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

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