Circumstellar shells around AGB stars

• Grant number: 23/05298-0
• Support Opportunities: Regular Research Grants
• Start date: September 01, 2023
• End date: February 28, 2026
• Field of knowledge: Physical Sciences and Mathematics - Astronomy - Stellar Astrophysics
• Principal Investigator: Roberto Pereira Ortiz
• Grantee: Roberto Pereira Ortiz
• Host Institution: Escola de Artes, Ciências e Humanidades (EACH). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• City of the host institution: São Paulo

Abstract

AGB (asymptotic giant branch) stars constitute the latest evolutionary statusbefore a intermediate-mass star becomes a planetary nebula. During this phase,the star undergoes a huge increase in radius and luminosity, favouring mass loss.Because of their characteristics (low temperature, large luminosity, the presenceof circumstellar matter), these stars are generally observed in the spectral rangewhere they are more luminous, i.e. the infrared. However, AGB stars also exhibitinteresting features in the ultraviolet and X-ray parts of the spectrum that havebeen largely overlooked in the literature. This work is intended to study the UVand X-ray parts of the spectrum of AGB stars. Their chromospheres are generallyvery thick in extension because of the low gravity, and exhibit a rich variety ofemission lines. In spite of the small number of reported cases, circumstellar shellscan also be detected in the UV. X-ray emission has also been reported in some AGBstars, even though it is believed to be originated either in a accretion disc arounda secondary component or in the chromosphere itself. I intend to take advantageof various public databases to collect X-ray and UV spectra and images. Findingnew X-ray and UV counterparts will be based on the public images, whereas theirphysical properties will be obtained from spectra. These methods have been used bythe author in previous studies. The materials requested in this proposal are mostlyintended to pay scientific visits and conference charges, transport, page charges, andpurchasing a new laptop. (AU)

Scientific publications

(4)

(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)

GUERRERO, M. A.; ORTIZ, R.. Three new identifications of extended UV emission around AGB stars. Monthly Notices of the Royal Astronomical Society, v. 527, n. 3, p. 9-pg., 2023-11-28. (23/05298-0)

MERC, JAROSLAV; GUERRERO, MARTIN A.; TOALA, JESUS A.; ORTIZ, ROBERTO. CGCS 6306, another X-ray-emitting asymptotic giant branch star confirmed to be a symbiotic binary. Astronomy & Astrophysics, v. 699, p. 8-pg., 2025-07-02. (23/05298-0)

GUERRERO, M. A.; MONTEZ JR, R.; ORTIZ, R.; TOALA, J. A.; KASTNER, J. H.. Asymptotic giant branch stars in the eROSITA-DE eRASS1 catalog. Astronomy & Astrophysics, v. 689, p. 14-pg., 2024-09-04. (23/05298-0)

GUERRERO, M. A.; VASQUEZ-TORRES, D. A.; RODRIGUEZ-GONZALEZ, J. B.; TOALA, J. A.; ORTIZ, R.. Y Gem, a symbiotic star outshone by its asymptotic giant branch primary component. Astronomy & Astrophysics, v. 693, p. 13-pg., 2025-01-17. (23/05298-0)