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Department Library

2019

Miriam Packard (Senior Thesis, April 2019, Advisor: Mike Joner )

Abstract

Variable stars, like RR Lyraes, can be useful for determining globular cluster characteristics. The globular cluster NGC 5466 has many RR Lyares in a relatively spacious field. The RR Lyraes in the globular cluster NGC 5466 were used to create light curves from data taken using photometry at West Mountain Observatory in Utah. This photometric data is input into a computer program called FITLC, which determines periods and amplitudes by fitting light curve templates to the data. These periods are compared with the periods found in Ferro et al. (2008). Metallicity of the cluster is solved for using three different methods outlined in Jeffery et al. (2011) that also depend on period: the Sarajendini, Alcock, and Bono method. The Alcock method provided metallicity results closest to Ferro et al. (2008) with the average metallicity of [Fe/H] = -2.127437 and a standard deviation of 0.062176.

2018

Sean Pearce (Senior Thesis, April 2018, Advisor: Mike Joner )

Abstract

To better understand the effects of high metallicity on white dwarf cooling processes, especially the white dwarf cooling age, we have analyzed images of the metal-rich open cluster NGC 6253, from the 8 m Gemini-South Observatory. To standardize the Gemini photometry of the cluster, we have also secured imaging data of both the cluster and standard star fields using the 0.6 m SARA Observatory at Cerro Tololo Inter-American Observatory. By comparing the photometric magnitudes and colors of additional stars in standard star fields of both the SARA data and the published Gemini zero-points of the standard star fields, we calibrated the data obtained for the cluster. These calibrations are an important part of the project to obtain a standardized deep color magnitude diagram and white dwarf luminosity function to analyze the cluster. With the standardized color magnitude diagram, we determined the cluster’s main sequence turnoff age to be 4.6±0.2 Gyr., much older than the earlier results showing an age ∼ 3.6 Gyr. Because the cluster is much older than expected, the white dwarfs have cooled and dimmed beyond our limits of detection. Since we were unable to detect the coolest white dwarfs, we could not make a white dwarf luminosity function with the current data set.

2017

Melissa Hallum (Senior Thesis, April 2017, Advisor: Mike Joner )

Abstract

Reverberation mapping is a technique used to determine the mass of the supermassive black hole at the center of an active galaxy. The technique uses both photometry and spectroscopy. This project focuses on the photometry aspect of reverberation mapping and seeks to determine if the photometric method used will significantly affect the results. The light curves of NGC 4151 produced using AstroImageJ, IRAF, and ISIS are compared. IRAF and AstroImageJ use differential aperture photometry with comparison stars, while ISIS uses image subtraction photometry. ISIS yielded light curves different to those created from AstroImageJ and IRAF. Furthermore, due to errors from comparison stars, it is concluded that image subtraction photometry may be more accurate than differential aperture photometry for this galaxy.

2015

Carla June Carroll (Masters Thesis, June 2015, Advisor: Mike Joner )

Abstract

For the past several decades, mass estimates for supermassive black holes hosted by active galactic nuclei (AGN) have been made with the reverberation mapping (RM) technique. This methodology has produced consistent results and has been used to establish several relations that link the characteristics of the host galaxy to the mass of the central black hole. Despite this success, there are less than 50 AGN with black hole masses derived from RM. This low number is generally attributed to the difficulties in coordinating large blocks of telescope time for making simultaneous photometric and spectroscopic observations. Spectroscopic observations also generally require several months of nightly observations with moderate to large size telescopes as the signal-to-noise ratio is too low for smaller telescopes. We have made photometric observations of NGC 5548 in four filters (a custom-made Hα10 filter, the Strömgren y filter, the Johnson/Cousins V filter and the Johnson/Cousins R filter) in order to evaluate a photometric methodology for determining the lag time between the variations observed in the continuum and the Hα emission from the broad-line region (BLR) gas. This time delay represents the mean light travel time to the BLR and is therefore a measurement of the mean BLR radius. Multiple JAVELIN analyses of the three continuum light curves (y, V, and R), relative to the light curve from the Hα10 filter yields a value for τ = 3.3 ± 0.1 days. Adopting a value of f = 5.5, along with a single-epoch spectroscopic measurement from Park et of Δv = 4354±25 km/s, enables us to estimate a black hole mass of M_BH = 67.2±2.2x10^6 M_sun.

2013

Carla Carroll (Senior Thesis, April 2013, Advisor: Mike Joner )

Abstract

The environment surrounding supermassive black holes in active galaxies can be probed through the reverberation mapping technique. This technique requires the galactic nuclei to be simultaneously observed spectroscopically with a large 2m-class telescope and photometrically with a smaller telescope. Since obtaining large telescope time for long observing campaigns is difficult, we present a new broadband photometric reverberation mapping technique that can be performed on meter-class telescopes. Observations in the R and V band filters provide a measurement of time variable emission in Hα and Hβ respectively mixed with an observation of the continuum. The I band filter provides a continuum-only measurement. We obtained photometric observations in VRI on the 0.9-meter telescope at the West Mountain Observatory of the very broad-line Seyfert I galaxy Mrk 926 to test this technique. We found Mrk 926 relatively quiescent during the fall of 2012, though we originally selected Mrk 926 due to its strong emission lines and strong variability. This made estimation of Mrk 926's supermassive black hole mass impossible. Despite the quiescent results of Mrk 926, we produced high precision light curves from all filters over the period of several months. Our data are sufficient that had our target AGN\index{AGN} been variable, we would have been able to measure delay times between the BLR and the nucleus.

Michelle Spencer (Senior Thesis, May 2013, Advisor: Mike Joner )

Abstract

This thesis will cover the research behind the recent supernovae SN 2010hh, 2011dh, 2011fe and 2012aw. The different types of supernovae will be introduced and discussed. The data gathering and processing will be described. The light curve resulting from Type IIb supernova 2011dh will be compared to the template.The light curve for Type II-P supernova 2012aw will be discussed. Finally, the Type Ia supernovae 2010hh and 2011fe will be used to calculate their distance modulus and thus the distance to their respective galaxies NGC 6524 and M101.

2009

Laura Adams (Senior Thesis, April 2009, Advisor: Mike Joner )

Abstract

Balmer series line strength is known to depend on photospheric stellar temper- ature. In the past astronomers relied on the H¯ line to determine the temperature of spectral type B, A, and F stars. The development of detectors that are more sensitive to red wavelengths now makes it easier to observe the H® line. This thesis presents a list of the H® values for several standard stars scattered throughout the sky and easily viewed from the northern hemisphere. Stars from the Pleiades, Hyades, Coma, and NGC 752 star clusters are included as well. This color index may be used to determine stellar temperature for spectral type B, A, F, G, and K stars. The obser- vation method is independent of instrumentation. Data were obtained at the West Mountain Observatory of Brigham Young University.

2008

E. Paul Iverson (Senior Thesis, April 2008, Advisor: Mike Joner )

Abstract

This thesis outlines the development and application of a new flux technique of aperture photometry under consideration at Brigham Young University (BYU). Previous to this method, researchers used a set aperture method to determine a star’s instrumental magnitude. This method does not compensate for changing atmospheric conditions nor does it optimize itself to the data. The new approach applies a separate aperture per point source. The radius of this aperture is determined by a user-defined percentage of the flux of the object’s point spread function (PSF). Apertures are, therefore, optimized for signal and changing atmospheric or telescope conditions and all are forced onto the same magnitude scale. This makes it possible to glean more accurate results from all data. Furthermore, the method is contained within a script that eliminates the need for excessive user interaction. The variable star CY Aquarii and the standard cluster M67 are used to demonstrate the application of this flux method.

Craig Swenson (Senior Thesis, April 2008, Advisor: Mike Joner )

Abstract

This thesis introduces a series of IRAF scripts written to facilitate the reduction of large amounts of data by students and faculty in the Astronomy Research Group of Brigham Young University. These automated reduction scripts provide a complete data-pipeline for frames taken using Brigham Young University’s Orson Pratt and West Mountain Observatory telescopes. The functionality of these scripts is described in detail, along with the thought processes involved in their writing. Observations of the variable stars DY Peg and AE UMa are used as a test case to demonstrate the use of the scripts and to show improvements made in the reduction process. 17 new times of maximum light are presented for DY Peg.

2007

Joel Jolley (Senior Thesis, August 2007, Advisor: Mike Joner )

Abstract

This research presents time-series photometric data on the short-period, doublemode  Scuti star AE Ursae Majoris based on new observations from 2007. Archival data from 1974 onward are used to evaluate reported period changes. There are 19 new times of maximum light with six times observed simultaneously on more than one telescope. Forty-three times of maximum light published from 2002 through 2006 have been incorporated into this research making a total of 62 new times of maximum used for period determinations. The ephemeris from Broglia & Conconi (1975) was corrected giving a new ephemeris of HJDmax = 2442062:58205 + 0:0860170734  E from which O-C values are reported. The observations and analysis support the previous ndings of Pocs & Szeidl (2001) and Zhou (2001) that the period of AE UMa has been constant over the past 33 years with a corrected value of P0 = 0d:0860170734. This data refutes the quickly decreasing period found by Hintz et al. (1997) of 􀀀1:14  10􀀀10dd􀀀1. Through Fourier analysis we calculated the rst overtone period P1 = 0d:066528768 and determined frequencies f0 = 11:6256845 and f1 = 15:0310915 corresponding to the two periods.

Cody Short (Senior Thesis, April 2007, Advisor: Mike Joner )

Abstract

The Astronomy Group of Brigham Young University has been actively involved in acquiring astronomical data from the Tenagra Remote Observatory located in the Sonoran Desert of southern Arizona. From September 17, 2006 through January 31, 2007 this data has undergone a holistic review to characterize the performance of a single CCD employed in the Tenagra II telescope’s imaging system. Several of the CCD’s main characteristics have been established. The CCD gain and readnoise were found to be approximately 4 e−/ADU and 29 e− respectively. The CCD’s response linearity has been confirmed and the dark current examined. The CCD has been examined for bad pixels and some results are included. Temperature stability of the CCD has also been evaluated and found to be consistent within ±1%. The results of this review, presented herein, will be employed by faculty and students to lead to the best possible calibration procedures for the raw data acquired from the Tenagra II telescope. The results will also be used to aid in the process of calibrating and evaluating CCD detectors that are used in future investigations.

2006

Mana Philip Vautier (Senior Thesis, April 2006, Advisor: Mike Joner )

Abstract

This thesis establishes a standard catalog for an H photometric system based on observation of selected field stars as well as main sequence stars in the nearby open cluster known as the Pleiades. All observations were made through H wide (210 Ang) and narrow (30 Ang) passbands. Using a color index centered on a single wavelength eliminates eff ects resulting from atmospheric extinction and produces a reddening free temperature index. The H index also has several advantages over the H index including greater CCD quantum efficiency, less line blanketing and the ability to detect a wider range of spectral types. As part of a bigger project, data from this thesis will be combined with data taken on other clusters to produce a master catalog. All data were collected from Brigham Young University's Orson Pratt and West Mountain observatories.

2004

Elizabeth Jeffery (Senior Thesis, January 2004, Advisor: Mike Joner )

Abstract

1995

Kenneth Nelson (Honors Thesis, April 1995, Advisor: Mike Joner )

Abstract