We report the binary fraction of Wolf–Rayet (W-R) stars within 0.5 pc of the Galactic center obtained through the longest time-baseline (1994–2024) kinematic study of this population of stars. The new radial velocity ( v z ) data we present are primarily from the W. M. Keck Observatory, with additional v z measurements from Gemini North Observatory. When combining our new v z measurements with literature measurements, we find v z variations that suggest the presence of a companion for five out of 27 W-R stars, of which two are newly identified here (IRS 13E4, S8-181), along with three previously detected binaries (IRS 16SW, IRS 16NE, S4-258). Based on our experimental sensitivity and expected properties of the underlying population, we infer the binary fraction of the W-R stars in the Galactic center to be 0.56 ± 0.18. This is consistent with previous photometric studies of the young stars in the Galactic center and with the binary fraction of field W-R stars. When our results are combined with the results of previous photometric work, we find a binary fraction of 0.69 ± 0.17 for the W-R stars.
", "doi": "10.3847/1538-4357/ae82d6", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2026-07-20", "series_number": "1", "volume": "1006", "issue": "1", "pages": "71" }, { "id": "authors:6sbd5-6x957", "collection": "authors", "collection_id": "6sbd5-6x957", "cite_using_url": "https://authors.library.caltech.edu/records/6sbd5-6x957", "type": "article", "title": "Near-infrared Flux Distribution of Sgr A* from 2005\u20132022: Evidence for an Enhanced Accretion Episode in 2019", "author": [ { "family_name": "Weldon", "given_name": "Grant C.", "orcid": "0000-0003-4081-1839" }, { "family_name": "Do", "given_name": "Tuan", "orcid": "0000-0001-9554-6062" }, { "family_name": "Witzel", "given_name": "Gunther", "orcid": "0000-0003-2618-797X" }, { "family_name": "Ghez", "given_name": "Andrea M.", "orcid": "0000-0003-3230-5055", "clpid": "Ghez-A-M" }, { "family_name": "Gautam", "given_name": "Abhimat K.", "orcid": "0000-0002-2836-117X" }, { "family_name": "Becklin", "given_name": "Eric E." }, { "family_name": "Morris", "given_name": "Mark R.", "orcid": "0000-0002-6753-2066" }, { "family_name": "Martinez", "given_name": "Gregory D.", "orcid": "0000-0002-7476-2521" }, { "family_name": "Sakai", "given_name": "Shoko", "orcid": "0000-0001-5972-663X" }, { "family_name": "Lu", "given_name": "Jessica R.", "orcid": "0000-0001-9611-0009" }, { "family_name": "Matthews", "given_name": "Keith", "clpid": "Matthews-Keith" }, { "family_name": "Hosek", "given_name": "Matthew W.", "orcid": "0000-0003-2874-1196" }, { "family_name": "Haggard", "given_name": "Zo\u00eb" } ], "abstract": "Sgr A* is the variable electromagnetic source associated with accretion onto the Galactic center supermassive black hole. While the near-infrared (NIR) variability of Sgr A* was shown to be consistent over two decades, unprecedented activity in 2019 challenges existing statistical models. We investigate the origin of this activity by recalibrating and reanalyzing all of our Keck Observatory Sgr A* imaging observations from 2005–2022. We present light curves from 69 observation epochs using the NIRC2 imager at 2.12 μm with laser-guide star adaptive optics. These observations reveal that the mean luminosity of Sgr A* increased by a factor of ∼3 in 2019, and the 2019 light curves had higher variance than in all time periods we examined. We find that the 2020–2022 flux distribution is statistically consistent with the historical sample and model predictions, but with fewer bright measurements above 0.6 mJy at the ∼2σ level. Since 2019, we have observed a maximum K_s (2.2 μm) flux of 0.9 mJy, compared to the highest pre-2019 flux of 2.0 mJy and highest 2019 flux of 5.6 mJy. Our results suggest that the 2019 activity was caused by a temporary accretion increase onto Sgr A*, possibly due to delayed accretion of tidally stripped gas from the gaseous object G2 in 2014. We also examine faint Sgr A* fluxes over a long time baseline to search for a quasi-steady quiescent state. We find that Sgr A* displays flux variations over a factor of ∼500, with no evidence for a quiescent state in the NIR.
", "doi": "10.3847/2041-8213/acf2f2", "issn": "2041-8205", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal Letters", "publication_date": "2023-09-01", "series_number": "1", "volume": "954", "issue": "1", "pages": "L33" } ]