Optical Counterparts of ULXs and Their Host Environments in NGC 4490/4485

Avdan, Senay; Akyüz, A.; Винокуров, А.; Aksaker, Nazım; Avdan, Hasan; Fabrika, S.; Valeev, A. F.; Akkaya-Oralhan, Inci; Balman, Ş.

doi:10.3847/1538-4357/ab10d9

Cited by 18 publications

(8 citation statements)

References 61 publications

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“…Most of the weaker in the optical range ultraluminous X-ray sources (with M V > −5. m 5) are objects with relatively "cold" energy distributions corresponding to supergiants of classes A-G (Avdan et al, 2016(Avdan et al, , 2019, which may indicate the predominance of the contribution of donor stars over the contribution of hot winds of supercritical disks . The reason for small contribution of wind radiation may be lower accretion rates in these objects.…”

Section: Optical Counterpartsmentioning

confidence: 99%

Ultraluminous X-Ray Sources

et al. 2021

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Ultraluminous X-ray sources (ULXs) were identified as a separate class of objects in 2000 based on data from the Chandra X-Ray Observatory. These are unique objects: their X-ray luminosities exceed the Eddington limit for a typical stellar-mass black hole. For a long time, the nature of ULXs remained unclear. However, the gradual accumulation of data, new results of X-ray and optical spectroscopy, and the study of the structure and energy of nebulae surrounding ULXs led to the understanding that most of the ultraluminous X-ray sources must be supercritical accretion disks like SS 433. The discovery of neutron stars in a number of objects only increased the confidence of the scientific community in the conclusions obtained, since the presence of neutron stars in such systems clearly indicates a supercritical accretion regime. In this review, we systematize the main facts about the observational manifestations of ULXs and SS 433 in the X-ray and optical ranges and discuss their explanation from the point of view of the supercritical accretion theory.

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Section: Optical Counterpartsmentioning

confidence: 99%

Ultraluminous X-Ray Sources

et al. 2021

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“…The studies in the optical band showed that majority of the ULXs are found to be associated with star forming regions or star clusters (Patruno & Zampieri 2010;Grisé et al 2011;Poutanen et al 2013;Avdan et al 2016Avdan et al , 2019Egorov et al 2017;Urquhart et al 2018). These associations were supported by the counterparts of ULXs as early type OB stars due to their observed blue color (Liu et al 2004;Grisé et al 2005;Soria et al 2005;Roberts et al 2008;Poutanen et al 2013).…”

Section: Introductionmentioning

confidence: 93%

Optical Counterparts of ULXs in Two Dwarf Galaxies: NGC 4861 and NGC 4449

Ela,

Akyuz,

Aksaker

et al. 2021

Preprint

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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 a precise astrometry, we confirm that NGC 4861 X1 associated with an HII complex as reported by Thuan et al. ( 2014) and we conclude that NGC 4861 X2 resides in a young star group with 400±80 M . We also find that NGC 4449 X7 is associated with three optical candidates within an error radius of 0. 2 at the 90% confidence level. Absolute magnitudes (M 𝑣 ) of these candidates are determined as −5.0 and −4.1. The age and mass values for the three candidates by using stellar evolutionary tracks are estimated as 40-50 Myr and ∼8 M , respectively. The locations of optical candidates suggest possible association with a nearby group of stars. In addition, we analyzed the previously unused archival data of XMM-Newton, Chandra and Swift where the sources 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.

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“…Although there are hundreds of ULXs known, only about 20 have singled out optical counterparts (Tao et al 2011;Gladstone et al 2013;Avdan et al 2019). For many other ULXs, multiple undecidable optical counterparts have been detected (Soria et al 2005;Mucciarelli et al 2007;Avdan et al 2016bAvdan et al , 2019Aksaker et al 2019). Mostly, they have very faint optical candidates showing star-like spectral energy distributions (SEDs).…”

Section: Introductionmentioning

confidence: 99%

Identification of a New Ultraluminous X-ray Source in NGC 1316

Allak,

Akyuz,

Aksaker

et al. 2020

Preprint

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In this study, we report identification of a new ultraluminous X-ray source (ULX) which we named as X-7 in NGC 1316, with an unabsorbed luminosity of 2.10×10 39 erg s −1 using two recent Chandra archival observations. The X-7 was detected in the Chandra 2001 observation and it was included in the X-ray source list of the NGC 1316 as CXOUJ032240.8-371224 with luminosity of 5.7×10 38 erg s −1 implying a luminosity increase of a factor of ∼ 4. The best fit spectral model parameters indicate that X-7 has a relatively hot disk and hard spectra. The mass of compact object is obtained as ∼ 8 M which is in the range of a stellar-mass black hole. The X-7 shows a relatively long-term count rate variability while no short-term variability is observed. We also identified a unique optical candidate within 0. 22 error circle at 95% confidence level for X-7 using the archival HST/ACS and HST/WFC3 data. Absolute magnitude (M V ) of this candidate is -7.8 mag. Its spectral energy distribution is adequately fitted a blackbody model with a temperature of 3100 K indicating an M type supergiant, assuming the donor star dominates the optical emission. In addition, we identified a transient ULX candidate (XT-1) has a high luminosity of ∼ 10 39 erg s −1 located 6 away from X-7 with no visible counterpart(s).

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Optical Counterparts of ULXs and Their Host Environments in NGC 4490/4485

Cited by 18 publications

References 61 publications

Ultraluminous X-Ray Sources

Ultraluminous X-Ray Sources

Optical Counterparts of ULXs in Two Dwarf Galaxies: NGC 4861 and NGC 4449

Identification of a New Ultraluminous X-ray Source in NGC 1316

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