An artistic rending of the star Gaia17bpp being partly eclipsed by the dust cloud surrounding a smaller companion star. Credit: Anastasios Tzanidakis
By their own admission, Anastasios “Andy” Tzanidakis and James Davenport are interested in unusual stars. The University of Washington astronomers were browsing for “stars acting weirdly” when they were informed by the Gaia study about Gaia17bpp. The survey information revealed that this star had slowly increased in brightness over a 2-and-a-half-year span.
Tzanidakis just recently reported at the 241st meeting of the American Astronomical Society that follow-up analyses exposed that Gaia17bpp wasnt going through any modifications itself. Rather, it is likely a part of an unique double star and its evident brightening was the conclusion of a multi-year eclipse triggered by its unusual excellent partner.
” We believe that this star becomes part of a remarkably unusual kind of binary system, between a big, puffy older star– Gaia17bpp– and a little buddy star that is surrounded by an expansive disk of dirty product,” said Tzanidakis, a UW doctoral trainee in astronomy. “Based on our analysis, these 2 stars orbit each other over an exceptionally long duration of time– as much as 1,000 years. So, capturing this bright star being eclipsed by its dirty companion is an once-in-a-lifetime opportunity.”
By their own admission, Anastasios “Andy” Tzanidakis and James Davenport are interested in uncommon stars. The University of Washington astronomers were browsing for “stars acting strangely” when they were notified by the Gaia study about Gaia17bpp.” We believe that this star is part of an exceptionally rare type of binary system, between a large, puffy older star– Gaia17bpp– and a little companion star that is surrounded by an expansive disk of dusty material,” said Tzanidakis, a UW doctoral student in astronomy. A handful of other similar, “dirty” systems have actually been recognized over the years, most notably Epsilon Aurigae, a star in the constellation Auriga that is eclipsed for two out of every 27 years by a relatively big, dim companion. Some preliminary information show that Gaia17bpps buddy might be a little, huge white dwarf star.
Considering that the Gaia spacecrafts observations about the star only returned to 2014, Tzanidakis and Davenport, a UW research assistant professor of astronomy and associate director of the DiRAC Institute, had to do a little detective work to reach this conclusion. They sewed together Gaias observations of the star with observations by other objectives extending back to 2010– including Pan-STARRS1, WISE/NEOWISE, and the Zwicky Transient Facility.
The star Gaia17bpp, circled in red, as shown by the Pan-STARRS1 and DSS objectives. Credit: Anastasios Tzanidakis/Pan-STARRS 1/DSS.
Those observations, combined with the Gaia data, revealed that Gaia17bpp dimmed by about 4.5 magnitudes– or roughly 63 times. The star stayed dim over the course of nearly 7 years, from 2012 to 2019. The lightening up that the Gaia survey had revealed was completion of that seven-year dim.
No other stars near Gaia17bpp revealed comparable dimming behavior. Through the DASCH program, a digital catalog of more than a centurys worth of astro-photographic plates at Harvard, Tzanidakis and Davenport evaluated observations of the star extending back to the 1950s.
” Over 66 years of observational history, we discovered no other indications of significant dimming in this star,” said Tzanidakis.
The 2 think that Gaia17bpp belongs to an uncommon type of binary star system, with an outstanding buddy that is– rather simply– dusty.
” Based on the data currently available, this star appears to have a slow-moving buddy that is surrounded by a large disk of product,” said Tzanidakis. “If that product were in the solar system, it would extend from the sun to Earths orbit, or farther.”.
During its eclipse, the unseen companion was obstructing about 98% of Gaia17bpps light, according to Davenport.
A handful of other similar, “dirty” systems have actually been recognized over the years, most notably Epsilon Aurigae, a star in the constellation Auriga that is eclipsed for two out of every 27 years by a relatively large, dim buddy. The system that Tzanidakis and Davenport discovered is special amongst these few dusty binaries in the length of the eclipse– at almost 7 years, it is by far the longest. Unlike the Epsilon Aurigae binary, Gaia17bpp and its buddy are also so far apart that it would be centuries or more before an astute observer in the world witnesses another such eclipse.
For Epsilon Aurigae and comparable systems, the identity of the dusty buddy is a matter of argument. Some initial information indicate that Gaia17bpps buddy might be a little, enormous white dwarf star. The source of its debris disk is likewise a secret.
” This was a serendipitous discovery,” said Tzanidakis. “If we had been a few years off, we wouldve missed it.
Reference: “Discovery of the Deepest and Longest Known Blinking Giant Star Gaia17bpp” by A. Tzanidakis, J. R. A. Davenport, E. C. Bellm and D. Wang, 10 January 2023, 241st conference of the American Astronomical Society.
Additional group members on this research study are Eric Bellm, a UW research assistant professor of astronomy, and David Wang, a UW college student in astronomy.