John R. Percy
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View article: The Long Secondary Period (LSP) Variables: Overview and Some Analysis
The Long Secondary Period (LSP) Variables: Overview and Some Analysis Open
We briefly review the phenomenon of long secondary periods (LSPs) in red giants, and the LSP variable stars classification introduced in the All-Sky Automated Survey for Supernovae (ASAS-SN) variable star catalog; they are red giant Long P…
View article: Long Secondary Periods in Pulsating Red Giants: A Century of Investigation
Long Secondary Periods in Pulsating Red Giants: A Century of Investigation Open
Red giants are unstable to radial pulsation. About a third of them also show a long secondary period, 5 to 10 times the pulsation period. The long secondary periods were recently ascribed to eclipses of the red giant by a low-mass dust-ens…
View article: Period Analysis of All-Sky Automated Survey for Supernovae (ASAS-SN) Data on Pulsating Red Giants
Period Analysis of All-Sky Automated Survey for Supernovae (ASAS-SN) Data on Pulsating Red Giants Open
The All-Sky Automated Survey for Supernovae (ASAS-SN) has recently used over 2000 days of data to identify more than 50,000 variable stars, automatically classify these, determine periods and amplitudes for those that are periodic -- part …
View article: ASAS-SN Observations of the Pulsation of some R Coronae Borealis (RCB) Stars
ASAS-SN Observations of the Pulsation of some R Coronae Borealis (RCB) Stars Open
Photometry from the All-Sky Automated Survey for Supernovae (ASAS-SN), along with the AAVSO VSTAR time-series analysis package has been used to study the pulsational properties of 31 R Coronae Borealis (RCB) stars. Periods have been derive…
View article: ASAS-SN Observations of the Pulsation of some R Coronae Borealis (RCB)\n Stars
ASAS-SN Observations of the Pulsation of some R Coronae Borealis (RCB)\n Stars Open
Photometry from the All-Sky Automated Survey for Supernovae (ASAS-SN), along\nwith the AAVSO VSTAR time-series analysis package has been used to study the\npulsational properties of 31 R Coronae Borealis (RCB) stars. Periods have been\nder…
View article: A Study of Pulsation and Fadings in some R Coronae Borealis Stars
A Study of Pulsation and Fadings in some R Coronae Borealis Stars Open
We have measured the times of onset of recent fadings in four R CrB stars -- V854 Cen, RY Sgr, R CrB, and S Aps. These times continue to be locked to the stars' pulsation periods, though with some scatter. In RY Sgr, the onsets of fading t…
View article: Long-Term Changes in the Variability of Pulsating Red Giants (and One R CrB Star)
Long-Term Changes in the Variability of Pulsating Red Giants (and One R CrB Star) Open
We have used many decades of visual observations from the AAVSO International Database, and the AAVSO time-series analysis package VSTAR, to study the long-term changes in period, amplitude, and mean magnitude in about 30 normal pulsating …
View article: Sparsely-Observed Pulsating Red Giants in the AAVSO Observing Program
Sparsely-Observed Pulsating Red Giants in the AAVSO Observing Program Open
This paper reports on time-series analysis of 156 pulsating red giants (21 SRa, 52 SRb, 33 SR, 50 Lb) in the AAVSO (American Association of Variable Star Observers) observing program for which there are no more than 150-250 observations in…
View article: Forty Years of Linking Variable Star Research with Education
Forty Years of Linking Variable Star Research with Education Open
In this review, I reflect on four decades of my experience in linking astronomy research and education by supervising variable-star research projects by undergraduates, and by outstanding senior high school students. I describe the evoluti…
View article: Amplitude Variations in Pulsating Red Giants. II. Some Systematics
Amplitude Variations in Pulsating Red Giants. II. Some Systematics Open
In order to extend our previous studies of the unexplained phenomenon of cyclic amplitude variations in pulsating red giants, we have used the AAVSO time-series analysis package VSTAR to analyze long-term AAVSO visual observations of 50 su…
View article: Studies of the Long Secondary Periods in Pulsating Red Giants. II. Lower-Luminosity Stars
Studies of the Long Secondary Periods in Pulsating Red Giants. II. Lower-Luminosity Stars Open
We have used AAVSO visual and photoelectric V data, and the AAVSO time-series package VSTAR and the Lomb-Scargle time-series algorithm to determine improved pulsation periods, "long secondary periods" (LSPs). and their amplitudes in 51 sho…
View article: Period Changes and Evolution in Pulsating Variable Stars
Period Changes and Evolution in Pulsating Variable Stars Open
We review ways in which observations of the changing periods of pulsating variable stars can be used to detect and directly measure their evolution. We briefly describe the two main techniques of analysis -- (O-C) analysis and wavelet anal…
View article: Studies of the Long Secondary Periods in Pulsating Red Giants
Studies of the Long Secondary Periods in Pulsating Red Giants Open
We have used systematic, sustained visual observations from the AAVSO International Database, and the AAVSO time-series analysis package VSTAR to study the unexplained "long secondary periods" (LSPs) in 27 pulsating red giants. In our samp…
View article: Studies of the Long Secondary Periods in Pulsating Red Giants. II. Lower-Luminosity Stars
Studies of the Long Secondary Periods in Pulsating Red Giants. II. Lower-Luminosity Stars Open
We have used AAVSO visual and photoelectric V data, and the AAVSO time-series package VSTAR and the Lomb-Scargle time-series algorithm to determine improved pulsation periods, long secondary (LSPs). and their amplitudes in 51 shorter-peri…