Related papers: PHL 1092 as a transient extreme X-ray weak quasar

We present two new XMM-Newton observations of an unprecedented low flux state in the Seyfert 1 Mrk 1048 (NGC 985), taken in 2013. The X-ray flux below 1 keV drops by a factor of 4-5, whereas the spectrum above 5 keV is essentially…

We report on a new XMM-Newton observation of NGC 247 from December 2009. The galaxy contains a supersoft, ultraluminous X-ray source (ULX) whose spectrum consists of a thermal component with a temperature about 0.1 keV and a power-law tail…

RZ2109 is the first of several extragalactic globular clusters shown to host an ultraluminous X-ray source. RZ2109 is particularly notable because optical spectroscopy shows it has broad, luminous [OIII] 4959,5007 emission, while also…

We analyze the 2.5--10 keV X-ray spectra of the luminous quasar 3C 273 and simultaneous observations in UV wavelengths from XMM--Newton between 2000 and 2015. The lowest flux level ever was observed in 2015. The continuum emission from 3C…

We present results from the spectral analysis of a long XMM-Newton observation of the radio-loud NLS1 galaxy PKS0558-504. The source is highly variable, on all sampled time scales. We did not observe any absorption features in either the…

We present the results of a 17 ks Chandra ACIS-S observation of the nearby dwarf spiral galaxy NGC 4395. Chandra affords the first high-quality, broadband X-ray detection of the active nucleus of this object that is uncontaminated by nearby…

We report results from the spectral analysis of pointed ROSAT PSPC observations of six PG quasars and the weak-bump quasar PHL 1657. Disregarding other frequency bands, the PSPC data are represented best by simple power-law source spectra…

We report the results of a 2019-2021 monitoring campaign with Swift and associated target-of-opportunity observations with XMM-Newton and NuSTAR, examining the spectral and timing behavior of the highly variable ultraluminous X-ray source…

We report on results from a one-year soft X-ray observing campaign of the ultraluminous X-ray pulsar NGC 300 ULX-1 by the Neutron star Interior Composition Explorer (NICER) during 2018--2019. Our analysis also made use of data from…

Optical and X-ray observations of the quadruply imaged quasar 1RXS J1131-1231 show flux ratio anomalies among the images factors of ~2 in the optical and \~3-9 in X-rays. Temporal variability of the quasar seems an unlikely explanation for…

By studying the variability of blazars across the electromagnetic spectrum, it is possible to resolve the underlying processes responsible for rapid flux increases, so-called flares. We report on an extremely bright X-ray flare in the…

We report on the results of the spectral and timing analysis of a BeppoSAX observation of the microquasar system LS 5039/RX J1826.2-1450. The source was found in a low-flux state with Fx(1-10 keV)= 4.7 x 10^{-12} erg cm^{-2} s^{-1}, which…

Obscuration events in type I active galactic nuclei (AGN) have been detected more frequently in recent years. The strong flux decrease in the soft X-ray band between observations has been caused by clouds with large column densities…

We report the detection of weak pulsations from the archetypal ultraluminous X-ray source (ULX) NGC 1313 X-2. Acceleration searches reveal sinusoidal pulsations in segments of two out of six new deep observations of this object, with a…

We present an in-depth study of the High Mass X-ray Binary (HMXB) GX 301-2 during its pre-periastron flare using data from the XMM-Newton satellite. The energy spectrum shows a power law continuum absorbed by a large equivalent hydrogen…

We report on the X-ray properties of the new transient Swift J0840.7$-$3516, discovered with Swift/BAT in 2020 February, using extensive data of Swift, MAXI, NICER, and NuSTAR. The source flux increased for $\sim 10^3$ s after the…

The X-ray transient XTE J1719-291 was discovered with RXTE/PCA during its outburst in 2008 March, which lasted at least 46 days. Its 2-10 keV peak luminosity is 7E35 erg/s assuming a distance of 8 kpc, which classifies the system as a very…

The mini Broad Absorption Line (BAL) quasar RX J0911.4+0551 was observed with the Advanced CCD Imaging Spectrometer (ACIS) of the Chandra X-ray Observatory for ~ 29 ks as part of a gravitational lens (GL) survey aimed at measuring…

We present results of the first dedicated observation of the young X-ray pulsar SXP 1062 in the broad X-ray energy band obtained during its 2019 outburst with the NuSTAR and XMM-Newton observatories. The analysis of the pulse-phase averaged…

We present near-infrared spectroscopy of ten weak emission-line quasars (WLQs) at redshifts of $z\sim2$, obtained with the Palomar 200-inch Hale Telescope. WLQs are an exceptional population of type 1 quasars that exhibit weak or no broad…