Analysis of forbidden neon emission lines in HAeBe stars using Spitzer IRS spectra
subject: infrared: stars; protoplanetary discs; stars: variables: T Tauri, Herbig Ae/Be
description: We analysed high-resolution mid-infrared spectra of 78 well-known Herbig Ae/Be (HAeBe) stars using Spitzer InfraRed Spectrograph data, focusing on the detection of [Ne ii] and [Ne iii] emission lines as indicators of ionized outflows or disc winds. Emission from [Ne ii] at 12.81 m or [Ne iii] at 15.55 m was identified in 25 sources, constituting the largest sample of HAeBe stars with these detected lines. Our analysis revealed a higher detection frequency of [Ne ii] in sources with lower relative accretion luminosity (Lacc/L?< 0.1), suggesting a connection to the disc dispersal phase. We examined correlations between neon lines and various spectral features and investigated [Ne iii]-to-[Ne ii] line flux ratios to explore potential emission mechanisms. Neon emission is predominantly observed in Group I sources (75 per cent), where their flared disc geometry likely contributes to the observed emission, potentially originating from the irradiated disc atmosphere. Interestingly, we also find that Group II sources exhibit a higher median relative [Ne ii] line luminosity (L/L), suggesting enhanced photoevaporation rates possibly associated with their more settled disc structures. However, larger samples and higher-resolution spectra are required to confirm this trend definitively. The high detection rate of the [Fe ii] and [S iii] lines, commonly associated with EUV-dominated regions, alongside a [Ne iii]-to-[Ne ii] emission ratio greater than 0.1 in sources where both lines detected, suggests that EUV radiation is the primary driver of neon emission in our sample. 2025 The Author(s).
creator: Akhila, D.; Mathew, Blesson; Nidhi, S.; Shridharan, B.; Arun, R.; Anilkumar, Hema; Maheswar, G.; Kartha, Sreeja S.; Manoj, P.; Bhattacharyya, Suman
source: Monthly Notices of the Royal Astronomical Society;Volume;540;Issue;4;pp.3330-3349
publisher: Oxford University Press
date: 01-01-2025
rights: All Open Access; Gold Open Access
relation: ISSN: 358711; CODEN: MNRAA
format: online
language: English
type: Article
coverage: Akhila D., Department of Physics and Electronics, CHRIST (Deemed to Be University), Bangalore, 560029, India, Instituto de Astronom y Ciencias Planetarias, Universidad de Atacama, Copayapu 485, Copiap Chile; Mathew B., Department of Physics and Electronics, CHRIST (Deemed to Be University), Bangalore, 560029, India; Nidhi S., Department of Physics and Electronics, CHRIST (Deemed to Be University), Bangalore, 560029, India, The Oxford College of Science, 19th Main road, Sector 4, HSR Layout, Karnataka, Bengaluru, 560102, India; Shridharan B., Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai, 400005, India; Arun R., Indian Institute of Astrophysics, 2nd Block Koramangala, Bangalore, 560034, India; Anilkumar H., Department of Physics and Electronics, CHRIST (Deemed to Be University), Bangalore, 560029, India; Maheswar G., Indian Institute of Astrophysics, 2nd Block Koramangala, Bangalore, 560034, India; Kartha S.S., Department of Physics and Electronics, CHRIST (Deemed to Be University), Bangalore, 560029, India; Manoj P., Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai, 400005, India; Bhattacharyya S., Department of Physics and Electronics, CHRIST (Deemed to Be University), Bangalore, 560029, India