TYC 5134-1820-1: A New Double Star Discovery

Shadow path of TYC 5134-01820-1 occulted by asteroid 1330 Spiridonia – June 26, 2023 UT

On 26 June 2023 UT, Vince Sempronio near Benson, Arizona and David Oesper near Tucson, Arizona observed an occultation of the 12.2-magnitude* star Tycho 5134-1820-1 in the constellation Aquila by the 15.1-magnitude asteroid 1330 Spiridonia. The predicted magnitude drop should have been around 2.9 magnitudes (15.1m-12.2m) by both observers, but I observed only about a 0.2-magnitude drop, and Vince a 1.5 magnitude-drop. After expert analysis by David Gault and David Herald in Australia, it was determined that we had discovered a new double star!

Observer locations for the June 26, 2023 occultation event

Fortuitously, Vince had observed 1330 Spiridonia covering up only the primary (brightest) component, and I had observed 1330 Spiridonia covering up only the secondary component. Both of us made our observations with 8-inch telescopes.

Vince Sempronio’s light curve (11.2 seconds, 70 data points)
David Oesper’s light curve (60.7 seconds, 455 data points)

The double star solution from our observations gives the following:

G magnitude of the primary component: 12.4

G magnitude of the secondary component: 13.9

Separation: 59.7 milliarcseconds (0.0597 arcseconds)

Position Angle: 141.8° (eastward from north)

The double star solution

Follow up observations over time will be needed to determine whether this is an optical double (chance alignment) or a true binary system. The distance to TYC 5134-1820-1 is currently estimated to be between 2,689 and 2,883 light years (SIMBAD). Definitely not in the neighborhood.

Even though double stars are common in our galaxy (and everywhere else in the universe), and understanding that our observations represent only the tiniest contribution to scientific knowledge, there is satisfaction in knowing that we discovered something not known by anyone else before. Besides, you never know when a discovery such as this will draw attention to an unusual and astrophysically-interesting system.

In conclusion, here is but one example showing that observations of stellar occultations by the minor planets of our solar system presents an exquisite method of discovering very close double (and possibly binary) stars, not assayable by any other technique.

*Gaia G magnitude

4 thoughts on “TYC 5134-1820-1: A New Double Star Discovery”

  1. What you and Vince discovered is a possible double star. Claiming that it is a double star is premature. What is needed is spectrographic follow-up to confirm the two-star hypothesis, since neither of you saw two events.

    In retrospect, it would have been better to not have published this claim at all until confirming spectroscopy was in hand and supported your case.

    Mark Trueblood, Director
    Winer Observatory

    1. Thank you for your comment, Mark. After the IOTA review team gave us the go ahead to write up a report for the Journal of Double Star Observations (JDSO), Vince called me and told me to hold off writing the first draft of the paper until he had had a chance to get some spectroscopy of this system done. I don’t know who he had enlisted to do this work (perhaps it was you?) or when it will be done, but I published this on my personal blog site to document the occultation results for this event and to illustrate how stellar occultations by minor planets can be an important tool in the astronomer’s toolbox for discovering double stars. I agree that spectroscopy would be quite useful in best characterizing the system, but is it essential to announcing a discovery? I honestly can’t imagine any other explanation for what we observed, especially given the detailed analysis by Dave Gault and Dave Herald that was performed. If, in fact, spectroscopy is essential, then follow-up spectroscopic examination needs to be added to the IOTA pipeline, as a number of these potential double star discoveries are made each year by occultation observers all over the world. We must keep in mind that most occultation observers have no access to spectroscopic equipment (myself included). This might be a good topic to take up with Dave Herald in Australia who is the leading expert on occultation science.

      1. David,

        Thanks for your thoughtful reply. Announcing the results of the occultation observations is one thing, but claiming that the data support only the conclusion of duplicity is something else. I suggest that you hold off on any further publications for the moment. We all want our discoveries published quickly, but sometimes doing good science requires a bit of patience.

        In my little backyard project near Sonoita, AZ, a group of mid-western colleges called the MACRO consortium uses a PlaneWave 20-inch scope with grisms in the filter wheel, one with R~600. Data were taken in May and analyzed by a student. The result was inconclusive, since the data were at the edge of detectability with a 20-inch scope.

        I have been using the Vatican Advanced Technology Telescope (VATT) on Mt. Graham for several years ago. I was up there June 14-17 and discussed using the VATTspec spectrograph to determine the duplicity of the star with the VATT director. He suggested that I contact the main user of that instrument. I have absolutely no knowledge of how to use a spectrograph for this purpose, so I need to contact a routine user and determine how to proceed. If this falls through, there is another option with a lower probability of success (but non-zero at this point).

        What I envision is a paper in the Astronomical Journal, a leading well-respected refereed journal. This paper would include as co-authors the spectroscopy expert, you and Vince, and the occultation referees in Australia. That is, everyone involved with this star’s being double.

        Again, this will take some time to arrange, and we are subject to the object’s visibility in the sky. I’ll keep you up to date on the spectrograph front.

        BTW, my email is winer.obs@gmail.com if you want to continue this discussion off-line.

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