English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We report the identification of the possible optical counterparts of five outof seven Ultraluminous X-ray Sources (ULXs) in NGC 4490/4485 galaxy pair. Usingarchival Hubble Space Telescope ({\it HST}) imaging data, we identified asingle optical candidate for two ULXs (X-4 and X-7) and multiple opticalcandidates for the other three ULXs (X-2, X-3 and X-6) within $\sim$ $0\farcs2$error radius at the 90\% confidence level. Of the two remaining ULXs, X-1 hasno {\it HST} imaging data and photometry could not be performed due to theposition of X-5 in NGC4490. Absolute magnitudes ($M_{V}$) of the opticalcandidates lie between $-5.7$ and $-3.8$. Color-Magnitude Diagrams (CMDs) havebeen used to investigate the properties of counterparts and their environments.The locations of the counterparts of X-2, X-4, and X-6 suggest possibleassociation with nearby group of stars while others have no association with astar cluster or group of stars. For comparison purposes, we analyzed previouslyunused three archival XMM-Newton observations. The long-term X-ray light curvesof the sources (except transient X-7) show variability by a factor of three ina time scale more than a decade. The use of disk blackbody model for the massof the compact objects indicates that these objects might have masses mostlikely in the range 10$-$15 $M_{\sun}$.

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