Fermi-LAT Research Articles

A Study of Broad Emission Line and Doppler Factor Estimation for Fermi Blazars

In this work, we obtained a sample of 979 Fermi blazars with broad emission lines, including 701 objects collected from published works and 278 objects developed in this work. For the 278 objects, we made a crossmatch from three catalogs, the Fermi Large Area Telescope Fourth Source Catalog (4FGL), the Sloan Digital Sky Survey, and the Large Sky Area Multi-Object Fiber Spectroscopic Telescope, and calculated the broad-line region (BLR) luminosity. Then, we estimated the Doppler factor and studied the correlations between the BLR luminosities and the γ-ray luminosities, the synchrotron peak frequency (ν p ), and Doppler factor (δ) for the whole sample. Our analyses and discussions came to the following main conclusions: For the 278 blazars, their BLR luminosity (log L BLR) ranges from 40.44 to 45.45 erg s−1, with a mean value of 43.39 erg s−1. The Doppler factor ranges from δ = 0.45 to δ = 88.52, with a mean value of 12.99 for the 979 Fermi blazars, which is consistent with the results in the literature. Both the BLR luminosity and the Doppler factor exhibit positive correlations with the γ-ray luminosity. The BLR luminosity is anticorrelated with synchrotron peak frequency, implying a Compton cooling. A line of logLBLR=1.58logνp−19.46 separating BL Lacertae objects and flat-spectrum radio quasars was obtained in the diagram of logLBLR against logνp using a machine-learning method. Based on the analysis of the equivalent width and the Doppler factors, we proposed five changing-look blazar candidates.

Broad-band spectral and temporal study of Ton 599 during the brightest 2023 January flare

ABSTRACT In this work, we provide a detailed analysis of the broad-band temporal and spectral properties of the blazar Ton 599 by using observations from the Fermi Large Area Telescope (LAT) and Swift X-Ray Telescope (XRT)/Ultraviolet–Optical Telescope (UVOT), during its brightest γ-ray flaring. The one-day bin γ-ray light curve exhibits multiple substructures with asymmetric and symmetric profiles. Notably, the γ-ray light curve shows a maximum flux of $\rm 3.63 \times 10^{-6}\, photon\, cm^{-2}\, s^{-1}$ on MJD 59954.50, which is the highest flux ever observed from this source. The correlation between the γ-ray flux and γ-ray spectral indices suggests a moderate ‘harder when brighter’ trend. Taking the γ-ray light curve as the reference, a strong correlation is observed with X-ray, optical, and UV energies. Additionally, the γ-rays and optical/UV emission exhibit higher variability compared with X-rays. To understand the parameter variation during the active state of the source, we conducted a statistical broad-band spectral modelling of the source in 10 flux intervals of equal duration. A one-zone leptonic model involving synchrotron, synchrotron-self-Compton, and external Compton processes successfully reproduces the broad-band spectral energy distribution (SED) in each of these flux intervals. We observed that flux variation during the active state is associated mainly with variation in the magnetic field and particle spectral indices.

Follow-up on the Supermassive Black Hole Binary Candidate J1048+7143: Successful Prediction of the Next Gamma-Ray Flare and Refined Binary Parameters in the Framework of the Jet Precession Model

Analyzing single-dish and very long baseline interferometry radio, as well as Fermi Large Area Telescope γ-ray observations, we explained the three major flares in the γ-ray light curve of FSRQ J1048+7143 with the spin–orbit precession of the dominant mass black hole in a supermassive black hole binary system. Here, we report on the detection of a fourth γ-ray flare from J1048+7143, appearing in the time interval that was predicted in our previous work. Including this new flare, we constrained the mass ratio into a narrow range of 0.062 < q < 0.088, and consequently we were able to further constrain the parameters of the hypothetical supermassive binary black hole at the heart of J1048+7143. We predict the occurrence of the fifth major γ-ray flare that would appear only if the jet will still lay close to our line of sight. The fourth major γ-ray flare also shows the two-subflare structure, further strengthening our scenario in which the occurrence of the subflares is the signature of the precession of a spine–sheath jet structure that quasiperiodically interacts with a proton target, e.g., clouds in the broad-line region.

Localisation of gamma ray bursts using AstroSat Mass Model

Abstract The Cadmium Zinc Telluride Imager (CZTI) aboard AstroSat has good sensitivity to Gamma Ray Bursts (GRBs), with close to 600 detections including about 50 discoveries undetected by other missions. However, CZTI was not designed to be a GRB monitor and lacks localisation capabilities. We introduce a new method of localising GRBs using ‘shadows’ cast on the CZTI detector plane due to absorption and scattering by satellite components and instruments. Comparing the observed distribution of counts on the detector plane with simulated distributions with the AstroSat Mass Model, we can localise GRBs in the sky. Our localisation uncertainty is defined by a two-component model, with a narrow Gaussian component that has close to 50% probability of containing the source, and the remaining spread over a broader Gaussian component with an 11.3 times higher σ. The width (σ) of the Gaussian components scales inversely with source counts. We test this model by applying the method to GRBs with known positions and find good agreement between the model and observations. This new ability expands the utility of CZTI in the study of GRBs and other rapid high-energy transients.

Search for quasi-periodic oscillations in TESS light curves of bright Fermi Blazars

ABSTRACT In a previous paper, we reported evidence for quasi-periodicities in the Transiting Exoplanet Survey Satellite (TESS) light curves of BL Lacerate and two other blazars found serendipitously in the Sloan Digital Sky Survey (SDSS) active galactic nuclei catalogue. In this work, we find tentative evidence for quasi-periodic features in the TESS observations of five sources in the fourth catalogue of the Fermi–Large Area Telescope sources: J090453.4−573503, J2345−1555, B0422+004, J002159.2−514028, and B0537−441. We analysed the TESS light curves of these blazars that we extracted using a customized approach. The quasi-periodic oscillations (QPOs) are searched for using two timing analysis techniques: generalized Lomb–Scargle periodogram and weighted wavelet Z-transform. Their apparent periods lie in the range of 2.8–6.5 d and have at least 3σ significance in both of these methods. QPOs at such time-scales can originate from the kink instability model which relates the quasi-periodic feature with the growth of kinks in the magnetized relativistic jets. We performed Markov Chain Monte Carlo simulations to obtain the posterior distribution of parameters associated with this model and found the kink period consistent with previous studies.

γCygni SNR morphology viewed in the electromagnetic spectrum

AbstractThe investigation of very high energy gamma‐ray sources touches on the problem of the cosmic ray origin and the role of the Galaxy in their generation. The SHALON observations have yielded the results on Cygni SNR Galactic supernova remnant. The observation results are presented with spectral energy distribution and emission map by SHALON in comparison with other experiment data obtained by ROSAT in x‐ray energy range, radio‐data by CGPS, and also observations of GeV–TeV gamma‐rays by Fermi LAT. The overall Cygni SNR characteristics detected in radio, x‐rays, and GeV–TeV gamma‐rays can be a result of the shocks at the interaction of the supernova ejecta and the surrounding medium. The collected experimental data help to make clear the origin of TeV ‐ray emission in the Cygni SNR. The density of target material in the SNR surroundings is enough to produce the observable TeV gamma‐ray flux via the shock acceleration of hadrons in the detected regions. The detection of gamma‐ray emission at 0.8–60 TeV from the North‐West and South‐East shells of Cygni SNR by SHALON would favor the hadronic origin of the gamma‐rays in this supernova remnant.

Modeling the Multiwavelength Spectral Energy Distributions of the Fermi-4LAC Bright Flat-spectrum Radio Quasars

In this paper, we present a long-term multiwavelength investigation focusing on 12 distinct samples of Fermi-4LAC bright flat-spectrum radio quasars (FSRQs). Detailed variability and spectral analyses of γ-ray, X-ray, and ultraviolet/optical data obtained by the Fermi Large Area Telescope, the Swift X-ray Telescope, and the Swift Ultraviolet and Optical Telescope were performed over a period of about 14 yr, spanning from 2008 October to 2022 October. These analyses provide insights into characterizing the variations within different activity states. To efficiently reproduce the multiwavelength simultaneous/quasi-simultaneous spectral energy distributions (SEDs) of the samples, we propose a novel approach for constraining the model parameters. By analyzing the parameters of the energy spectral curvature (β), the peak frequency (ν pk), the peak luminosity (L pk), the Compton dominance parameter (A C), and the variability timescale (t var) in different activity states, we can estimate the values of the jet radiation region parameters for the samples. Subsequently, we utilize the synchrotron-self-Compton and external Compton processes, employing a logarithmic-parabolic spectral shape to approximate the observed spectra of the sample sources, while considering the induced regime for the physical parameters. The model results show that: (1) by effectively reproducing SEDs in various active states of bright FSRQs, the parameters within the emission region were reasonably constrained; (2) compared to other active states, the emission region of the jet exhibits a reduced radius during the high state, while the magnetic field strength increases during the low state; and (3) for bright FSRQs in a high-activity state, there is an enhancement of the Doppler factor, often exhibiting a tendency toward energy equipartition.

Evidence for a Compact Stellar Merger Origin for GRB 230307A From Fermi-LAT and Multiwavelength Afterglow Observations

GRB 230307A is the second-brightest gamma-ray burst (GRB) ever detected over 50 yr of observations and has a long duration in the prompt emission. Two galaxies are found to be close to the position of GRB 230307A: (1) a distant (z ∼ 3.87) star-forming galaxy, located at an offset of ∼0.″2–0.″3 from the GRB position (with a projected distance of ∼1–2 kpc); (2) a nearby (z = 0.065) spiral galaxy, located at an offset of 30″ (with a projected distance of ∼40 kpc). Though it has been found that the brightest GRBs are readily detected in GeV emission by the Fermi Large Area Telescope, we find no GeV afterglow emission from GRB 230307A. Combining this with the optical and X-ray afterglow data, we find that a circumburst density as low as ∼10−5–10−4 cm−3 is needed to explain the nondetection of GeV emission and the multiwavelength afterglow data, regardless of the redshift of this GRB. Such a low-density disfavors the association of GRB 230307A with the high-redshift star-forming galaxy, since the proximity of the GRB position to this galaxy would imply a higher-density environment. Instead, the low-density medium is consistent with the circumgalactic medium, which agrees with the large offset between GRB 230307A and the low-redshift galaxy. This points to the compact stellar merger origin for GRB 230307A, consistent with the detection of an associated kilonova.

Yet Another Sunshine Mystery: Unexpected Asymmetry in GeV Emission from the Solar Disk

The Sun is one of the most luminous γ-ray sources in the sky and continues to challenge our understanding of its high-energy emission mechanisms. This study provides an in-depth investigation of the solar disk γ-ray emission, using data from the Fermi Large Area Telescope spanning 2008 August to 2022 January. We focus on γ-ray events with energies exceeding 5 GeV, originating from 0.°5 angular aperture centered on the Sun, and implement stringent time cuts to minimize potential sample contaminants. We use a helioprojection method to resolve the γ-ray events relative to the solar rotation axes and combine statistical tests to investigate the distribution of events over the solar disk. We found that integrating observations over large time windows may overlook relevant asymmetrical features, which we reveal in this work through a refined time-dependent morphological analysis. We describe significant anisotropic trends and confirm compelling evidence of energy-dependent asymmetry in the solar disk γ-ray emission. Intriguingly, the asymmetric signature coincides with the Sun’s polar field flip during the cycle 24 solar maximum, around 2014 June. Our findings suggest that the Sun’s magnetic configuration plays a significant role in shaping the resulting γ-ray signature, highlighting a potential link between the observed anisotropies, solar cycle, and the solar magnetic fields. These insights pose substantial challenges to established emission models, prompting fresh perspectives on high-energy solar astrophysics.

Sub-GeV Gamma Rays from Nearby Seyfert Galaxies and Implications for Coronal Neutrino Emission

Recent observations of high-energy neutrinos by IceCube and gamma rays by the Fermi Large Area Telescope (LAT) and the MAGIC telescope have suggested that neutrinos are produced in gamma-ray opaque environments in the vicinity of supermassive black holes. In this work, we present 20 MeV–1 TeV spectra of three Seyfert galaxies whose nuclei are predicted to be active in neutrinos, NGC 4151, NGC 4945, and the Circinus galaxy, using 14.4 yr of Fermi LAT data. In particular, we find evidence of sub-GeV excess emission that can be attributed to gamma rays from NGC 4945, as was also seen in NGC 1068. These spectral features are consistent with predictions of the magnetically powered corona model, and we argue that NGC 4945 is among the brightest neutrino active galaxies detectable for KM3Net and Baikal-GVD. On the other hand, in contrast to other reported results, we do not detect gamma rays from NGC 4151, which constrains neutrino emission from the accretion shock model. Future neutrino detectors such as IceCube-Gen2 and MeV gamma-ray telescopes such as AMEGO-X will be crucial for discriminating among the theoretical models.

Broad-band study of gamma-ray blazars at redshifts z = 2.0–2.5

ABSTRACT High redshift blazars are among the most powerful non-explosive sources in the Universe and play a crucial role in understanding the evolution of relativistic jets. To understand these bright objects, we performed a detailed investigation of the multiwavelength properties of 79 γ-ray blazars with redshifts ranging from z = 2.0 to 2.5, using data from Fermi LAT, Swift XRT/UVOT, and NuSTAR observations. In the γ-ray band, the spectral analysis revealed a wide range of flux and photon indices, from 5.32 × 10−10 to 3.40 × 10−7 photon cm−2 s−1 and from 1.66 to 3.15, respectively, highlighting the diverse nature of these sources. The detailed temporal analysis showed that flaring activities were observed in 31 sources. Sources such as 4C+71.07, PKS 1329-049, and 4C + 01.02, demonstrated significant increase in the γ-ray luminosity and flux variations, reaching peak luminosity exceeding 1050 erg s−1. The temporal analysis extended to X-ray and optical/ultraviolet (UV) bands, showed clear flux changes in some sources in different observations. The time-averaged properties of high redshift blazars were derived through modeling the spectral energy distributions with a one-zone leptonic scenario, assuming the emission region is within the broad-line region (BLR) and the X-ray and γ-ray emissions are due to inverse Compton scattering of synchrotron and BLR-reflected photons. This modeling allowed us to constrain the emitting particle distribution, estimate the magnetic field inside the jet, and evaluate the jet luminosity, which is discussed in comparison with the disc luminosity derived from fitting the excess in the UV band.

Energy-dependent Analyses of the Gamma-Ray Emission from HESS J1857+026 with Fermi-LAT

We report the discovery of the energy-dependent morphology of the GeV gamma-ray emission from HESS J1857+026 with more than 13 yr of Fermi Large Area Telescope data. The GeV gamma-ray emission from this region is composed of two extended components. The hard component with an index of 1.74 ± 0.07 in the energy range of 0.5–500 GeV is spatially coincident with HESS J1857+026, and its 68% containment radius varies from ∼0.°44 below 40 GeV to ∼0.°30 above 140 GeV. The hard GeV gamma-ray spectrum and the energy-dependent morphology of HESS J1857+026 make it favor a pulsar wind nebula origin, which is associated with the energetic pulsar PSR J1856+0245. The soft component with an index of 2.70 ± 0.16 and another extended gamma-ray source detected in this region, 4FGL J1857.9+0313e, with an index of 2.55 ± 0.07, are spatially coincident with two molecular clumps in the northeast and southwest of HESS J1857+026, which favors the hadronic process, and the protons could be accelerated by the hypothetical supernova remnant associated with PSR J1856+0245.

Small-scale Magnetic Fields Are Critical to Shaping Solar Gamma-Ray Emission

The Sun is a bright gamma-ray source due to hadronic cosmic-ray interactions with solar gas. While it is known that incoming cosmic rays must generally first be reflected by solar magnetic fields to produce outgoing gamma rays, theoretical models have yet to reproduce the observed spectra. We introduce a simplified model of the solar magnetic fields that captures the main elements relevant to gamma-ray production. These are a flux tube, representing the network elements, and a flux sheet, representing the intergranular sheets. Both the tube and sheet have a horizontal size of order 100 km and serve as sites where cosmic rays are reflected and gamma rays are produced. While our simplified double-structure model does not capture all the complexities of the solar-surface magnetic fields, such as Alfvén turbulence from wave interactions or magnetic fluctuations from convection motions, it improves on previous models by reasonably producing both the hard spectrum seen by Fermi Large Area Telescope at 1–200 GeV and the considerably softer spectrum seen by the High Altitude Water Cherenkov Observatory (HAWC) at near 103 GeV. We show that lower-energy (≲10 GeV) gamma rays are primarily produced in the network elements and higher-energy (≳few × 10 GeV) gamma rays in the intergranular sheets. Notably, the spectrum softening observed by HAWC results from the limited effectiveness of capturing and reflecting ∼104 GeV cosmic rays by the finite-sized intergranular sheets. Our study is important for understanding cosmic-ray transport in the solar atmosphere and will lead to insights into small-scale magnetic fields at the photosphere.

Dissecting the γ-Ray Emissions of the Nearby Galaxies NGC 1068 and NGC 253

Intrigued by recent high-energy study results for nearby galaxies with γ-ray emission and in particular NGC 1068 that has been detected as a neutrino-emitting source by the IceCube Neutrino Observatory, we conduct a detailed analysis of the γ-ray data of the galaxies NGC 1068 and NGC 253, obtained with the Large Area Telescope on board the Fermi γ-ray Space Telescope. By checking their possible spectral features and then constructing light curves in the corresponding energy ranges, we identify spectral-change activity from NGC 1068 in the ≥2 GeV energy range and long-term, statistically significant changes for NGC 253 in the ≥5 GeV energy range. In the former, the emission appears harder in two half-year periods than in the otherwise “quiescent” state. In the latter, an ∼two-fold decrease in the detection significance after MJD = 57023 is clearly revealed by the test-statistic maps we obtain. Considering the previous studies carried out and the various models proposed for the γ-ray emissions of the two sources, we discuss the implications of our findings. We suspect that a jet (or outflow) in NGC 1068 might contribute to the γ-ray emission. The nature of the long-term statistically significant changes for NGC 253 is not clear, but since the part of the GeV emission may be connected to the very-high-energy (VHE) emission from the center of the galaxy, it could be further probed with VHE observations.

The challenge of identifying INTEGRAL sources on the Galactic plane

The International Gamma-ray Astrophysics Laboratory (INTEGRAL) has been surveying the sky above 20 keV since its launch in 2002 providing new insights into the nature of the sources that populate our Universe at soft γ-ray energies. The latest IBIS/ISGRI survey lists 929 hard X-ray sources, of which 113 are reported as unidentified, i.e. lacking a lower energy counterpart or simply not studied in other wavebands. To overcome this lack of information, we either browsed the X-ray archives, or, if no data in the X-ray band were available, we requested Target of Opportunity (ToO) observations with the X-ray Telescope (XRT) on-board the Neil Gehrels Swift Observatory. Following this approach, we selected a sample of 10 objects for which X-ray data were key to investigate their nature. We found a single X-ray association for all of the sources, except for IGR J16267−3303, for which two X-ray detections were spotted within the IBIS positional uncertainty. We then browsed multi-waveband archives to search for counterparts to these X-ray detections at other wavelengths and analysed X-ray spectral properties to determine their nature and association with the high-energy emitter. As a result of our analysis, we identified the most likely counterpart for 7 sources, although in some cases its nature/class could not be definitely assessed on the basis of the information collected. Interestingly, SWIFT J2221.6+5952, first reported in the 105-month Swift/Burst Alert Telescope (BAT) survey, is the only source of the sample for which we did not find any counterpart at radio/optical/IR wavebands. Finally, we found that two IBIS source, IGR J17449−3037 and IGR J17596−2315 are positionally associated with a Fermi Large Area Telescope (LAT) object.

Gamma-ray blazar classification using machine learning with advanced weight initialization and self-supervised learning techniques

ABSTRACT Machine learning has emerged as a powerful tool in the field of gamma-ray astrophysics. The algorithms can distinguish between different source types, such as blazars and pulsars, and help uncover new insights into the high-energy universe. The Large Area Telescope onboard the Fermi gamma-ray telescope has significantly advanced our understanding of the Universe. The instrument has detected a large number of gamma-ray-emitting sources, among which a significant number of objects have been identified as active galactic nuclei. The sample is primarily composed of blazars; however, more than one-third of these sources are either of an unknown class or lack a definite association with a low-energy counterpart. In this work, we employ multiple machine learning algorithms to classify the sources based on their other physical properties. In particular, we utilized smart initialization techniques and self-supervised learning for classifying blazars into BL Lacertae (BL Lac, also BLL) objects and flat-spectrum radio quasars (FSRQs). The core advantage of the algorithm is its simplicity, usage of minimum number of features and easy deployment due to lesser number of parameters without compromising on the performance along with increase in inference speed (at least seven times more than existing algorithms). As a result, the best-performing model is deployed on multiple platforms so that any user irrespective of their coding background can use the tool. The model predicts that out of the 1115 sources of uncertain type in the 4FGL-DR3 catalogue, 820 can be classified as BL Lacs and 295 can be classified as FSRQs.

GRB 230911A: The First Discovery of a Fermi GRB Optical Counterpart with the Gravitational-wave Optical Transient Observer (GOTO)

We report on the detection of candidate optical counterpart GOTO23akf/AT2023shv to the GRB 230911A with the Gravitational-wave Optical Transient Observer (GOTO) instruments located at La Palma, Canary Islands, and Siding Spring Observatory, Australia. The Fermi Gamma-ray Burst Monitor, which finds gamma-ray bursts (GRBs) nearly every two days, detected GRB 230911A with a statistical uncertainty of 4.°1. However, the large (∼10–100 deg2) localization areas mostly impede the rapid identification of an optical counterpart. GOTO facilities fully covered 90% localization area of the GRB 230911A. We proposed GOTO23akf as the optical afterglow of GRB 230911A, subsequently confirmed through Swift-X-Ray Telescope observations in which an uncatalogued X-ray source spatially coincident with the GOTO candidate was detected. This is the first optical afterglow discovery for a Fermi GRB with the newly expanded GOTO network.

A high-energy study of the supernova remnant G296.5+10.0

ABSTRACT We report a detailed multi-wavelength study of the supernova remnant G296.5+10.0 using archival data from XMM–Newton and Fermi-LAT complemented with ATCA observations. In the X-ray band, we performed an adaptive smoothing on the double background subtracted images to construct an X-ray mosaic map with six individual observations. Below 2.0 keV, G296.5+10.0 is asymmetrical, with the south-east side of the radio shell brighter than the south-west one. The spatially resolved X-ray spectral study confirms the thermal origin of the plasma, with enhanced metal abundances, probably arising from ejecta material according to the H i and infrared ($140~{\mu \rm m}$) distributions. In the γ-ray band, we analysed 14 years of accumulated Fermi observations below 500 GeV via different fitting processes. To discuss the origin of the γ-ray emission, we compare the GeV results with H i structures probably associated with the SNR and with the radio spectral indices found at various positions towards the radio shell. Moreover, we identified diverse sources candidates to contribute γ-ray emissions observed. Also, we calculated the lepto-hadronic spectral energy distribution of the remnant for synchrotron, inverse Compton, Bremsstrahlung, and proton–proton processes. The emission at low energies can be explained by electron-synchrotron radiation, with a weak magnetic field of $B=25\, {\rm \mu G}$, while the γ-ray data can be explained by hadronic interactions. Employing the reddening-distance method, we computed a distance of 1.4 kpc for the SNR, implying an age of 14 000 yr.

Chandra X-Ray Observatory Observations of 13 Fermi LAT Sources

In the latest data release from the Fermi Gamma-ray Space Telescope (the 4th Fermi LAT 14 yr Catalog, or 4FGL), more than 50% of the Galactic sources are yet to be identified. We observed 13 unidentified Fermi LAT sources with the Chandra X-Ray Observatory to explore their nature. We report the results of the classification of X-ray sources in the fields of these γ-ray sources and discuss the implications for their nature. We use multiwavelength (MW) data for a machine-learning classification, accompanied by a more detailed spectral/variability analysis for brighter sources. Eight 4FGL sources have γ-ray pulsars within their position error ellipses. We consider three of these pulsars (PSR J1906+0722, PSR J1105–6037, and PSR J1358–6025) to be detected in X-rays, while PSR J1203–6242 shows a hint of X-ray emission. Within the positional uncertainties of three of the 4FGL sources, we detect X-ray sources that may be yet unknown pulsars, depending on the MW association. In addition to point sources, we discovered two extended sources, one of which is likely to be a bow-shock pulsar-wind nebula associated with PSR J1358–6025. Finally, we classify other X-ray sources detected in these observations and report the most interesting classifications.

A Possible γ-Ray Pulsation from PSR J1740−5340B in the Globular Cluster NGC 6397

Recently, a new radio millisecond pulsar (MSP) J1740−5340B, hosted in the globular cluster (GC) NGC 6397, was reported with a 5.78 ms spin period in an eclipsing binary system with a 1.97 days orbital period. Based on a modified radio ephemeris updated by tool tempo2, we analyze the ∼15 yr γ-ray data obtained from the Large Area Telescope on board the Fermi Gamma-ray Space Telescope and detect PSR J1740−5340B’s γ-ray pulsation at a confidence level of ∼4σ with a weighted H-test value of ∼26. By performing a phase-resolved analysis, the γ-ray luminosity in on-pulse interval of PSR J1740−5340B is L γ ∼ 3.8 × 1033 erg s−1 using NGC 6397's distance of 2.48 kpc. And γ-rays from the on-pulse part of PSR J1740−5340B contribute ∼90% of the total observed γ-ray emissions from NGC 6397. No significant γ-ray pulsation of another MSP J1740−5340A in the GC is detected. Considering that the previous four cases of MSPs in GCs, more data in γ-ray, X-ray, and radio are encouraged to finally confirm the γ-ray emissions from MSP J1740−5340B, especially starving for a precise ephemeris.