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Gaia17bpp is a rare M-type
Gaia17bpp was initially discovered through the ESA's 
red giant
A red giant is a luminous giant star of low or intermediate mass (roughly 0.3–8 solar masses ()) in a late phase of stellar evolution. The stellar atmosphere, outer atmosphere is inflated and tenuous, making the radius large and the surface t ...
star that exhibited a single large dimming event (G-16-20.5 mag) over 6.5 years. It is located in the Sagitta
Sagitta is a dim but distinctive constellation in the northern sky. Its name is Latin for 'arrow', not to be confused with the significantly larger constellation Sagittarius 'the archer'. It was included among the 48 constellations listed by t ...
constellation and is about 27,600 light years away from Earth.
Astronomical characteristics
The variable star is located in the constellation ofSagitta
Sagitta is a dim but distinctive constellation in the northern sky. Its name is Latin for 'arrow', not to be confused with the significantly larger constellation Sagittarius 'the archer'. It was included among the 48 constellations listed by t ...
roughly 27,600 ly (8.5 kpc). Current hypothesis and archival data suggest that Gaia17bpp belongs to a rare family of ultra-long period binary stars where the companion is enshrouded in large optically thick disks reminiscent of Epsilon Aurigae
Epsilon Aurigae is a multiple star system in the northern constellation of Auriga, the charioteer. Its name is a Bayer designation that is Latinized from ε Aurigae, and abbreviated Epsilon Aur or ε Aur. It is an unusual eclipsing b ...
, VVV-WIT-07, and AS Leonis Minoris. The proposed secondary star and disk remain unconfirmed due to the copious amount of intervening interstellar dust, and likely due to the remarkable long timescale period of the system.
Discovery and dimming event
Gaia17bpp was initially discovered through the ESA's Gaia
In Greek mythology, Gaia (; , a poetic form of ('), meaning 'land' or 'earth'),, , . also spelled Gaea (), is the personification of Earth. Gaia is the ancestral mother—sometimes parthenogenic—of all life. She is the mother of Uranus (S ...
Photometric Science Alerts (GPSA) in 2022 by astronomers at the University of Washington. The remarkable Gaia17bpp dimming event occurred in mid 2012, however the GPSA issued an alert back in 2017 when the star began re-brightening. Due to the large duration of the dimming event, the entirety of the Gaia17bpp dimming event was recovered from several public data archives such as Pan-STARRS
The Panoramic Survey Telescope and Rapid Response System (Pan-STARRS1; List of observatory codes, obs. code: IAU code#F51, F51 and Pan-STARRS2 obs. code: IAU code#F52, F52) located at Haleakala Observatory, Hawaii, US, consists of astronomical ...
, and NASA's Wide-field Infrared Survey Explorer
Wide-field Infrared Survey Explorer (WISE, List of observatory codes, observatory code C51, Explorer 92 and MIDEX-6) was a NASA infrared astronomy Space observatory, space telescope in the Explorers Program launched in December 2009.. . WISE L ...
(WISE) where the dimming event was also observed in the near-infrared.
Researchers employed archival image searching and conducted spectroscopic follow-up observations on Gaia17bpp using the Apache Point Observatory 3.5m ARC Telescope. Throughout their analysis, they successfully ruled out several suspected variable star classes with similar dimming event such as R Coronae Borealis, Cataclysmic variable star
In astronomy, cataclysmic variable stars (CVs) are stars which irregularly increase in brightness by a large factor, then drop back down to a quiescent state. They were initially called novae (), since those with an outburst brightness visible t ...
, or Young stellar object
Young stellar object (YSO) denotes a star in its early stage of evolution. This class consists of two groups of objects: protostars and pre-main-sequence stars.
Classification by spectral energy distribution
A star forms by accumulation of mate ...
.
Modeling of the dimming event suggest that a possible scenario includes the occultation of an extended oblate optically thick disk with 1.4 AU radius, moving with a transverse velocity of approximately 0.005 km/s. It is unclear how such large optically thick disks can form such in the case of Gaia17bpp and other analog systems. One study suggests that previous mass-transfer interaction between a close binary can produce large disks and lose angular momentum to produce the observed long period binary system.
See also
*Epsilon Aurigae
Epsilon Aurigae is a multiple star system in the northern constellation of Auriga, the charioteer. Its name is a Bayer designation that is Latinized from ε Aurigae, and abbreviated Epsilon Aur or ε Aur. It is an unusual eclipsing b ...
* List of stars that have unusual dimming periods
A list is a set of discrete items of information collected and set forth in some format for utility, entertainment, or other purposes. A list may be memorialized in any number of ways, including existing only in the mind of the list-maker, but ...
* Tabby's Star
Notes
References
{{Sagitta Sagitta M-type giants J19372316+1759029