C. Pinto

Interstellar medium composition through X-ray spectroscopy of low-mass X-ray binaries

Astronomical Institute, Utrecht University, P.O. Box 80000, 3508 TA Utrecht, The Netherlands.Received 2 October 2012 / Accepted 7 January 2013ABSTRACTContext.The diffuse interstellar medium (ISM) is an integral part of the evolution of the entire Galaxy. Metals are produced by starsand their abundances are the direct testimony of the history of stellar evolution. However, the interstellar dust composition is not wellknown and the total abundances are yet to be accurately determined.Aims.We probe ISM dust composition, total abundances, and abundance gradients through the study of interstellar absorption featuresin the high-resolution X-ray spectra of Galactic low-mass X-ray binaries (LMXBs).Methods.We use high-quality grating spectra of nine LMXBs taken withXMM-Newton. We measure the column densities of O, Ne,Mg, and Fe with an empirical model and estimate the Galactic abundance gradients.Results.The column densities of the neutral gas species are in agreement with those found in the literature. Solids are a significa ntreservoir of metals like oxygen and iron. Respectively, 15–25% and 65–90% of the total amount of O iand Feiis found in dust.The dust amount and mixture seem to be consistent along all the lines-of-sight (LOS). Our estimates of abundance gradients andpredictions of local interstellar abundances are in agreement with those measured at longer wavelengths.Conclusions.Our work shows that X-ray spectroscopy is a very powerful method to probe the ISM. For instance, on a large scalethe ISM appears to be chemically homogeneous showing similar gas ionization ratios and dust mixtures. The agreement between theabundances of the ISM and the stellar objects suggests that the local Galaxy is also chemically homogeneous.Key words. ISM: abundances – ISM: dust, extinction – ISM: molecules – IS M: structure – X-rays: ISMContext. The diffuse interstellar medium (ISM) is an integral part of the evol uti n of the entire Galaxy. Metals are produced by stars and their abundances are the direct testimony of the history of stellar evolution. However, the interstellar dust compo siti n is not well known and the total abundances are yet to be accurately deter mined. Aims. We probe ISM dust composition, total abundances, and abunda nce gradients through the study of interstellar absorption features in the high-resolution X-ray spectra of Galactic low-mass X -ray binaries (LMXBs). Methods. We use high-quality grating spectra of nine LMXBs taken with XMM-Newton. We measure the column densities of O, Ne, Mg, and Fe with an empirical model and estimate the Galactic a bundance gradients. Results. The column densities of the neutral gas species are in agreem ent with those found in the literature. Solids are a significa nt reservoir of metals like oxygen and iron. Respectively, 15– 25% and 65–90% of the total amount of O i and Fei is found in dust. The dust amount and mixture seem to be consistent along all th e ines-of-sight (LOS). Our estimates of abundance gradien ts a d predictions of local interstellar abundances are in agreem ent with those measured at longer wavelengths. Conclusions. Our work shows that X-ray spectroscopy is a very powerful met hod to probe the ISM. For instance, on a large scale the ISM appears to be chemically homogeneous showing simila r gas ionization ratios and dust mixtures. The agreement bet ween the abundances of the ISM and the stellar objects suggests that t he local Galaxy is also chemically homogeneous.

Discovery of an ∼2-h high-frequency X-ray QPO and iron Kα reverberation in the active galaxy MS 2254.9−3712

ABSTRACT We report the discovery of a ∼1.5×10 −4 Hz (∼2hr) X-ray quasi-periodic oscillation (QPO)in the active galaxy MS 2254.9–3712, using a ∼70ks XMM-Newtonobservation. The QPOis significantly detected ( ∼3.3σ) in the 1.2−5.0keV band only, connecting its origin withthe primary X-ray power-law continuum. We detect a highly coherent soft lag between the0.3−0.7keV and 1.2−5.0keV energy bands at the QPO frequency and at a frequency bandin a 3:2 ratio, strongly suggesting the presence of a QPO harmonic. An iron Kαreverbera-tion lag is found at the harmonic frequency, indicating the reflecting material subtends someangle to the primary continuum, which is modulated by the QPO mechanism. Frequencyresolved spectroscopy reveals the QPO and harmonic to have a hard energy dependence.These properties of the QPO variability, together with the current black hole mass estimate,M BH ∼4×10 6 M ⊙ , are consistent with the QPO originating from the same process as thehigh frequency QPO phenomenon observed in black hole X-ray binaries. Principle compo-nent analysis reveals the spectral variability in MS 2254.9–3712is similar to that of the activegalaxy RE J1034+396, a source which also displays an X-ray QPO. This suggests a distinctspectral variability pattern for accreting black holes when in a state where QPOs are present.Key words: galaxies: individual: MS 2254.9-3712 – galaxies: Seyfert – X-rays: galaxies

A phenomenological model for the X-ray spectrum of nova V2491 Cygni

The X-ray flux of nova V2491Cyg reached a maximum some forty days after optical maximum. The X-ray spectrum at that time, obtained with the RGS of XMM-Newton, shows deep, blue-shifted absorption by ions of a wide range of ionization. We show that the deep absorption lines of the X-ray spectrum at maximum, and those observed nine days later, are well described by a phenomenological model with emission from a central blackbody and from a collisionally ionized plasma (CIE). The blackbody spectrum (BB) is absorbed by three main highly ionized expanding shells; the CIE and BB are absorbed by cold circumstellar and interstellar matter that includes dust. The outflow density does not decrease monotonically with distance. The abundances of the shells indicate that they were ejected from an O-Ne white dwarf. We show that the variations on time scales of hours in the X-ray spectrum are caused by a combination of variation in the central source and in the column density of the ionized shells. Our phenomenological model gives the best description so far of the supersoft X-ray spectrum of nova V2491 Cyg, but underpredicts, by a large factor, the optical and ultraviolet flux. The X-ray part of the spectrum must originate from a very different layer in the expanding envelope, presumably much closer to the white dwarf than the layers responsible for the optical/ultraviolet spectrum. This is confirmed by the absence of any correlation between the X-ray and UV/optical observed fluxes.

Chasing obscuration in type-I AGN: Discovery of an eclipsing clumpy wind at the outer broad-line region of NGC 3783

In 2016 we carried out a Swift monitoring program to track the X-ray hardness variability of eight type-I AGN over a year. The purpose of this monitoring was to find intense obscuration events in AGN, and thereby study them by triggering joint XMM-Newton, NuSTAR, and HST observations. We successfully accomplished this for NGC 3783 in December 2016. We found heavy X-ray absorption produced by an obscuring outflow in this AGN. As a result of this obscuration, interesting absorption features appear in the UV and X-ray spectra, which are not present in the previous epochs. Namely, the obscuration produces broad and blue-shifted UV absorption lines of Ly

Is there a UV/X-ray connection in IRAS 13224-3809?

alpha

The remarkable X-ray variability of IRAS 13224-3809 I: the variability process

, C IV, and N V, together with a new high-ionisation component producing Fe XXV and Fe XXVI absorption lines. In soft X-rays, only narrow emission lines stand out above the diminished continuum as they are not absorbed by the obscurer. Our analysis shows that the obscurer partially covers the central source with a column density of few

Evidence for a Variable Ultrafast Outflow in the Newly Discovered Ultraluminous Pulsar NGC 300 ULX-1

10^{23}

Multiwavelength campaign on Mrk 509: Reverberation of the Fe Kalpha line

cm

A Potential Cyclotron Resonant Scattering Feature in the Ultraluminous X-Ray Source Pulsar NGC 300 ULX1 Seen by NuSTAR and XMM-Newton

^{-2}

A stratified ultrafast outflow in 1H0707-495?

, outflowing with a velocity of few thousand km s