellar Spectra
The Astrophysical Journal2021
The Hobby–Eberly Telescope Dark Energy Experiment (HETDEX) is an unbiased, massively multiplexed spectroscopic survey, designed to measure the expansion history of the universe through low-resolution (R ∼ 750) spectra of Lyα emitters. In its search for these galaxies, HETDEX will also observe a few times 105 stars. In this paper, we present the first stellar value-added catalog within the internal second data release of the HETDEX Survey (HDR2). The new catalog contains 120,571 low-resolution spectra for 98,736 unique stars between 10
The Hobby–Eberly Telescope Dark Energy Experiment (HETDEX) Survey Design, Reductions, and Detections
The Astrophysical Journal2021
Wedescribe the survey design, calibration, commissioning, and emission-line detection algorithms for the HobbyEberly Telescope Dark Energy Experiment (HETDEX). The goal of HETDEX is to measure the redshifts of over a million Lyα emitting galaxies between 1.88 < z
Seismological Studies of Pulsating DA White Dwarfs Observed with the Kepler Space Telescope and K2 Campaigns 1–8
The Astrophysical Journal2023
AllS single stars that are born with masses up to 8.5–10 Me will end their lives as white dwarf (WD) stars. In this evolutionary stage, WDs enter the cooling sequence, where the stars radiate away their thermal energy and are basically cooling. As these stars cool, they reach temperatures and conditions that cause the stars to pulsate. Using differential photometry to produce light curves, we can determine the observed periods of pulsation from the WD. We used the White Dwarf Evolution Code (WDEC) to calculate a grid of over one million models with various temperature, stellar mass, and mass of helium and hydrogen layers and calculated their theoretical pulsation periods. In this paper, we describe our approach to WD asteroseismology using WDEC models, and we present seismological studies for 29 observed DAVs in the Kepler and K2 data sets, 25 of which have never been analyzed using these observations and 19 of which have never been seismically analyzed in any capacity before. Learning about the internal structure of WDs places important constraints on the WD cooling sequence and our overall understanding of stellar evolution for low-mass stars.
Astrophysical Properties of the Sirius Binary System Modeled with MESA
The Astrophysical Journal2024
Sirius is the brightest star in the night sky and, despite its proximity, this binary system still imposes intriguing questions about its current characteristics and past evolution. H. E. Bond et al. published decades of astronometric measurements of the Sirius system, determining the dynamical masses for Sirius A and B, and the orbital period. We have used these determinations, combined with photometric determinations for luminosity and spectroscopic determinations of effective temperature (Teff) and metallicity, to model the evolution of the Sirius system using Modules for Experiments in Stellar Astrophysics. We have constructed a model grid calculated especially for this system and were able to obtain, for Sirius B,aprogenitormassof6.0±0.6Me, yielding a white dwarf mass of 1.015 ±0.189 Me. Our best determination for the age of the system is 203.6 ±45Myr with a metallicity of 0.0124. We have compared our best-fit models with the ones computed using TYCHO, YREC, and PARSEC, establishing external uncertainties. Our results are consistent with the observations and support a noninteracting past.
White Dwarfs with Infrared Excess in the HET Dark Energy Experiment
The Astrophysical Journal2025
White dwarfs with infrared excess emission provide a window into the late stages of stellar evolution and the dynamics of circumstellar environments. Using data from the Hobby–Eberly Telescope Dark Energy Experiment, we characterized 30 white dwarfs exhibiting infrared excess, including 29 DA and 1 DB stars. While an infrared excess can arise from dusty disks or cool (sub)stellar companions, our sample is limited to stellar companions, due to our selection based on SDSS photometry, which is sensitive to excess emission at wavelengths λ < 1μm. Our sample contains 22 newly identified excess sources not previously reported in the literature. Spectroscopic observations are available for 10 sources via SDSS, of which only 8 have prior spectroscopic classifications in the literature. In this paper, we present the determination of the effective temperature and surface gravity of these white dwarfs. We used the Balmer line profiles to compare with current atmospheric models in order to determine the photospheric parameters of the white dwarfs, minimizing contamination introduced by the infrared source. We used photometric data from the SDSS and the Gaia mission to resolve the degeneracies between hot and cold solutions from spectroscopy, constraining the photospheric parameters.
