Abstracts of the 235th AAS Meeting (Honolulu, HI)
American Astronomical Society
January, 2020
Special Session 001 — HAD I:
Centennial of Eddington’s
Solar-Eclipse Tests of Einstein’s
General Relativity
001.02 — Einstein’s Jury: The Race to Test Relativity
J. Crelinsten1
1 University of Toronto, Toronto, ON, Canada
While Einstein’s theory of relativity ultimately laid the foundation for modern studies of the universe, it took a long time to be accepted. Its acceptance was largely due to the astronomy community, which at Einstein’s urging undertook precise measurements to test his astronomical predictions. This paper fo-cuses on astronomers’ attempts to measure the bend-ing of light by the sun’s gravitational field. The work started in Germany and America before Einstein had completed his general theory, which he published during the depths of the First World War. Only a handful of astronomers, including Arthur Stanley Eddington in England, could understand the theory. Most astronomers were baffled by it and focused on testing its empirical predictions. The well-known 1919 British eclipse expeditions that made Einstein famous did not convince most scientists to accept rel-ativity. The 1920s saw numerous attempts to mea-sure light bending, amid much controversy and in-ternational competition.
001.03 — No Shadow of a Doubt: The 1919 Eclipse That Confirmed Einstein’s Theory of Relativity
D. Kennefick1
1 University of Arkansas, Fayetteville, Fayetteville, AR
Abstract not available.
001.01 — Eclipse Tests of General Relativity in the 21st Century
J. M. Pasachoff1
1 Hopkins Observatory, Williams College, Williamstown, MA
The analysis of the results, and their reception over the years, of the 1919 total solar eclipse observations from Principe by Arthur Eddington and colleague Edwin Cottingham, and from Sobral (Brazil) by An-drew Crommelin and Charles Davidson, all in col-laboration with Astronomer Royal Sir Frank Wat-son DyWat-son, will be discussed by experts Daniel Ken-nefick (US) and Jeffrey Crelinsten (Canada). At this Centennial, I will discuss current repetitions of this ”Eddington Experiment” and future plans.
JMP’s eclipse research receives major support from grant AGS-903500 from the Solar Terrestrial Program, Atmospheric and Geospace Sciences Divi-sion, U.S. National Science Foundation.
Plenary Prize Lecture 101 — Kavli
Foundation Plenary Lecture
101.01 — Black Holes Snacking on Stars: A Systematic Exploration of Transients in Galaxy Nuclei
S. Gezari1
1 University of Maryland, College Park
they have enabled important progress in our under-standing of the physical mechanisms powering these events, and how they are shedding light onto the ac-cretion physics and demographics of massive black holes lurking in galaxy nuclei.
Poster Session 102 — New Results
From The North American
Nanohertz Observatory For
Gravitational Waves
102.01 — Joint search for isolated sources and an unresolved confusion background in PTA data
N. Cornish1; B. Becsy2
1 Montana State Univ., Bozeman, MT 2 Physics, Montana State Univ., Bozeman, MT
The dominant source of gravitational waves in the nano-Hertz frequency band is thought to come from a cosmological population of supermassive black hole binaries. Current searches using pulsar timing data either look for signals from isolated systems, or for a stochastic background formed by a large popu-lation of sources. In reality the signal will lie some-where between these extremes. We have developed a new, optimal search technique that spans the ex-tremes using trans-dimensional Bayesian inference.
102.02 — NANOGrav: cyberinfrastructure supporting training and outreach
A. Brazier1; S. Chatterjee1; J. Cordes1; T. Dolch2; N. Garver-Daniels3; O. Haggerty4; M. Lam5
1 Cornell University, Ithaca, NY 2 Hillsdale College, Hillsdale, MI
3 West Virginia University, Morgantown, WV 4 Oregon State University, Corvallis, OR 5 Rochester Institute of Technology, Rochester, NY
A decades-long project, NANOGrav needs to con-tinually train new members, ranging in experience from high school students and undergraduates to es-tablished research scientists and, in addition, edu-cating the public is a core element of NANOGrav’s mission. Training and illuminating such a diverse and continually-replenished group benefits enor-mously from scientists and cyberinfrastructure ex-perts working together to provide training tools which are maximally available, maintained indefi-nitely and updated as appropriate.
102.03 — Balancing The Solar System With Pulsar Timing Arrays
S. R. Taylor1; M. Vallisneri2; J. Simon2; NANOGrav
Physics Frontier Center1
1 Department of Physics & Astronomy, Vanderbilt University, Nashville, TN
2 Jet Propulsion Laboratory, Pasadena, CA
Pulsar timing arrays are galactic-scale gravitational wave detectors, whose target signal is the aggre-gate background from a population of supermas-sive binary black holes. Robust inference of the small timing perturbations caused by these gravita-tional waves requires accurate posigravita-tional knowledge of the Earth with respect to the Solar System barycen-ter. Current pulsar timing datasets, like those pro-duced by the North American Nanohertz Obser-vatory for Gravitational Waves (NANOGrav), have reached a sensitivity level where searches for the gravitational wave background have become biased by the errors in current Solar System ephemerides. NANOGrav’s new Bayesian ephemeris approach marginalizes gravitational wave results over the un-certainties in Earth’s orbit, thereby producing the first pulsar timing constraints on the stochastic back-ground that are robust against ephemeris error. We present this work and comment on the prospects for pulsar timing data to be used in conjunction with di-rect observations to enhance our understanding of the orbits of Solar System bodies.
102.04 — An improved model for burst with memory searches, or We’ve been doing this all wrong
S. McWilliams1; A. Choudhary1 1 West Virginia University, Morgantown, WV
for the very massive sources being considered, as the memory can build over timescales much larger than the observing cadence. When we correct for this ef-fect, we find, for instance, that more massive sources do not necessarily induce larger residuals, since the quadratic subtraction that must be applied to gener-ate the residuals can better fit a very massive source, and thereby yield a smaller residual. We present de-tailed studies of the corrected residuals, and propose an improved model that can be used for searches.
102.06 — Timing an Exotic Binary Pulsar
G. Y. Agazie1; M. G. Mingyar1; M. A. McLaughlin1; J. K. Swiggum2; B. J. Shapiro-Albert1
1 Dept. of Physics and Astronomy, West Virginia University, Mor-gantown, WV
2 Dept. of Physics, University of Wisconsin-Milwaukee, Milwau-kee, WI
The Green Bank North Celestial Cap (GBNCC) sur-vey is a 350 MHz all-sky sursur-vey using the Robert C. Byrd Green Bank Telescope in West Virginia carried out in order to discover pulsars. To date, the survey has discovered over 161 pulsars, including 20 mil-lisecond pulsars (MSPs) and 11 rotating radio tran-sients (RRATs). The survey has covered declinations from -40 degrees and upwards. Several exotic pul-sars have been discovered in the survey, including J1800+50, an intermittent binary pulsar with a 176 milliseconds spin period. It has a binary period of 2 days, an eccentricity of 0.3, and a semimajor axis of 7 light seconds. This pulsar has a much longer period than millisecond pulsars with white dwarf compan-ions, and therefore most likely has a neutron star or main sequence companion, making it a rarity among binary pulsars. We are currently calculating a tim-ing solution over several years of data, which will re-sult in an accurate position, so we may search for a possible optical companion. Timing this pulsar has proved difficult as more than half of all observations of the pulsar have been unable to detect it. Future studies will also show whether this pulsar’s intermit-tency is related to its binary nature, intrinsic to the pulsar, or due to modulations from the interstellar medium.
102.07 — Student Teams of Astrophysics ResearcherS (STARS) in the North American Nanohertz Observatory for Gravitational Waves
T. Dolch1; F. Crawford2; NANOGrav Physics Frontiers
Center1
1 Physics, Hillsdale College, Hillsdale, MI 2 Franklin and Marshall College, Lancaster, PA
The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) collaboration, a NSF Physics Frontiers Center, searches for gravi-tational waves (GWs) in pulsar timing data from Arecibo Observatory (AO) and the Green Bank Tele-scope (GBT). The Student Teams of Astrophysics Re-searchers (STARS) program engages undergraduates through training in key science areas of NANOGrav that contribute to GW detection - in particular, searching survey data for new pulsars and conduct-ing remote timconduct-ing observations with AO and the GBT. Weekly STARS telecons and student sessions at collaboration meetings train students in these skills, as well as in soft skills such as presenting, leadership, and networking with senior researchers. Students participate in research abroad through the Interna-tional Research Experiences for Students (IRES) pro-gram. Students’ pulsar discoveries are essential for GW detection, as the signal-to-noise of the GW back-ground amplitude scales linearly with the number of pulsars regularly timed.
102.08 — Quantifying Pulse Profile Features to Determine Long-Term Utility for Pulsar Timing Arrays
J. A. Cutter1
1 Electrical & Computer Engineering, University of Washington, Seattle, WA
is to determine much sooner after initial observation whether a pulsar’s TOA will be precise over time and therefore the pulsar will be a valuable addition to a high-precision PTA.
102.10 — Multifrequency Single-Pulse Study of Millisecond Pulsars
G. L. Siebert1; N. T. Palliyaguru2; B. B. Perera2
1 Department of Physics, University of Wisconsin-Madison, Madi-son, WI
2 Arecibo Observatory, Arecibo, PR
Single-pulse studies of millisecond pulsars (MSPs) may provide important clues about their noise prop-erties and emission mechanism. However, single-pulse studies of MSPs have been sparse due to their low flux densities. J1022+1001 and J1713+0747 are two MSPs which can also be detected in sin-gle pulses. We observed individual pulses of these two pulsars with the Arecibo 305-m radio telescope at multiple frequencies. We present search results for various single pulse phenomena such as pulse-to-pulse modulation, drifting sub-pulses and giant pulses. We discuss the possibility of constraining the geometry of these pulsars using their linear polariza-tion measurements.
102.11 — Double Neutron Stars Formed in Globular Clusters: Simulating an Evolutionary Route
E. Chwalik1; E. Rigby2; M. Bagchi3; S. Bates4; D.
Lorimer5; M. McLaughlin5; N. Pol5; D. Stinebring2;
C. Tenney6
1 Department of Physics and Astronomy, West Virgnia University, Morgantown, WV
2 Oberlin College, Oberlin, OH
3 Institute of Mathematical Sciences, Chennai, India 4 Tessella, Stevenage, United Kingdom
5 Department of Physics and Astronomy, West Virginia University, Morgantown, WV
6 SciTech, Inc., Boulder, CO
As extremely dense objects generating intense grav-itational fields, double neutron star (DNS) systems are integral to many tests of general relativity. While their orbital precessions have been used as a direct strong field test, they can also be used more indi-rectly as probes for gravitational waves, and tests of well timed pulsar systems could eventually lead to direct observations of gravitational waves from dis-tant supermassive black hole binaries. Even so, very few DNS systems are known, totalling only 19 sys-tems out of nearly 3000 known pulsars. While future
surveys will almost certainly reveal more systems of this nature, optimizing these surveys using theoret-ical information on the evolutionary paths of DNS systems could greatly expedite the process. One pos-sible formation route is through interactions of neu-tron stars with main sequence stars in globular clus-ters. As these stars orbit, the neutron star accretes material and angular momentum from its main se-quence companion. This increases the neutron star rotation, sometimes up to millisecond periods, and potentially causes its companion to undergo a super-nova explosion and collapse into a neutron star. The velocity kick given to the system by the second com-panion’s supernova could jettison the system out of the cluster, leaving it with a small final velocity as it slowly begins to fall into a path set by the gravita-tional potential of the galaxy. We modeled a popu-lation of DNS systems of this nature, evolving their spin and trajectory forward from formation to the present day. By running simulated surveys on these systems and comparing the resulting population to the known population of DNS systems using Kol-mogorov Smirnov tests, we draw conclusions about the possibility of globular clusters serving as birth locations for DNS systems.
102.12 — Double Neutron Stars Formed in Globular Clusters: Detecting the Population
E. Rigby1; E. Chwalik2; M. Bagchi3; D. Lorimer2; M.
McLaughlin2; N. Pol2; S. Bates4; D. Stinebring5; C. Tenney6
1 Department of Chemistry and Biochemistry, Oberlin College, Oberlin, OH
2 Department of Physics and Astronomy, West Virginia University, Morgantown, WV
3 Institute of Mathematical Sciences, Chennai, India 4 Tessella, Stevenage, United Kingdom
5 Department of Physics and Astronomy, Oberlin College, Oberlin, OH
6 SciTech, Inc., Boulder, CO
algo-rithm that searched for pulsars that might be de-tectable using various pulsar surveys. From these results, we plan to statistically compare the detected population from our simulation to the known dou-ble neutron star binaries to determine the likelihood that the known double neutron stars formed through this route. With these results, we aim to determine the plausibility of this formation route, along with characterizing the features of double neutron star systems that form this way, giving us insight into if this is the formation route for any of the known sub-populations. The results could be important to un-derstand the most likely locations of these systems which could help us detect more, enabling more op-portunities to study exotic physics and extend tests of general relativity.
102.13 — Correlations Between the Nulling Fraction and Key Pulsar Characteristics in Nulling Pulsars
A. Guo1; G. Hickman1; I. Stanescu1 1 Morgantown High School, Morgantown, WV
Pulsar nulling is a phenomenon of the sudden cessa-tion of pulse emission for a number of periods. There are two types of nulls: Type 1, which recur on av-erage every 50 pulses, and Type 2, which recur on average every three to ten pulses. While the mech-anism behind this anomaly is still unknown, there are several theories, none of which are universally accepted. Keeping these unexplained observations in mind, this project focuses on finding relationships between possible parameters, for example, the age of the pulsar vs its nulling fraction (fraction of time the pulsar spends in a null state). Thus, studying the behavior of nulling pulsars is vital in order to have a better understanding of the nulling phenomenon. This project used data on 22 known nulling pulsars listed in Wang et. al. The nulling fraction was com-pared to the ages of different nulling pulsars, but no correlation between age and nulling fraction was de-ducted from this analysis. More data would need to be collected to be able to justify this conclusion.
102.14 — Investigating Pulsar Spin Period Evolution
B. Sikole1; J. Long1
1 Wheeling Park High School, Wheeling, WV
With a grant from the National Science Founda-tion in cooperaFounda-tion with West Virginia University and Green Bank Observatory, we spent time at
Green Bank researching pulsars. Through the Pul-sar Search Collaboratory, we were provided with access to data collected with the Green Bank Tele-scope and were also able to collect our own data with the 20-meter telescope. Over a two-year period, we have become passionate about pulsar research and have made some interesting observations and corre-lations. Using the 20-meter telescope with Skynet, we collected data from known pulsars to see if the spin period changes over time, and if so, does it oc-cur at a constant rate. We also used data from pul-sars discovered through the Pulsar Search Collabora-tory. We have observed that the spin period of some pulsars decreases, while in other cases it increases slightly. From our research, we find that younger pulsars may show a sudden increase. We use the av-erage spin-down rates to calculate ages for the pul-sars we studied.
102.15 — Multi-Wavelength Investigations of the high magnetic field pulsars J1809-1943, J1847-0130, and J1821-1419.
C. Winters1; S. Jett2; T. Pannuti3
1 Craft Academy for Excellence in Science and Mathematics, More-head, KY
2 Green Bank Observatory, Green Bank, WV 3 Morehead State University, Morehead, KY
hydrogen absorption measured through X-ray obser-vations. Ultimately, this research could help extend knowledge about pulsar properties and add to the current understanding of high energy neutron stars.
102.16 — PINT, A New Generation of Pulsar Timing software
J. LUO1; S. Ransom; P. Demorest; P. Ray; A. Archibald 1 The University of Texas at San Antonio / The University of Texas, Brownsville, TX
Over the past several decades, high precision pulsar-timing experiments have continued to advance, reaching a precision of ∼10 ns where many subtle phenomena can be observed. At this level of preci-sion, extremely careful data handling and sophisti-cated timing models are required. In this poster we present a Python-based high-precision pulsar tim-ing data analysis package, called PINT (PINT Is Not Tempo3). PINT is a well-tested, validated, object-oriented, and modular package, enabling interactive data analysis and providing an extensible and flex-ible development platform for timing applications. PINT utilizes well-debugged public Python pack-ages (e.g., the NumPy and Astropy libraries) and modern software development schemes (e.g., ver-sion control and development with git and GitHub, and various types of testing) for increased develop-ment efficiency and enhanced stability. PINT has been developed and implemented completely inde-pendently from traditional pulsar timing software (e.g. Tempo) and is, therefore, a robust tool for cross-checking timing analyses and simulating data. We describe the design, usage, and validation of PINT, and compare timing results between it and Tempo and Tempo2.
102.17 — Characterizing RFI in Pulsar Search Data
C. Ye1
1 Eastlake High School, Sammamish, WA
Under the Pulsar Search Collaboratory, I analyzed over 100 sky pointings, which included 3000 plots of pulsar candidates resulting from a periodicity search. Of these, I labeled 813 plots as Radio Fre-quency Interference (RFI). I chose a sample of these RFI plots for a detailed analysis. These include the barycenter-adjusted period and period derivative (P and P-dot), dispersion measure (DM), reduced chi-square, frequency spread, presence of pulsar-like pe-riodicity in the phase vs. time plot, primary narrow-band frequencies, and narrownarrow-band RFI shape. The
primary purpose of this analysis is to study distri-butions of different features in RFI and extract any common parameters or types of RFI, which is appli-cable to improving RFI models for future observing runs as well as processing for RFI. We categorize the different types of RFI we found and discuss possible origins.
102.18 — Pulse Nulling and Age
J. Yocco1; J. Gian1; S. Zarin1
1 Upper Darby High School, Drexel Hill, PA
Using data we collected with the 20-Meter Telescope at the Green Bank Observatory and information in the Australia Telescope National Facility (ATNF) pul-sar catalogue, our research analyzed the nulling rate of 15 known pulsars. Specifically, we searched for a correlation between pulse nulling and the pulsar’s age and stage in its “evolution”, as shown by its posi-tion in the P-Pdot diagram. Pulse nulling is an irreg-ular phenomenon in which a pulsar’s periodic emis-sions momentarily drop to zero, or near zero, before immediately returning to normal. As previous stud-ies have come to contradictory conclusions on the connection between age and nulling, our study has arrived at its own conclusion on this phenomenon.
102.19 — Predictive Modeling in Pulsar Timing
C. Phillips1; S. Ransom
1 University of Virginia, Charlottesville, VA
102.20 — Efficacy of Student Developed Machine Learning Algorithm to Sort Pulsar Plots
G. Singh1; B. Millar1
1 Stanford Online High School, Redwood City, CA
The search for pulsars generates a massive amount of data. It is tedious to analyze the data by hand, but having done so, we identified some visual patterns in the preprocessed Fast Fourier Transform (FFT) plots on the PSC database. We wrote a machine learning algorithm to view and sort these pulsar plots accord-ing to how confident the program was that the plot represented a pulsar. In this analysis, the program generates a confidence level for different parts of the plot. The phase-subband plot is weighted 90%, the two pulses of best profile are weighted 10%, and a modifier based on the sigma value is added to the final confidence value. The program has analyzed 21186 plots, which is the equivalent of about 700 FFT data sets. In this work, we study the efficacy of the algorithm by comparing its output to similar analy-sis by human researchers, and explore some of the patterns identified in the course of this classifica-tion. Our investigation found significant variation between the confidence levels of human researchers and the confidence generated by the program.
102.21 — Using a 20 m Radio Telescope to Test a Simple Method for Estimating the Orbital Period of Binary Millisecond Pulsars
A. Preiser1; X. Chen1; A. Zuckerman1
1 Burr and Burton Academy, Manchester, VT
We have developed a simple method for estimat-ing the orbital period of binary millisecond pulsars. Using the ATNF catalog we selected four binary millisecond pulsars that could be observable with the 20 m telescope at the Green Bank Observatory. We observed each pulsar two times a day over the time period of at least two orbital periods. From the observations, we recorded the barycentric time and the barycentric pulsar spin period and looked for periodic behavior in the pulsar period variations to determine if the periodic behavior we observed matched the orbital period. This simple method us-ing many short observations to estimate the orbital period could be used with younger students or stu-dents with less experience as an introduction to bi-nary pulsars as our method does not require any higher-level computing skills. This method might also be good for a hands-on activity in an introduc-tory astronomy class. To compare our method with other methods, we recorded several longer observa-tions of each pulsar with the 20 m telescope. We used
the raw data and fitted to a Keplerian model to esti-mate the period. We also tested a method described by Freire et al (2001) for estimating the orbital period. We compared our results from all methods with the orbital periods reported in the ATNF catalog. Fi-nally, we used the 2 m telescopes in the Faulkes tele-scope network to observe the binary companions of these pulsars.
102.22 — Accuracy of Student-led Analysis of Pulsar Search Data
C. Priddy1; M. Dew1; G. Burke1; J. Dempsey1
1 Riverside High School, Belle, WV
The Pulsar Search Collaboratory is a program that pairs high school students with in-field profession-als. The program teaches students how to interpret data taken with the Greenbank Observatory’s GBT (Green Bank Telescope). After completing the initial training, students can be invited to participate in a week long Pulsar Astronomy Camp. At this camp, students learn hands-on how to make observations with the telescopes. Thus, gathering data which stu-dents can use to conduct their own research. In this project, historical Pulsar Search Collaboratory data was analyzed to check for accuracy of previous data analysis. We broke the range of data into three time frames (2007–2009), (2010–2012), and (2013–2016), with approximately 7500 pieces of data per student. The plots examined had all resulted in a score of 5 or better as ranked by previous PSC students. The team was specifically looking for misidentified sars, missed or wrongly classified RFI, missed pul-sars within the data, and other anomalies that may be of interest that were not observed during the first period of data examination. We kept track of statis-tics concerning the accuracy of the initial data anal-ysis and performed statistical analanal-ysis to determine if there was a significant error in PSC student data analysis.
102.23 — Observing Pulsar Scintillation with a 20 Meter Radio Telescope
A. Jeffrey1; H. Sullivan1
1 Spring Valley High School, Huntington, WV
to gas clouds in our galaxy, known as the interstel-lar medium (ISM). Three known pulsars were ob-served. Once data was obtained, it was modified to make the signal stronger by removing the radio fre-quency interference (RFI) to create a dynamic spec-trum of the data. The results showed that of the three pulsars that were studied, two showed scintillation. The Pulsar Search Collaboratory (PSC) is a program that pairs high school students with in-field profes-sionals to work on real astronomy projects. This pro-gram teaches students how to interpret data taken with the Green Bank Observatory’s radio telescopes. After completing initial training on how to interpret data, students can be invited to participate in a two-day long seminar at West Virginia University (WVU) and a week- long camp at the Green Bank Obser-vatory. At this camp, students become involved in hands on research with the facilities equipment, in-cluding the 20-meter telescope with which students conduct their own research. It was during this sum-mer camp that the scintillation project was initiated.
102.24 — Pulsar search results from University of Puerto Rico
J. Lebron Medina1; N. Palliyaguru; N. Miranda
Colon1; M. McLaughlin; N. Santiago2; L. Mendez2; H.
Radovan1
1 Physics, University of Puerto Rico Mayagüez Campus, Mayagüez, PR
2 University of Puerto Rico Mayagüez Campus, Mayagüez, PR
The North American Nanohertz Observatory for Gravitational waves (NANOGrav) involves under-graduate students in pulsar research through mul-tiple programs. This poster presents our initial ef-forts to involve undergraduate students from uni-versity of Puerto Rico, Mayagüez in pulsar and fast transient searches. The students first visited the ob-servatory and got an understanding of frontends, backends, and signal processing. Then a work-shop was conducted in August 2019 where 20 stu-dents were trained in Unix systems, pulsar data pro-cessing, and public speaking. The students were then trained through the Pulsar Search Collabora-tory (PSC) and exposed to real data from the Arecibo Observatory. Here we present the search for periodic radio signals from Arecibo data of nearby gamma ray bursts, which show evidence for the birth of a magnetar, conducted at 1.5 GHz and 5 GHz. We also present results of using machine learning tech-niques to differentiate between radio frequency in-terference (RFI) and real pulsar signals. We plan to apply this training model at other universities and expand the program by offering summer research
opportunities, semester-long internship opportuni-ties at the Arecibo Observatory, and course credit to trained students. As part of the outreach com-ponent, students will visit high schools in PR and deliver public talks in English and Spanish to help reach a broader audience. We also plan to involve students in the development of a travelling exhibit on pulsar timing arrays.
102.25 — Pulse Portraits for 30+ Millisecond Pulsars in Terzan 5
L. Schult1; S. Ransom2; T. Pennucci3; J. Roy4
1 Astronomy Department, University of Virginia, Charlottesville, VA
2 National Radio Astronomy Observatory, Charlottesville, VA 3 Eötvös Loránd University, Budapest, Hungary
4 National Centre for Radio Astrophysics, Pune, India
The science of pulsar timing is dependent upon pulse times-of-arrival (TOAs) and their precision, so im-proving them is of the utmost importance with re-gards to the future of pulsar timing science and Pulsar Timing Arrays (PTAs). The most common method to generate TOAs is to use a high signal-to-noise ratio (S/N) pulse profile to perform tem-plate matching with folded time-series data. This has worked well previously, but the advent of new wide-band receivers with larger fractional wide-bandwidth (Bandwidth/Center Frequency of the band>0.4) in-troduces new challenges such as non-negligible pro-file evolution and interstellar scattering changes across the band and huge numbers of frequency-dependent TOAs. Tim Pennucci’s PulsePortraiture (Pennucci et al. 2016; Pennucci & Demorest 2018) code and algorithms allow for the creation of pulse portraits which are models of the pulse profile of the pulsar as a function of radio frequency. These por-traits can be used for wideband timing that can mit-igate the issues mentioned and improve TOA preci-sion. I have investigated the merits of using Pulse-Portraiture to create high S/N pulse portraits and applied them to time the millisecond pulsar (MSP) J1646-2142. I then applied this method to more than 30 MSPs in the globular cluster Terzan 5.
102.26 — The NANOGrav 12.5-year Data Set: High-precision timing of 48 Millisecond Pulsars
J. Swiggum1; The NANOGrav Collaboration1 1 Lafayette College, Easton, PA
Center monitors a growing array of Millisecond pul-sars (MSPs) and conducts high-precision timing over decades-long timescales with the aim of directly de-tecting gravitational waves (GWs) from merging su-permassive black hole binary systems. GWs pass-ing through our galaxy induce correlated fluctua-tions in the observed pulse arrival times from MSPs; monitoring a large (>∼50) set of pulsars with sub-us precision is necessary for GW detection. The NANOGrav observing program currently monitors a set of 76 MSPs using primarily the Green Bank and Arecibo radio telescopes; a smaller set of pul-sars is observed with the VeryLarge Array. Ob-servational results are organized around a set of data releases; every few years, data from all pul-sars are compiled, reduced, and used as the basis for a new set of GW analyses. Described here is the NANOGrav observing program, and the latest ”12.5-year” data set, including observations of 48 MSPs taken through mid-2017 with the GBT and Arecibo analyzed in parallel with independent pulsar timing software, TEMPO and PINT.This analysis incorpo-rates new advances in removal of spurious instru-mental signals, improvements in calibration and RFI excision, and automated identification of outlier data points. It also makes use of new methods for process-ing wide-bandwidth radio data into a sprocess-ingle time of arrival. This approach accounts for intrinsic varia-tion in pulse shape as a funcvaria-tion of frequency, and will result in an order of magnitude less data needed for subsequent GW analyses.
102.27 — Comparison of Binary Pulsar Systems
S. Kannan1
1 Westfield High School, Chantilly, VA
In this project, I investigate whether the type of com-panion in a binary pulsar system impacts the sys-tem. The effects of the companion type on param-eters such as orbital speed, rotational period, esti-mated lifetime, and the distance between the two objects are explored. Data from different types of systems, including white dwarf, double pulsar, and planet-pulsar systems are recorded and plotted in a variety of graphical representations. The results are then analyzed for the presence of any patterns that might be correlated to the differences in evolutionary history of these different types of binary systems.
102.28 — Emission Heights and Possible Radius-to-Intensity Mapping
N. Miranda-Colon1
1 University of Puerto Rico, Mayaguez, Mayagüez, Puerto Rico
Pulsars are highly magnetized, rapidly spinning neutron stars. One of their most notable character-istics is that they emit narrow beams (in the form of a cone) of electromagnetic (EM) radiation from the space above the magnetic poles defined by the last open magnetic field lines. Their magnetic and ro-tational axes are not aligned, causing a “lighthouse effect” whenever one of the beams crosses our line of sight. Every time one of the beams crosses our line of sight we see a “pulse” of EM radiation. Soon after discovery of the first pulsar it was found that average profiles, obtained by integrating many sin-gle pulses synchronously with the period of the pul-sar, depend strongly on the observing frequency. This effect is known as Radius-to-Frequency Map-ping (RFM). The simplest explanation is that higher frequencies are generated in the narrow part of the emission cone, closer to the surface of the star, and lower frequencies are produced in the wider part of the cone, which is further away from the star. While the scientific community agrees that RFM generally is working, it is not quite clear how thick a layer pro-ducing one radio frequency may be, and if it is pos-sible that two or more radio frequencies could origi-nate from the same layer of the magnetosphere. Pre-vious results also show that not only average pro-files depend on frequency, but also on intensity. We studied the intensity dependence of the average pro-files of 7 pulsars, 5 of them at two different frequen-cies. For each frequency we integrated pulses in 10 intensity bins to produce 10 average profiles, one for each frequency. We found that, in general, the width of the profiles are intensity dependent. The profiles of the strongest pulses were always narrower than those of the weakest. Additionally, we found that in most pulsars, component peak-to-peak sepa-ration decreased with increasing inten- sity. We in-terpret this as different intensities being emitted at different emission heights, where the highest inten-sities (for one frequency) are emitted closer to the star and lower intensities further away, we call this Radius-to-Intensity Mapping (RIM). We calculated emission heights by measuring the width of the aver-age profiles at different intensities at 1% of the maxi-mum level. For the 5 pulsars studied at more than one frequency, 4 have overlapping regions, which challenges conventional views that each frequency is produced in a separate layer of the beam emitting the radiation.
102.29 — Pulsar Phase Domain Timing on GBNCC Pulsars
1 Department of Physics and Astronomy, West Virginia University, Morgantown, WV
Standard pulsar timing analysis involves long timescale observations of individual sources and collecting those data in the form of pulse times of arrival (TOAs). The template profile is typically derived from averaging pulses over an entire ob-servation and compiling them into a single profile, which is then used as the model to which all TOAs are compared. The likelihood of this model is then determined by the residual fit of each TOA over long time scales. In Pulsar Phase Domain Timing (PPDT), we instead do away with TOAs and look at entire observations in the phase domain. Typical timing analyses result in ephemerides that allow one to determine a precise rotational phase based off the given parameters at a specific point in time. PPDT exploits this feature and performs a Bayesian series of log likelihood comparisons of a model’s predicted phase and the phase given by the data. Here, we generate a single “profile” for each observation that is dependent on each timing parameter of our data, and we vary each parameter of the model iteratively while comparing the log likelihood of the variance between the data and the model with typical Gaussian error. The Monte Carlo sampler package PyMC3 is used to perform a modified Hamiltonian Monte Carlo simulation to intelligently determine in what manner each parameter must be altered, improving both accuracy and required computational time. This comparison is done for each profile bin for all frequency channels over all included observations, giving a uniquely compre-hensive method of pulsar parameter estimation. We apply this method to pulsars detected from the GBNCC survey and compare the speed, precision, and accuracy of the results to those which resulted from typical pulsar timing analysis, and discuss the applications and benefits of this work to the NANOGrav pulsar timing array.
102.30 — Quasi-real-time Analysis Pipelines for Data Quality Assurance/Quality Control for Pulsar-based Gravitational Wave Detectors
M. T. Lam1; A. Brazier2; S. Chatterjee3; J. M. Cordes3; N. Garver-Daniels4; O. Haggarty5
1 School of Physics and Astronomy, Rochester Institute of Technol-ogy, Rochester, NY
2 Department of Astronomy, Cornell University, Ithaca, NY 3 Cornell University, Ithaca, NY
4 Department of Physics and Astronomy, West Virginia University, Morgantown, WV
5 Oregon State University, Corvallis, OR
Pulsar timing array detectors require large num-bers of observations for the purpose of detection and characterization of low-frequency gravitational waves. Currently, the North American Nanohertz Observatory for Gravitational Waves observes 77 pulsars with weekly-to-monthly cadence, requiring significant automation in the data transfer and re-duction pipelines. Given the increasing automation on our current and future observing schemes, we re-quire methods to check the quality of the data en-tering the pipeline. We describe our framework for generating metrics and figures for interactive data quality assurance and control. Our analyses are ca-pable of identifying problems with the data that may be imperceptible with the online data viewing tools during the observations themselves. We also provide a generic framework for identifying other features of interest in our data, such as transient noise pro-cesses or rapid changes in the interstellar medium. Given the ease of access, even students are able to investigate the data and build upon their observing skills. Our system will be publicly available, pro-viding other pulsar astronomers with tools for data quality assurance and control of their observations as well.
102.31 — Assessing Chromatic Arrival Time Perturbations for NANOGrav’s Error Budget
S. K. Ocker1; J. Cordes1; S. Chatterjee1; M. Lam2; R.
Jennings1
1 Astronomy, Cornell University, Ithaca, NY
2 Physics and Astronomy, Rochester Institute of Technology, Rochester, NY
density, e.g. through bow shocks and pulsar wind nebulae, may also be significant, perhaps underly-ing abrupt changes in the apparent DM. We assess the potential contributions of refraction and disper-sion through the ISM, along with the pulsar’s phys-ical role, in chromatic arrival time perturbations af-fecting NANOGrav MSPs.
102.32 — The NANOGrav search for nanohertz gravitational waves
X. Siemens1; NANOGrav Physics Frontiers Center1
1 Oregon State University, Corvallis, OR
Supermassive black hole binaries (SMBHBs), and possibly other sources, generate gravitational waves in the nanohertz part of the spectrum. For over a decade the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) has been us-ing the Green Bank Telescope, the Arecibo Obser-vatory, and, more recently, the Very Large Array to observe millisecond pulsars. Our goal is to di-rectly detect nanohertz gravitational waves, which cause small correlated changes to the times of arrival of radio pulses from millisecond pulsars. We cur-rently monitor almost 80 millesecond pulsars with sub-microsecond precision and weekly to monthly cadences. A detection of the stochastic gravitational-wave background produced by all the SMBHBs in the universe is close at hand. I will present an overview of NANOGrav Physics Frontiers Center (PFC) activities and summarize our most recent gravitational-wave search results. This poster is one of a collection of NANOGrav PFC posters and talks at the AAS meeting, which present detailed results of our research activities, outreach programs, and im-portant scientific broader impacts of our work.
102.33 — Results from the search for a stochastic gravitational wave background in the NANOGrav 12.5-year data set
J. Simon1; The NANOGrav Physics Frontier Center1
1 Jet Propulsion Laboratory, Pasadena, CA
Pulsar timing arrays are galactic-scale low-frequency gravitational wave observatories sensitive to the nanohertz frequency band. The primary source of gravitational radiation in this regime is expected to be a stochastic background, formed by a cos-mic population of supermassive black hole bina-ries. We present the results obtained by analyzing the 12.5-year data release from the North Ameri-can Nanohertz Observatory for Gravitational Waves
(NANOGrav). We also discuss advanced noise mod-eling techniques for individual millisecond pulsars in the NANOGrav dataset, which has improved our sensitivity.
102.34 — Analysis of time-correlated noise processes in the NANOGrav 12.5-year data set
J. Sun1; N. Laal1; X. Siemens1; NANOGrav Physics
Frontiers Center1
1 Oregon State University, Corvallis, OR
In the search for a stochastic background of gravita-tional waves, NANOGrav employs various Bayesian and frequentist data analysis techniques. In one analysis of the recent 12.5-year dataset, we used Markov Chain Monte Carlo sampling techniques to calculate posterior probability distributions for the intrinsic red [time-correlated] and white noise pa-rameters of 45 pulsars along with a common red noise signal present in all pulsars. The common red noise process could be the result of a stochastic back-ground of gravitational waves. We show that a sub-set of our pulsars supports the existence of a com-mon red noise process.
102.35 — NANOGrav Space Public Outreach Team (SPOT)
N. McMann1; J. Key2; J. Page3; T. Littenberg4 1 Vanderbilt University, Nashville, TN
2 University of Washington Bothell, Bothell, WA 3 University of Alabama Huntsville, Huntsville, AL 4 NASA Marshall Space Flight Center, Huntsville, AL
Poster Session 103 —
Gravitational-wave Astronomy:
The LIGO-Virgo Third Observing
Run and Plans for the Future
103.01 — Update on standard siren science
D. Holz1
1 University of Chicago, Chicago, IL
We review the present and future of gravitational-wave standard siren constraints. We discuss existing measurements from GW170817 and GW170814, fo-cusing on both counterpart and statistical standard siren approaches. For counterpart standard sirens, we capitalize on the identification of an electromag-netic transient to independently determine the red-shift to the source. The counterpart GW170817 stan-dard siren constrains the Hubble constant to ∼15%. For statistical standard sirens, we combine standard siren measurements for a sample of galaxies within the three-dimensional gravitational-wave localiza-tion volume, considering every galaxy as a poten-tial host. This method is of particular utility for dark sirens such as binary black holes, which are not expected to be associated with an electromag-netic counterpart. We make projections for upcom-ing gravitational-wave detector networks, showupcom-ing that future standard sirens are expected to measure the Hubble constant to 2% within five years.
103.02 — The TOROS project status report
M. Diaz1; D. Garcia Lambas2; L. Macri3
1 Center for Gravitational Wave Astronomy, The University of Texas Rio Grande Valley, Brownsville, TX
2 IATE, Observatorio Astronomico de Cordoba, Cordoba, Argentina 3 George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, Texas A&M University, College Station, TX
We present the current status of the TOROS project. The Transient Optical Robotic Observatory of the South (TOROS) is a telescope designed to follow up transient gravitational wave events. In this contri-bution we describe the location of the astronomical site, the telescope main instrumental characteristics as well as the current status of the project. We present preliminary observations and discuss the estimated completion with its final design sensitivity. We also discuss the projected contributions to the O4 LIGO VIRGO observational campaign. This work is sup-ported by award NSF-HRD 1242090 and supplement from the Windows on the Universe program.
103.03 — Discovery and Analysis with Public LIGO and Virgo Data
J. Kanner1; the LIGO Scientific Collaboration and the
Virgo Collaboration1 1 Caltech, Pasadena, CA
LIGO and Virgo data are available for down-load through the Gravitational Wave Open Science Center (GWOSC). The GWOSC web site, at gw-openscience.org, includes a suite of tools for data ac-cess, along with tutorials, documentation, and online web courses on data analysis. Over the next year, dozens of gravitational wave events will be pub-lished, and their associated strain data and source parameters will become available through online cat-alogs, representing an unprecedented view of the universe. This talk will provide an overview of cur-rent and planned public data sets and tools to help support your research with gravitational wave data.
Poster Session 104 — Astronomy
Education at, with, and by
Observatory Facilities
104.01 — The NRAO NINE Program and NRAO-TTU NINE Hub
H. Harbin1; A. Saravia2; A. Corsi1; A. Fourie3; B.
Kent3; L. Von Schill3
1 Physics and Astronomy, Texas Tech University, Lubbock, TX 2 National Autonomous University of Honduras, Tegucigalpa, Honduras
3 National Radio Astronomy Observatory, Charlottesville, VA
able to generate simple image displays and multi-wavelength comparisons, using data from the VLA Sky Survey (VLASS) as well as other surveys. We also comment on how Virtual Radio Interferometer (VRI) software can be used as an educational tool in radio astronomy courses. We conclude by describing future steps we plan to take to help create a network for knowledge exchange and broadening diversity in the radio astronomy community.
104.02 — Presenting the LSST Education and Public Outreach Program
L. Corlies1; A. Bauer; &. the EPO Team1
1 LSST / AURA, Tucson, AZ
LSST Education and Public Outreach (EPO) is cur-rently constructing a diverse suite of materials to pro-vide worldwide access to, and context for, LSST data through accessible and engaging online experiences so anyone can explore the universe and be part of the discovery process. This poster illustrates the four main audiences we are aiming to reach and the prod-ucts we are building to do so. Our website intends to combine new discoveries, telescope updates, and as-tronomy information in the landscape of social me-dia and mobile-only users. Our formal education products represent the fundamental science goals of LSST while addressing the needs of educators who may wish to use them. Our citizen science projects look to involve the public in the scientific process and to enable scientists to easily create and manage such projects. Finally, our media production for science centers and planetaria provides assets to facilitate the creation of shows and exhibits using LSST data. Our program is still under construction and we welcome ideas and look forward to discussions at the poster.
104.03 — The AstronomUrs: A High Impact Astronomy Outreach Program
V. Vankayalapati1; P. Ricketts1
1 Physics and Astronomy, University of Utah, Salt Lake City, UT
The AstronomUrs is an outreach group, run from the South Physics Observatory at the University of Utah, which conducts extensive outreach activities of wide and far-reaching scope, from physics demonstra-tions, star parties, K-12 presentademonstra-tions, astronomy fes-tivals, and much more. We also host weekly star par-ties at the observatory, open to the public. Our out-reach team is composed of a permanent staff mem-ber and several student employees paid as teaching assistants. Our operations utilize 7 rooftop and 13 portable telescopes in addition to over 25 physics
and astronomy demos and numerous educational presentations. The program also travels extensively across the state and beyond, allowing our activities to be accessible to rural and tribal areas. The pro-gram grew out of a lack of accessible astronomy ed-ucation/outreach resources in Utah and has since become the largest astronomy outreach program in the state. In the past year alone, we hosted 171 events reaching approximately 26,000 people. Our audience is also broad, including, but not limited to, K-12 schools, state and national parks, community groups, amateur astronomers, university organiza-tions, and dark-sky advocacy groups. Our program operations are funded primarily through donations and indicates our community support and recogni-tion.
104.04 — The NRAO NINE program in Central America: Promoting Diversity, Inclusion and Astronomy for Development
A. Saravia1; H. Harbin2; A. Fourie3; B. Kent3; L. von
Schill3
1 Department of Astronomy and Astrophysics, National Au-tonomous University of Honduras, Tegucigalpa, Honduras
2 Texas Tech University, Lubbock, TX
3 National Radio Astronomy Observatory, Charlottesville, VA
NINE Hub’s plan consists of: a nine-month re-search project using VLA and ALMA data which will involve faculty and undergraduate students from UNAH’s astronomy department mentored by NRAO staff scientists; the implementation of an outreach plan which provides early training in radio astronomy and data science to high school students; and an exchange experience with another NINE Hub. The Honduras NINE Hub will be the first institution of its kind in the region and will support Central American astronomers to promote growth in the field; make astronomy an attractive field for future undergraduate students; and attract funds investment from local institutions. The latter will contribute to drive job creation in a more diverse range of sectors, such as research.
104.05 — Lakeshore Environment and Night Sky Sensor (LENSS) — Student Engagement in Dark Skies Monitoring Through Nested Mentorship and Environmental Action
K. Meredith1; A. McCulloch1
1 Geneva Lake Astrophysics and STEAM, Williams Bay, WI
Over the past five years, Yerkes Education Out-reach (now Geneva Lake Astrophysics and STEAM or GLAS) has been working with community groups to draw attention to the light pollution issues in the Geneva Lakes area of Wisconsin. Although a public access walking path circles Geneva Lake completely, there is a limited number of entry points, and safety is an issue for conducting sky quality monitoring. In response, GLAS launched a new project called LENSS (Lakeshore Environment and Night Sky Sen-sor). The long term goal of LENSS is to positively affect the quality of the dark skies around Geneva Lake and measure secondary effects on astronomy, boating safety, and wildlife. The first step in this project is to build and calibrate a sky quality me-ter that can be remotely operated while building a team of students, mentors, and community organi-zations that can handle all aspects of the project. Students working with mentors and STEAM profes-sionals work in the areas of engineering and web design, data management, coding, and communica-tions. This poster provides an overview of the first six months of LENSS, recruiting, sensor design and testing, and community building.
104.06 — An Instrument for Cultural Change at the Center for Astrophysics | Harvard & Smithsonian: Correcting the Lens of the Great Refractor
C. Crowley1; R. Montez2; A. MacLeod3
1 Director’s Office, Smithsonian Astrophysical Observatory, Cam-bridge, MA
2 Smithsonian Astrophysical Observatory, Cambridge, MA 3 University of Massachusetts, Lowell, MA
Since its inception, the Smithsonian Astrophysical Observatory (SAO) Fellowship Program at the Cen-ter for Astrophysics | Harvard & Smithsonian has hosted upwards of 240 interns and researchers per year. Although the number of SAO fellowships awarded has grown steadily throughout the years, the number of SAO fellowships awarded to under-represented minorities had never risen above 1% of the population. In an effort to correct this trend, SAO partnered with the Smithsonian Latino Center, the Urban Massachusetts Louis Stokes Alliance for Minority Participation Programs at the University of Massachusetts, and the National Science Foun-dation to form the SAO Latino Initiative Program (SAO/LIP). In the five years since its establishment in 2015, SAO/LIP has increased the number fel-lowships awarded to underrepresented minorities at SAO by 16%. We detail the ongoing develop-ment of our program from the beginning; including lessons learned on recruiting, professional develop-ment, mentor training, research practices, and a sam-ple of student outcomes.
104.08 — Place Based Education for Teaching Astronomy in Hawai‘i
A. Grace1; NSF’s National Optical-Infrared Astronomy Research Laboratory1
1 Communications, Education and Engagement, Gemini Observa-tory, Hilo, HI
topics such as geology, meteorology, etc., the places and stories specific to Hawai‘i can be used as anchors in teaching various astronomical concepts. Learn about the phenomena we use with our local students and why Hawai‘i is a unique place for teaching as-tronomy, and planetary science. Gemini Observa-tory is a program within NSF’s National Optical In-frared Astronomy Research Laboratory and an inter-national partnership with twin 8.1 meter telescopes in Hawai‘i and Chile. The Gemini North Com-munications, Education and Engagement office has been active within its host community for decades through programs such as Family Astro, Summer Starlabs, Astro Day, and our flagship outreach pro-gram, Journey Through the Universe. Through these programs, classroom visits, and school-led careers fairs and family nights, Gemini reaches 15,000 stu-dents per year.
104.09 — Construction of a Radio Telescope to detect the 21 cm Hydrogen Line
E. Rodriguez Arzaga1
1 Physics, El Paso Community College, El Paso, TX
Despite our vast knowledge regarding Radio Astron-omy and the techniques Astronomers use to observe the Cosmos, the technology that Radio Telescopes use has always been very complex and mysterious to some. How do Radio Telescopes work? What are the fundamentals to real world astronomical inves-tigations? One may assume that we just receive sig-nals from outer space, but the reality is much more complex and difficult to answer. This research will involve the construction of a basic Horn Antenna Radio Telescope and the explanation on how every-thing is assembled. The construction will be made with easy to gather materials. This research will also provide students, and anyone interested in Radio As-tronomy with instructions on how to build their own homemade Radio Telescope. The main goal to be ac-complished by this build, would be to obtain data from the 21 cm wavelength line of Hydrogen gas emissions found in the Milky Way Galaxy. This type of data has been used by previous Astronomers to create a map of our Galaxy!
104.10 — Expanding Observatory Capabilities using Engineering Student Projects
D. A. Ludovici1; H. Alisafaee1
1 Physics and Optical Engineering, Rose-Hulman Institute of Tech-nology, Terre Haute, IN
Many colleges and universities have an on cam-pus observatory with one or more moderately sized
(D∼0.25 - 1.0 m) telescopes. These telescopes are often equipped with eyepieces and imaging CCDs, though more advanced equipment such as spec-trometers is often lacking. While these telescopes are often used for public outreach and undergrad-uate physics and astronomy laboratories, they of-fer a unique opportunity for engineering students as well. Constructing instrumentation such as fiber feeds, spectrometers, and specialty imaging systems offers opportunities for optical, mechanical, electri-cal, and software engineers to work on unique design projects that will benefit their careers. Additionally these projects also benefit the public and the astron-omy students at the observatory by improving the ca-pabilities of the observatory. We will discuss a few projects that are underway at the Oakley Observa-tory at the Rose-Hulman Institute of Technology and how we expect them to improve the educational and science impact of the observatory.
104.11 — Making Instrumentation Accessible: A Homemade Meter-scale Galvanic Resistivity Array
M. Hess1; S. Liss1; R. Herman1 1 Physics, Radford University, Radford, VA
Poster Session 105 — White
Dwarfs
105.01 — White dwarf luminosity function in GALEX and Gaia DR2
A. Muñiz1; S. Mohammed1; D. Schiminovich1
1 Department of Astronomy, Columbia University, New York, NY
Using data from the Galaxy Evolution Explorer (GALEX) and Gaia DR2, we calculate white dwarf luminosity functions (WDLF) in the near-ultraviolet (NUV), visible bands (e.g. GAIA G), and for derived total bolometric luminosities. These WDLFs take ad-vantage of the high number of white dwarfs with accurate distances, increasing the volume and pre-cision as compared to previous results. In comput-ing our WDLFs, we use the V/Vmax method and account for parallax error and other flux-dependent selection effects. Our results show relationships con-sistent down to M = 13-14 with other LFs in the lit-erature, although we report on key differences and calculate separately the WDLF for thin and thick disk populations.
105.02 — The Dry Crust of a Rocky Planet Being Accreted by the White Dwarf
SDSSJ073110.35+241704.2
C. McDermott1; C. Melis2; P. Dufour3; A. Weinberger4;
S. Xu5; B. Zuckerman6; B. Klein6 1 San Jose State University, San Jose, CA
2 University of California, San Diego, San Diego, CA 3 Université de Montréal, Montreal, QC, Canada
4 Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington D.C., DC
5 Gemini Observatory, Hilo, HI
6 University of California, Los Angeles, Los Angeles, CA
Most stars will end their lives as white dwarfs, the inert cores of stars like the Sun. The planetary sys-tems that orbit the white dwarfs can become desta-bilized, parts of which are often accreted onto these dead stars. Via spectroscopy of the accreted material we can measure the chemical composition and struc-ture of extrasolar planets at levels unobtainable even for most Solar system bodies. Here we report on the polluted white dwarf SDSSJ0731+2417. We obtained spectroscopic observations of this star at Lick, Keck, and Magellan Observatories and analyzed the chem-ical composition of the accreted body. We find strong signatures from silicon and oxygen, but a dearth of iron; this is suggestive of the crust of a massive, planet-like body. Accounting for the pairing of oxy-gen with metals as metal oxides, we determine that
this planet’s crust likely had a small fraction of water by mass and thus would have been very dry.
105.03 — Detecting Double White Dwarf Binaries using H alpha imaging survey
B. Ma1; C. Chen
1 Sun Yat-sen University, Guangzhou, China
We are presenting our simulation results using H Alpha imaging survey to find double white dwarf binaries (DWDs). Our results show that using H Alpha imaging survey, we can successfully de-tect some DWDs, which are important gravitational wave sources for future space based GW detection missions, such as LISA and TianQin.
105.04 — Eclipsing Binary and White Dwarf Features Associated with K2 Target EPIC 251248385
S. Yoshida1
1 Punahou School, Honolulu, HI
the potential sources and relative sizes for the poten-tial eclipsing white dwarf candidate, or whether the eclipses come from the white dwarf target cannot be confirmed without additional data.
105.05 — Search for DBVs with Gemini Observatory’s ‘Alopeke
A. Nitta1; S. Kleinman1; E. Dennihy2; A. Stephens1;
S. Xu1; J. Provencal3; Z. Vanderbosch4; J. Hermes5; A.
Kannan6; S. Kepler7 1 Gemini Observatory, Hilo, HI 2 Gemini Observatory, La Serena, Chile 3 University of Delaware, Newark, DE 4 University of Texas at Austin, Austin, TX 5 Boston University, Boston, MA
6 Universidade Federal de Santa Catarina, Florianópolis, Brazil 7 Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
We are using Gemini Observatory’s resident instru-ment ‘Alopeke to search for new He atmosphere pulsating white dwarf stars (DBVs). Our goal is to explore various processes of convection and stellar neutrino production via asteroseismology using the new white dwarf pulsators. White dwarf stars are ideal laboratories for investigating both high energy physics and astrophysics, as they are very hot and dense. More than 97% of all stars evolve to white dwarfs. As white dwarfs evolve and cool, they pul-sate within certain temperature ranges known as in-stability strips. We can therefore study the interi-ors of these stars through asteroseismology. One of the advantages of studying their structures is to learn the boundary conditions to late stage of stel-lar evolution which involves dynamical processes, especially mass loss which have large uncertainties. Studying their interior structure also gives us oppor-tunities to test our knowledge of high energy physics not reproducible in Earth-based labs. The most nu-merous of the pulsating white dwarf stars are the H atmosphere pulsating white dwarf stars, the DAVs or ZZ Ceti stars. The DBVs pulsate at a higher ef-fective temperatures than do the DAVs and there are far fewer known DBVs than DAVs. We have started a search to identify new DBVs and are par-ticularly searching around the hot and cool ends of the instability strip to better determine the bound-aries of the strip. The hottest DBVs will be useful in studying stellar neutrino production via asteroseis-mology. And other DBVs at various effective tem-peratures will help study the changes in convection as the white dwarf stars evolve through the instabil-ity strip. Here we report the project’s progress and the data obtained using ‘Alopeke at Gemini Obser-vatory. ‘Alopeke is a fast, low-noise, dual-channel,
and dual-plate-scale imager based on the Differen-tial Speckle Survey Instrument (DSSI). We use it in the wide-field imaging mode to allow observations of at least one reference star along with our target DBV candidate.
Poster Session 106 — Pulsating
Variable Stars
106.01 — Studying the Population of Variable Stars in the Dark Energy Survey
J. Locke1
1 University of Pennsylvania, Philadelphia, PA
It has been proven that locating variable stars such as quasars and RR Lyrae can be very helpful for ob-servational cosmology, such as probing galaxy evo-lution and mapping black hole growth, and locating low-luminosity dwarf satellites in the Milky Way, re-spectively. We want to use the LombScargle peri-odogram to implement an algorithm to locate vari-able stars, which could help the Large Synoptic Sur-vey Telescope (LSST) to discover more objects when it opens in the early 2020s. Dark Energy Survey data can often sample data unevenly in time, so we need to test the periodogram’s reliability. We aim to im-plement an algorithm that can build statistical sam-ples of different types of variable stars in DES and LSST data, and to find the best method of implemen-tation through simulation testing.
106.02 — M33 Miras in griz
T. Konchady1; L. Macri2; X. Yan3
1 Department of Physics and Astronomy, Texas A&M University, College Station, College Station, TX
2 Department of Physics and Astronomy, Texas A&M University, College Station, TX
3 Department of Statistics, Texas A&M University, College Station, College Station, TX
106.03 — Radio Emission from delta Cephei: Evidence of Mass Loss Via an Ionized Wind?
L. D. Matthews1; N. R. Evans2; M. P. Rupen3 1 MIT Haystack Observatory, Westford, MA
2 Center for Astrophysics | Harvard-Smithsonian, Cambridge, MA 3 National Research Council, Penticton, BC, Canada
Mass loss during the Cepheid evolutionary phase has long been suspected as a means of accounting for the so-called Cepheid mass discrepancy — i.e., the persistent 10–15% disagreement between stellar masses derived from stellar evolution models versus those derived from the Period-Luminosity relation or orbital dynamics. Recently, the Cepheid archetype delta Cephei was found to exhibit sharp, periodic increases in X-ray emission during the stellar pulsa-tion phase associated with maximum radius. These X-rays are thought to originate either from flare-like coronal emission or pulsationally-driven shocks and may be linked with mass loss. Such processes are predicted to result in partial ionization of the stellar atmosphere. To search for evidence of such ionized gas, we recently used the Karl G. Jansky Very Large Array (VLA) to search for radio continuum emission from delta Cephei during epochs near maximum ra-dius. Here we report a detection of the star at 15 GHz (∼6 sigma). To our knowledge, this is the first re-ported detection of radio emission from a Cepheid. Implications for the origin of the periodic X-ray emis-sion and the possible presence of ongoing mass loss will be discussed.
106.04 — Confirmation of Short Period Pulsating Variables Discovered by the ATLAS Survey — The Faint End
E. G. Hintz1; M. D. Joner1; M. L. Bighetti1; J. S. Jensen1; J. L. Hansen1; E. E. Banks1; S. F. Liechty1; K. A. Epps1; E. Wilson1; G. G. Apolonio1; N. Warden1
1 Brigham Young University, Provo, UT
The Asteroid Terrestrial-Impact Last Alert System (ATLAS) is a program to detect near-Earth asteroids that would soon impact the Earth. The system con-sists of two telescopes which scan the sky for mov-ing objects that could be these asteroids. While look-ing for asteroids the system also secures photomet-ric data on a large number of stellar objects, over a wide magnitude range. The ATLAS program pub-lishes lists of potential variable stars that can then be examined in greater detail to fully describe their nature. We selected a number of targets from the PULSE and MPULS lists, provided by ATLAS, to ex-amine with the telescope systems at Brigham Young
University. This includes the 3 telescopes of the BYU West Mountain Observatory (WMO) and the 5 tele-scopes of the BYU Orson Pratt Observatory (OPO). With the fainter targets being examined with the WMO telescopes. We will give an overview of the entire follow-up program, but then focus on the 9 faint targets that were examined with the WMO fa-cilities from May to August 2019. A combination of our data, ATLAS data, and measurements from the GAIA satellite show that a number of these targets are likely SX Phoenicis variables. In addition, to the observational component of the research, we are test-ing idealized data with random cadence structures with a Monte Carlo approach. This gives us an idea of the robustness of our results.
106.05 — An Analysis of the Optical and Near-Infrared Variability of Super Fast X-Ray Transient IC 10 X-2
M. Mancuso1; J. Gelfand; D. Russell1; M. Bogosavljevic 1 New York University Abu Dhabi, Abu Dhabi, United Arab Emi-rates
High Mass X-ray Binaries are a type of binary system involving a massive star, above 10M⊙, and a com-pact object, either a neutron star or a black hole, in which material from the massive star accretes onto the compact object. IC 10 X-2 is a known HMXB and has been identified as a Supergiant Fast X-ray Tran-sient (SFXT), a subclass of HMXBs known to produce fast, bright X-ray flares. Two large flares of IC 10 X-2 were observed by ZTF in 2018 that are of a compa-rable magnitude to a flare observed in October 2013. An analysis of the flare events is presented and con-straints on the behavior of the system are proposed through an analysis of the light-curves in both g-and R-bg-and from ZTF, as well as g’, r’, g-and i’ data from LCO in 2019. By analyzing the optical and near-infrared light curve of IC 10 X-2, as measured by both ZTF and our recent LCO monitoring campaign, we will evaluate different models for the origins of its flares and the consequences for the nature of its stel-lar companion and accretion onto its compact com-panion.
106.06 — Pyriod: Frequency Analysis Software for Python
K. J. Bell1
1 University of Washington, Seattle, WA
