Monitoring and identification of the variable components of HD 83742 / HD 302301
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.
Requested Data Types:
Photometry
Targets
| Name | Magnitude | Variability Type | Photometry Notes | Spectroscopy Notes |
|---|---|---|---|---|
| HD 83742 | 7.17 | EA+DSCT |
Cadence: Custom Precision: 100 |
Not Requested |
| HD 302301 | 8.18 | None |
Cadence: Custom Precision: 100 |
Not Requested |
Spectroscopy Lines:
No spectroscopy lines provided
Photometry Filters:
V (Johnson), Other (Please Specify)
Comparison Stars:
Finder charts with comparison stars may be created using the AAVSO's Variable Star Plotter (VSP; https://apps.aavso.org/vsp/).
Co-Authorship
Observers are not eligible for co-authorship.
Additional Observer Input:
Additional input for observers: Please obtain hourly observations of both HD 83742 and HD 302301 around the time of predicted eclipses, until we determine the correct identifications. Once the identification is established we will update the strategy in the campaign page. V data are preferred but multicolor observations are welcomed. You can also submit unfiltered observations if you do not have standard filters, since the first goal of this campaign is identifying the object showing the eclipses. But do not submit them if you are not going to obtain time series or monitor the star in the long term, so your observations can be shifted to the standard V zero point. That is, a single unfiltered point is not useful. Ephemerides for primary and secondary eclipses for April – September 2025 are given in this file [https://www.aavso.org//sites/default/files/Otero-Ephemerides-HD83742-HD302301.pdf]. For those who want to calculate predicted eclipses themselves, please use the following: Best elements for Min I (based on TESS data 2019-2023): BJD 2459304.467 + 9.1914 x E. Min II elements: BJD 2460016.587 + 9.1842 x E. The primary eclipse lasts 10 hours; it starts 5 hours before the published mid-eclipse time and ends 5 hours later. The secondary eclipse lasts 12 hours and 20 minutes, it starts 6 hours and 10 minutes before the published mid-eclipse time and ends 6 hours and 10 minutes later.
Additional Submission Location:
Not provided
Forum URL
N/A
Notes:
Public notes: Cadence will vary depending on the stage of the project. Hourly observations around the eclipse times will be enough to identify the correct variable. When the identification is established and the long-term monitoring campaign starts, continuous observations around the time of the eclipse (keep in mind that the ephemeris will have an increasing error with time due to the star behaviour) are encouraged. Dense time series with the aim of obtaining a precision close to 0.001 mag. are needed to detect the DSCT variations (P= 0.14 d.). Combined range recorded by surveys is V = 7.17 - 7.27. If the eclipsing binary is HD 83742 (09 38 26.33 -57 31 50.8, J2000.0), the corrected range will be V = 7.72 - 7.89 (Min II = 7.87). If the eclipsing binary is HD 302301 (09 38 25.20 -57 31 45.0, J2000.0), the corrected range will be V = 8.17 - 8.44 (Min II = 8.41).