Finding Phase-Step delta Scuti Variables with Ground-based Observations
Abstract:
During a summer REU program in 2024 a number of strange O-C diagrams were found in data from the NASA TESS satellite. The original pattern looked like saw-tooth O-C but can also be seen as a set of phase-steps. These patterns were easy to see in the TESS data given nearly continuous coverage for 27 straight days. The question that arises is "Can a set of ground-based observations see the phase-step pattern?". Could there also be other delta Scuti that are phase-step stars, but the pattern is unseen in sparse times-of-maximum light data. We are requesting a campaign over the next year to examine this question.
Justification:
Dr. Hintz writes in the summer of 2024, we found 8 members of a new group of variables from a search of more than 700 newly discovered delta Scuti. Information regarding this class of variables is discussed in Felvus-Richmond & Hintz (2026) (AJ, 171, 170). Since that time, one additional target has been found. Amazingly, the stars are fairly evenly distributed between hemispheres and across the year, so a target is almost always available. We desire a set of ground-based times-of-maximum light to determine if the pattern can be seen in a dedicated campaign, or if the phase-step pattern can only be seen in data from satellites like TESS. We request that the observers monitor each target long enough on a given night to provide clear maximum light coverage over at least one cycle per night (prefer multiple cycles). Then examine the star on as many nights as possible. Data can be collected in any filter although there is a slight preference for V data. Authorship will be offered to all who provide a minimum of 5 times-of-maximum light. After that the authors will be listed in order of number of times-of-maximum light provided from high to low. In addition to submitting the data to the AAVSO, we ask that a text file with HJD (or JD) and magnitude be emailed to phasestep.ground@gmail.com. Please also email your best estimate for each time-of-maximum light. Publications are planned for October 2026 and May 2027. Note: This is part of a Master's Thesis project.
Requested Data Types:
Photometry
Targets
| Name | Magnitude | Variability Type | Photometry Notes | Spectroscopy Notes |
|---|---|---|---|---|
| MW Cam | 9.25 | DSCT |
Cadence: Continuous Precision: 50 mmag |
Not Requested |
| MP UMa | 11.67 | DSCT |
Cadence: Continuous Precision: 50 mmag |
Not Requested |
| AA LMi | 11.40 | DSCT |
Cadence: Continuous Precision: 50 mmag |
Not Requested |
| V0336 Aps | 11.12 | DSCT |
Cadence: Continuous Precision: 50 mmag |
Not Requested |
| CH Ant | 9.68 | DSCT |
Cadence: Continuous Precision: 50 mmag |
Not Requested |
| ATO J103.0204-08.2002 | 12.41 | DSCT |
Cadence: Continuous Precision: 50 mmag |
Not Requested |
| V0952 Ara | 10.19 | DSCT |
Cadence: Continuous Precision: 50 mmag |
Not Requested |
| GSC 03308-00462 | 12.13 | DSCT |
Cadence: Continuous Precision: 50 mmag |
Not Requested |
| CzeV616 | 10.92 | DSCT |
Cadence: Continuous Precision: 50 mmag |
Not Requested |
Spectroscopy Lines:
No spectroscopy lines provided
Photometry Filters:
B (Johnson), V (Johnson), R (Cousins), I (Cousins), g (Sloan), r (Sloan), i (Sloan)
Comparison Stars:
Finder charts with comparison stars may be created using the AAVSO Variable Star Plotter (VSP).
Co-Authorship
Observers are eligible for co-authorship.
Additional Observer Input:
The only real additional information is to make sure you have a fast enough cadence of observations to provide clear times-of-maximum light. Also, the photometric precision just needs to be high enough for clean maxima. In some cases 100 mmag might be sufficient. However, if possible, get below the 100 mmag.
Additional Submission Location:
Email to phasestep.ground@gmail.com (only light curve text file and/or time-of-maximum light)
Notes:
No public notes