# Total Solar Eclipse: August 21, 2017

## News and Events

Distorted galaxy NGC 2442 can be found in the southern constellation of the flying fish, (Piscis) Volans. Located about 50 million light-years away, the galaxy's two spiral arms extending from a pronounced central bar have a hook-like appearance in wide-field images. But this mosaicked close-up, constructed from Hubble Space Telescope and European Southern Observatory data, follows the galaxy's structure in amazing detail. Obscuring dust lanes, young blue star clusters and reddish star forming regions surround a core of yellowish light from an older population of stars. The sharp image data also reveal more distant background galaxies seen right through NGC 2442's star clusters and nebulae. The image spans about 75,000 light-years at the estimated distance of NGC 2442.
Check current conditions and historical weather data at the ESC.
The BYU Department of Physics and Astronomy invites applications for two faculty positions to begin August 2021. The application deadline is October 15, 2020.
Notice of Intent to File a Labor Condition Application to Employ an Alien H-1B Temporary Worker at Brigham Young University
A new study from researchers at Brigham Young University and Pennsylvania State University provides the most accurate estimate of the number of Earth-like planets in the universe. The team looked at the frequency of planets that are similar to Earth in size and in distance from their host star, stars similar to our Sun. Knowing the rate that these potentially habitable planets occur will be important for designing future astronomical missions to characterize nearby rocky planets around Sun-like stars that could support life.
Physics professor Ben Frandsen recently received an Early Career Award from the United States Department of Energy

## Selected Publications

BYU Authors: M. D. Joner and M. Spencer, published in Astrophys. J.
We model the ultraviolet spectra of the Seyfert 1 galaxy NGC 5548 obtained with the Hubble Space Telescope during the 6 month reverberation mapping campaign in 2014. Our model of the emission from NGC 5548 corrects for overlying absorption and deblends the individual emission lines. Using the modeled spectra, we measure the response to continuum variations for the deblended and absorption-corrected individual broad emission lines, the velocity-dependent profiles of Lyα and C iv, and the narrow and broad intrinsic absorption features. We find that the time lags for the corrected emission lines are comparable to those for the original data. The velocity-binned lag profiles of Lyα and C iv have a double-peaked structure indicative of a truncated Keplerian disk. The narrow absorption lines show a delayed response to continuum variations corresponding to recombination in gas with a density of ∼105 cm−3. The high-ionization narrow absorption lines decorrelate from continuum variations during the same period as the broad emission lines. Analyzing the response of these absorption lines during this period shows that the ionizing flux is diminished in strength relative to the far-ultraviolet continuum. The broad absorption lines associated with the X-ray obscurer decrease in strength during this same time interval. The appearance of X-ray obscuration in ∼2012 corresponds with an increase in the luminosity of NGC 5548 following an extended low state. We suggest that the obscurer is a disk wind triggered by the brightening of NGC 5548 following the decrease in size of the broad-line region during the preceding low-luminosity state.
BYU Authors: J W Moody, published in Mon. Not. Roy. Astron. Soc.
The object 4C 71.07 is a high-redshift blazar whose spectral energy distribution shows a prominent big blue bump and a strong Compton dominance. We present the results of a two-year multiwavelength campaign led by the Whole Earth Blazar Telescope (WEBT) to study both the quasar core and the beamed jet of this source. The WEBT data are complemented by ultraviolet and X-ray data from Swift, and by γ-ray data by Fermi. The big blue bump is modelled by using optical and near-infrared mean spectra obtained during the campaign, together with optical and ultraviolet quasar templates. We give prescriptions to correct the source photometry in the various bands for the thermal contribution, in order to derive the non-thermal jet flux. The role of the intergalactic medium absorption is analysed in both the ultraviolet and X-ray bands. We provide opacity values to deabsorb ultraviolet data, and derive a best-guess value for the hydrogen column density of $N_{\rm H}^{\rm best}=6.3 \times 10^{20} \rm \, cm^{-2}$ through the analysis of X-ray spectra. We estimate the disc and jet bolometric luminosities, accretion rate, and black hole mass. Light curves do not show persistent correlations among flux changes at different frequencies. We study the polarimetric behaviour and find no correlation between polarisation degree and flux, even when correcting for the dilution effect of the big blue bump. Similarly, wide rotations of the electric vector polarisation angle do not seem to be connected with the source activity.
BYU Authors: Burke Boyer, Zacory D. Shakespear, Christiana Zaugg, Mayalen Laker, Daniel Jones, Nicholas Van Alfen, and J. Ward Moody, published in Res. Notes AAS
The stellar mass function is assumed to be constant through time. If it is constant, then the flux contribution to HII regions from hot, high mass stars would remain uniform with redshift. If this contribution has changed, then the mean H ii region temperature would change with increasing redshift. To quantify how mean stellar temperature may have evolved with time, we mapped the temperature of H ii regions to a redshift of about z = 0.7 using SDSS spectral data. We find no distance dependence with temperature.