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.
Looking at a 20’x20’ square field (not so wide?), if you center near 12 27 15 +81 35 (J2000), then you’ll have four pretty good comp stars for reference.
Even at 40’x40’, my request in VSP only returns two comps.
Most these are not visible to me at 31 degrees latitude - looks like best for southern hemisphere observers. The one that is in my FOV during the night only has a listed mag delta of 0.15mag, so likely not a good candidate for my 8" scope. Best regards. Mike
Hi Jim,
Yes I did read the announcement, however, I also noted in the past some principle observers did not want DSLR data for some reason, so I was just making sure. Thanks for the reply!
Sam
What comp(s) did you use for CzeV616? I have a full nights data from last night (7/20-21) and there seems to be an issue with the single comp visible to me (the 119 star) in the 14x14 arc minute field that I have. About 2/3 of the way through the night, there is a sudden offset in the data for an hour or so and then it returns to where it should be. If I use other stars in the field (non-AAVSO stars) then my curve looks just like yours. This was in Johnson B-- I haven’t looked at the other filters yet.
I have just changed my comps to 119 and 105 and revised my data in AID. Much closer to most others now. My check is 109.
I think you might check 119 in the other filters first or move your center just a bit to get the 105 comp in your FOV. My FOV is about 30’. OR, you could try a different APASS comp?
Not sure that the shift was caused by the comp companion? I recall seeing it but it was in my sky annulus? Perhaps it was some stray light?
Hello! The proposal asks that the data be sent to an email as well as to the AAVSO database. However, the proposal also asks for estimate of times of maximum brightness in the email.
Does the author want all observations sent to email or just the estimated times of maximum brightness?
Also, I submitted data in filters B,V, and I. Does the author want multiple filters? Or is just one needed since it is the time of maximum brightness that is only being evaluated? Best regards. Mike
I’m reporting the times of brightness extrema (minimum & maximum) for CzeV616 identified from the observations obtained so far for each of the filters used. The periods were determined using the Generalized Lomb–Scargle method implemented in Astropy. The phase was calculated based on the derived model and does not match the official ephemeris.
I see much smaller amplitude tonight (262.8). When looking at our full lightcurve since start of campaign, I think I’m seeing an amplitude trend with a several day (4) period? Thoughts?
My check is 109.
