Optical counterparts of ULXs in two dwarf galaxies: NGC 4861 and NGC 4449
Yükleniyor...
Dosyalar
Tarih
2021
Dergi Başlığı
Dergi ISSN
Cilt Başlığı
Yayıncı
Oxford University Press
Erişim Hakkı
info:eu-repo/semantics/closedAccess
Özet
We present the results of a search for optical candidates of ultraluminous X-ray sources (ULXs) in two dwarf galaxies, NGC 4861 and NGC 4449, using Hubble Space Telescope (HST) archival data. With precise astrometry, we confirm that NGC 4861 X1 is associated with an H II complex and we conclude that NGC 4861 X2 resides in a young star group of mass 400 ± 80 M☉. We also find that NGC 4449 X7 is associated with three optical candidates within an error radius of 0.2 arcsec at the 90 per cent confidence level. Absolute magnitudes (Mv) of these candidates are determined as −5.0 and −4.1. The age and mass values for the three candidates are estimated as 40–50 Myr and ∼8 M☉, respectively, using stellar evolutionary tracks. The locations of optical candidates suggest a possible association with a nearby group of stars. In addition, we analysed previously unused archival data of XMM–Newton, Chandra, and Swift where the sources were detected. Although the X-ray spectral data do not allow us to discriminate between physical models, long-term data at hand are consistent with the sources being in luminous hard states.
Açıklama
Anahtar Kelimeler
Galaxies, Individual, NGC4861–galaxies, NGC4449–X-rays, Binaries
Kaynak
Monthly Notices of the Royal Astronomical Society
WoS Q Değeri
Q1
Scopus Q Değeri
Cilt
505
Sayı
1
Künye
Özdogan Ela, M., Akyüz, A., Aksaker, N., Avdan, S., Akkaya Oralhan, I., Vinokurov, A., . . . Bizyaev, D. (2021). Optical counterparts of ULXs in two dwarf galaxies: NGC 4861 and NGC 4449. Monthly Notices of the Royal Astronomical Society, 505(1), 771-782. doi:10.1093/mnras/stab1321
