arXiv subjects

Steven Kraemer

Publications and source records attributed to Steven Kraemer.

3 recordsLinked to original sources

arXiv2026

Winds of Change: XRISM Resolve X-ray spectroscopy of NGC 4051

NGC 4051 is a nearby (16.7 Mpc), Narrow Line Seyfert 1 galaxy (NLS1), which has a low black hole mass of $10^6$ M$_{\odot}$. It is also known for its rapid X-ray variability, on timescales of kilo-seconds and has a complex, multi component wind in both the soft X-ray and Fe K bands. Here we present the first high resolution XRISM Resolve spectrum of NGC 4051, which was captured in a historically bright state for a 150 ks exposure. XRISM resolves two blue-shifted Fe K shell absorption troughs in the mean spectrum, which can be ascribed to H-like iron and arises from two outflow components with outflow velocities of 0.025c and 0.04c. A time dependent spectral analysis shows that the iron K absorption is variable on timescales of less than a day, increasing in velocity over the duration of the observation. The velocity changes may be explained either by the passage of two separate transiting absorbers, of different velocities, or by a single accelerating outflow of approximately constant column density. In the latter case, the wind acceleration is likely to be too large to be caused by radiation pressure and instead magnetic driving is favored to accelerate the wind up to 0.04c. The outflow can originate from an accretion disk wind, whose kinetic power is sub-Eddington in contrast to recent examples of winds from powerful, luminous quasars observed by XRISM.

astro-ph.HE↗

arXiv2026

Resolving the Multiple Component Outflows in PG 1211+143: II. The Soft X-ray View of the Ultra Fast Outflow

The nearby quasar, PG 1211+143, has one of the prototype examples of an ultra fast outflow (UFO), as seen in several past XMM-Newton and Chandra observations. In December 2024, PG 1211+143 was observed simultaneously with XRISM Resolve and XMM-Newton, allowing both the Fe K and soft X-ray outflows to be examined at high resolution simultaneously. The Resolve spectrum revealed a forest of Fe K band absorption lines from the UFO (Mizumoto et al. 2026), comprising of up to six discrete velocity components ranging from $v/c=-0.074$ to $v/c=-0.40$. Here we present the simultaneous XMM-Newton RGS (Reflection Grating Spectrometer) spectrum, where three lower ionization counterparts of the Fe K velocity zones are observed; at $v/c=-0.074, -0.12$ and $-0.33$. The soft X-ray absorbers tend to be somewhat less ionized than their Fe K counterparts, with their opacity mainly arising from Fe L shell lines and highly ionized Oxygen. From comparing the Resolve and RGS absorbers, we show that the outflow can be parameterized with a density profile varying with radius as $r^{-5/3}$, while the lower ionization zones likely originate from denser clumps of gas. Pure electron scattering appears insufficient to provide enough thrust to power the wind, unless sufficient low ionization gas capable of radiative line driving exists outside of the line of sight. Overall, PG 1211+143 provides further evidence for the clumpy nature of accretion disk winds, as was recently revealed in the quasar PDS 456 with XRISM.

astro-ph.HE↗

arXiv2018

Bipolar ionization cones in the Extended Narrow-Line Region of nearby QSO2s

We have used narrow-band [OIII]$λλ$4959,5007 and H$α$+[NII]$λ\lambda6548,84$ Hubble Space Telescope (HST) images of 9 luminous (L[OIII]$>10^{42}$erg s$^{-1}$) type 2 QSOs with redshifts $0.1<z<0.5$ in order to constrain the geometry of their Extended Narrow-Line Regions (ENLR), as recent ground-based studies suggest these regions become more spherical at high luminosities due to destruction of the torus. We find instead elongated ENLRs reaching 4 to 19 kpc from the nucleus and bipolar ionization cones in [OIII]/(H$α$+[NII]) excitation maps indicating that the torus survives these luminosities, allowing the escape of $\approx$10 times higher ionizing photon rates along the ionization axis than perpendicularly to it. The exceptional HST angular resolution was key to our success in arriving at these conclusions. Combining our measurements with previous ones based on similar HST data, we have revisited the relation between the ENLR radius R$_{maj}$ (in pc) and L[OIII] (in erg s$^{-1}$) over the range $39<$log(L[OIII])$<43.5$: log(R$_{maj}) = (0.51\pm0.03)$ log(L[OIII])$-18.12\pm0.98$. The radius of the ENLR keeps increasing with L[OIII] in our data, implying that the ENLR can extend to distances beyond the limit of the galaxy if gas is present there $-$ e.g. from AGN outflows or interactions, seen in 6 objects of our sample. We attribute the flattening previously seen in this relation to the fact that the ENLR is matter-bounded, meaning that ionizing photons usually escape to the intergalactic medium in luminous AGN. Estimated ionized gas masses of the ENLRs range from 0.3 to $2\times10^8$ M$_{\odot}$, and estimated powers for associated outflows range from $<0.1\%$ to a few percent of the QSO luminosity.

astro-ph.GA↗