X-ray Point Sources Research Articles

Identification of AGN in the XMM-Newton X-ray survey of the SMC

Context. Finding active galactic nuclei (AGN) behind the Magellanic Clouds (MCs) is difficult because of the high stellar density in these fields. Although the first AGN behind the Small Magellanic Cloud (SMC) were reported in the 1980s, it is only recently that the number of AGN known behind the SMC has increased by several orders of magnitude. Aims. The mid-infrared colour selection technique has proven to be an efficient means of identifying AGN, especially obscured sources. The X-ray regime is complementary in this regard and we use XMM-Newton observations to support the identification of AGN behind the SMC. Methods. We present a catalogue of AGN behind the SMC by correlating an updated X-ray point-source catalogue from our XMM-Newton survey of the SMC with previously identified AGN from the literature as well as a list of candidates obtained from the ALLWISE mid-infrared colour-selection criterion. We studied the properties of the sample with respect to their redshifts, luminosities, and X-ray spectral characteristics. We also identified the near-infrared counterpart of the sources from the VISTA observations. Results. The redshift and luminosity distributions of the sample (where known) indicate that we detect sources ranging from nearby Seyfert galaxies to distant and obscured quasars. The X-ray hardness ratios are compatible with those typically expected for AGN, and the VISTA colours and variability are also consistent with AGN. A positive correlation was observed between the integrated X-ray flux (0.2–12 keV) and the ALLWISE and VISTA magnitudes. We further present a sample of new candidate AGN and candidates for obscured AGN. Together these make an interesting subset for further follow-up studies. An initial spectroscopic follow-up of 6 out of the 81 new candidates showed that all six sources are active galaxies, although two have narrow emission lines.

Discovery of an Active Intermediate-mass Black Hole Candidate in the Barred Bulgeless Galaxy NGC 3319

Abstract We report the discovery of an active intermediate-mass black hole (IMBH) candidate in the center of nearby barred bulgeless galaxy NGC 3319. The point X-ray source revealed by archival Chandra and XMM-Newton observations is spatially coincident with the optical and UV galactic nuclei from Hubble Space Telescope observations. The spectral energy distribution derived from the unresolved X-ray and UV-optical flux is comparable with active galactic nuclei rather than ultraluminous X-ray sources, although its bolometric luminosity is only . Assuming an Eddington ratio range between 0.001 and 1, the black hole mass ( ) will be in the range 3 × 102 −3 × 105 , placing it in the so-called IMBH regime and making it possibly one of the lowest reported so far. Estimates from other approaches (e.g., fundamental plane, X-ray variability) also suggest ≲ 105 . Similar to other BHs in bulgeless galaxies, the discovered IMBH resides in a nuclear star cluster with mass of ∼6 × 106 . The detection of such a low-mass BH offers us an ideal chance to study the formation and early growth of SMBH seeds, which may result from the bar-driven inflow in late-type galaxies with a prominent bar such as NGC 3319.

The XXL Survey

We present the version of the point source catalogue of the XXL Survey that was used, in part, in the first series of XXL papers. In this paper we release, in our database in Milan and at CDS: (i) the X-ray source catalogue with 26 056 objects in two areas of 25 deg2 with a flux limit (at 3σ) of ~10−15 erg s−1 cm−2 in [0.5–2] keV, and ~ 3 × 10−15 erg s−1 cm−2 in [2–10] keV, yielding a 90% completeness limit of 5.8 × 10−15 and 3.8 × 10−14 respectively;(ii) the associated multiwavelength catalogues with candidate counterparts of the X-ray sources in the infrared, near-infrared, optical, and ultraviolet (plus spectroscopic redshift when available); and (iii) a catalogue of spectroscopic redshifts recently obtained in the southern XXL area. We also present the basic properties of the X-ray point sources and their counterparts. Other catalogues described in the second series of XXL papers will be released contextually, and will constitute the second XXLdata release.

A Catalog of X-Ray Point Sources in the Abell 133 Region

As an evolutionary phase of galaxies, active galactic nuclei (AGN) over a large range of redshift have been utilized for understanding cosmic evolution. In particular, the population and evolution of AGNs have been investigated through the study of the cosmic X-ray background in various fields. As one of the deep fields observed by Chandra with a total of 2.8 Msec exposures, Abell 133 is a special region to investigate AGNs, providing a testbed for probing the environmental effect on AGN trigger, since cluster environments can be different from field environments. The achieved flux limit of data at 50% completeness level of 6.95x10^(-16), 1.43x10^(-16), and 1.57x10^(-15) ergs cm^(-2) in 0.5-8, 0.5-2, and 2-8 keV. Using the wavdetect and no-source binomial probability (i.e., p<0.007), we analyze the combined \textit{Chandra} image, detecting 1617 (in 0.5-8 keV), 1324 (in 0.5-2 keV), and 1028 (in 2-8 keV), X-ray point sources in the Abell 133 region. Here, we present the X-ray point source catalogue with the source fluxes, which can be combined with multiwavelength data for future works. We find that the number count distribution of the X-ray point sources is well reproduced with a broken power-law model while the best-fit model parameters are sensitive to the fitting range of the number count distribution. Finally, we find an excess of the number density (decrease of AGN fraction) at the central region of the cluster, which reflects the effect of dense environments on AGN trigger, as similarly found in studies of other galaxy clusters.

Intraoperative Radiotherapy With the Intrabeam® Device for the Treatment of Resectable Pancreatic Adenocarcinoma

IntroductionThe application of intraoperative radiation therapy to the tumor bed after resection of pancreatic cancer has been shown to be beneficial in the local control of the disease. The objective of this study was to evaluate the preliminary outcomes after the application of a single intraoperative dose to the tumor bed with a new intraoperative radiotherapy device (Intrabeam®) in terms of viability, safety and short-term results. MethodsWe studied 5 patients who underwent pancreaticoduodenectomy for resectable pancreatic cancer in which a radiotherapy boost (5Gy) was intraoperatively applied to the tumoral bed using the portable Intrabeam® device, a low-energy point-source X-ray. Postoperative complications, hospital stay and mortality, recurrences and short-term survival were analyzed. ResultsMean patient age was 68 years. All patients had a T3-stage tumor and one of them N1. In 3 patients, R0 resection was performed, while R1 resection was conducted in 2. Perioperative mortality was 0%. The only complications included delayed gastric emptying and postoperative hemorrhage. There were no pancreatic fistulas. During follow-up (mean: 11.2 months), there was a relapse in the patient who had undergone R1 resection. ConclusionsThe application of radiotherapy with the Intrabeam® device in selected patients has not resulted in increased perioperative morbidity or mortality; therefore, this is a safe procedure for the treatment of resectable cancer.

Black Holes and Neutron Stars in Nearby Galaxies: Insights from NuSTAR

Abstract Nearby galaxy surveys have long classified X-ray binaries (XRBs) by the mass category of their donor stars (high-mass and low-mass). The NuSTAR observatory, which provides imaging data at E &gt; 10 keV, has enabled the classification of extragalactic XRBs by their compact object type: neutron star (NS) or black hole (BH). We analyzed NuSTAR/Chandra/XMM-Newton observations from a NuSTAR-selected sample of 12 galaxies within 5 Mpc having stellar masses (M ⋆) 107–11 M ⊙ and star formation rates (SFRs) ≈ 0.01–15 M ⊙ yr−1. We detected 128 NuSTAR sources to a sensitivity of ≈1038 erg s−1. Using NuSTAR color-intensity and color–color diagrams we classified 43 of these sources as candidate NSs and 47 as candidate BHs. We further subdivide BHs by accretion states (soft, intermediate, and hard) and NSs by weak (Z/Atoll) and strong (accreting pulsar) magnetic field. Using eight normal (Milky Way-type) galaxies in the sample, we confirm the relation between the SFR and galaxy X-ray point source luminosity in the 4–25 and 12–25 keV energy bands. We also constrained galaxy X-ray point source luminosity using the relation L X = α M ⋆ + βSFR, finding agreement with previous work. The X-ray luminosity function (XLF) of all sources in the 4–25 and 12–25 keV energy bands matches the α = 1.6 slope for high-mass XRBs. We find that NS XLFs suggest a decline beginning at the Eddington limit for a 1.4 M ⊙ NS, whereas the BH fraction shows an approximate monotonic increase in the 4–25 and 12–25 keV energy bands. We calculate the overall ratio of BH to NS to be ≈1 for 4–25 keV and ≈2 for 12–25 keV.

Deep Chandra Observations of X-Ray Point Sources in M87

Abstract We present a study of X-ray source populations in M87, the cD galaxy of the Virgo cluster, using 12 archival Chandra observations with a total exposure of ∼680 ks spanning about a decade. A total of 346 point-like sources are detected down to a limiting 0.5–8 keV luminosity of 4 × 1037 erg s−1 and out to a galactocentric radius of ∼40 kpc. We cross-correlate the X-ray sources with published catalogs of globular clusters (GCs), derived from the ACS Virgo Cluster Survey and the Next Generation Virgo Cluster Survey. This results in 122 matches, making it one of the largest samples of GC-hosting X-ray sources in an external galaxy. These sources, most likely low-mass X-ray binaries (LMXBs), correspond to ∼5% of all known GCs within the Chandra field-of-view. Conversely, ∼50% of the detected X-ray sources are found in a GC. Moreover, red (metal-rich) GCs are ∼2.2 times more likely to host an X-ray source than blue (metal-poor) GCs. We also examine 76 currently known ultra-compact dwarf galaxies around M87 but find no significant X-ray counterparts. After statistically accounting for the cosmic X-ray background, we identify ∼110 field-LMXBs. The GC-LMXBs and field-LMXBs differ in their luminosity function and radial distribution, which indicates that the latter cannot be primarily originated from GCs. Using another set of deep Chandra observations toward ∼100 kpc northwest of the M87 center, we statistically constrain the abundance of field-LMXBs in the stellar halo, which is consistent with that found in the central region. We also identify 40 variable X-ray sources, among which one source is likely a black hole binary residing in a GC.

Radioterapia intraoperatoria con Intrabeam® para el tratamiento del adenocarcinoma de páncreas resecable

IntroductionThe application of intraoperative radiation therapy to the tumor bed after resection of pancreatic cancer has been shown to be beneficial in the local control of the disease. The objective of this study was to evaluate the preliminary outcomes after the application of a single intraoperative dose to the tumor bed with a new intraoperative radiotherapy device (Intrabeam®) in terms of viability, safety and short-term results. MethodsWe studied 5 patients who underwent pancreaticoduodenectomy for resectable pancreatic cancer in which a radiotherapy boost (5Gy) was intraoperatively applied to the tumoral bed using the portable Intrabeam® device, a low-energy point-source X-ray. Postoperative complications, hospital stay and mortality, recurrences and short-term survival were analyzed. ResultsMean patient age was 68 years. All patients had a T3-stage tumor and one of them N1. In 3 patients, R0 resection was performed, while R1 resection was conducted in 2. Perioperative mortality was 0%. The only complications included delayed gastric emptying and postoperative hemorrhage. There were no pancreatic fistulas. During follow-up (mean: 11.2 months), there was a relapse in the patient who had undergone R1 resection. ConclusionsThe application of radiotherapy with the Intrabeam® device in selected patients has not resulted in increased perioperative morbidity or mortality; therefore, this is a safe procedure for the treatment of resectable cancer.

Infrared and X-ray study of the Galactic SNR G15.9+0.2

G15.9+0.2 is a Galactic shell-type supernova remnant (SNR), which was detected in radio and has been confirmed in X-rays based on Chandra observations. An X-ray point source CXOUJ181852.0-150213 has been detected and suggested to be an associated neutron star. In a recent study, we have confirmed the source to be a central compact object (CCO). We have studied the SNR using high-resolution X-ray data taken with Chandra in combination with infrared (IR) data in order to understand its emission and to derive its physical parameters. This will also help to constrain, e.g., the age of the CCO and the environment in which it was born. The spectral analysis of the X-ray emission using the new Chandra data and the comparison to the IR data have shown that the SNR is relatively young with an age of a few thousand years and that its emission is dominated by that of shocked interstellar medium (ISM). However, the analysis of the spectrum of the bright eastern shell shows that there is an additional emission component with enhanced abundances of {\alpha} elements and Fe, suggesting ejecta emission. The multi-wavelength emission is consistent with SNR G15.9+0.2 expanding in an ISM with a density gradient, while there is also colder material located in front of the SNR, which absorbs its thermal X-ray emission in the softer bands.

The XMM-SERVS survey: new XMM–Newton point-source catalogue for the XMM-LSS field

We present an X-ray point-source catalog from the XMM-Large Scale Structure survey region (XMM-LSS), one of the XMM-Spitzer Extragalactic Representative Volume Survey (XMM-SERVS) fields. We target the XMM-LSS region with $1.3$ Ms of new XMM-Newton AO-15 observations, transforming the archival X-ray coverage in this region into a 5.3 deg$^2$ contiguous field with uniform X-ray coverage totaling $2.7$ Ms of flare-filtered exposure, with a $46$ ks median PN exposure time. We provide an X-ray catalog of 5242 sources detected in the soft (0.5-2 keV), hard (2-10 keV), and/or full (0.5-10 keV) bands with a 1% expected spurious fraction determined from simulations. A total of 2381 new X-ray sources are detected compared to previous source catalogs in the same area. Our survey has flux limits of $1.7\times10^{-15}$, $1.3\times10^{-14}$, and $6.5\times10^{-15}$ erg cm$^{-2}$ s$^{-1}$ over 90% of its area in the soft, hard, and full bands, respectively, which is comparable to those of the XMM-COSMOS survey. We identify multiwavelength counterpart candidates for 99.9% of the X-ray sources, of which 93% are considered as reliable based on their matching likelihood ratios. The reliabilities of these high-likelihood-ratio counterparts are further confirmed to be $\approx 97$% reliable based on deep Chandra coverage over $\approx 5$% of the XMM-LSS region. Results of multiwavelength identifications are also included in the source catalog, along with basic optical-to-infrared photometry and spectroscopic redshifts from publicly available surveys. We compute photometric redshifts for X-ray sources in 4.5 deg$^2$ of our field where forced-aperture multi-band photometry is available; $>70$% of the X-ray sources in this subfield have either spectroscopic or high-quality photometric redshifts.

Identification of the central compact object in the young supernova remnant 1E 0102.2–7219

Oxygen-rich young supernova remnants 1 are valuable objects for probing the outcome of nucleosynthetic processes in massive stars, as well as the physics of supernova explosions. Observed within a few thousand years after the supernova explosion 2 , these systems contain fast-moving oxygen-rich and hydrogen-poor filaments visible at optical wavelengths: fragments of the progenitor’s interior expelled at a few thousand kilometres per second during the supernova explosion. Here we report the identification of the compact object in the supernova remnant 1E 0102.2–7219 in reprocessed Chandra X-ray Observatory data, enabled by the discovery of a ring-shaped structure visible primarily in optical recombination lines of Ne i and O i. The optical ring has a radius of (2.10 ± 0.35)″ ≡ (0.63 ± 0.11) pc, and is expanding at a velocity of $$90.{5}_{-30}^{+40}$$ 90 . 5 - 30 + 40 km s−1. It surrounds an X-ray point source with an intrinsic X-ray luminosity L i (1.2–2.0 keV) = (1.4 ± 0.2) × 1033 erg s−1. The energy distribution of the source indicates that this object is an isolated neutron star: a central compact object akin to those present in the Cas A3–5 and Pup A 6 supernova remnants, and the first of its kind to be identified outside of our Galaxy.

The Massive Star-forming Regions Omnibus X-ray Catalog, Second Installment

Abstract We present the second installment of the Massive Star-forming Regions (MSFRs) Omnibus X-ray Catalog (MOXC2), a compilation of X-ray point sources detected in Chandra/ACIS observations of 16 Galactic MSFRs and surrounding fields. MOXC2 includes 13 ACIS mosaics, three containing a pair of unrelated MSFRs at different distances, with a total catalog of 18,396 point sources. The MSFRs sampled range over distances of 1.3 kpc to 6 kpc and populations varying from single massive protostars to the most massive Young Massive Cluster known in the Galaxy. By carefully detecting and removing X-ray point sources down to the faintest statistically significant limit, we facilitate the study of the remaining unresolved X-ray emission. Through comparison with mid-infrared images that trace photon-dominated regions and ionization fronts, we see that the unresolved X-ray emission is due primarily to hot plasmas threading these MSFRs, the result of feedback from the winds and supernovae of massive stars. The 16 MSFRs studied in MOXC2 more than double the MOXC1 sample, broadening the parameter space of ACIS MSFR explorations and expanding Chandra's substantial contribution to contemporary star formation science.

An Ultradeep Chandra Catalog of X-Ray Point Sources in the Galactic Center Star Cluster

Abstract We present an updated catalog of X-ray point sources in the inner 500″ (∼20 pc) of the Galactic center (GC), where the nuclear star cluster (NSC) stands, based on a total of ∼4.5 Ms of Chandra observations taken from 1999 September to 2013 April. This ultradeep data set offers unprecedented sensitivity for detecting X-ray sources in the GC, down to an intrinsic 2–10 keV luminosity of 1.0 × 1031 erg s−1. A total of 3619 sources are detected in the 2–8 keV band, among which ∼3500 are probable GC sources and ∼1300 are new identifications. The GC sources collectively account for ∼20% of the total 2–8 keV flux from the inner 250″ region where detection sensitivity is the greatest. Taking advantage of this unprecedented sample of faint X-ray sources that primarily traces the old stellar populations in the NSC, we revisit global source properties, including long-term variability, cumulative spectra, luminosity function, and spatial distribution. Based on the equivalent width and relative strength of the iron lines, we suggest that in addition to the arguably predominant population of magnetic cataclysmic variables (CVs), nonmagnetic CVs contribute substantially to the detected sources, especially in the lower-luminosity group. On the other hand, the X-ray sources have a radial distribution closely following the stellar mass distribution in the NSC, but much flatter than that of the known X-ray transients, which are presumably low-mass X-ray binaries (LMXBs) caught in outburst. This, together with the very modest long-term variability of the detected sources, strongly suggests that quiescent LMXBs are a minor (less than a few percent) population.

The Second Nucleus of NGC 7727: Direct Evidence for the Formation and Evolution of an Ultracompact Dwarf Galaxy*

Abstract We present new observations of the late-stage merger galaxy NGC 7727, including Hubble Space Telescope/WFPC2 images and long-slit spectra obtained with the Clay telescope. NGC 7727 is relatively luminous ( = −21.7) and features two unequal tidal tails, various bluish arcs and star clusters, and two bright nuclei 480 pc apart in projection. These two nuclei have nearly identical redshifts, yet are strikingly different. The primary nucleus, hereafter Nucleus 1, fits smoothly into the central luminosity profile of the galaxy and appears—at various wavelengths—“red and dead.” In contrast, Nucleus 2 is very compact, has a tidal radius of 103 pc, and exhibits three signs of recent activity: a post-starburst spectrum, an [O iii] emission line, and a central X-ray point source. Its emission-line ratios place it among Seyfert nuclei. A comparison of Nucleus 2 ( = −15.5) with ultracompact dwarf galaxies (UCDs) suggests that it may be the best case yet for a massive UCD having formed through tidal stripping of a gas-rich disk galaxy. Evidence for this comes from its extended star formation history, long blue tidal stream, and elevated dynamical-to-stellar-mass ratio. While the majority of its stars formed ago, ∼1/3 formed during starbursts in the past 2 Gyr. Its weak active galactic nucleus activity is likely driven by a black hole of mass . We estimate that the former companion’s initial mass was less than half that of then NGC 7727, implying a minor merger. By now this former companion has been largely shredded, leaving behind Nucleus 2 as a freshly minted UCD that probably moves on a highly eccentric orbit.

NuSTAR view of the central region of M31

Our neighbouring large spiral galaxy, the Andromeda galaxy (M 31 or NGC 224), is an ideal target to study the X-ray source population of a nearby galaxy. NuSTAR observed the central region of M 31 in 2015 and allows studying the population of X-ray point sources at energies higher than 10 keV. Based on the source catalogue of the large XMM-Newton survey of M 31, we identified counterparts to the XMM-Newton sources in the NuSTAR data. The NuSTAR data only contain sources of a brightness comparable (or even brighter) than the selected sources that have been detected in XMM-Newton data. We investigate hardness ratios, spectra and long-term light curves of individual sources obtained from NuSTAR data. Based on our spectral studies we suggest four sources as possible X-ray binary candidates. The long-term light curves of seven sources that have been observed more than once show low (but significant) variability.

X-ray reflection from cold white dwarfs in magnetic cataclysmic variables

We model X-ray reflection from white dwarfs (WD) in magnetic cataclysmic variables (mCVs) with a Monte Carlo simulation. A point source with a power-law spectrum or a realistic post-shock accretion column (PSAC) source irradiates a cool and spherical WD. The PSAC source emits thermal spectra of various temperatures stratified along the column according to the PSAC model. In the point source simulation, we confirm (1) a source harder and nearer to the WD enhances the reflection, (2) higher iron abundance enhances the equivalent widths (EWs) of fluorescent iron K${\alpha}_{1,2}$ lines and their Compton shoulder, and increases cut-off energy of a Compton hump, and (3) significant reflection appears from an area that is more than 90 deg apart from the position right under the point X-ray source because of the WD curvature. The PSAC simulation reveals that (1) a more massive WD basically enhances the intensities of the fluorescent iron K${\alpha}_{1,2}$ lines and the Compton hump, except for some specific accretion rate, because the more massive WD makes the hotter PSAC from which higher energy X-rays are preferentially emitted, (2) a larger specific accretion rate monotonically enhances the reflection because it makes the hotter and shorter PSAC, and (3) the intrinsic thermal component hardens by occultation of the cool base of the PSAC by the WD. We quantitatively evaluate influences of the parameters on the EWs and the Compton hump with both types of sources. We also calculate X-ray modulation profiles brought about by the WD spin. They depend on angles of the spin axis from the line of sight and from the PSAC, and whether the two PSACs can be seen. The reflection spectral model and the modulation model involve the fluorescent lines and the Compton hump and can directly be compared to the data which allow us to evaluate these geometrical parameters with unprecedented accuracy.

On the Spatially Resolved Star Formation History in M51. II. X-Ray Binary Population Evolution

Abstract We present a new technique for empirically calibrating how the X-ray luminosity function (XLF) of X-ray binary (XRB) populations evolves following a star formation event. We first utilize detailed stellar population synthesis modeling of far-UV-to-far-IR photometry of the nearby face-on spiral galaxy M51 to construct maps of the star formation histories (SFHs) on subgalactic (≈400 pc) scales. Next, we use the ≈850 ks cumulative Chandra exposure of M51 to identify and isolate 2–7 keV detected point sources within the galaxy, and we use our SFH maps to recover the local properties of the stellar populations in which each X-ray source is located. We then divide the galaxy into various subregions based on their SFH properties (e.g., star formation rate (SFR) per stellar mass and mass-weighted stellar age) and group the X-ray point sources according to the characteristics of the regions in which they are found. Finally, we construct and fit a parameterized XLF model that quantifies how the XLF shape and normalization evolves as a function of the XRB population age Our best-fit model indicates that the XRB XLF per unit stellar mass declines in normalization, by ∼3–3.5 dex, and steepens in slope from ≈10 Myr to ≈10 Gyr. We find that our technique recovers results from past studies of how XRB XLFs and XRB luminosity scaling relations vary with age and provides a self-consistent picture for how XRB XLFs evolve with age.

Study of X-ray point sources in NGC 5643 and NGC 7457 with Chandra

In the present study we have analysed Chandra Observational data of 2 galaxies: NGC 5643 and NGC 7457. Four point sources from NGC 5643 and two point sources from NGC 7457 with net counts ${\ge} 100$ were considered for the present study. The spectra of these sources were fitted using two spectral models- an absorbed powerlaw and an absorbed disk blackbody. The spectrum of all the sources can be explained almost equally by both the models. We report here the discovery of 3 Ultraluminous X-ray sources (ULXs), X-1, X-2 and X-3 in the galaxy NGC 5643 and one ULX, X-5 in the galaxy NGC 7457. The spectral parameters suggest that all the above four ULX sources are in hard state ( $\varGamma \sim 1.42\mbox{--}1.86$ ), which may be due to thermal comptonization. If explained by absorbed diskblackbody model, the Black Hole (BH) mass of these sources are estimated to be stellar mass BHs with X-2, & X-5 accreting at super-Eddington rate while X-1 and X-3 at sub-Eddington rate. Another ULX, X-4 in NGC 5643 which is also accreting at super-Eddington rate is found to be a variable ULX with its luminosity reducing from $4.4 \times 10^{40}~\mbox{ergs}\,\mbox{s}^{-1}$ to $2.27 \times 10^{40}~\mbox{ergs}\,\mbox{s}^{-1} $ in the 0.3–10.0 keV energy range within a period of 11 years.

Efficient picosecond x-ray pulse generation from plasmas in the radiation dominated regime

The efficient conversion of optical laser light into bright ultrafast x-ray pulses in laser created plasmas is of high interest for dense plasma physics studies, material science, and other fields. However, the rapid hydrodynamic expansion that cools hot plasmas has limited the x-ray conversion efficiency (CE) to 1% or less. Here we demonstrate more than one order of magnitude increase in picosecond x-ray CE by tailoring near solid density plasmas to achieve a large radiative to hydrodynamic energy loss rate ratio, leading into a radiation loss dominated plasma regime. A record 20% CE into hν>1 keV photons was measured in arrays of large aspect ratio Au nanowires heated to keV temperatures with ultrahigh contrast femtosecond laser pulses of relativistic intensity. The potential of these bright ultrafast x-ray point sources for table-top imaging is illustrated with single shot flash radiographs obtained using low laser pulse energy. These results will enable the deployment of brighter laser driven x-ray sources at both compact and large laser facilities.

A Deep Chandra X-Ray Study of Neutron Star Coalescence GW170817

Abstract We report Chandra observations of GW170817, the first neutron star–neutron star merger discovered by the joint LIGO-Virgo Collaboration, and the first direct detection of gravitational radiation associated with an electromagnetic counterpart, Fermi short γ-ray burst GRB 170817A. The event occurred on 2017 August 17 and subsequent observations identified an optical counterpart, SSS17a, coincident with NGC 4993 (∼10″ separation). Early Chandra ( days) and Swift ( days) observations yielded non-detections at the optical position, but ∼9 days post-trigger Chandra monitoring revealed an X-ray point source coincident with SSS17a. We present two deep Chandra observations totaling ∼95 ks, collected on 2017 September 01–02 ( days). We detect X-ray emission from SSS17a with erg s−1, and a power law spectrum of . We find that the X-ray light curve from a binary NS coalescence associated with this source is consistent with the afterglow from an off-axis short γ-ray burst, with a jet angled ≳23° from the line of sight. This event marks both the first electromagnetic counterpart to a LIGO-Virgo gravitational-wave source and the first identification of an off-axis short GRB. We also confirm extended X-ray emission from NGC 4993 ( erg s−1) consistent with its E/S0 galaxy classification, and report two new Chandra point sources in this field, CXOU J130948 and CXOU J130946.