(ORDO NEWS) — Using the XMM-Newton and NuSTAR satellites, astronomers conducted a comprehensive, long-term, multiwavelength survey of an active galaxy known as RXJ0134.2-4258.
The results of the observation campaign, published March 25 on the arXiv website, shed light on the nature of this source, revealing its special properties.
Active galactic nuclei (AGNs) are accreting supermassive black holes located at the centers of some galaxies that emit powerful, high-energy radiation as they absorb gas and dust. These cores can form jets that are generally cylindrical, conical or parabolic in shape, which are observed even at megaparsec scales.
Narrow-line Seyfert1 (NLS1) galaxies are a subclass of AGN characterized by a Balmer line width (Hβ) that is narrow compared to standard wide-line AGNs, but still wider than narrow lines.
They generally have smaller black hole masses and higher Eddington coefficients compared to the entire AGN population, however, some NLS1s can accrete with normal or low Eddington coefficients.
RXJ0134.2-4258 with a redshift of 0.237 is one such NLS1 galaxy. Discovered in 1999 by the ROSAT All-Sky Survey, the galaxy exhibits the typical optical spectrum of extreme NLS1, including narrow Balmer lines.
The mass of the black hole in this system is estimated at about 15 million solar masses, and its Eddington coefficient has been calculated to be relatively high at about 10.0.
Previous observations of RXJ0134.2-4258 have shown it to have some unusual properties compared to other typical NLSs.
For example, it shows a sharp X-ray variability reminiscent of the NLS1 X-ray complex, but the spectrum becomes harder-brighter, which is not usually observed in AGN with a high Eddington coefficient.
A team of astronomers led by Chichuan Jin at the University of the Chinese Academy of Sciences in Beijing, China, has examined this source in X-rays using XMM-Newton and NuSTAR, hoping to shed more light on this mysterious nature.
Two space telescopes observed RXJ0134.2-4258 in one of its lowest X-ray states. The time-averaged X-ray spectra of this source were found to show dramatic changes in both ﬂux and spectrum shape over the past 23 years. It was also added that no significant soft excess was found in any of these spectra.
The researchers emphasized that the time-averaged spectrum obtained from the XMM-Newton observations shows a steep rise above 4 keV, indicating the presence of a separate hard X-ray component.
They also performed a time delay analysis and found that this component lags soft X-rays by about 4,000 seconds in the low frequency range. No other delays below 4 keV were found.
In addition, the astronomers compared their results with previous studies of RXJ0134.2-4258. As a result, it was found that this NLS1 experienced very different X-ray spectral-temporal characteristics during the low and high flux X-ray states, which includes much weaker X-ray variability in the low flux state.
The authors of the paper concluded that the observed properties and X-ray variability of RXJ0134.2-4258 may indicate the presence of a bunch disk wind in this source. They added that such winds are expected in the highly over-Eddington NLS1.
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