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Schedule

Abstracts

Author Index

 

Schedule

Saturday

Saturday, May 21, 2011, 2:00 PM - 5:00 PM

AAVSO Paper Session I

Sunday

Sunday, May 22, 2011, 9:30 AM - 12:00 PM

AAVSO Paper Session II

Sunday, May 22, 2011, 1:30 PM - 3:00 PM

HAD I: Women in the History of Variable Star Astronomy

Sunday, May 22, 2011, 3:20 PM - 5:30 PM

HAD II: Variable Star Astronomy in Theory and Practice

Monday

Monday, May 23, 2011, 8:00 AM - 7:00 PM 125

Stellar Evolution, Stellar Populations

AAVSO Poster Session

Supernovae. Planetary Nebulae, Evolved Stars, Cataclysmic Variables, Novae

Extrasolar Planets: Detection and Characterization

Molecular Clouds, HII Regions, Interstellar Medium and Dust

Galactic & Extra-Galactic Star Formation

Computation, Data Handling, Image Analysis

Instrumentation: Ground Based or Airborne

Star Clusters and Associations - Galactic & Extra-galactic

Laboratory Astrophysics and Catalogs

Monday, May 23, 2011, 8:00 AM - 8:30 AM 100

Welcoming Address

Monday, May 23, 2011, 8:30 AM - 9:20 AM 101

Kavli Lecture: The 2050 Decadal Survey of Astronomy and Astrophysics

Monday, May 23, 2011, 10:00 AM - 11:30 AM 102

12-Years of Science with Chandra: Chandra Observations of the Solar System

AAVSO: Astrophysics with Small Telescopes

";New Worlds, New Horizons";: The Science of Astro2010

Spiral Galaxies, Computation, Data Handling, Image Analysis & Other Topics

Black Holes

The Galactic Center

Monday, May 23, 2011, 11:40 AM - 12:30 PM 109

Stars, Planets and The Weather: If You Don't Like It Wait 5 Billion Years

Monday, May 23, 2011, 2:00 PM - 3:30 PM 110

12-Years of Science with Chandra: The X-ray Life of Stars

Nuclear Physics I – Stellar Nucleosynthesis

Searching for Exoplanets with Kepler

Early Science From Pan-STARRS 1

AAVSO: Variable Stars in the Imaging Era

Hard X-ray Surveys of AGN

Astronomy Unexpected! Innovative Strategies for Reaching Non-Traditional Students

Remembering John Huchra

Monday, May 23, 2011, 3:40 PM - 4:30 PM 118

Stellar Astrophysics from the Kepler Mission

Monday, May 23, 2011, 4:30 PM - 6:00 PM 119

Evolution of Galaxies I

Dark Matter & Dark Energy/Large Scale Structures, Cosmic Distance Scale

Stars, Dwarfs, Stellar, Circumstellar Disks

Binary Stellar Systems, X-ray Binaries

Quasars, AGN, Starbursts, and SEDs

Tuesday

Tuesday, May 24, 2011, 8:00 AM - 7:00 PM 224

The Sun and The Solar System

Circumstellar Disks

Young Stellar Objects, Very Young Stars, T-Tauri Stars, H-H Objects

Results From Kepler

12-Years of Science with Chandra

Black Holes

Binary Stellar Systems, X-ray Binaries

The Milky Way, the Galactic Center

Pulsars, Neutron Stars and Related Topics

Cosmology

Dark Matter & Dark Energy/Large Scale Structures, Cosmic Distance Scale

Relativistic Astrophysics, Gravitational Lenses & Waves

Galaxy Clusters

Gamma Ray Bursts

Evolution of Galaxies

Tuesday, May 24, 2011, 8:30 AM - 9:20 AM 200

The Pan-STARRS Wide-Field Imaging Survey

Tuesday, May 24, 2011, 10:00 AM - 11:30 AM 201

12-Years of Science with Chandra: SNR and Compact Objects

Nuclear Physics II – Gamma-Ray Spectroscopy and Radioactive Nuclei

Kepler and the Architecture of Planetary Systems

SMARTS: Science Results

What's New under the Suns? I

Cosmic Evolution from Galaxy Zoo

Cosmic Microwave Background/ Relativistic Astrophysics, Gravitational Lenses & Waves

Tuesday, May 24, 2011, 11:40 AM - 12:30 PM 208

Russell Prize: Mapping the Universe with Redshift Surveys and Weak Lensing

Tuesday, May 24, 2011, 2:00 PM - 3:30 PM 209

12-Years of Science with Chandra: Galaxies

Nuclear Physics III – Neutrino Astrophysics

Exoplanet Characterization with Kepler

SMARTS: Current and Future Capabilities

What's New under the Suns? II

Astronomy Education & Public Outreach

Tuesday, May 24, 2011, 3:40 PM - 4:30 PM 216

Early Science with the Expanded Very Large Array

Tuesday, May 24, 2011, 4:30 PM - 6:00 PM

Star Formation, the Milky Way, Star Clusters

Extrasolar Planets: Detection and Characterization

Supernovae, PNe, Evolved Stars and other Topics

Cosmology

Prospects for High Resolution Low Energy X-ray Spectroscopy

Tuesday, May 24, 2011, 7:00 PM - 8:00 PM

SPD Hale Prize: The Sun's Magnetic Surface

Wednesday

Wednesday, May 25, 2011, 8:00 AM - 7:00 PM

Variable Stars

Stellar Atmospheres, Winds

SPICA

Low-Mass Stellar Science

M Dwarfs, Brown Dwarfs, White Dwarfs

Blazars, Quasars, and Other AGN

Surveys and Large Programs

Spiral Galaxies

Herschel

Instrumentation: Space Missions & Related Topics

Intergalactic Medium & QSO Absorption Line Systems

Astronomy Education & Public Outreach

Dwarf Galaxies

Wednesday, May 25, 2011, 8:30 AM - 9:20 AM

Demographics in Astronomy and Astrophysics

Wednesday, May 25, 2011, 10:00 AM - 11:30 AM

12-Years of Science with Chandra: AGN and SMBHs

Particle Physics I – Dense Matter

Astrophysics with Kepler I

The Panchromatic View of Star Formation and Protoplanetary Disks in Diverse Environments I

The Literature-Data Connection: Meaning, Infrastructure and Impact

Low-Mass Stellar Science in the Era of Large Surveys

Wednesday, May 25, 2011, 11:40 AM - 12:30 PM

From Hot Jupiters to Habitable Worlds

Wednesday, May 25, 2011, 2:00 PM - 3:30 PM

12-Years of Science with Chandra: Clusters and Groups of Galaxies

Particle Physics II – High Energy Astrophysics

Astrophysics with Kepler II

The Panchromatic View of Star Formation and Protoplanetary Disks in Diverse Environments II

The Oort Cloud: How is it Filled? How is it Emptied?

SPICA and the Promise of the Far-Infrared

Using the Discoveries of Astronomy to Teach Physics

Wednesday, May 25, 2011, 3:40 PM - 4:30 PM

What Drives the Growth of Black Holes?

Wednesday, May 25, 2011, 4:30 PM - 6:00 PM

AGN, Mergers, and Jets

Dust and Star Formation

Galaxy Clusters

Pulsars and Neutron Stars

Molecular Clouds, HII Regions, Interstellar Medium

Thursday

Thursday, May 26, 2011, 8:00 AM - 12:00 PM

The Sun and Solar System II

Extrasolar Planets

Stars, Star Formation and Associated Topics

Galaxies, Galaxy Clusters and Friends

Instrumentation, Surveys and Data

High Energy, Cosmology and Other Topics

Education

Thursday, May 26, 2011, 8:30 AM - 9:20 AM

The Least Luminous Galaxies in the Universe

Thursday, May 26, 2011, 10:00 AM - 11:30 AM

Particle Physics III: Variations of Fundamental Constants and Dark Matter Searches

Extrasolar Planets: Theory and Characterization

Evolution of Galaxies II

Thursday, May 26, 2011, 11:40 AM - 12:30 PM

GALEX: Mapping the Hidden Side of Galaxy Evolution and the UV Universe

 

Saturday

Abstracts

Saturday, May 21, 2011, 2:00 PM - 5:00 PM

AAVSO Paper Session I

Special Session

Harbour/Ipswich, Turner Fisheries


Recent Changes in the Orbital Periods of Some Eclipsing SW Sextantis Stars

David Boyd1
1BAA, United Kingdom.

2:00 PM - 2:20 PM

Harbour/Ipswich, Turner Fisheries

We present the results of a project to look for changes in the orbital periods of 18 eclipsing cataclysmic variables known as SW Sextantis stars by combining new measurements of eclipse times with historical data stretching back in some cases over 50 years. While the O-C plots for many of these binary systems are consistent with a constant orbital period, for some there is persuasive evidence that their orbital periods have changed over this time interval. These changes have been investigated and quantified. New ephemerides are provided for all 18 stars to facilitate observation of future eclipses.

Secular Variation of the Mode Amplitude-Ratio of the Double-Mode RR Lyrae Star NSVS 5222076, Part 2

David A. Hurdis1, T. Krajci1
1AAVSO.

2:20 PM - 2:40 PM

Harbour/Ipswich, Turner Fisheries

In 2008, a campaign of time-series observations (Hurdis 2009) was conducted in the V and I bands for NSVS 5222076, a double-mode RR Lyrae (RRd) field star in Bootes. Comparison of those results with the earlier observations of Oaster, Smith, and Kinemuchi (2006) suggested that a rapid and significant decrease might be occurring in the amplitude ratio, A0/A1, of the star‘Äôs fundamental and first-overtone pulsation modes. To follow up on this interesting result, additional campaigns of time-series observations were conducted in 2009, 2010 and 2011. This paper will describe how the amplitude ratio of the star has continued to change.


The Pulsational Behaviour of the High Amplitude Delta Scuti Star RS Gruis

Jaime Garcia1
1Instituto Copernico, Argentina.

2:40 PM - 3:00 PM

Harbour/Ipswich, Turner Fisheries

RS Gruis is a high amplitude delta Scuti type variable star with a mean amplitude of almost a half of a magnitude in V, and a period of almost 3.5 hours. The most recent study of this star due to Derekas et al. (2009) suggests the presence of a low-mass dwarf star companion close to the variable star with a period of 11.5 days. Rodriguez et al (1995) had also shown a decreasing rate of the period of dP/Pdt= -10.6 E-8/y.
Using a extended dataset comprising BVIc CCD observations aquired at the Astronomical Observatory of the Instituto Copérnico (1000 datapoints), a data set from ASAS (500) and the existing data in the AAVSO International Database (3900), we have performed an extensive periodogram analyses looking for long term variations.
As a preliminary result, we have confirmed the period variation rate but we also found an harmonic in good shape with the period suggested for the binary companion.


Ha Emission extraction using Narrowband Photometric Filters

Gary E. Walker1
1Maria Mitchell Association Observatory.

3:00 PM - 3:20 PM

Harbour/Ipswich, Turner Fisheries

Maria Mitchell Observatory has explored using Narrowband Photometric (<100A) filters to substitute for spectroscopic observations. The method is thought to have significant signal to noise advantages over spectroscopic observations for small telescopes. These small telescopes offer advantages for projects requiring intensive monitoring where telescope time is limited on larger telescopes. RR Tau, a suspected UXOR, was intensively observed by the MMO 0.6 M RC in Nantucket, Mass and the .29M W28 AAVSOnet telescope from Cloudcroft, New Mexico during the 2010 Winter & Spring season. Observations were made in Ha with 45A and 100A narrowband filters as well as the continuum at 6450 A with 50A and 100A filters. Ha emission was extracted with an error of 8% and compared to the change in the continuum. RR Tau exhibited a 30% change in emission while the continuum change by over a factor of 5.


Preliminary Analysis of MOST Observations of the Trapezium

Matthew R. Templeton1, J. Guzik2, A. Henden1, W. Herbst3
1AAVSO, 2Los Alamos National Laboratory, 3Wesleyan University.

3:20 PM - 3:40 PM

Harbour/Ipswich, Turner Fisheries

We present our first assessment of light curves of the Trapezium stars obtained by the MOST satellite in early 2011. The data sets consist of four stars of the Theta 01 Ori system (A,B,C, and D), along with 34 GSC stars in the field nominally used for guiding. The photometry of the brightest stars is sufficient to detect variability at a level well below one mmag, while photometry of the fainter guide stars has not yet been assessed. An early look at the data indicates intrinsic signals are clearly present; non-trivial systematics also related to the spacecraft and sampling are also present, and we discuss potential means for dealing with these issues. We will also discuss our plans for analyzing the data and deriving physical information on these stars.

AAVSO Estimates and the Nature of Type C Semiregulars: Progenitors of Type II Supernovae
David G. Turner
1, K. Moncrieff1, C. Short1, R. Wing2, A. Henden3
1Saint Mary's Univ., Canada, 2Ohio State University, 3AAVSO.
3:40 PM - 4:00 PM
Harbour/Ipswich, Turner Fisheries
The nature of the variability in the M supergiant type C semiregular (SRC) variables is examined using new and archival spectroscopic and spectrophotometric observations of the stars phased according to AAVSO magnitude estimates. SRC variables appear to be more regular than sometimes suggested, although the nature of their pulsation remains unclear in some cases. Some SRCs appear to undergo irregular fading episodes that may result from dust ejection. But recent light curves of the stars display large scatter that hinders reliable determination of their cycle lengths, a problem that needs to be addressed to improve the usefulness of AAVSO data for learning more about massive stars as they approach the terminal stage of their evolution as Type II supernovae.

The Hunt for the Quark-Nova: A Call for Observers
David Lane
1, R. Ouyed2, D. Leahy2, D. Welch3
1Saint Mary's University, Canada, 2University of Calgary, Canada, 3McMaster University, Canada.
4:00 PM - 4:20 PM
Harbour/Ipswich, Turner Fisheries
A Quark Nova is the explosive transition from a neutron star to a quark star that is theorized to take place days or weeks after a small fraction of ”normal” Type II supernova events. The Quark Nova signature is the delayed brightening of the new object by about five magnitudes. The proposed close long-term monitoring of Type II supernova events should reveal the presence or absence of the signature double-hump of a Quark Nova and allow us to estimate the frequency or upper limit to the rate of such events.
Normal supernova search techniques and follow-up activities may miss the subsequent brightening that takes place during the Quark Nova event. We seek CCD-equipped observers with modest-sized telescopes to join a collaborative effort to search for these events. Your job would begin after Type II supernovae are discovered by others. You, with a team of other observers, would follow all new Type II discoveries for about 1-2 months looking for the signature ”double-bump.” As there are not many known Type II supernovae active at any given time, the observational commitment is not expected to exceed about one-hour per night.
We have set up an on-line database to manage the process and record the observations and a communications forum to provide support to the observers and structure to the project (see http://quarknova.ucalgary.ca).
The confirmation that these objects exist will be a significant event in supernova research.

 

 

 

 

 

 

                                                                                                                                                                                              

Sunday

Sunday, May 22, 2011, 9:30 AM - 12:00 PM

AAVSO Paper Session II

Special Session

Staffordshire


New Life for Old Data: Digitization of Data Published in the Harvard Annals

Matthew R. Templeton1, M. Saladyga1, K. Paxson1, R. Stine1, C. Froschlin1, A. Rupp1
1AAVSO.

9:30 AM - 9:50 AM

Staffordshire

We describe the volunteer-driven project to digitize published visual observations found in the Annals of the Harvard College Observatory, the publication of record for Harvard's variable star data archives prior to the founding of the AAVSO. The addition of published data from the 19th and early 20th centuries to the AAVSO International Database has the potential to enable significant new science by extending long-term light curves farther back in time with high-quality visual and photographic data. AAVSO volunteers working on this project have together digitized over well over ten thousand observations from the Harvard Annals, adding decades to the light curves of some stars. We highlight the work done so far, and show the potential to expand the project by both AAVSO Headquarters and by the volunteers themselves.

The Effect of Online Sunspot Data on Visual Solar Observers
Kristine Larsen
1
1Central Connecticut State University.
9:50 AM - 10:10 AM
Staffordshire
The Spaceweather website () hosts a daily picture of the near-side of the sun from SDO/HMI which identifies sunspot groups by number. The site also includes an overall Boulder sunspot number from the past 24 hours. While this information can be helpful for visual sunspot observers who are just beginning to learn the techniques of careful visual sunspot counts (for example, how to identify complex groups and how to carefully examine the limb of the sun), the “power of suggestion” this data might have on an observer cannot be ignored. An observer can check their observation against this “standard” in nearly real-time and may be tempted to alter their data to conform to what they consider to be a more reliable standard. This preliminary study first examined the effects of the Spaceweather site on a class of college students just beginning to learn white light solar observing, and then compared the results of an experienced solar observer with the Spaceweather data.

The World Science Festival
John Pazmino
1
1AAVSO.
10:10 AM - 10:30 AM
Staffordshire
New York City in the late 20th century rose to be a planetary capital for the sciences, not just astronomy. This growth is mainly in the academic sector but a parallel growth occurred in the public and home field.
With the millennium crossing scientists in New York agitated for a celebration of the City as a place for a thriving science culture. In 2008 they began World Science Festival. 2011 is the fourth running, on June 1st-5th, following AAVSO/AAS. World Science Festival was founded by Dr Brian Greene, Columbia University, and is operated thru World Science Foundation. The Festival is 'saturation science' all over Manhattan in a series of lectures, shows, exhibits, performances. It is staged in 'science' venues like colleges and musea, but also in off-science spaces like theaters and galleries. It is a blend of hard science, with lectures like those by us astronomers to science-themed works of art, dance, music. Events are fitted for the public, either for free or a modest fee. While almost all events are on Manhattan, effort is done to geographicly disperse them, even to the outer boros. The grand finale of World Science Festival is a street fair in Washington Square. Science centers in booths, tents, pavilions highlight their work. This fair drew in past years 100,000 to 150,000 visitors. The entire Festival attracts about a quarter million.
NYSkies is a proud participant at the Washington Square fair. It interprets the 'Earth to the Universe' display, debuting during IYA-2009. Attendance at 'Earth ...' on just the day of the fair plausibly is half of all visitors in America. The presentation shows the scale and scope of World Science Festival, its relation to the City, and how our astronomers work with it.

Variable Star Observing with the Bradford Robotic Telescope
Richard C. S. Kinne
1
1AAVSO.
10:30 AM - 10:50 AM
Staffordshire
With the recent addition of Johnson BVRI filters on the Bradford Robotic Telescope's 24 sq. arc minute camera, this scope has become a possibility to be considered when monitoring certain stars such as LPVs. This presentation will examine the mechanics of observing with the BRT and show examples of work that has been done by the author and how that data has been reduced using VPhot.

Cosmology with Type Ia Supernovae

Kevin Krisciunas1
1Texas A&M University.

10:50 AM - 11:10 AM

Staffordshire

Phillips (1993) discovered a correlation between the maximum optical brightness of Type Ia supernovae and the rate at which the light curves decline. Within 10 years it was clear that the slope of the decline rate relation was shallower at longer wavelengths. Since 2004 it has been known that in the near-infrared Type Ia supernovae are very nearly standard candles. This makes them particularly useful for determining distances to the host galaxies because a combination of optical and near-IR photometry allows us to determine the extinction by dust even if the dust is very different than normal Milky Way dust. Questions on the grandest scale such as, ";What is the ultimate fate of the universe?"; hinge on getting accurate distances to objects in the universe. We discuss the advantages of using Type Ia supernovae for cosmology and summarize recent results, such as those of the ESSENCE supernova search, which was carried out with the Cerro Tololo 4-m telescope.

Edwin Hubble's Famous Plate of 1923, and a Hubble-Hubble Connection

David R. Soderblom1
1STScI.

11:10 AM - 11:30 PM

Staffordshire

On October 6, 1923 Edwin Hubble used the Mount Wilson 100-inch telescope to take a 45 minute exposure of a field in the Andromeda galaxy. This is the now-famous plate marked with his ";VAR!"; notation. I will discuss this plate and that notation. I will also tell the story of flying copies of that plate on the deployment mission for HST in 1990 as a Hubble memento and then locating those copies afterwards, and how copies were flown on Servicing Mission 4 on 2009 as well. This has led to an effort in which AAVSO members joined to identify and reobserve that noted star, arguably the most important object in the history of cosmology, but largely ignored since Hubble's time.


Sunday, May 22, 2011, 1:30 PM - 3:00 PM

HAD I: Women in the History of Variable Star Astronomy

Special Session

Staffordshire



The Legacy of Annie Jump Cannon: Discoveries and Catalogs of Variable Stars.

Barbara L. Welther1
1Smithsonian.

1:35 PM - 1:55 PM

Staffordshire

This paper will review the many variable-star projects and publications that Cannon brought to fruition in her 45-year career at Harvard College Observatory.
In 1896, when Cannon joined the ";Corps of Women Computers"; at HCO, Williamina Fleming already enjoyed world-wide acclaim for her discoveries of novae on photographs of stellar spectra.
Antonia Maury had also become renowned: she had discovered and analyzed a rare spectroscopic binary star, Beta Aurigae. At that time, such discoveries made headlines in newspapers, especially because they were made by women who studied astronomy by day!
When Cannon was not actively involved in classifying stellar spectra, she took up HCO's project of cataloging observations of variables. As a result, she discovered thousands of long-period variable stars and half a dozen novae in the Milky Way. In 1903 she published ";A Provisional Catalogue of Variable Stars"; in Harvard Annals 48. Subsequently, Margaret Walton Mayall and Florence Campbell Bibber continued cataloging the variables through 1941, when Cannon died.
In 1918, when Cannon and others such as Edward Pickering and Solon Bailey, were made honorary members of the American Association of Variable Star Observers, Cannon wrote: ";I assure you it is a pleasure to be associated in this way, with a company of ardent observers and investigators, whose results are of so much value and carried on with such enthusiasm. It well be a spur to me in my future work, especially as to the new Catalogue of Variable Stars, which I hope to finish before very long.";


Anne S. Young: Professor and Variable Star Observer Extraordinaire

Katherine Bracher1
1Whitman College.

1:55 PM - 2:10 PM

Staffordshire

Anne Sewell Young (1871-1961) was one of the eight original members of the AAVSO, to which she contributed more than 6500 observations over 33 years. She also taught astronomy for 37 years at Mount Holyoke College; among her students was Helen Sawyer Hogg. This paper will look at her life and career both at Mount Holyoke and with the AAVSO.

The Stars Belong to Everyone: Astronomer and Science Writer Dr. Helen Sawyer Hogg (1905-1993)

Maria J. Cahill1
1Edison State College.

2:10 PM - 2:40 PM

Staffordshire

University of Toronto astronomer and science writer Helen Sawyer Hogg (President of
the AAVSO 1939-41) served her field through research, teaching, and administrative leadership.
Additionally, she reached out to students and the public through her Toronto Star newspaper
column entitled “With the Stars” for thirty years; she wrote The Stars Belong to Everyone, a
book that speaks to a lay audience; she hosted a successful television series entitled Ideas; and
she delivered numerous speeches at scientific conferences, professional women’s associations,
school programs, libraries, and other venues. This paper will illumine her life and the
personal and professional forces that influenced her work.


Variable Stars and Constant Commitments: The Stellar Career of Dorrit Hoffleit

Kristine Larsen1
1Central Connecticut State University.

2:40 PM - 3:00 PM

Staffordshire

Astronomer, educator, and science historian Dorrit Hoffleit (1907-2007) was widely respected by the amateur and professional astronomical community as a mentor and an ardent supporter of independent research. Her more than 600 catalogues, books, articles, book reviews, and news columns cover myriad aspects of astronomy, from variable stars and stellar properties to meteor showers, quasars, and rocketry. She also made important contributions to the history of astronomy. Hoffleit worked at the Harvard College Observatory from 1927-1956, where she discovered over 1200 variable stars. When Director Harlow Shapley retired from Harvard, Hoffleit gave up her tenured position and moved to Yale University, where she was placed in charge of the Yale Catalog of Bright Stars. At the same time, she was offered a position as director of the Maria Mitchell Observatory on Nantucket Island in Massachusetts. Hoffleit split her dual positions into six-month stints and remained director at the Mitchell Observatory for 21 years, developing a summer research program that engaged more than 100 undergraduate students (all but three of them women) in variable star research. Up until shortly before her death, she continued to work tirelessly on selected projects, and she was in high demand as a collaborator with colleagues at Yale and elsewhere. She was especially devoted to the American Association of Variable Star Observers (AAVSO) in part because it brought together amateur and professional astronomers in collaboration. She served on the organization’s council for 23 years and as its president from 1961-1963. In 2002, the AAVS0 published her autobiography, Misfortunes as Blessings in Disguise, in which Hoffleit explains how she always felt blessed by the opportunities in her life, even those which initially seemed misfortunes, and above all else valued creativity, flexibility, collegiality, and intellectual freedom in her professional life.


Sunday, May 22, 2011, 3:20 PM - 5:30 PM

HAD II: Variable Star Astronomy in Theory and Practice

Special Session

Staffordshire


King Charles` Star: A Multidisciplinary Approach to Dating the Supernova Known as Cassiopeia A

Martin Lunn1
1Yorkshire Museum, United Kingdom.

3:25 PM - 3:40 PM

Staffordshire

Few astronomical phenomena have been as studied as the supernova known as Cassiopeia A. Widely believed to have occurred in the latter half of the seventeenth century, it is also thought to have gone unrecorded. This paper will argue that Cas A did not go unobserved, but in fact was seen in Britain on May 29, 1630, and coincided with the birth of the future King Charles II of Great Britain. This ‘noon-day star’ is an important feature of Stuart/Restoration propaganda, the significance of which has been widely acknowledged by historians and literary experts. The argument here, however, is that in addition the historical accounts provide credible evidence for a genuine astronomical event, the nature of which must be explained. Combining documentary analysis with an overview of the current scientific thinking on dating supernova, the authors put forward their case for why Charles’ star should be recognized as a sighting of Cas A. Finally, it will be argued that a collaborative approach between the humanities and the sciences can be a valuable tool, not just in furthering our understanding of Cas A, but in the dating of supernovae in general.


John Goodricke, Edward Pigott, and Their Study of Variable Stars

Linda M. French1
1Illinois Wesleyan Univ..

3:40 PM - 4:00 PM

Staffordshire

John Goodricke (1764-1786) and Edward Pigott (1753-1825) are credited with determining the first accurate periods for several important variable stars. Goodricke's name is associated with the determination of the period of the eclipsing binary Algol (Beta Persei); for this he was awarded the Copley Prize of the Royal Society of London. He also determined the periods of the contact binary Beta Lyrae and of Delta Cephei, the prototype Cepheid variable. Around the same time, Edward Pigott obtained the period of Eta Aquilae, another Cepheid. In actuality, the two collaborated on all these observations; today we would call them co-discoverers. Goodricke is the better known of the two, in part because he won the Copley Medal, in part because of his tragically short life, and in part because he was deaf. Edward Pigott was the more experienced observer, having worked with his father Nathaniel on determining the longitudes of several cities on the Continent. Evidence shows, however, that Goodricke had some astronomical experience while a student at the Warrington Academy. The journals of the two show that they developed a partnership that made the most of both their talents over the brief time (less than five years) they worked together before Goodricke's death. Today, the two are remembered as having suggested eclipses as the cause for the periodic dimming of Algol. This explanation is accepted today as the correct one. In their day, however, most eminent astronomers believed that starspots were a more likely cause for the dimming. By the time of John Goodricke's death, he seems to have accepted that explanation as well. A study of the work of Goodricke and Pigott contains many lessons for today's observers of variable stars.
This work was supported by an AAS Small Research Grant and by the Pollack Award of the Dudley Observatory.


The development of early pulsation theory, or, how Cepheids are like steam engines";

Matthew Stanley1
1New York University.

4:00 PM - 4:25 PM

Staffordshire

The pulsation theory of Cepheid variable stars was a major breakthrough of early twentieth-century astrophysics. At the beginning of that century, the basic physics of normal stars was very poorly understood, and variable stars were even more mysterious. Breaking with accepted explanations in terms of eclipsing binaries, Harlow Shapley and A.S. Eddington pioneered novel theories that considered Cepheids as pulsating spheres of gas. These theoretical models relied on highly speculative physics, but nonetheless returned very impressive results despite attacks from figures such as James Jeans. Surprisingly, the pulsation theory not only depended on developments in stellar physics, but also drove many of those developments. In particular, models of stars in radiative balance and theories of stellar energy were heavily inspired and shaped by ideas about variable stars. Further, the success of the pulsation theory helped justify the new approaches to astrophysics being developed before World War II.

Frank Elmore Ross and his Variable Star Discoveries
Wayne Osborn
1
1Yerkes Observatory/Central Mich. U.
4:30 PM - 4:45 PM
Staffordshire
Frank Elmore Ross (1874-1960) was a talented astronomer that excelled in such diverse fields as computational astronomy, optical instrument design and astrophotography. Today he is remembered in astronomy mainly for his lists of stars of high proper motion, many of which are among our closest neighbors. A by-product of his searches for high proper motion stars was the discovery of 379 new variable stars. The identities of a number of these “Ross variables” are still uncertain and the variability yet to be confirmed more than eighty years after publication, largely due to imprecise or erroneous coordinates. Ross’s original observing cards and plates have been located and are being used to re-examine the stars. The cases of uncertain identity or variability are being resolved, and better magnitudes are being determined for these early-epoch observations. Many of the Ross variables are poorly studied and follow-up observations of a few of these stars have yielded some interesting results.

Stellar Pulsation Theory from Arthur Stanley Eddington to Today
Steven D. Kawaler
1, C. J. Hansen2
1Iowa State Univ., 2University of Colorado.
4:45 PM - 5:05 PM
Staffordshire
While one could question that Eddington was the pioneer in theoretical work directly addressing the pulsating variable stars, there is no doubt that his work in the first part of the 20th Century set the stage for a transformation of theoretical astrophysics. After Eddington (the 1940s to the present day) stellar pulsation theory evolved from analytic theory into the realm of computational physics. Starting from Eddington's formulation, the flexibility provided by numerical solutions enabled exploration of systematics of pulsating variable stars in vastly greater detail. In this talk, we will trace this development that led to theoretical explanations of period-luminosity relations, new mechanisms of pulsation driving, connections with mass loss and stellar hydrodyamics, and to modern asteroseismic probes of the Sun and the stars.

The AAVSO Photoelectric Photometry Program in its Scientific and Socio-Historic Context
John R. Percy
1
1Univ. of Toronto, Canada.
5:05 PM - 5:30 PM
Staffordshire
Photoelectric photometry began in the 1900s through the work of Guthnick, Stebbins, and others who constructed and used photometers based on the recently-discovered photoelectric effect. The mid 20th century saw a confluence of several areas of amateur interest: astronomy, telescope making, radio and electronics, and general interest in space. This is the time when AAVSO photoelectric photometry (PEP) began, with observers using mostly hand-built photometers on hand-built telescopes. The 1980s brought a revolution: affordable off-the-shelf solid-state photometers, and infrastructure such as the International Amateur-Professional Photoelectric Photometry (IAPPP) conferences, books, and journal. The AAVSO developed a formal PEP program in the early 1980s. Its emphasis was on long-term monitoring of pulsating red giants. It was competing, not always successfully, with programs such as active sun-like binaries (RS CVn stars) which offered ";instant gratification"; in the form of publicity and quick publications. Nevertheless, the AAVSO PEP program has, through careful organization, motivation, and feedback to observers, produced extensive scientific results. In this presentation, I shall describe, as examples, my own work, its scientific significance, its educational benefit to dozens of my students, and its satisfaction to the observers. To some extent, the AAVSO PEP program has been superceded by its CCD program, but there is still a useful place for ongoing PEP observations of thousands of variable stars. Reference: /sites/default/files/newsletter/PEP/lastpepnl.pdf Acknowledgements: I thank NSERC Canada for research support, my students, and AAVSO staff and observers, especially Howard Landis.

Monday

Monday, May 23, 2011, 8:00 AM - 7:00 PM
125

Stellar Evolution, Stellar Populations

Poster Session

Essex Ballroom


125.01
Using High Precision Stellar Observations to Constrain the Physics of Convection in Stars
Timothy Carleton
1, C. Meakin1
1Steward Observatory.
8:00 AM - 7:00 PM
Essex Ballroom
Arguably the most significant barrier to our full comprehension of stellar structure and evolution is the uncertainty in our understanding of stellar convection and its attendant mixing. Our current understanding of stellar convection, mixing length theory (MLT), describes convection as a process in which warmer pockets of fluid flow to the surface through a temperature gradient. The efficiency at which this transfers heat is dependent on the ratio of the surface area to the volume of the globule, gml. We use the stellar evolution simulation package MESA (Modules for Experiments in Stellar Astrophysics) together with new high precision observations of non-interacting binaries to constrain convection physics in low mass stars (M<1.2 Msun), specifically gml. Our data set contains 45 stars with precision mass, temperature and luminosity measurements (uncertainties at the few percent level) as well as observed relationships between turbulent surface velocity, surface gravity, and luminosity. This research was supported by the Arizona Space Grant Consortium.


125.02

The Physics of AGB Mass Loss

Lee Anne M. Willson1, Q. Wang1
1Iowa State Univ..

8:00 AM - 7:00 PM

Essex Ballroom
To investigate the importance of physical processes in the stellar atmosphere on the mass loss rates of AGB stars, we have run a substantial grid of dynamical atmosphere models using a code that approximates non-LTE, dust formation, and radiative transfer via one or two parameters each, and using R(L, M, Z, l/H) to investigate the importance of low gravity and metallicity. This gives us six parameters to investigate: Criticial density (for the onset of non-LTE), opacity kappa (determines the photospheric density), Tcondensation and ΔTcondensation (for dust formation), mixing length parameter l/H, and Z, M (for the initial stellar model). We find the location of the Deathline, where dlnM/dt = dlnL/dt, is quite stable, shifting by ΔlogLdeath < ~0.1 with variation of any of the parameters inside reasonable limits. We find that the biggest uncertainty in the model-based Deathline is introduced by the uncertainty in R(L, M, Z) represented by varying l/H in the models. The condensation of dust and the non-LTE transfer both have a great effect on the structure of the atmosphere, and affect the outflow velocity in the wind, but neither of these makes a large difference in the predicted Deathline. Observational constraints on the Deathline include the Mira P-L relation and a variety of published empirical mass loss formulae. Research supported by NSF AST0708143.


125.03
The Wfpc2 Uv Survey Of Globular Clusters: The Case Of Ngc 6229
Nicoletta Sanna
1, R. T. Rood1, G. Beccari2, E. Dalessandro3, F. R. Ferraro3, B. Lanzoni3
1University of Virginia, 2European Southern Observatory, Germany, 3University of Bologna, Italy.
8:00 AM - 7:00 PM
Essex Ballroom
One of the valedictory projects undertaken by WFPC2 was a survey of UV bright objects in 30 globular clusters. Eventually these results will be
combined with similar results obtained by our group for 15 clusters. For most of these clusters observations were obtained with 4 or more filters.
For a subset of clusters we also have observations from GALEX which will allow us see if the sort radial variations previously found in blue
straggler stars (BSS) also exists in the hottest stellar populations.
Here we present the case of NGC 6229. The data set has been obtained by combining high-resolution (HST/WFPC2 and ACS) and wide-field space (GALEX)
observations and ground-based (MegaCam-CFHT) images. The photometric sample covers the entire cluster extension from the very
central regions up to the tidal radius and beyond. We determine the radial density profile and we study the BSS population and its radial distribution.


125.04
IRAS 20050+2720: Time Scales Of Pre-main Sequence Evolution
Hans Moritz Guenther
1, S. J. Wolk1, B. Spitzbart1, R. A. Gutermuth2
1SAO, 2Smith College/UMass.
8:00 AM - 7:00 PM
Essex Ballroom
We present results of our multiwavelength study of IRAS 20050+2720, a young stellar cluster, which is thought to be located at 700 pc. IRAS 20050+2720 displays an exceptionally low 24 micron background, because no massive stars are present. We concentrate on Chandra and Spitzer data and compare cluster properties of an IR sample (as previously presented by Guthermuth et al. 2009) and an X-ray selected sample. Compared to previous works the IR coverage has been extended with new observations. Foreground X-ray sources are separated with optical photometry and we treat the remaining disk-less sources as the class III population of the cluster. It turns out, that the class III sources are much less clustered than class I and II sources.
The low 24 micron background allows us to achieve a more complete sample at this wavelength than in other star forming regions. Therefore, our census of transition disk objects between class II and class III should be more complete. We use this to put limits on the time scale of disk dispersal.
This work has been funded by Chandra award GO6-7017X.


125.05



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