Molecular Clouds, HII Regions, Interstellar Medium…………………………………...315 Thursday Thursday, May 26, 2011, 8:00 AM – 12:00 PM………………………………………………….320 The Sun and Solar System II….………………………………………………………….320 Stars, Star Formation and Associated Topics………………………………………….....326 Galaxies, Galaxy Clusters and Friends………………………………………………...…333 Instrumentation, Surveys and Data……………………………………………………….343 High Energy, Cosmology and Other Topics……………………………………………...349 Education…………………………………………………………………………………356 Thursday, May 26, 2011, 8:30 AM – 9:20 PM……………………………………………………358 The Least Luminous Galaxies in the Universe…………………………………………...358 Thursday, May 26, 2011, 10:00 AM – 11:30 PM…………………………………………………359 Particle Physics III: Variations of Fundamental Constants and Dark Matter Searches…..359 Extrasolar Planets: Theory and Characterization…………………………………………360 Evolution of Galaxies II…………………………………………………………………..363 Thursday, May 26, 2011, 11:40 AM – 12:30 PM…………………………………………………366 GALEX: Mapping the Hidden Side of Galaxy Evolution and the UV Universe…………366
Abstracts Saturday, May 21, 2011, 2:00 PM - 5:00 PM AAVSO Paper Session I Special Session
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. Turner1, 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 Lane1, 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.
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