Region of Excessive Flux of PeV Cosmic Rays in the Direction Toward Pulsars PSR J1840+5640 and LAT PSR J1836+5925
G. V. Kulikov, M. Yu. Zotov
备注：
14 pages; v.2: a few remarks to match a version accepted for Astronomy Letters added. They can be found by redefining the \NEW command in the preamble of the LaTeX file
An analysis of arrival directions of extensive air showers (EAS) registered with the EAS MSU and EAS-1000 prototype arrays has revealed a region of excessive flux of PeV cosmic rays in the direction toward pulsars PSR J1840+5640 and LAT PSR J1836+5925 at significance level up to 4.5sigma. The first of the pulsars was discovered almost 30 years ago and is a well-studied old radio pulsar located at the distance of 1.7pc from the Solar system. The second pulsar belongs to a new type of pulsars, discovered by the space gamma-ray observatory Fermi, pulsations of which are not observed in optical and radio wavelengths but only in the gamma-ray range of energies (gamma-ray-only pulsars). In our opinion, the existence of the region of excessive flux of cosmic rays registered with two different arrays provides a strong evidence that isolated pulsars can give a noticeable contribution to the flux of Galactic cosmic rays in the PeV energy range.
We report a discovery of diffuse X-ray emission around the supernova remnant (SNR) G106.3+2.7, which is associated with VER J2227+608 and HAWC J2227+610 and is known as a candidate for a PeV cosmic ray accelerator (PeVatron). We analyze observational data of Suzaku around the SNR and the adjacent pulsar PSR J2229+6114. We find diffuse X-ray emission that is represented by either thermal or non-thermal one. However, the metal abundance for the thermal emission is <0.13 Z_sun, which may be too small in the Milky Way and suggests that the emission is non-thermal. The intensity of the diffuse emis…
HAWC J1826-128 is one of the brightest Galactic TeV gamma-ray sources detected by the High Altitude Water Cherenkov (HAWC) Observatory, with photon energies extending up to nearly $\sim$100 TeV. This HAWC source spatially coincides with the H.E.S.S. TeV source HESS J1826-130 and the "Eel" pulsar wind nebula (PWN), which is associated with the GeV pulsar PSR J1826-1256. In the X-ray band, Chandra and XMM-Newton revealed that the Eel PWN is composed of both a compact nebula ($\sim$15") and diffuse X-ray emission ($\sim$6'$\times$2') extending away from the pulsar. Our NuSTAR observation detected…
HAWC J0630+186 Could Not Be Powered by PSR J0630+19
National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；Kavli Institute for Astronomy and Astrophysics, Peking University（北京大学科维理天文与天体物理研究所）
The candidate PeVatron MGRO J1908+06, which shows a hard spectrum beyond 100 TeV, is one of the most peculiar $γ$-ray sources in the Galactic plane. Its complex morphology and some possible counterparts spatially related with the VHE emission region, preclude to distinguish between a hadronic or leptonic nature of the $γ$-ray emission. In this paper we illustrate a new multiwavelength analysis of MGRO J1908+06, with the aim to shed light on its nature and the origin of its ultra high-energy emission. We performed an analysis of the $^{12}$CO and $^{13}$CO molecular line emission demonstrating …
We report on broadband X-ray properties of the Rabbit pulsar wind nebula (PWN) associated with the pulsar PSR J1418-6058 using archival Chandra and XMM-Newton data, and a new NuSTAR observation. NuSTAR data above 10 keV allowed us to detect the 110-ms spin period of the pulsar, characterize its hard X-ray pulse profile, and resolve hard X-ray emission from the PWN after removing contamination from the pulsar and other overlapping point sources. The extended PWN was detected up to $\sim$20 keV and is well described by a power-law model with a photon index $Γ\approx$2. The PWN shape does not var…
The existence of a "knee" at energy ~1 PeV in the cosmic-ray spectrum suggests the presence of Galactic PeV proton accelerators called "PeVatrons". Supernova Remnant (SNR) G106.3+2.7 is a prime candidate for one of these. The recent detection of very high energy (0.1-100 TeV) gamma rays from G106.3+2.7 may be explained either by the decay of neutral pions or inverse Compton scattering by relativistic electrons. We report an analysis of 12 years of Fermi-LAT gamma-ray data which shows that the GeV-TeV gamma-ray spectrum is much harder and requires a different total electron energy than the radi…
Tibet AS-gamma collaboration has recently reported detection of gamma-rays with energies up to Peta-electronvolt from parts of the Galactic plane. We notice that the analysis of gamma-ray flux by the Tibet AS-gamma experiment also implies an upper bound on the diffuse gamma-ray flux from high Galactic latitudes(|b|>20 degrees) in the energy range between 100 TeV and 1 PeV. This bound is up to an order-of-magnitude stronger than previously derived bounds from GRAPES3, KASCADE and CASA-MIA experiments. We discuss the new TibetAS-gamma limit on high Galactic latitude gamma-ray flux in the context…
We present a detailed analysis of broadband X-ray observations of the pulsar PSR J1420-6048 and its wind nebula (PWN) in the Kookaburra region with Chandra, XMM-Newton, and NuSTAR. Using the archival XMM-Newton and new NuSTAR data, we detected 68 ms pulsations of the pulsar and characterized its X-ray pulse profile which exhibits a sharp spike and a broad bump separated by ~0.5 in phase. A high-resolution Chandra image revealed a complex morphology of the PWN: a torus-jet structure, a few knots around the torus, one long (~7') and two short tails extending in the northwest direction, and a bri…
We report the detection of the pulsed signal of the radio-quiet magnetar-like pulsar PSR J1846-0258 in the high-energy \gr-ray data of the Fermi Large Area Telescope (Fermi LAT). We produced phase-coherent timing models exploiting RXTE PCA and Swift XRT monitoring data for the post- (magnetar-like) outburst period from 2007 August 28 to 2016 September 4, with independent verification using INTEGRAL ISGRI and Fermi GBM data. Phase-folding barycentric arrival times of selected Fermi LAT events from PSR J1846-0258, resulted in a 4.2 sigma detection (30--100 MeV) of a broad pulse consistent in sha…
We consider the newly found high mass and low magnetic field binary pulsar PSR J1614-2230 in a model in which magnetars owe their strong magnetic fields to a high baryon density, magnetized core. In our magnetar model all neutron stars above a certain threhold mass are magnetars. This confronts us with the very basic paradox as to why this high mass star, PSR J1614-2230, remains a pulsar and shows no magnetar characteristics. This is a star that has acquired its large mass by accretion from its binary companion over 5 gigayears. In this work we show that the maximum rate of energy gain from th…
New Hard X-Ray and Multiwavelength Study of the PeVatron Candidate PWN G0.9+0.1 in the Galactic Center Region
Università di Bologna（博洛尼亚大学）；INAF - Osservatorio di Astrofisica e Scienza dello spazio di Bologna（意大利国家天体物理研究所博洛尼亚天文与空间科学观测站）；Department of Astronomy and Space Science, Chungbuk National University（忠北国立大学天文与空间科学系）；NASA Goddard Space Flight Center（美国宇航局戈达德太空飞行中心）；New York University Abu Dhabi（阿布扎比纽约大学）；Kavli Institute For Astrophysics and Space Research, Massachusetts Institute of Technology（麻省理工学院卡弗里天体物理学与空间研究研究所）；Department of Physics, University of Tokyo（东京大学物理学系）
PSR B1259-63 is a $γ$-ray binary system, where the compact object is a pulsar. The system has an orbital period of 1236.7 days and shows peculiar $γ$-ray flares (in 100\,MeV--300\,GeV) after its periastron time. We analyzed the \textit{Fermi}-LAT observation of PSR B1259-63 during its latest periastron passage, as well as its previous three periastrons. The bright GeV flares started about 60 days after the periastron epoch in 2021. This delay is larger than that around the 2017 periastron and much larger than earlier periastrons. The delay of the GeV flux peak time in each periastron passage i…
Considering about seven years of Fermi-Large Area Telescope (LAT) data, we present a systematic search for variability possibly related to transitions between states in redbacks and black widow systems. Transitions are characterized by sudden and significant changes in the gamma-ray flux that persist on a timescale much larger than the orbital period. This phenomenology was already detected in the case of two redback systems, PSR J1023+0038 and PSR J1227-4853, for which we present here a dedicated study. We show the existence of only one transition for each of these systems over the past seven…
Cosmic rays (protons and other atomic nuclei) are believed to gain energies of petaelectronvolts (PeV) and beyond at astrophysical particle accelerators called 'PeVatrons' inside our Galaxy. Although a characteristic feature of a PeVatron is expected to be a hard gamma-ray energy spectrum that extends beyond 100 teraelectronvolts (TeV) without a cutoff, none of the currently known sources exhibits such a spectrum due to the low maximum energy of accelerated cosmic rays or insufficient detector sensitivity around 100 TeV. Here we report the observation of gamma-ray emission from the supernova r…
The Fermi Large Area Telescope (LAT) data have confirmed the pulsed emission from all six high-confidence gamma-ray pulsars previously known from the EGRET observations. We report results obtained from the analysis of 13 months of LAT data for three of these pulsars (PSR J1057-5226, PSR J1709-4429, and PSR J1952+3252) each of which had some unique feature among the EGRET pulsars. The excellent sensitivity of LAT allows more detailed analysis of the evolution of the pulse profile with energy and also of the variation of the spectral shape with phase. We measure the cutoff energy of the pulsed e…
Starburst galaxies represent one of the most plausible origins of the cosmic high-energy neutrino flux recently discovered by IceCube. At $\sim$ PeV energies, the neutrino flux from starburst galaxies is expected to exhibit a characteristic spectral break due to cosmic-rays escaping the galaxy. We examine the 'smearing' of this spectral break by a population of starburst galaxies with varying properties. We incorporate galaxy distribution w.r.t. star-formation rate and redshift. Our results (i) show characteristic spectral softening in IceCube's energy band; (ii) resolve the conflicting observ…
Tibet-AS$γ$ collaboration has recently reported a measurement of diffuse $γ$-ray flux from the outer Galactic disk in the energy range reaching PeV. We complement this measurement with the Fermi/LAT measurement of the diffuse flux from the same sky region and study the pion decay model of the combined Fermi/LAT+Tibet-AS$γ$ spectrum. We find that within such a model the average cosmic ray spectrum in the outer Galactic disk has the same characteristic features as the local cosmic ray spectrum. In particular, it experiences a hardening at several hundred GV rigidity and a knee feature in the PV …
Institutt for fysikk, NTNU, Trondheim, Norway（挪威特隆赫姆挪威科技大学物理系）；Department of Physics, School of Natural Sciences, Technical University Munich, Germany（德国慕尼黑工业大学自然科学学院物理系）
PSR B1259-63/LS 2883 is a gamma-ray binary system containing a radio pulsar in a highly elliptical ~3.4-year orbit around a Be star. In its 2010 periastron passage, multiwavelength emission from radio to TeV was observed, as well as an unexpected GeV flare measured by the Fermi Large Area Telescope (LAT). Here, we report the results of LAT monitoring of PSR B1259-63 during its most recent 2014 periastron passage. We compare the gamma-ray behavior in this periastron with the former in 2010 and find that PSR B1259-63 shows a recurrent GeV flare. The similarities and differences in the phenomenol…
There are only few very-high-energy sources in our Galaxy which might accelerate particles up to the knee of the cosmic-ray spectrum. To understand the mechanisms of particle acceleration in these PeVatron candidates, \textit{Fermi}-LAT and H.E.S.S. observations are essential to characterize their $γ$-ray emission. HESS J1640$-$465 and the PeVatron candidate HESS J1641$-$463 are two neighboring (\ang[astroang]{0.25}) $γ$-ray sources, spatially coincident with the radio supernova remnants (SNRs) G338.3$-$0.0 and G338.5+0.1. Detected both by H.E.S.S. and \textit{Fermi}-LAT, we present here a mor…
The IceCube collaboration has reported neutrinos with energies between ~30 TeV and a few PeV that are significantly enhanced over the cosmic-ray induced atmospheric background. Viable high-energy neutrino sources must contain very high-energy and ultra-high energy cosmic rays while efficiently making PeV neutrinos. Gamma-ray Bursts (GRBs) and blazars have been considered as candidate cosmic-ray accelerators. GRBs, including low-luminosity GRBs, can be efficient PeV neutrino emitters for low bulk Lorentz factor outflows, although the photopion production efficiency needs to be tuned to simultan…
Blazars are potential candidates of cosmic-ray acceleration up to ultrahigh energies ($E\gtrsim10^{18}$ eV). For an efficient cosmic-ray injection from blazars, $pγ$ collisions with the extragalactic background light (EBL) and cosmic microwave background (CMB) can produce neutrino spectrum peaks near PeV and EeV energies, respectively. We analyze the contribution of these neutrinos to the diffuse background measured by the IceCube neutrino observatory. The fraction of neutrino luminosity originating from individual redshift ranges is calculated using the distribution of BL Lacs and FSRQs provi…
In this research, the simulation of lateral distribution function (LDF) of Cherenkov radiation was performed using CORSIKA software for two hadronic models QGSJET and GHEISHA. This simulation was performed for several elementary particles such as protons, iron nuclei, electrons and gamma quanta, in the range of energies 1-20 PeV for three zenith angles 0, 20 and 30 degrees. A parameterization of Cherenkov light LDF was performed for that simulated curves using Lorentzian function. The comparison between the obtained results for LDF of Cherenkov light with that measured with Yakutsk EAS array g…
IceCube has detected a cumulative flux of PeV neutrinos, which origin is unknown. Blazars, active galactic nuclei with relativistic jets pointing to us, are long and widely expected to be one of the strong candidates of high energy neutrino sources. The neutrino production depends strongly on the cosmic ray power of blazar jets, which is largely unknown. The recent null results in stacking searches of neutrinos for several blazar samples by IceCube put upper limits on the neutrino fluxes from these blazars. Here we compute the cosmic ray power and PeV neutrino flux of Fermi-LAT blazars, and fi…
We argue that the excess of sub-PeV/PeV neutrinos recently reported by IceCube could plausibly originate through pion-production processes in the same sources responsible for cosmic rays (CRs) with energy above the second knee around $10^{18}\,$eV. The pion production efficiency for escaping CRs that produce PeV neutrinos is required to be $\gtrsim 0.1$ in such sources. On the basis of current data, we identify semi-relativistic hypernova remants as possible sources that satisfy the requirements. By virtue of their fast ejecta, such objects can accelerate protons to EeV energies, which in turn…
We performed deep observations to search for radio pulsations in the directions of 375 unassociated Fermi Large Area Telescope (LAT) gamma-ray sources using the Giant Metrewave Radio Telescope (GMRT) at 322 and 607 MHz. In this paper we report the discovery of three millisecond pulsars (MSPs), PSR J0248+4230, PSR J1207$-$5050 and PSR J1536$-$4948. We conducted follow up timing observations for around 5 years with the GMRT and derived phase coherent timing models for these MSPs. PSR J0248$+$4230 and J1207$-$5050 are isolated MSPs having periodicities of 2.60 ms and 4.84 ms. PSR J1536-4948 is a …
We report the discovery of pulsed γ-ray emission and X-ray emission from the black widow millisecond pulsar PSR J2051-0827 by using the data from the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope and the Advanced CCD Imaging Spectrometer array (ACIS-S) on the Chandra X-ray Observatory. Using 3 years of LAT data, PSR J2051-0827 is clearly detected in γ-ray with a signicance of \sim 8σ in the 0.2 - 20 GeV band. The 200 MeV - 20 GeV γ-ray spectrum of PSR J2051-0827 can be modeled by a simple power- law with a photon index of 2.46 \pm 0.15. Significant (\sim 5σ) γ-ray pul…
In this work, we study the X-ray bow-shock nebula powered by the mature pulsar PSR B1929+10 using data from XMM-Newton, with an effective exposure of $\sim$ 300 ks, offering the deepest investigation of this system thus far. We found the X-ray axial outflow extends as long as $\sim$ 8 arc minute behind the proper motion direction, which is a factor of two longer than the result reported in the previous study. Furthermore, we found evidence of two faint lateral outflows extending laterally with respect to the proper motion. We also found indications of spectral hardening along the axial outflow…
We report on high-energy properties of the black widow pulsar PSR J2241$-$5236 in the X-ray and the Fermi-LAT (GeV gamma-ray) bands. In the LAT band, the phase-averaged gamma-ray light curve shows orbital modulation below $\sim$1 GeV with a chance probability ($p$) monotonically decreasing with time to $p\sim 10^{-5}$. The peak of the light curve is near the superior conjunction of the pulsar (binary phase $ϕ_{\rm B}\approx 0.25$). We attribute the modulation to the intra-binary shock (IBS) emission and search for IBS signatures in the archival X-ray data. We find that the X-ray spectral fit r…
We report on X-ray studies of the gamma-ray pulsar PSR J1418$-$6058 in the Rabbit pulsar wind nebula (PWN) carried out using archival Chandra and XMM-Newton observations. A refined timing analysis performed with the 120-ks XMM-Newton data finds significant ($p\approx10^{-7}$) pulsation at $P\approx110$ ms which is consistent with that measured with the Fermi large area telescope (LAT). In the Chandra image, we find extended emission around the pulsar similar to those seen around other pulsars in young PWNe, which further argues for association between PSR J1418$-$6058 and the Rabbit PWN. The X…
We present Nuclear Spectroscopic Telescope Array (NuSTAR) hard X-ray timing and spectroscopy of the three exceptionally energetic rotation-powered millisecond pulsars PSRs B1821-24, B1937+21, and J0218+4232. By correcting the NuSTAR onboard clock for phase and frequency drifts between observation intervals, we are able to recover the intrinsic hard X-ray pulse profiles of all three pulsars with a resolution down to < 15 microsec. The substantial reduction of background emission relative to previous broadband X-ray observations allows us to detect for the first time pulsed emission up to ~50 ke…
The IceCube (IC) collaboration recently reported the detection of TeV-PeV extraterrestrial neutrinos whose origin is yet unknown. By the photon-neutrino connection in $pp$ and $pγ$ interactions, we use the \fermi-LAT observations to constrain the origin of the IC detected neutrinos. We find that Galactic origins, i.e., the diffuse Galactic neutrinos due to cosmic ray (CR) propagation in the Milky Way, and the neutrinos from the Galactic point sources, may not produce the IC neutrino flux, thus these neutrinos should be of extragalactic origin. Moreover, the extragalactic gamma-ray bursts (GRBs…
We report the detection of gamma-ray pulsations (> 0.1 GeV) from PSR J2229+6114 and PSR J1048-5832, the latter having been detected as a low-significance pulsar by EGRET. Data in the gamma-ray band were acquired by the Large Area Telescope aboard the Fermi Gamma-ray Space Telescope, while the radio rotational ephemerides used to fold the gamma-ray light curves were obtained using the Green Bank Telescope, the Lovell telescope at Jodrell Bank, and the Parkes telescope. The two young radio pulsars, located within the error circles of the previously unidentified EGRET sources 3EG J1048-5840 and 3…
We report on the detection of pulsations from PSR B1706-44 based on 28.3 hours of observations with the H.E.S.S. II array with CT5 in monoscopic mode. The lightcurve is similar to that obtained with the Fermi-LAT above 15 GeV and the pulsations exhibit a steep spectrum with index ~ -3.8 in the sub 20 GeV to sub-100 GeV energy range. While a significant signal of ~ 1000 events is detected at energies ~ 70 GeV, it is not possible to either confirm or rule out a power-law behaviour of PSR B1706-44 spectrum in this range.
We present the first measurement of a non-zero magnetic field in the eclipsing material of a black widow pulsar. Black widows are millisecond pulsars which are ablating their companions; therefore they are often proposed as one potential source of isolated millisecond pulsars. PSR J2256-1024 is an eclipsing black widow discovered at radio wavelengths and later also observed in the X-ray and gamma parts of the spectrum. Here we present the radio timing solution for PSR J2256-1024, polarization profiles at 350, 820, and 1500~MHz and an investigation of changes in the polarization profile due to …
We report on the latest discovery of an extended Very High Energy (VHE) gamma-ray source near the 67 ms pulsar PSR J1831-0952 during the H.E.S.S. Galactic Plane Survey (GPS). The dispersion measure distance of the pulsar (4.3 kpc) would imply that less than 1% of its spin-down energy is required to provide the observed VHE luminosity of the source. No other plausible counterparts have yet been found through preliminary multi- wavelength searches. The most likely scenario is that the VHE emission originates from the -yet unseen at other wavelengths-wind nebula of PSR J1831-0952. If so this woul…
PSR B1259-63 is a $γ$-ray emitting high mass X-ray binary system, in which the compact object is a millisecond pulsar. The system has an orbital period of 1236.7 d and shows peculiar $γ$-ray flares when the neutron star moves out of the stellar disk of the companion star. The $γ$-ray flare events were firstly discovered by using Fermi-LAT around the 2010 periastron passage, which was repeated for the 2014 and 2017 periastron passages. We analyze the Fermi-LAT data for all the three periastron passages and found that in each flare the energy spectrum can be represented well by a simple power la…
Long-term monitoring of PSR J2021+4026 in the heart of the Cygnus region with the Fermi Large Area Telescope (LAT) unveiled a sudden decrease in flux above 100 MeV over a time scale shorter than a week. The "jump" was near MJD 55850 (2011 October 16), with the flux decreasing from $(8.33\pm0.08) \times 10^{-10}$ erg cm$^{-2}$ s$^{-1}$ to $(6.86\pm0.13) \times 10^{-10}$ erg cm$^{-2}$ s$^{-1}$. Simultaneously, the frequency spindown rate increased from $(7.8\pm 0.1) \times 10^{-13}$ Hz s$^{-1}$ to $(8.1\pm 0.1) \times 10^{-13}$ Hz s$^{-1}$. Significant (> 5 sigma's) changes in the pulse profile …
We present an analysis of archival Gemini g', r', K and Keck H, K_s imaging of this nearby short period binary (P_B=95.8min) 2.87ms pulsar. The heated companion is clearly detected. Direct pulsar heating provides an acceptable model at the revised >700pc parallax distance. The relatively shallow light curve modulation prefers an inclination i<40deg; this high latitude view provides a likely explanation for the lack of radio signatures of wind dispersion or eclipse. It also explains the low minimum companion mass and, possibly, the faintness of the source in X- and gamma-rays.
The binary system PSR B1259-63/LS 2883 is well sampled in radio, X-rays, and TeV gamma-rays, and shows orbital phase-dependent variability in these frequencies. The first detection of GeV gamma-rays from the system was made around the 2010 periastron passage. In this Letter, we present an analysis of X-ray and gamma-ray data obtained by the Swift/XRT, NuSTAR/FPM, and Fermi/LAT, through the recent periastron passage which occurred on 2014 May 4. While PSR B1259-63/LS 2883 was not detected by the LAT before and during this passage, we show that the GeV flares occurred at a similar orbital phase …
Two kinds of Galactic source populations could explain the cosmic-ray observation up to the "knee" region
Beihang University（北京航空航天大学）；Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所）；University of Chinese Academy of Sciences（中国科学院大学）
Observations of the Galactic Plane performed by the H.E.S.S. telescope array have revealed a significant excess at very-high-energies (VHE; E>0.1 TeV) from the direction of PSR J1459-60, a rather old gamma-ray pulsar (64 kyr) with a spindown energy of ~10^36 erg/s, discovered by the Fermi/LAT satellite in high-energy (HE) gamma-rays. The X-ray pulsar counterpart has been recently detected using the Suzaku satellite. In this contribution, we present the discovery of a new VHE gamma-ray source, including morphological and spectral analyses. Its association with the gamma-ray pulsar in a PWN scen…
PSR B1259-63/LS 2883 is a gamma-ray binary system composed of an O9.5Ve main sequence star, LS 2883, and a 47.8 ms spinning neutron star in a highly eccentric 3.4 yr orbit (eccentricity e = 0.87). PSR B1259-63/LS 2883 is so far the only gamma-ray binary in which the compact object has been firmly identified. H.E.S.S. observed this system around its periastron passages in 2004, 2007, 2011 and 2014. For this latter event, a detailed campaign was organised making use of the new capabilities of H.E.S.S. II, in particular its improved sensitivity and a lower energy threshold. This campaign covered …
We present the results of the analysis of 8 years of Fermi-LAT data of the pulsar/pulsar wind nebula complex PSR J0205+6449/3C 58. Using a contemporaneous ephemeris, we carried out a detailed analysis of PSR J0205+6449 both during its off-peak and on-peak phase intervals. 3C 58 is significantly detected during the off-peak phase interval. We show that the spectral energy distribution at high energies is the same disregarding the phases considered, and thus that this part of the spectrum is most likely dominated by the nebula radiation. We present results of theoretical models of the nebula and…
