William Nielsen Brandt

FF03. 00001: Latest Results from the XMM-SERVS X-ray Survey of the LSST Deep-Drilling Fields*

The growth of supermassive black holes is strongly linked to their galaxies. It has been shown that the population mean black hole accretion rate (

" Changing-look" AGN (CL-AGN)-systems where the characteristic AGN continuum and/or broad line emission has essentially (dis-) appeared-are challenging our basic ideas about the physics of accretion flow and circumnuclear gas in supermassive black holes (SMBHs). Using first-year Sloan Digital Sky Survey V (SDSS-V) spectroscopy from the Black Hole Mapper program, dedicated follow-up spectroscopic observations, and publicly available optical light-curves (eg, ZTF), we've identified over 100 CL-AGN, and many more extremely variable systems, most of which reside at z< 1. This sample is among the largest reported to date, and probes (extreme) spectral AGN variability on timescales of months to decades, including some interesting examples of recurring transitions on surprisingly short timescales (a few months). We find that CL-AGN events are preferentially found in lower Eddington ratio systems …

Mrk 817 is a bright and variable Seyfert 1.2 active galactic nucleus (AGN). X-ray monitoring of Mrk 817 with the Neil Gehrels Swift Observatory in 2022 revealed that the source flux had declined to a lower level than recorded at any prior point in the then 19 yr mission. We present an analysis of deep XMM-Newton and NuSTAR observations obtained in this low flux state. The spectra reveal a complex X-ray wind consisting of neutral and ionized absorption zones. Three separate velocity components are detected as part of a structured ultrafast outflow (UFO), with

Cen A hosts the closest active galactic nucleus to the Milky Way, which makes it an ideal target for investigating the dynamical processes in the vicinity of accreting supermassive black holes. In this paper, we present 14 Chandra HETGS spectra of the nucleus of Cen A that were observed throughout 2022. We compared them with each other, and contrasted them against the two previous Chandra HETGS spectra from 2001. This enabled an investigation into the spectral changes occurring on timescales of months and 21 years. All Chandra spectra could be well fitted by an absorbed power law with a strong and narrow Fe Kα line, a leaked power-law feature at low energies, and Si and SK α lines that could not be associated with the central engine. The flux of the continuum varied by a factor of 2.74±0.05 over the course of the observations, whereas the Fe line only varied by 18.8%±8.8%. The photon index increased …

We present a catalog of hard X-ray serendipitous sources detected in the first 80 months of observations by the Nuclear Spectroscopic Telescope Array (NuSTAR). The NuSTAR serendipitous survey 80-month (NSS80) catalog has an unprecedented 62 Ms of effective exposure time over 894 unique fields (a factor of three increase over the 40-month catalog), with an areal coverage of 36 deg, larger than all NuSTAR extragalactic surveys. NSS80 provides 1274 hard X-ray sources in the keV band (822 new detections compared to the previous 40-month catalog). Approximately 76% of the NuSTAR sources have lower-energy ( keV) X-ray counterparts from Chandra, XMM-Newton, and Swift-XRT. We have undertaken an extensive campaign of ground-based spectroscopic follow-up to obtain new source redshifts and classifications for 427 sources. Combining these with existing archival spectroscopy provides redshifts for 550 NSS80 sources, of which 547 are classified. The sample is primarily composed of active galactic nuclei (AGN), detected over a large range in redshift ( = 0.012-3.43), but also includes 58 spectroscopically confirmed Galactic sources. In addition, five AGN/galaxy pairs, one dual AGN system, one BL Lac candidate, and a hotspot of 4C 74.26 (radio quasar) have been identified. The median rest-frame keV luminosity and redshift of the NSS80 are = 1.2 10 erg s and . We investigate the optical properties and construct composite optical spectra to search for subtle signatures not present in the individual spectra, finding an excess of redder BL AGN compared to optical quasar surveys …

The X-ray and UV instruments on STAR-X are uniquely designed to study three powerful components of the rapidly-varying" fast" Universe: supernova shock breakouts, binary neutron star mergers, and stellar flares in planet-hosting systems. In this iPoster, I will outline these central science objectives:

The Survey and Time-domain Astrophysics Research eXplorer (STAR-X) is a proposed MIDEX mission that was recently selected for a competitive MIDEX Phase A study. As an X-ray and UV facility designed to study the fast, furious and forming universe, STAR-X will conduct time-domain surveys and respond rapidly to transient events discovered by other observatories such as LIGO, Rubin/LSST, Roman/WFIRST, and SKA. Thus, it is a timely response to Astro2020's recommendation for a space-based, sustaining time-domain and multi-messenger program. This talk will cover the STAR-X observing plan, which, for the 2 year prime mission, allocates 62% to time domain surveys. The two main surveys are the Deep Survey, which covers 12 deg 2 in the Rubin Deep-Drilling Fields, and a Medium Survey that covers 300 deg 2 in well-studied survey fields such as Stripe 82, the Subaru fields and the Rubin Deep …