Abstract: Sebastián Otero (AAVSO) writes: HD 83742 / HD 302301 is a visual binary, one component of which is an eclipsing binary and one of which shows delta Scuti (DSCT) pulsations. This small amplitude eclipsing binary was discovered by data-mining the TESS and ASAS-3 databases as a 9.2-day eccentric binary with very fast apsidal motion and milimagnitude pulsations. There are three main goals for this campaign: 1) Identifying which component of this 11" visual binary is the actual eclipsing binary (that hasn’t been resolved by TESS and ASAS); 2) Identifying which of the two stars shows the observed DSCT pulsations; 3) Monitoring the eclipses to determine the apsidal motion period. Note: The end-date for goal 3 of this campaign will be several years after the campaign end-date given above. Either this campaign will be extended, or a separate campaign will be issued later for goal 3.
Justification: AAVSO observers able to separate objects 11" apart will be able to determine the identifications of the involved variable stars and provide long-term coverage of the eclipse changes in order to determine the apsidal motion and improve the orbital period. Milimagnitude precision will be required to detect the 0.003 mag. pulsations in one of the stars and identify it.
I will try to see whether I can observe this target with my remote observatory. If successful I will submit data to the AAVSO database in B and V filters.
I got data from last night in time series in V and B band. Still trying to figure out how to analyse those images the best way. I am analysing both stars.
Josch
Hi, the AAVSO’s VPHOT application is very effective and convenient if you’re an AAVSO member. Otherwise, Peransano seems a very good alternative and is low cost. You’ll need to set up Comp and Check Star sequences for each target Star. Good luck.
It depends what you wish to do, but the photometry software is Phoranso. I have it on my laptop. Peranso is the light curve plotting and analysis package, which I also have.
My apologies for the missing comp stars! A comparison star sequence for these targets has been requested and will be available as soon as possible. In the meantime please hold on to your images. Thanks for your suggested comp stars, Roy.
Good observing, everyone,
Elizabeth Waagen, AAVSO HQ
A sequence of comparison stars has been created for HD 83742 / HD 302301 and may be accessed via the AAVSO Variable Star Plotter (Variable Star Plotter). Thanks go to Mike Poxon of the AAVSO Sequence Team for his very fast response! Mike said that he will be adding more R and I comps.
Good observing,
Elizabeth
People may have ready access to TESS light curves of HD 83742 / HD 302301, but in case not here is a VStar plot of raw SAP_FLUX from 12 Feb to 10 Mar 2023 and a zoomed-in view of an out-of-eclipse part of the light curve to show the delta Scuti pulsations. The pulsating star has a period of roughly 4 hours.
for what is worth, the EA variability is more likely to originate from the brighter HD 83742. I tried to determine the source using TESS data with 3 different methods. They all point to HD 83742 as the source.
The changes in eclipse timing does appear to be very large. If one plans observations using the ephemeris on VSX (period 9.1914 d), I wouldn’t be surprised if it’s off by hours.
For example, when I look at TESS data from sectors 62 - 64 ( 2023-02-12 to 2023-05-03 ), the period that’d best fit the first and the last eclipse is ~9.182 d. Even when I use the period, localized to the ~3 months observation, the eclipse timing is still visibly off, by as much as close to half an hour. (See this plot)
Hi.
Was able to get some images using the Las Cumbras telescopes in Chile. Data added so have a look at the light curve. Looks like the brighter HD 83742 is the eclipsing star.
