arXiv subjects

Martin Elvis

Publications and source records attributed to Martin Elvis.

At least 19 recordsLinked to original sources

arXiv2026

Lynx2030 Science Analysis Group: Final Report

The Lynx2030 Science Analysis Group (SAG) was convened to reassess the scientific goals and technical drivers of the Lynx mission concept amid a rapidly evolving astrophysics landscape. Building on the original Lynx Concept Study, the SAG examined how recent discoveries, emerging facilities, and advances in instrumentation influence the scientific opportunities for a next-generation flagship X-ray observatory. Through focused working groups, the SAG investigated the scientific impact of enhanced capabilities: (i) improved angular resolution, (ii) broader bandpass coverage, (iii) an enhanced microcalorimeter, (iv) new capabilities and observing modes, and (v) larger fields of view. Across a broad range of topics, from the formation of the first black holes and the evolution of galaxies to the baryon cycle, compact objects, stellar explosions, multi-messenger astrophysics, and the dynamic high-energy Universe, the SAG finds that the scientific motivation for a Lynx-class observatory remains compelling and, in many areas, has significantly strengthened over the past decade, prominently through JWST's discovery of the "Little Red Dots", likely massive accreting black holes in infant galaxies whose nature is fundamentally an X-ray question. This report shows that modest extensions beyond the original Lynx design reference mission can unlock transformative science while preserving the observatory's core architecture. Powerful current and future facilities such as Roman, Rubin, JWST, SKA, ngVLA, LISA, and NewAthena highlight the unique role a high-angular-resolution, high-throughput X-ray observatory would play in the multi-wavelength and multi-messenger ecosystem of the 2030s and beyond. The findings of the Lynx2030 SAG confirm Lynx's central vision: an unprecedented view of the hot and energetic Universe, enabling discoveries that will define high-energy astrophysics in the coming decades.

astro-ph.IM↗

arXiv2026

The Dyson Minds 2025 Workshop: SETI around Black Holes

The Dyson Minds 2025 Workshop, held at the Center for Brains, Minds & Machines at MIT and organized by Penn State, MIT, and The Ultraintelligence Foundation, brought together researchers in astrophysics, engineering, artificial intelligence, computer science, and philosophy to examine "Dyson Minds" -- large-scale post-biological intelligences powered by energy harvested from supermassive black holes (SMBHs). Building on the ideas of F. J. Dyson (1960, 1966) and I. J. Good (1966), participants explored the physical, engineering, behavioral, and observational consequences of civilizations embodied as machinery operating near the universe's most powerful energy sources. The workshop aimed to develop new observational strategies capable of detecting signatures of such systems. Despite the highly cross-disciplinary scope, discussions centered on how a Dyson Mind might be constructed, how it might behave, and how those factors would shape strategies for the search for extraterrestrial intelligence. Key themes included the thermodynamic, mechanical, and stability limits of Dyson swarms; the trade-offs between power availability and communication latency in distributed minds; and how observability changes depending on whether Dyson Minds act as coherent entities or as loosely coordinated collectives. Across these topics, the consensus was that details of architecture and behavior strongly influence observational signatures. A major recommendation was to apply anomaly-detection methods to archival datasets, including those from WISE, JWST, and the Event Horizon Telescope, to identify unusual sources potentially overlooked by standard reduction pipelines. By integrating insights from multiple disciplines, the meeting advanced concrete, observation-focused strategies for future technosignature searches around SMBHs.

astro-ph.GA↗

arXiv2026

PACHA: Probing AGN Coronae with High-redshift AGN

The X-ray emission of active galactic nuclei (AGN) is generally attributed to inverse Compton scattering of accretion-disk photons by hot electrons in a compact corona. In local AGN, directly constraining coronal properties is challenging because the high-energy cutoff often lies beyond the NuSTAR bandpass. High-redshift, luminous quasars enable systematic constraints on the high-energy cutoff, as cosmological redshift shifts the spectal cutoff into the observable hard X-ray band. We present first results from the ``Probing the AGN Coronae with High-redshift AGN'' (PACHA) project, based on quasi-simultaneous NuSTAR and XMM-Newton observations of 13 radio-quiet AGN at $z>1$. We constrain the high-energy cutoff and coronal temperature at 90\% confidence level for 10 and 9 sources, respectively. The sample exhibits a mean cutoff energy of $E_{\rm cut}=80.8\pm8.1$ keV and a mean coronal temperature of $kT_{\rm e}=18.4\pm1.6$ keV, both significantly lower than those measured in local {\it Swift}-BAT AGN, while the mean optical depth ($\tau=4.8\pm0.3$) is significantly higher. The uncertainties are at 1~$\sigma$. Combining our high-redshift sample with local AGN, we find a potential anti-correlation between cutoff energy and both X-ray luminosity and black hole mass, with no significant dependence on Eddington ratio. Within a hybrid coronal framework, the inferred temperatures lie well below the pair-production limits for purely thermal coronae, indicating a substantial efficient Compton cooling and/or non-thermal electron component. The detection of low coronal temperatures in high-luminosity AGN is broadly consistent with predictions from recent radiation MHD simulations that consider purely thermal electron populations, implying that non-thermal electrons may not be the primary drivers of the observed coronal properties in these systems.

astro-ph.HE↗

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↗

arXiv2025

X-ray view of a massive node of the Cosmic Web at z=3 II. Discovery of extended X-ray emission around a hyperluminous QSO

While the warm, ionized gas in the CGM at z>3 is now routinely observed around bright QSOs in Lya emission, little is known about the CGM hot phase due to its expected faintness in the X-ray band, often referred to as the ICM. Here, we report the analysis of 634 ks of Chandra X-ray observations in the MQN01 Cosmic Node, a region containing one of the brightest Lya nebulae and the largest galaxy overdensity discovered so far at z>3. We detect 66 net counts of X-ray emission in the 0.5-2 keV band extending to at least 30 kpc from the brightest QSO in MQN01. The morphology and spectrum are consistent with thermal emission from hot plasma in CIE. Photoionization is negligible, and IC is disfavored. A joint spatial and spectral MCMC analysis provides consistency with a beta-model with a steep density profile and a gas temperature kT~1.8 keV and virial halo mass Mvir~3e13 Mo. The inferred hot gas mass is Mhot(<Rvir)~2.6e12 Mo, which is ~8.3% of Mvir, or ~56% of the theoretical cosmological baryon budget of the halo. The hot gas also emits an exceptionally high Lx, with a measured L2-10~2.3e45 erg/s within the central 30 kpc. This system is a clear outlier in the Lx-Tx plane, indicating a thermodynamic state distinct from that of evolved lower-redshift hot halos. The cooling time in the inner 15-30 kpc is comparable to the local dynamical time, suggesting that the gas could become locally unstable in the absence of heating or feedback. Moreover, the thermal pressure associated with the detected CGM hot phase is large enough to confine the cold and dense clumps, which are required to reproduce the high Lya emission associated with the inner regions of the MQN01 structure. Although limited to a single system, our results provide unique information on the multi-phase properties of the CGM and a view of the nascent thermal hot gas phase observed in local galaxy clusters.

astro-ph.GA↗

arXiv2025

On ore-bearing asteroid remnants in lunar craters

We modify the probabilistic formalism developed by Elvis (2014) to estimate the number of lunar craters that contain ore-bearing asteroid remnants. When we consider craters at or above a threshold diameter of 1 km, we estimate an upper limit of ${\sim}6,500$ craters with asteroid remnants containing significant amounts of platinum group metals and an upper limit of ${\sim}3,400$ craters with asteroid remnants that contain significant amounts of water in the form of hydrated minerals. For a more conservative threshold of 5 km, we estimate $\lesssim400$ craters with asteroid remnants that contain significant amounts of platinum group metals. These values are one to two orders of magnitude larger than the number of ore-bearing near-Earth asteroids estimated by Elvis (2014), implying that it may be more advantageous, and hence more profitable, to mine asteroids that have impacted the Moon rather than the ones that are in orbit.

astro-ph.EP↗

arXiv2024

Chandra Discovery of a Candidate Hyper-Luminous X-ray Source in MCG+11-11-032

We present a multi-wavelength analysis of MCG+11-11-032, a nearby AGN with the unique classification of both a binary and a dual AGN candidate. With new Chandra observations we aim to resolve any dual AGN system via imaging data, and search for signs of a binary AGN via analysis of the X-ray spectrum. Analyzing the Chandra spectrum, we find no evidence of previously suggested double-peaked Fe K$\alpha$ lines; the spectrum is instead best fit by an absorbed powerlaw with a single Fe K$\alpha$ line, as well as an additional line centered at $\approx$7.5 keV. The Chandra observation reveals faint, soft, and extended X-ray emission, possibly linked to low-level nuclear outflows. Further analysis shows evidence for a compact, hard source -- MCG+11-11-032 X2 -- located 3.27'' from the primary AGN. Modeling MCG+11-11-032 X2 as a compact source, we find that it is relatively luminous ($L_{\text{2$-$10 keV}} = 1.52_{-0.48}^{+0.96}\times 10^{41}$ erg s$^{-1}$), and the location is coincident with an compact and off-nuclear source resolved in Hubble Space Telescope infrared (F105W) and ultraviolet (F621M, F547M) bands. Pairing our X-ray results with a 144 MHz radio detection at the host galaxy location, we observe X-ray and radio properties similar to those of ESO 243-49 HLX-1, suggesting that MCG+11-11-032 X2 may be a hyper-luminous X-ray source. This detection with Chandra highlights the importance of a high-resolution X-ray imager, and how previous binary AGN candidates detected with large-aperture instruments benefit from high-resolution follow-up. Future spatially resolved optical spectra, and deeper X-ray observations, can better constrain the origin of MCG+11-11-032 X2.

astro-ph.HE↗

arXiv2024

Cosmic Himalayas: The Highest Quasar Density Peak Identified in a 10,000 deg$^2$ Sky with Spatial Discrepancies between Galaxies, Quasars, and IGM HI

We report the identification of a quasar overdensity in the BOSSJ0210 field, dubbed Cosmic Himalayas, consisting of 11 quasars at $z=2.16-2.20$, the densest overdensity of quasars ($17\sigma$) in the $\sim$10,000 deg$^2$ of the Sloan Digital Sky Survey. We present the spatial distributions of galaxies and quasars and an HI absorption map of the intergalactic medium (IGM). On the map of 465 galaxies selected from the MAMMOTH-Subaru survey, we find two galaxy density peaks that do not fall on the quasar overdensity but instead exist at the northwest and southeast sides, approximately 25 $h^{-1}$ comoving-Mpc apart from the quasar overdensity. With a spatial resolution of 15 $h^{-1}$ comoving Mpc in projection, we produce a three-dimensional HI tomography map by the IGM Ly$\alpha$ forest in the spectra of 23 SDSS/eBOSS quasars behind the quasar overdensity. Surprisingly, the quasar overdensity coincides with neither an absorption peak nor a transmission peak of IGM HI but lies near the border separating opaque and transparent volumes, with the more luminous quasars located in an environment with lesser IGM HI. Hence remarkably, the overdensity region traced by the 11 quasars, albeit all in coherently active states, has no clear coincidence with peaks of galaxies or HI absorption densities. Current physical scenarios with mixtures of HI overdensities and quasar photoionization cannot fully interpret the emergence of Cosmic Himalayas, suggesting this peculiar structure is an excellent laboratory to unveil the interplay between galaxies, quasars, and the IGM.

astro-ph.GA↗

arXiv2024

Deep Chandra Observation of the Remarkable Ionization Cones of NGC 5252

Seyfert galaxy NGC 5252 harbors enormously extended ionization cones, which have been previously detected in the optical and X-ray band, offering a unique opportunity to investigate the interaction between the central active galactic nucleus (AGN) and the surrounding gas in the AGN host galaxy. We present deep Chandra imaging spectroscopy of NGC 5252 with a total exposure time of 230 ks. The morphology in the soft X-rays shows resolved extended structure from nucleus to a large radial distance, and for the first time we detect the outermost X-ray arc at $\sim$20 kpc. The X-ray cone mostly follows the direction of the optical ionization cones in the southeast and northwest direction, about 20 degrees misaligned with the major axis of the galactic disk of NGC 5252. Fitting the spectra extracted from radial sectors with photoionization models supports that extended emission is mainly photoionized by the central AGN. We also examine the variation of the photoionization parameter along the radial extension, and infer a decreasing ionizing continuum of the central engine by a factor of $\sim$50 over the past 64000 years. These findings are consistent with previous suggestion that NGC 5252 resembles a quasar relic with a $M\sim 10^9 M_{\odot}$ supermassive black hole, which went through a minor merger event and switched to a low accretion rate state.

astro-ph.HE↗

arXiv2023

Lunar Far-Side Radio Arrays: A Preliminary Site Survey

The origin and evolution of structure in the Universe could be studied in the Dark Ages. The highly redshifted HI signal between 30 < z < 80 is the only observable signal from this era. Human radio interference and ionospheric effects limit Earth-based radio astronomy to frequencies > 30 MHz. To observe the low-frequency window with research from compact steep spectrum sources, pulsars, and solar activity, a 200 km baseline lunar far-side radio interferometer has been much discussed. This paper conducts a preliminary site survey of potential far-side craters, which are few in number on the mountainous lunar far-side. Based on LRO LOLA data, 200 m resolution topographic maps of eight far-side sites were produced, and slope and roughness maps were derived from them. A figure of merit was created to determine the optimum site. Three sites are identified as promising. There is a need to protect these sites for astronomy.

astro-ph.IM↗

arXiv2023

The most luminous blue quasars at 3.0<z<3.3 -- III. LBT spectra and accretion parameters

We present the analysis of the rest frame ultraviolet and optical spectra of 30 bright blue quasars at $z\sim3$, selected to examine the suitability of AGN as cosmological probes. In our previous works, we found an unexpectedly high fraction ($\approx 25 \%$) of X-ray weak quasars in the sample. The latter sources also display a flatter UV continuum and a broader and fainter CIV profile in the archival UV data with respect to their X-ray normal counterparts. Here we present new observations with the LBT in both the $zJ$ (rest-frame $\simeq$2300-3100 $\rm \mathring{A}$) and the $K_S$ ($\simeq$4750-5350 $\rm \mathring{A}$) bands. We estimated black hole masses ($M_{\rm BH}$) and Eddington ratios ($\lambda_{\rm Edd}$) from the from the H$\beta$ and MgII emission lines, finding that our $z\sim3$ quasars are on average highly accreting ($\langle \lambda_{\rm Edd} \rangle\simeq 1.2$ and $\langle M_{\rm BH} \rangle\simeq 10^{9.7}M_\odot$), with no difference in $\lambda_{\rm Edd}$ or $M_{\rm BH}$ between X-ray weak and X-ray normal quasars. From the $zJ$ spectra, we derive flux and equivalent width of MgII and FeII, finding that X-ray weak quasars display higher FeII/MgII ratios with respect to typical quasars. FeII/MgII ratios of X-ray normal quasars are instead consistent with other estimates up to $z\simeq6.5$, corroborating the idea of already chemically mature BLRs at early cosmic time. From the $K_S$ spectra, we find that all the X-ray weak quasars present generally weaker [OIII] emission (EW<10 $\rm \mathring{A}$) than the normal ones. The sample as a whole, however, abides by the known X-ray/[OIII] luminosity correlation, hence the different [OIII] properties are likely due to an intrinsically weaker [OIII] emission in X-ray weak objects, associated to the shape of the spectral energy distribution. We interpret these results in the framework of accretion-disc winds.

astro-ph.GA↗

arXiv2023

Accurate dust temperature and star formation rate in the most luminous $z>6$ quasar in the HYPerluminous quasars at the Epoch of ReionizatION (HYPERION) sample

We present ALMA Band 9 continuum observation of the ultraluminous quasi-stellar object (QSO) SDSS J0100+2802, providing a $\sim 10\sigma$ detection at $\sim 670$ GHz. SDSS J0100+2802 is the brightest QSO with the most massive super massive black hole (SMBH) known at $z>6$, and we study its dust spectral energy distribution in order to determine the dust properties and the star formation rate (SFR) of its host-galaxy. We obtain the most accurate estimate so far of the temperature, mass and emissivity index of the dust, having $T_{\rm dust}=48.4\pm2.3$ K, $M_{\rm dust}=(2.29\pm0.83)\times 10^7$ M$_\odot$, $\beta=2.63\pm 0.23$. This allows us to measure the SFR with the smallest statistical error for this QSO, SFR$=265\pm 32\ \rm M_\odot yr^{-1}$. Our results enable us to evaluate the relative growth of the SMBH and host galaxy of J0100+2802, finding that the SMBH is dominating the process of BH-galaxy growth in this QSO at $z=6.327$, when the Universe was $865$ Myr old. Such unprecedented constraints on the host galaxy SFR and dust temperature can only be obtained through high frequency observations, and highlight the importance of ALMA Band 9 to obtain a robust overview of the build-up of the first quasars' host galaxies at $z>6$.

astro-ph.GA↗

arXiv2023

Extended hard X-ray emission in highly obscured AGN

Kilo-parsec scale hard ($>$ 3 keV) X-ray continuum and fluorescent Fe K$\alpha$ line emission has been recently discovered in nearby Compton-thick (CT) active galactic nuclei (AGN), which opens new opportunities to improve AGN torus modeling and investigate how the central supermassive black hole interacts with and impacts the host galaxy. Following a pilot Chandra survey of nearby CT AGN, we present in this paper the Chandra spatial analysis results of five uniformly selected non-CT but still heavily obscured AGN to investigate the extended hard X-ray emission by measuring the excess emission counts, excess fractions, and physical scales. Three of them show extended emission in the 3.0-7.0 keV band detected at $>$ 3$\sigma$ above the Chandra PSF with total excess fractions ranging from $\sim$8% - 20%. The extent of the hard emission ranges from at least $\sim$250 pc to 1.1 kpc in radius. We compare these new sources with CT AGN and find that CT AGN appear to be more extended in the hard band than the non-CT AGN. Similar to CT AGN, the amounts of extended hard X-ray emission relative to the total emission of these obscured AGN are not negligible. Together with other extended hard X-ray detected AGN in the literature, we further explore potential correlations between the extended hard X-ray component and AGN parameters. We also discuss the implications for torus modeling and AGN feedback. Considering potential contributions from X-ray binaries (XRBs) to the extended emission, we do not see strong XRB contamination in the overall sample.

astro-ph.HE↗

arXiv2022

A UFO Seen Edge-On: Resolving Ultrafast Outflow Emission on $\sim$200-pc Scales with $Chandra$ in the Active Nucleus of Mrk 34

We present $Chandra$ ACIS imaging spectroscopy of the nucleus of the Seyfert 2 Galaxy Mrk 34. We identify spatially and spectrally resolved features in the band that includes Fe K$\alpha$, Fe XXV and Fe XXVI. These features indicate high-velocity ($\gtrsim15,000\,\rm{km\,s}^{-1}$ line-of-sight) material separated spanning $\sim$0.5 arcsec, within $\sim200$ pc of the nucleus. This outflow could have deprojected velocities $\sim12-28\times$ greater than the [O III] emitting outflows, and could potentially dominate the kinetic power in the outflow. This emission may point to the origins of the optical and X-ray winds observed at larger radii, and could indicate a link between ultra-fast outflows and AGN feedback on $\gtrsim$kpc scales.

astro-ph.HE↗

arXiv2022

Termination Shocks and the Extended X-ray Emission in MRK 78

Sub-arcsecond imaging of the X-ray emission in the type 2 AGN Mrk 78 with Chandra shows complex structure with spectral variations on scales from $\sim$200 pc to $\sim$ 2 kpc. Overall the X-ray emission is aligned E-W with the radio (3.6 cm) and narrow emission line region as mapped in [OIII], with a marked E-W asymmetry. The Eastern X-ray emission is mostly in a compact knot coincident with the location where the radio source is deflected, while the Western X-ray emission forms a loop or shell $\sim$2 kpc from the nucleus with radius $\sim$0.7 kpc. There is suggestive evidence of shocks in both the Eastern knot and the Western arc. Both these positions coincide with large changes in the velocities of the [OIII] outflow. We discuss possible reasons why the X-ray shocks on the Western side occur $\sim1$ kpc farther out than on the Eastern side. We estimate that the thermal energy injected by the shocks into the interstellar medium corresponds to $0.05-0.6$% of the AGN bolometric luminosity.

astro-ph.HE↗

arXiv2021

Research Programs Arising from 'Oumuamua Considered as an Alien Craft

The controversial hypothesis that 'Oumuamua (1I/2017 U1) was an alien craft dominated by a solar sail is considered using known physics for the two possible cases: controlled and uncontrolled flight. The reliability engineering challenges for an artifact designed to operate for 10^5 - 10^6 yr are also considerable. All three areas generate research programs going forward. The uncontrolled case could be either "anonymous METI" (messaging extraterrestrial intelligence) or "inadvertent METI". In the controlled case the nature of the origin star, trajectory guidance from the origin star to the Sun, and the identity of a destination star are all undecided. The "controlled" case has more strikes against it than the "uncontrolled" case, but neither suffers a knock-out blow, as yet. Some of the issues turn out not to be major obstacles to the alien craft hypothesis, but others weaken the case for it. Most, however, imply new studies. Some of these, e.g., intercept missions for new interstellar objects, are concepts being developed, and will be of value whatever these objects turn out to be. Overall, these considerations show that a many pronged, targeted, research program can be built around the hypothesis that'Oumuamua is an alien craft. The considerations presented here can also be applied to other interstellar visitors, as well as to general discussions of interstellar travel.

astro-ph.EP↗

arXiv2021

The Chandra view of the relation between X-ray and UV emission in quasars

We present a study of the relation between X-rays and ultraviolet emission in quasars for a sample of broad-line, radio-quiet objects obtained from the cross-match of the Sloan Digital Sky Survey DR14 with the latest Chandra Source Catalog 2.0 (2,332 quasars) and the Chandra COSMOS Legacy survey (273 quasars). The non-linear relation between the ultraviolet (at 2500 A, $L_{O}$) and the X-ray (at 2 keV, $L_{X}$) emission in quasars has been proved to be characterised by a smaller intrinsic dispersion than the observed one, as long as a homogeneous selection, aimed at preventing the inclusion of contaminants in the sample, is fulfilled. By leveraging on the low background of Chandra, we performed a complete spectral analysis of all the data available for the SDSS-CSC2.0 quasar sample (i.e. 3,430 X-ray observations), with the main goal of reducing the uncertainties on the source properties (e.g. flux, spectral slope). We analysed whether any evolution of the $L_{X}-L_{O}$ relation exists by dividing the sample in narrow redshift intervals across the redshift range spanned by our sample, $z \simeq 0.5-4$. We find that the slope of the relation does not evolve with redshift and it is consistent with the literature value of $0.6$ over the explored redshift range, implying that the mechanism underlying the coupling of the accretion disc and hot corona is the same at the different cosmic epochs. We also find that the dispersion decreases when examining the highest redshifts, where only pointed observations are available. These results further confirm that quasars are `standardisable candles', that is we can reliably measure cosmological distances at high redshifts where very few cosmological probes are available.

astro-ph.GA↗

arXiv2021

The most luminous blue quasars at 3.0<z<3.3. II. CIV/X-ray emission and accretion disc physics

We analyse the properties of the CIV broad emission line in connection with the X-ray emission of 30 bright SDSS quasars at z~3.0-3.3 with pointed XMM-Newton observations, which were selected to test the suitability of AGN as cosmological tools. In our previous work, we found that a large fraction (~25%) of the quasars in this sample are X-ray underluminous by factors of >3-10. As absorbing columns of >10$^{23}$ cm$^{-2}$ can be safely ruled out, their weakness is most likely intrinsic. Here we explore possible correlations between the UV and X-ray features of these sources to investigate the origin of X-ray weakness. We fit their UV SDSS spectra and analyse their CIV properties (e.g., equivalent width, EW; line peak velocity, $\upsilon_{\rm peak}$) as a function of the X-ray photon index and 2-10 keV flux. We confirm the trends of CIV $\upsilon_{\rm peak}$ and EW with UV luminosity at 2500 angstrom for both X-ray weak and X-ray normal quasars, as well as the correlation between X-ray weakness and CIV EW. In contrast to some recent work, we do not observe any clear relation between the 2-10 keV luminosity and $\upsilon_{\rm peak}$. We find a correlation between the hard X-ray flux and the integrated CIV flux for X-ray normal quasars, whilst X-ray weak quasars deviate from the main trend by more than 0.5 dex. We argue that X-ray weakness might be interpreted in a starved X-ray corona picture associated with an ongoing disc-wind phase. If the wind is ejected in the vicinity of the black hole, the extreme-UV radiation that reaches the corona will be depleted, depriving the corona of seeds photons and generating an X-ray weak quasar. Yet, at the largest UV luminosities (>10$^{47}$ erg s$^{-1}$), there will still be an ample reservoir of ionising photons that can explain the excess CIV emission observed in the X-ray weak quasars with respect to normal sources of similar X-ray luminosities.

astro-ph.GA↗