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89th Spring Meeting of the AAVSO: Paper Session Abstracts

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Paper abstracts and schedule from Spring Meeting 2000

The 89th Spring Meeting of the
American Association of Variable Star Observers
Huntsville Marriott Hotel
Huntsville, Alabama
April 15, 2000

Schedule

Saturday, April 15
8:30am      AAVSO Meeting Registration
8:30am - 9:00am     Coffee Break
9:00 am - 10:50am     AAVSO Membership Meeting
10:00am - 10:20am     Coffee Break
10:50am - 12:00pm     AAVSO Paper Session (see abstracts below)
12:00pm - 1:00pm     Lunch Buffet
1:00pm - 5:30pm     AAVSO Paper Session (see abstracts below)
3:00pm - 3:30pm     Coffee Break
7:00pm Pre-banquet Cash Bar
7:30pm AAVSO Banquet
9:00pm     Awards Presentation and Special Lecture: Astronaut Dr. John Grunsfeld "The 1999 HST Servicing Mission and Remarks on High Energy Astrophysics"


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Paper Abstracts

AAVSO Paper Session


10:50am - 12:00pm:

Kevin Marvel
Grassroots Astronomy
Congress has a large impact on the amount and quality of astronomical research that takes place in the United States. By funding NASA and NSF, as well as other agencies such as DoE and DoD, the Federal Government enables US astronomers to perform cutting edge research. However, Congress makes its decisions based on input from citizens. If the citizens are silent on an issue, Congress does not know it exists. Last summer the US amateur community rallied in support of professional research, resulting in a healthy budget for both NASA and NSF astronomy research. I will present a summary of how the funding process works and how and why amateurs can and should help ensure continued research funding for US astronomy.

Aaron Price
Automation & Innovation For Information Addicts (101)
The AAVSO presence on the Internet is about to take a leap forward with new exciting initiatives involving automation of the new Gamma-Ray Burst network, new methods of submitting nightly and monthly observations online, and the cooperation between the AAVSO and the open-source community for better support of variable star research in popular astronomical software applications.

Roger Pickard
The BAA Variable Star Section
A description of the Section, its database, with observations going back to 1888, observing programs, covering visual, photoelectric and CCD observations, and the issuing of charts.

Guy M. Hurst
The UK Nova/Supernova Patrol - The first 25 years!
The photographic sky patrol of 1974-1976 was the forerunner of the UK Nova/Supernova Patrol. The original aim was merely to make photographic records of the sky to help investigate later queries. Both were promoted by 'The Astronomer' organization ('TA') which itself had been formed in 1964 to encourage monitoring of any observable objects in the night sky. The discovery of HS Sagittae (Nova Sge 1977) by John Hosty was the catalyst for a major launch of the present patrol which would now include thorough checking for novae and supernovae. Later, the patrol of the British Astronomical Association and that of 'TA' were merged. Techniques involving visual, photographic and CCD will be discussed. Although George Alcock is not a member, preferring an individual approach, his support and achievements will be mentioned. The details of discoveries to date by patrol members which involve four novae and 24 supernovae will be presented. The latest CCD Nova Patrol, launched early in 2000 by the author will be described. The patrol is keen to foster links with amateur astronomers throughout the world with similar interests in these exciting objects. Ways in which international co-operation can be fostered will be explored.

Alexander Murphy
The Super Nova Early Warning System Collaboration
The world's leading neutrino and gravitational wave detectors, and several projects nearing completion, have come together in a collaboration to provide a robust early warning of a supernova's occurrence to the astronomical community. This talk will address the motivation for such a collaboration, the current status, including the signal we hope to observe, and a brief discussion of how best to utilize the alert we can provide.

12:00pm - 1:00pm: Lunch Break

1:00pm - 3:00pm:

David B. Williams
A Photographic Investigation of Four Bamberg Variables
The variable stars ST, SU, and SV Lep and NSV 1966 were discovered at Bamberg in 1974. The three stars with official designations entered the General Catalogue of Variable Stars without known periods. Neither type nor period was determined for NSV 1966. Investigation of these variables on Harvard plates confirms SU Lep as an eclipsing binary but with minima three times as deep as previously thought. ST and SV Lep are confirmed as Mira variables. NSV 1966 is also a Mira variable that becomes bright enough for addition to the AAVSO visual program. Periods, magnitude ranges, and accurate positions for all four stars are reported.

Arne Henden
The M67 Experiment
Observations of the standard open cluster M67 have been made by sites with typical amateur CCD equipment: front- and back-illuminated CCDs, unfiltered, IR-filtered and Johnson-Cousins filtration. This dataset has been used to investigate whether unfiltered CCDs can be transformed onto the Johnson-Cousins system, both for V- and R-band photometry, and the quality of the transformation. The general results are that an unfiltered front-illuminated CCD loosely corresponds to a wide-R bandpass, and an unfiltered back-illuminated CCD is roughly equivalent to a wide-V bandpass.

Mark Slovak
Using the Landolt Selected Areas (SA) For Photometric Identification of Faint Supernova and Optical Counterparts to Gamma Ray Bursters
We propose to use the Landolt selected areas (SA) to establish a photometric baseline against which to quickly instigate a rapid search for faint supernova candidates or optical counterparts to gamma ray bursters upon receiving a neutrino alert or gamma ray burst occurrence.

Robert S. Fritzius
A Ritzian Interpretation of Variable Stars
A revived version of de-Sitter's 1913 "binary stars" argument against Ritz's 1908 ballistic theory of light is presented. De-Sitter's "contention" provides an observationally falsifiable explanation for the apparent magnitude and color modulation of variable stars. Spectral evidence for variables being comprised of close binary systems is being sought.

Tom Cragg
Current Phase of the Sunspot Cycle
A brief description of how sunspot numbers are derived is discussed. A 200-year sunspot curve is discussed and presented with emphasis on the cycle alternation since 1850. Predictions of the current maximum are presented demonstrating that the chances of continuation of the 150-year alternation are in doubt.

France B. Berger and James C. Carlson (presented by Casper Hossfield)
Evidence From Sunspot Statistics that the Sun Has Changed Activity Modes During the Last Ten Cycles
An examination of the sunspot cycle data suggests that the Sun has occupied two activity modes in the years for which the most reliable records are available. Evidence for this is found, first, in the graph of the yearly averages of the daily sunspot numbers dating from 1882 to the present (Figure 1); and second, from statistical comparisons of various data sets for the years 1882 to 1946 (Early period) with their counterparts for 1947 to 1996 (Late period). Examination of a plot of the running correlation coefficient between the number of days per year when the Sun's disk was devoid of spots and the yearly average sunspot number, starting in 1882 (Figure 2), is quite consistent with the two mode hypothesis and a transition around 1946. The most compelling quantitative evidence for separate modes comes from comparing the Early with the Late daily sunspot numbers averaged over each cycle. The former (the average over cycles 13 - 17) is 42.0 +/- 8.7. The latter (cycles 18 - 22) is 78.2 +/- 13.1. The separation of the averages is 36.2 +/- 15.7, or 2.3 standard deviations. Finding distributions this compact compared to their separation lends considerable support to the correctness of the hypothesis.

Edward M. Sion, Paula Szkody, Boris Gaensicke, F.H. Cheng, C. LaDous, and B. Hassall
Hubble Space Telescope Spectroscopy of the Dwarf Nova RX Andromedae I: The Underlying White Dwarf
{*} Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. We obtained Hubble GHRS (G140L grating) phase-resolved spectroscopic observations of the dwarf nova RX Andromedae at three times in its AAVSO-recorded outburst cycle: (1) near the end of an extraordinarily deep and long dwarf nova quiescence, 3 months after the last previous outburst; (2) during the rise to outburst and; (3) near the end of a decline from outburst. The spectral wavelength range covered was 1150A to 1425A. All of the spectra are dominated by absorption lines with weak to moderately strong emission wings due to the continued presence of disk material. Uncertainties in line velocities preclude a K_1 determination or mass information. We find that the Teff of the white dwarf is 35,000K near the end of quiescence and it is spinning at the globally averaged rate of V sin i= 150 km/s. These values are very similar to the Teff and rotation rate of the white dwarf in U Gem, the only other dwarf nova above the period gap with a measured rotation rate. Accurate abundances are complicated by line emission. We report approximate subsolar chemical abundances of Carbon and Silicon for RX And with C down by 0.05 and Si = 0.1 solar while other elements are at essentially their solar values. We see no evidence of thermonuclear-processed abundance ratios. If the white dwarf mass is 0.8 Msun (Ritter 1999), then the corresponding white dwarf cooling age, 4E+6 years, is a lower limit to the age of this CV. If the peculiar line features seen in the spectrum on the late decline from outburst are inverse P Cygni in nature, then infall velocities of 2000 km/s are indicated during the decline from outburst. We compare the surface properties of the RX And white dwarf with the properties of other CV degenerates studied to date with HST, HUT and IUE.

3:00pm - 3:30pm: Coffee Break

3:30pm - 5:30pm:

Lee Anne Willson
Miras and the Ultimate Fate of the Earth
What do AAVSO's favorite stars have to do with the ultimate fate of Earth? We have been learning about the most extreme conditions that the planets will encounter as the Sun ages. In about 7 Gyr, when the Sun is a Mira, the Earth will most likely be in serious trouble. Some results of recent calculations will be presented showing what is most likely to occur, and giving a couple of possible (but unlikely) "outs".

Kevin B. Marvel
Water Maser Proper Motions near Evolved Stars
I will present a summary of recent observations obtained using very long baseline interferometry of water masers near evolved stars. We find that the masers do not have simple kinetic motions such as radial outflow at constant velocity. Recent results from infrared speckle imaging hint at very clumpy mass loss, which could lead to confused kinematics in the water maser region.

Hideo Sato, Kazuo Yoshioka, and Keiichi Saijo
Wavelength Dependence and Long-term Time Variation of Polarization of Three RV Tau Stars
The authors have studied polarimetric photometry data collected at Dodaira Observatory using a 91cm eight-channel polarimeter. Three RV Tau stars (U Mon, SS Gem and RV Tau) will be discussed which show some interesting behavior in the light variation with the pulsation period.

George Hawkins and Janet Mattei
The Unusual Long Term Light Curve of the MIRA Variable R Cen
The long term light curve of the unusual MIRA variable R Cen from 1918-2000 will be discussed. The most unusual aspect of the light curve is a double maxima at a period of 273 days, alternating with deep minima at 545-day intervals. While a few other MIRA variables in the AAVSO database are also known to have double maxima, none show such regularity or strength in the secondary maxima as R Cen. The most likely explanation for the double maxima of R Cen is a resonance phenomena where a higher overtone mode at 273 days pulsates at exactly the first harmonic (2x frequency) of the fundamental mode at 545 days. R Cen also has a third prominent period at 818 days. The peak-to-peak amplitude of R Cen has also declined gradually in the last 40 years, going from 5.5-11.5 magnitude from 1918 to 1960, to 6.5-9.5 magnitude in recent years. If it continues this trend, the star may be completely constant in the next 10-20 years. The recent amplitude decline of R Cen will be discussed in terms of the evolutionary status of MIRA and semiregular variables, and will be compared to a few Cepheids that have been known to turn off their variability.

Eric Broens, Christian Sterken, and Chris Koen
On the Observational History of Chi Cygni
Since its discovery in 1686 by Gottfried Kirch, Chi Cygni attracted the attention of many observers. Until 1738 the star was mainly monitored by G. Kirch and C. Kirch and occasionally by Cassini and Halley. Later on, Le Gentil, Pigott, and Olbers, among others, provided series of observations, although these had long interruptions in between. During the 19th century significant contributions came from Argelander and contemporaries. In the second half of the 19th century J. Schmidt obtained observations covering nearly 40 years! From the end of the 19th century on, amateurs gathered an uninterrupted series of observations. An analysis of the available observations since the discovery date yields substantial cycle-to-cycle variations in the pulsation period with quite strong evidence for a linearly increasing period. A quadratic fit Tmax=T0 + Pe E + 1/2 dP/dE E**2 over the complete range of available data yields a period change dP/dE = 0.014 d/c (Pe = 405.27), implying that Chi Cygni's pulsation period has increased by about 4 days since the discovery date three centuries ago.

Richard W. Schmude, Jr., Joy Jones, and Benjamin Jimenez
Photoelectric Magnitude Measurements of RX Cephei
Extensive visual and photometric studies of the star RX Cephei, carried out in 1999-2000 are summarized here. Photometric measurements of RX Cephei were taken to determine if the star is variable. A total of 44 measurements were taken of RX Cephei using a 10 cm refracting telescope and an SSP-3 solid-state photometer with filters that have been transformed to the Johnson B and V system. Measurements were taken during a 186-day period between Sept. 14, 1999 and March 18, 2000. Observations were generally made in Barnesville, GA, which is at: 33.1
ºN and 84.2ºW. The average B-filter measurement of RX Cephei is 8.41, and the V-filter measurement of RX Cephei is 7.29. The difference between B and V filters, called the B-V value is 1.12. After construction a graph of the measured magnitude of RX Cephei versus time, it was concluded that RX Cephei did not change brightness by over 0.15 magnitudes over the 186-day period.

Raymond R. Thompson
"Differential Photoelectric Photometry, Sine Waves and RS Cancri"
RS Cancri (M6e Ib-II) is listed as SRc? and has been observed by the Photoelectric Photometry Division of AAVSO since 1983, with a total of 657 observations in the archive. The author noticed from his own observations, that in 1990 and again in 1994, the star's light-curve was a near-perfect sine wave, resembling that of a typical Mira such as R Draconis. At other times the star produced the usual uneven fluctuations of a semi-regular variable. A search was made of the visual light-curves to see if there were earlier examples of this phenomenon. The inevitable scatter made this difficult, but possible instances were found in 1969 and 1983. The latter was confirmed by the work of a single PEP observer.

During 10 years of photoelectric photometry of two dozen SR stars, the author had not encountered anything like this before. In a personal communication, Dr. John Percy stated that, as a super-giant with an amplitude of less than 2.5 magnitudes, RS Cnc was definitely in a different class from the long-period Miras. He also pointed out that some SRd stars occasionally exhibit "more or less sinusoidal light-curves with amplitudes of a few tenths of a magnitude."

Casper H. Hossfield
A Very Low Frequency Gravitational Wave Antenna
A very low frequency gravitational wave antenna can detect binary neutron stars, the likely source of gamma ray bursts, many years before they coalesce to produce the gamma ray burst. I have designed an antenna an amateur can build from materials that cost a few hundred dollars. It is a small antenna that can fit in the corner of a basement or garage.

AAVSO 49 Bay State Rd. Cambridge, MA 02138 aavso@aavso.org 617-354-0484