Exploring the heartbeat of stars—measuring rapid pulsations in Cepheids, RR Lyrae, δ Scuti, and other short‑period variable stars.
What We Do
Short period pulsators (SPPs) are stars whose brightness varies due to internal pulsations, caused by a variety of factors including periodic expansions and contractions in their radii and changes in temperature. These pulsations happen on timescales ranging from minutes to months, making them both challenging and scientifically rich targets.
We focus on a wide variety of SPP types, including classical Cepheids, Population II Cepheids (W Virginis), RR Lyrae, δ Scuti, γ Doradus, β Cephei, slowly pulsating B stars, and pulsating white dwarfs.
Your observations help tackle fundamental astrophysical questions: from refining the period–luminosity relationships (used for distance measurements) to probing a star’s internal structure via asteroseismology. We also track period changes over time, which may indicate stellar evolution in action.
How We Do It
Observations are primarily performed using CMOS/CCD photometry through standard filters, which allow for high-precision measurements required for SPP research. Multiple filters are recommended as this can give valuable information on temperature changes. Because many SPP stars have very small amplitude changes (often less than a tenth of a magnitude), precise filtered photometry is preferred.
We maintain a program list of target stars (including RR Lyrae, high-amplitude δ Scuti, Cepheids, etc.) for observers to use. We also publish an ephemeris of times of maximum for certain stars each year, to see how these stars and their pulsations evolve over time.
After collecting data, observers reduce their images (e.g., via standard photometry software), then submit their measurements to the AAVSO International Database. These data feed into long-term studies of pulsation behavior, amplitude modulation (e.g., Blazhko effect), and period change.
Additionally, the SPP section supports communication and collaboration via the AAVSO SPP Forum, where observers and researchers exchange ideas, coordinate observing strategies, and discuss scientific findings.
Is It Right for Me?
Level: Moderate to Advanced. Observing short period pulsators requires stable, high-precision photometry and often a cadence sufficient to sample full pulsation cycles, which can be as short as hours.
Equipment: A telescope with CMOS/CCD camera, coupled with standard photometric filters, is strongly recommended. For the most scientifically useful observations, using a filter system is preferred to minimize color-dependent variation over the pulsation cycle.
Observing Requirements: Observations often require continuous monitoring over several hours to capture a full pulsation cycle for many SPPs. Because the phenomena are rapid and may be multi-periodic, consistent, well-timed observations are more valuable than occasional snapshots. For certain RR Lyrae or δ Scuti stars, timing the maximum (or minimum) precisely is critical.
Additional Considerations: Observers should be comfortable reducing CMOS/CCD data and working with photometry software. Submitting standardized, accurate measurements to the AAVSO International Database is essential to whole‑program science goals. For multi-periodic stars (e.g., Blazhko RR Lyrae or multi-mode δ Scuti), long-term and high-cadence data are especially scientifically valuable.