Multiwavelength Spectral Analysis Research Articles

Multi-wavelength spectroscopic analysis of the ULX Holmberg II X-1 and its nebula suggests the presence of a heavy black hole accreting from a B-type donor

Ultra-luminous X-ray sources (ULXs) are high-mass X-ray binaries with an X-ray luminosity above $10^ $. These ULXs can be powered by black holes that are more massive than $20M_ accreting in a standard regime, or lighter compact objects accreting supercritically. There are only a few ULXs with known optical or ultraviolet (UV) counterparts, and their nature is debated. Determining whether optical/UV radiation is produced by the donor star or by the accretion disc is crucial for understanding ULX physics and testing massive binary evolution. We conduct, for the first time, a fully consistent multi-wavelength spectral analysis of a ULX and its circumstellar nebula. We aim to establish the donor star type and test the presence of strong disc winds in the prototypical ULX Holmberg\,II X-1 ( Furthermore, we aim to obtain a realistic spectral energy distribution of the ionising source, which is needed for robust nebula analysis. We acquired new UV spectra of with the Hubble Space Telescope ( ) and complemented them with archival optical and X-ray data. We explored the spectral energy distribution of the source and analysed the spectra using the stellar atmosphere code and the photoionisation code Our analysis of the X-ray, UV, and optical spectra of and its nebula consistently explains the observations. We do not find traces of disc wind signatures in the UV and the optical, rejecting previous claims of the ULX being a supercritical accretor. The optical/UV counterpart of is explained by a B-type supergiant donor star. Thus, the observations are fully compatible with being a close binary consisting of an $ 66\,M_ black hole accreting matter from an $ 22\,M_ B-supergiant companion. Furthermore, we propose a possible evolution scenario for the system, suggesting that is a potential gravitational wave source progenitor.

A Multiwavelength Study of the Hard and Soft States of MAXI J1820+070 During Its 2018 Outburst

We present a comprehensive multiwavelength spectral analysis of the black hole (BH) X-ray binary MAXI J1820+070 during its 2018 outburst, utilizing AstroSat far-UV, soft X-ray, and hard X-ray data, along with (quasi-)simultaneous optical and X-ray data from the Las Cumbres Observatory and NICER, respectively. In the soft state, we detect soft X-ray and UV/optical excess components over and above the intrinsic accretion disk emission (kT in ∼ 0.58 keV) and a steep X-ray power-law component. The soft X-ray excess is consistent with a high-temperature blackbody (kT ∼ 0.79 keV), while the UV/optical excess is described by UV emission lines and two low-temperature blackbody components (kT ∼ 3.87 and ∼0.75 eV). Employing continuum spectral fitting, we determine the BH spin parameter (a = 0.77 ± 0.21), using the jet inclination angle of 64° ± 5° and a mass spanning 5–10 M ☉. In the hard state (HS), we observe a significantly enhanced optical/UV excess component, indicating a stronger reprocessed emission in the outer disk. Broadband X-ray spectroscopy in the HS reveals a two-component corona, each associated with its reflection component, in addition to the disk emission (kT in ∼ 0.19 keV). The softer coronal component dominates the bolometric X-ray luminosity and produces broader relativistic reflection features, while the harder component gets reflected far from the inner disk, yielding narrow reflection features. Furthermore, our analysis in the HS suggests a substantial truncation of the inner disk (≳51 gravitational radii) and a high disk density (∼1020 cm−3).

Likely optical counterpart of the cool middle-aged pulsar J1957+5033

ABSTRACT The 840-kyr-old pulsar PSR J1957+5033, detected so far only in γ- and X-rays, is a nearby and rather cool neutron star with a temperature of 0.2–0.3 MK, a distance of $\lesssim 1$kpc, and a small colour reddening excess E(B − V) ≈ 0.03. These properties make it an ideal candidate to detect in the optical to get additional constraints on its parameters. We thus performed the first deep optical observations of the pulsar with the 10.4 m Gran Telescopio Canarias in the g′ band and found its possible counterpart with g′ = 27.63 ± 0.26. The counterpart candidate position is consistent with the X-ray coordinates of the pulsar within the 0.5 arcsec accuracy. Assuming that this is the real counterpart, we analysed the pulsar X-ray spectrum together with the derived optical flux density. As a result, we found that the thermal emission from the bulk surface of the cooling neutron star can significantly contribute to its optical flux. Our multiwavelength spectral analysis favours the pulsar nature of the detected optical source, since it provides physically adequate parameters of the pulsar emission. We show that the optical data can provide new constraints on the pulsar temperature and distance.

Multiwavelength Spectral Analysis and Neural Network Classification of Counterparts to 4FGL Unassociated Sources

Abstract The Fermi-LAT unassociated sources represent some of the most enigmatic gamma-ray sources in the sky. Observations with the Swift-XRT and -UVOT telescopes have identified hundreds of likely X-ray and UV/optical counterparts in the uncertainty ellipses of the unassociated sources. In this work we present spectral fitting results for 205 possible X-ray/UV/optical counterparts to 4FGL unassociated targets. Assuming that the unassociated sources contain mostly pulsars and blazars, we develop a neural network classifier approach that applies gamma-ray, X-ray, and UV/optical spectral parameters to yield a descriptive classification of unassociated spectra into pulsars and blazars. From our primary sample of 174 Fermi sources with a single X-ray/UV/optical counterpart, we present 132 P bzr > 0.99 likely blazars and 14 P bzr < 0.01 likely pulsars, with 28 remaining ambiguous. These subsets of the unassociated sources suggest a systematic expansion to catalogs of gamma-ray pulsars and blazars. Compared to previous classification approaches our neural network classifier achieves significantly higher validation accuracy and returns more bifurcated P bzr values, suggesting that multiwavelength analysis is a valuable tool for confident classification of Fermi unassociated sources.

Non-invasive cell counting of adherent, suspended and encapsulated mammalian cells using optical density.

In situ measurement to determine mammalian cell number in a non-invasive, non-destructive and reagent-free manner is needed to enable continuous cell manufacturing. An analytical method is presented for non-invasive cell counting by conducting multiwavelength spectral analysis of mammalian cells achieving a minimal detectable cell count of 62,500 at 295 nm. Light absorbance was insensitive to culture volume, giving an absolute cell count rather than a concentration. The activation state of cells was also considered. The study was extended to quantification within polymeric microcapsules as an advanced substrate for mammalian cell growth in bioreactor formats and resulted in an offset directly correlating with the absorbance maxima of the polymer. These studies provide feasibility for optical density as a simple end point to indirectly quantify mammalian cell number for continuous monitoring of cell cultures.

Multi-wavelength Spectral Analysis of Ellerman Bombs Observed by FISS and IRIS

Abstract Ellerman bombs (EBs) are a kind of solar activity that is suggested to occur in the lower solar atmosphere. Recent observations using the Interface Region Imaging Spectrograph (IRIS) show connections between EBs and IRIS bombs (IBs), which imply that EBs might be heated to a much higher temperature (8 × 104 K) than previous results. Here we perform a spectral analysis of EBs simultaneously observed by the Fast Imaging Solar Spectrograph and IRIS. The observational results show clear evidence of heating in the lower atmosphere, indicated by the wing enhancement in Hα, Ca ii 8542 Å, and Mg ii triplet lines and also by brightenings in images of the 1700 Å and 2832 Å ultraviolet continuum channels. Additionally, the intensity of the Mg ii triplet line is correlated with that of Hα when an EB occurs, suggesting the possibility of using the triplet as an alternative way to identify EBs. However, we do not find any signal in IRIS hotter lines (C ii and Si iv). For further analysis, we employ a two-cloud model to fit the two chromospheric lines (Hα and Ca ii 8542 Å) simultaneously, and obtain a temperature enhancement of 2300 K for a strong EB. This temperature is among the highest of previous modeling results, albeit still insufficient to produce IB signatures at ultraviolet wavelengths.

BARYON LOADING EFFICIENCY AND PARTICLE ACCELERATION EFFICIENCY OF RELATIVISTIC JETS: CASES FOR LOW LUMINOSITY BL LACS

ABSTRACT Relativistic jets launched by supermassive black holes, so-called active galactic nuclei (AGNs), are known as the most energetic particle accelerators in the universe. However, the baryon loading efficiency onto the jets from the accretion flows and their particle acceleration efficiencies have been veiled in mystery. With the latest data sets, we perform multi-wavelength spectral analysis of quiescent spectra of 13 TeV gamma-ray detected high-frequency-peaked BL Lacs (HBLs) following one-zone static synchrotron self-Compton (SSC) model. We determine the minimum, cooling break, and maximum electron Lorentz factors following the diffusive shock acceleration (DSA) theory. We find that HBLs have and the radiative efficiency , where P B and P e is the Poynting and electron power, respectively. By assuming 10 leptons per one proton, the jet power relates to the black hole mass as , where and is the jet power and the Eddington luminosity, respectively. Under our model assumptions, we further find that HBLs have a jet production efficiency of and a mass loading efficiency of . We also investigate the particle acceleration efficiency in the blazar zone by including the most recent Swift/BAT data. Our samples ubiquitously have particle acceleration efficiencies of , which is inefficient to accelerate particles up to the ultra-high-energy-cosmic-ray (UHECR) regime. This implies that the UHECR acceleration sites should not be the blazar zones of quiescent low power AGN jets, if one assumes the one-zone SSC model based on the DSA theory.

Science with the VO: Spectroscopic Studies of Herbig Ae/Be Stars

Abstract The Virtual Observatory (VO) is opening up new ways of exploiting the huge amount of data provided by the ever growing number of ground-based and space facilities. Using VOSpec, a multi-wavelength spectral analysis tool developed by the ESA-VO Team at ESAC, and new developments on scripting with VOSpec (VOScript), we have started to undertake a comprehensive study of spectroscopic and photometric data in the VO on Herbig Ae/Be stars. By studying line strengths, variabilities and spectral energy distributions, from the X-ray to sub-millimeter ranges, we aim to gain insights into processes and disk properties of a large sample of these objects. This paper presents initial findings of the spectroscopic analysis and initial spectral energy distribution classifications.

LOOKING INTO THE FIREBALL: ROTSE-III ANDSWIFTOBSERVATIONS OF EARLY GAMMA-RAY BURST AFTERGLOWS

We report on a complete set of early optical afterglows of gamma-ray bursts (GRBs) obtained with the Robotic Optical Transient Search Experiment (ROTSE-III) telescope network from 2005 March through 2007 June. This set is comprised of 12 afterglows with early optical and Swift/X-Ray Telescope observations, with a median ROTSE-III response time of 45 s after the start of γ-ray emission (8 s after the GCN notice time). These afterglows span 4 orders of magnitude in optical luminosity, and the contemporaneous X-ray detections allow multi-wavelength spectral analysis. Excluding X-ray flares, the broadband synchrotron spectra show that the optical and X-ray emission originate in a common region, consistent with predictions of the external forward shock in the fireball model. However, the fireball model is inadequate to predict the temporal decay indices of the early afterglows, even after accounting for possible long-duration continuous energy injection. We find that the optical afterglow is a clean tracer of the forward shock, and we use the peak time of the forward shock to estimate the initial bulk Lorentz factor of the GRB outflow, and find 100 ≲ Γ_0 ≲ 1000, consistent with expectations.

Observation of an Extended Very High Energy Gamma‐Ray Emission from MSH 15‐52 with CANGAROO‐III

We have observed the supernova remnant MSH 15-52 (G320.4-1.2), which contains the gamma-ray pulsar PSR B1509–58, using the CANGAROO-III imaging atmospheric Cerenkov telescope array from 2006 April to June. We detected gamma rays above 810 GeV at the 7 σ level during a total effective exposure of 48.4 hr. We obtained a differential gamma-ray flux at 2.35 TeV of (7.9 ± 1.5stat± 1.7sys) × 10−13 cm−2 s−1 TeV−1, with a photon index of 2.21 ± 0.39stat± 0.40sys, which is compatible with that of the H.E.S.S. observation in 2004. The morphology shows extended emission compared to our point spread function. We consider the plausible origin of the high-energy emission based on a multiwavelength spectral analysis and energetics arguments.

42 Protective Effects of Galacto- and Fructoolico-Saccharides on Neonatal Jaundice

Background: Neonatal hypebilirubinaemia occurs in approximately 8% to 20% of healthy, full-term newborn infants. Several mechanisms are implicated in pathogenesis of jaundice: decreased hepatic clearance, large hemoglobin mass degradation, and intestinal reabsorption. Reduction of bilirubin to urobilinoiods by the intestinal microbial flora may be enhanced by modification of intestinal microflora.Aim: To examine whether supplementing formula with oligosaccharide mixture may modulate bilirubin total (BT) levels in formula fed infants during the first weeks of life.Methods: Fifty healthy full-term infants born at the maternity ward of San Giovanni di Dio Hospital, Crotone, Italy, and formula fed from birth participated in the study. Written parental consent was obtained. Infants were double blind randomly allocated into two groups to receive either supplementation of oligosacharides mixture (galactooligosaccharides [gos-fos], derived from lactose, and long-chain fructooligosaccharides, derived from chicory) at the dosage of 0.8 g/100ml (n=27) or placebo (maltodexrine) (n=23), from birth through the first 28 days of life. BT level was determined by multiwavelength spectral analysis, using a portable BiliCheck device (SpectRx Inc, Norcross, GA), clinically equivalent to measurement of total serum bilirubin (transcutaneous bilirubin, TcB) within 2 hours after birth (T0), at 24, 48, 72 h and at completed 5, 7, 10, 28 (T8) days of life. Hematocrit (HT) was further determined by conventional methodsResults: Groups were comparable for birth weight, gestational age, maternal age, type of delivery, baseline (T0) plasma TcB level (mean [SD; range], gos-fos 3.0 [0.7; 2.1–4.8] vs. placebo 3.0 [0.8; 1.6–5.0] mg/dl, and HT level. Pattern of TcB significantly differed between groups through the study (P<0.01; Anova for repeated measures). Infants in supplemented group exhibited lower plasma TcB levels than placebo group from 72 h of life onwards (0.01<P<0.02). At T8, mean [SD; range] TcB level was 2.4 [0.5; 1.1–3.6] mg/dl (gos-fos) vs. 2.8 [0.4; 1.8–3.8] mg/dl (placebo). HT significantly decreased from birth to day 28 in both groups (P<0.0001) but no difference between groups was found (P>0.55).Conclusions: In formula fed infants, supplementation of a mixture of gos-fos significantly lowers bilirubin level after 72 hours of life. It may be hypothesize that stimulating the intestinal growth of bifidobacteria and lactobacilli enhances bilirubin excretion by reducing it to urobilinoids. Larger randomized trials would be of interest to evaluate prophylactic and therapeutic use of gos-fos in neonatal hyperbilirubinaemia.