What can be learnt from a highly informative X-ray occultation event in NGC 6814? A marvellous absorber

A unique X-ray occultation event in NGC 6814 during an XMM-Newton observation in 2016 has been reported, providing useful information of the absorber and the corona. We revisit the event with the aid of the hardness ratio (HR) - count rate (CR) plot and comparison with two other absorption-free XMM exposures in 2009 and 2021. NGC 6814 exhibits a clear "softer-when-brighter" variation pattern during the exposures, but the 2016 exposure significantly deviates from the other two in the HR - CR plot. While spectral fitting does yield transient Compton-thin absorption corresponding to the eclipse event in 2016, rather than easing the tension between exposures in the HR - CR plot, correcting the transient Compton-thin absorption results in new and severe deviation within the 2016 exposure. We show that the eclipsing absorber shall be clumpy (instead of a single Compton-thin cloud), with an inner denser region composed of both Compton-thin and Compton-thick clouds responsible for the previously identified occultation event, and an outer sparser region with Compton-thin clouds which eclipses the whole 2016 exposure. With this model, all the tension in the HR - CR plots could be naturally erased, with the observed spectral variability during the 2016 exposure dominated by the variation of absorption. Furthermore, the two warm absorbers (with different ionization and column densities but similar outflowing velocities) detected in the 2016 exposure shall also associate with the transient absorber, likely due to ablated or tidal stretched/disrupted fragments. This work highlights the unique usefulness of the HR - CR plot while analysing rare occultation events.Comment: 13 pages, 9 figures, accepted by MNRAS. For the video of the eclipsing cloud, see https://drive.google.com/file/d/1CEsPEWE-b5W8PfZINyI5K1sE6klHaYMa/view?usp=sharing . Comments are welcome

The X-ray Nature of Nucleus in Seyfert 2 Galaxy NGC 7590

We present the result of the Chandra high-resolution observation of the Seyfert~2 galaxy NGC 7590. This object was reported to show no X-ray absorption in the low-spatial resolution ASCA data. The XMM observations show that the X-ray emission of NGC 7590 is dominated by an off-nuclear ultra-luminous X-ray source (ULX) and an extended emission from the host galaxy, and the nucleus is rather weak, likely hosting a Compton-thick AGN. Our recent Chandra observation of NGC 7590 enables to remove the X-ray contamination from the ULX and the extended component effectively. The nuclear source remains undetected at ~4x10^{-15} erg/s/cm^-2 flux level. Although not detected, Chandra data gives a 2--10 keV flux upper limit of ~6.1x10^{-15} erg/s/cm^-2 (at 3 sigma level), a factor of 3 less than the XMM value, strongly supporting the Compton-thick nature of the nucleus. In addition, we detected five off-nuclear X-ray point sources within the galaxy D25 ellipse, all with 2 -- 10 keV luminosity above 2x10^{38} erg/s (assuming the distance of NGC 7590). Particularly, the ULX previously identified by ROSAT data was resolved by Chandra into two distinct X-ray sources. Our analysis highlights the importance of high spatial resolution images in discovering and studying ULXs.Comment: 8 pages, 5 figures, RAA accepte

Methyl 3-(cyclo­propyl­meth­oxy)-4-hy­droxy­benzoate. Corrigendum

Corrigendum to Acta Cryst. (2010), E66, o2004

Methyl 3-(cyclo­propyl­meth­oxy)-4-hy­droxy­benzoate

In the title compound, C12H14O4, the dihedral angle between the benzene ring and the cyclo­propyl ring is 60.3 (4)°. In the crystal structure, mol­ecules are linked by inter­molecular O—H⋯O hydrogen bonds into chains running parallel to [101]

Bis{2-[6-(1H-benzimidazol-2-yl-κN 3)-2-pyridyl-κN]benzimidazolato-κN}manganese(II)

In the title compound, [Mn(C19H12N5)2], each MnII atom lies on a position of site symmetry 222 and has a distorted octa­hedral coordination geometry made up from six N atoms of two tridentate 2-[6-(1H-benzimidazol-2-yl)-2-pyrid­yl]benz­imidazolate ligands. The complex mol­ecules are linked into layers parallel to (001) by N—H⋯N hydrogen bonds, with the H atoms disordered over four symmetry-equivalent non-coordinated N atoms

4,4,5,5-Tetra­methyl-2-(4-pyridyl)­imidazolidin-1-oxyl-3-oxide trichloroacetic acid solvate

In the title compound, C12H16N3O2·C2HCl3O2, the imidazolidine ring adopts a twist conformation. The crystal structure is stabilized by inter­molecular O—H⋯N hydrogen bonds

4,5,6,7-Tetra­chloro-2-(4-fluoro­phen­yl)isoindoline-1,3-dione

The title compound, C14H4Cl4FNO2, has crystallographic twofold symmetry with the N and F atoms and two C atoms of the benzene ring located on a twofold rotation axis. The isoindole­dione ring system is almost planar [maximum atomic deviation = 0.036 (3) Å], and is twisted with respect to the florobenzene ring, making a dihedral angle of 58.56 (16)°. Weak inter­molecular C—H⋯Cl hydrogen bonding is present in the crystal structure