tokens: fractional rms variability spectrum and the best-fit model in Figure 12 (right). The fractional variations in the normalization of the illuminating continuum and reflected emission are and , respectively. 7. Summary and Discussion We present the first results from our XMM-Newton observation of the NLS1 galaxy PG 1404+226. Here, we investigated the large-amplitude X-ray variability, the origin of the soft X-ray excess emission, and its connection with the intrinsic power-law emission through a detailed analysis of the time-averaged as well as time-resolved X-ray spectra, and frequency-averaged ( ν ∼ [1.4–100] × 10 −5 Hz) X-ray fractional rms spectrum. Below we summarize our results. 1. PG 1404+226 showed a short-term, large-amplitude variability event in which the X-ray (0.3–8 keV) count rate increased exponentially by a factor of ∼7 in about 10 ks and dropped sharply during the 2016 XMM-Newton observation. The hard X-ray (1–8 keV) Chandra /ACIS light curve also showed a rapid variability (a factor of ∼2 in about 5 ks) with an exponential rise and a sharp fall in 2000 (Dasgupta et al. 2005 ). The rapid X-ray variability had been observed in a few NLS1 galaxies (e.g., NGC 4051: Gierliński Done 2006 ; 1H 0707–495: Fabian et al. 2012 ; Mrk 335: Wilkins et al. 2015 ). However, the UV ( λ eff = 2910 Å) emission from PG 1404+226 is much less variable () than the X-ray (0.3–8 keV) variability (). 2. The source exhibited strong soft X-ray excess emission below ∼1 keV, which was fitted by both the intrinsic disk Comptonization and relativistic reflection models. The EPIC-PN spectral data revealed the presence of a highly ionized ( ξ ∼ 600 erg cm s −1 ) Ne x Ly α absorbing cloud along the line of sight with a column density of N H ∼ 5 × 10 22 cm −2 and a possible O viii Ly α emission line. However, we did not detect the presence of any outflow as found by Dasgupta et al. ( 2005 ). 3. The modeling of the RGS spectrum not only confirms the presence of the Ne x Ly α absorbing cloud and O viii Ly α emission line but also reveals an O viii Ly β emission line. 4. The time-resolved spectroscopy showed a significant variability in both the soft X-ray excess and primary power-law flux, although there were no noticeable variations in the soft X-ray excess temperature ( eV) and photon index of the primary power-law continuum. 5. In the disk Comptonization scenario, the rapid X-ray variability can be attributed to a variation in the source luminosity as indicated by the time-resolved spectroscopy. However, the modeling of the X-ray fractional rms spectrum using the “one-component disk Comptonization” model cannot reproduce the observed hard X-ray variability pattern and indicates a reflection origin for the soft X-ray excess emission (see Figure 12 , left). 6. In the relativistic reflection scenario, the observed large-amplitude X-ray variability was predominantly due to two components: an illuminating continuum and smeared reflected emission; both of them are
ner_tags: O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Telescope O O O B-Survey O B-CelestialObject I-CelestialObject O O O O O B-Wavelength O O O O O B-Wavelength I-Wavelength O O O O O O O O O O O O O O O O O O O O O B-Wavelength O O O O B-Formula I-Formula I-Formula I-Formula I-Formula I-Formula I-Formula B-Wavelength O O O O O O O O O B-CelestialObject I-CelestialObject O O O O O O O O O B-Wavelength B-Wavelength I-Wavelength O O O O O O O O O O O O O O O O O O O B-Telescope O O B-Wavelength I-Wavelength B-Wavelength I-Wavelength B-Telescope B-Instrument O O O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation O O O B-Wavelength O O O O O O O B-Survey O O B-CelestialObject I-CelestialObject B-CelestialObject I-CelestialObject I-CelestialObject O B-CelestialObject I-CelestialObject B-CelestialObject I-CelestialObject I-CelestialObject I-CelestialObject O B-CelestialObject I-CelestialObject B-CelestialObject I-CelestialObject I-CelestialObject I-CelestialObject O O O B-Wavelength O O O O B-Wavelength I-Wavelength O O B-CelestialObjectRegion I-CelestialObjectRegion O O O O B-TextGarbage O O B-Wavelength B-Wavelength I-Wavelength O O O O O O O B-Wavelength I-Wavelength O O O B-Wavelength I-Wavelength O O O O O O O O O O O O O O B-Instrument O O O O O O O O O O B-Formula I-Formula I-Formula I-Formula I-Formula I-Formula I-Formula O O O B-Wavelength I-Wavelength O O O O O O O O O O O O B-Formula I-Formula I-Formula I-Formula I-Formula I-Formula I-Formula I-Formula I-Formula O O O O O B-Wavelength I-Wavelength O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation I-Citation I-Citation O O O O O B-Instrument O O O O O O O O O O B-Wavelength I-Wavelength O O O O O B-Wavelength I-Wavelength O O O O O O O O B-Wavelength I-Wavelength O O O O O O O O O O O O O B-Wavelength I-Wavelength O O O O O O O O O O O O O B-Wavelength I-Wavelength O O O O O O O O O O O O O O O O O O O O B-Wavelength O O O O O O O O O O O O O O O O O O O O O O B-Wavelength O O O O O O O O O O O O O B-Wavelength I-Wavelength O O O O O O O O O B-Wavelength I-Wavelength O O O O O O O O O O O O O O O O B-Wavelength O O O O O O O O O O O O O O O O O O