Research Setup
Adapted from Kalée Tock and Ryan Caputo
Once you've selected potential double star targets, you need to verify them with more precise data, gather historical information, and set up your observations. This page guides you through these essential steps.
Finding Your Target in Gaia Data Release 3 (DR3)
First, go to this Collaboratory and use File → Make a Copy to make a copy of it.
Run the first cell. Then copy the coordinates from the WDS Coord arcsec 2000 into the "coordinates" field of the second cell and adjust the format to include the hms,dms notation for "hours minutes seconds" of RA and "degrees minutes seconds" of Dec and run that. The output will look like what is shown in Figure 5:
[FIGURE 5: Output from the Gaia_TESS_NEA_WDS.ipynb Colab.]
The first star in the list is probably your primary star, because the stars are listed in order of proximity to the search coordinates. Make sure that its Gmag (Gaia G filter magnitude) is close to the magnitude that you expect from the WDS. It will not be exactly the same, because the Gaia G filter lets through slightly different wavelengths of light than the visual or clear filters that are used by other double star astronomers, but it should at least be within 1 magnitude. If not, scan down the list until you find it. It will not be more than a few (maximum of 5) arcseconds away from the search coordinates. In other words, "Sep" should be less than 5.
Then find the secondary star. The secondary will be a little farther down, should have a Gmag approximately within one magnitude of the Stelledoppie-listed magnitude of your secondary star, and the PA and Sep of the secondary should be approximately equal to the most recently listed PA and Sep in Stelledoppie.
If you cannot unambiguously identify your primary and secondary star in Gaia DR3, pick a different target until you can.
Once you have your primary and secondary stars, copy their Gaia data into the pink, yellow, and green columns of the spreadsheet linked above. Make sure that both the primary and secondary star of your pair have similar parallaxes (Plx's) and proper motions (PM's). Again, they do not have to be exactly the same, but they should be reasonably similar. You should also check the system's radial velocity (RV) but radial velocity data are often missing in Gaia DR3. If your system's RV data are missing, enter "N/A" into the corresponding cell.
If your stars' Gaia DR3 parallaxes and proper motions are not similar, pick a different target.
Requesting Historical Data of Your Target
Now that you have a few promising targets, you will want to see measurements that have been made on the target by other astronomers. Stelledoppie lists the first measurement, made by the discoverer of the system, and the most recent measurement listed in the Washington Double Star Catalog. However, in most cases, there have been previous measurements of the system. Sometimes there are lots of previous measurements. Possibly there is even a solved orbit for the system, or a "linear solution" that would indicate the stars are not thought to be orbiting.
To obtain these historical data, you would need to send an email to the US Naval Observatory (USNO). However, this year I will be doing that for you so as to avoid overwhelming the USNO staff. (My understanding is that there are plans to get the individual historical data points into a database soon, but it does not seem to be ready yet.)
What you can do, however, is look up whether your system has a solved orbit or a linear solution. To find a previously-solved orbit, go to the Sixth Orbit Catalog and do a find-in-page for your system's WDS code (five digits for RA, a plus or minus, and then four digits for Dec, in this format: 00114+5850). If your system does not appear on that page, that means that it does not have a solved orbit. If it does appear on that page, scroll all the way to the right and click on the blue "P" to see the orbit. To find a previously-proposed linear solution, go to the Rectilinear Elements Catalog and follow the same process.
Even if you do not find your particular system, it is a good idea to check out some of the blue "P" links on both pages linked above to get a feel for what orbital and linear solutions look like. In particular, note the scale of the plot axes.
Imaging Your Target Using Las Cumbres Observatory Robotic Telescopes
While you are waiting for the historical data about your system to be returned, you should get observations of your systems underway. First, log into the Las Cumbres Observatory Global Telescope network website at https://observe.lco.global/. Click on "Submit Observation", enter a title for your observation and enter "Stanford Online High School' as the proposal. For "Instrument", select 0m4 SCICAM QHY60. For Filter, select Bessel-V. If you do not see a choice for "Bessel-V" filter, then go to your Profile at the top right of the LCO Observation portal and un-check the "Simple Interface" checkbox. (The "Simple Interface" assumes that you would only ever want red, green, and blue filters for astrophotography.) The configuration sections should look like Figure 7 below. Note that "Exposure Count" is 10 to request 10 images. Leave other fields set to their default values.
[FIGURE 7: Instrument configuration on the Las Cumbres Observatory portal.]
Choosing the appropriate exposure time can be tricky. LCO has an exposure time calculator here, and we have the formula we used in OASTR1 shown below. This formula is specific to the V filter. If your V filter exposure time is longer than about 30 seconds, please save telescope time by cutting the exposure time in half and using the PanSTARRS-w filter, which has a wider bandpass (meaning that it lets through more wavelengths of light).
[FORMULA: Exposure time calculation]
As a sanity check, anything brighter than 8th magnitude is bright and will need short exposure times (about 2 seconds or less). Anything over 13th magnitude is faint and will require longer exposures (60 seconds or more). Make a guess at the right exposure time, and plan to re-request any images that are compromised. Unlike exoplanet transits, we do not care when exactly the images get taken, so just leave the "Window" at its default setting of 24 hours. Note that the green "copy" button will allow you to make additional requests of the same target without filling out the form twice, as shown in Figure 7.
Publication and Sharing Results
Once your LCO images are returned and you measure them, you need to share your measurements with other astronomers. However, your double star measurements will only be added to the Washington Double Star Catalog if they are part of published papers. This is because the US Naval Observatory, keeper of the Washington Double Star Catalog, uses the scientific journal review process to ensure that measurements have been vetted before adding them. The Journal of Double Star Observations is generally friendly to student authors, so that is a good choice of journal.
Here are some examples of JDSO papers that were written by students. As you can see, each double star system is unique! Each double star pair has some mystery about it, and the study often ends up going in unexpected directions.
Next Steps
Once you've completed your research setup, you'll be ready to begin the data analysis phase of your project.