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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

43941 results found.

  1. GRB 250502A: NOT optical observations
  2. GRB 250502a: Liverpool Telescope optical follow-up
  3. GRB 250502B: AstroSat CZTI detection
  4. GRB 250502A: AKO Optical Afterglow Detection
  5. GRB 250502A: LCO optical counterpart detection
  6. GRB 250502A: Swift ToO observations
  7. GRB 250502A: Redshift from OSIRIS+/GTC z = 2.163
  8. GRB 250502C: Fermi GBM Final Localization
  9. GRB 250407A: VZLUSAT-2 detection
  10. Fermi-LAT Gamma-ray Observations of IceCube-250429A
  11. GRB 250502B: DDOTI Optical Observations
  12. GRB 250430A: Swift-XRT refined Analysis
  13. GRB 250502A: Early optical counterpart detection by LCO.
  14. GRB 250502A: SVOM/VT optical bump
  15. GRB 250502A: TRT optical afterglow confirmation
  16. GRB 250430A: Enhanced Swift-XRT position
  17. Fermi GRB 250502B: Global MASTER-Net observations report
  18. GRB 250430A: Optical Observations via Virtual Telescope Project, Italy
  19. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  20. GRB 250502B: Fermi GBM Final Real-time Localization
  21. GRB 250502A: SVOM detection of a burst
  22. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  23. GRB 250430A: SVOM/VT optical observations
  24. GRB 250430A: KAIT optical observations
  25. EP250428b: Pan-STARRS follow-up, upper limit on the optical counterpart, and possible host galaxy.
  26. GRB 250430A / EP250430a: J-band upper limits with WINTER
  27. GRB 250430A: NUTTelA-TAO Early Measurements
  28. EP250427a / GRB 250427A: OHP/T193 photometric observations: third visit
  29. GRB 250430A: DDOTI Optical Observations
  30. GRB 250430A: Leavitt Observatory optical upper limit
  31. GRB 250430A: Bassano Bresciano Observatory upper limit
  32. GRB 250430A : MITSuME Akeno optical upper limits
  33. GRB 250430A / EP250430a: VLT/X-shooter spectroscopic redshift z = 0.767
  34. SVOM/sb25043004: EP-FXT observations
  35. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  36. GRB 250424A: CALET Gamma-Ray Burst Monitor detection
  37. IceCube-250429A: Upper limits from a search for additional neutrino events in IceCube
  38. IceCube-250426A: Upper limits from a search for additional neutrino events in IceCube
  39. GRB 250430A: AKO Optical Afterglow Detection
  40. GRB 250430A: Kanata optical upper limit
  41. EP 250427A: Optical counterpart detection by LCO.
  42. GRB 250430A: Swift detection of a burst with optical counterpart
  43. Swift GRB250430.73: Global MASTER-Net observations report
  44. EP250428b: FTW optical and NIR observations
  45. EP250427a/GRB250427A: HCT optical follow-up
  46. EP250427a / GRB 250427A: OHP/T193 continued photometric observations
  47. SVOM/sb25043004: SVOM detection of a X-ray transient
  48. Fermi trigger No 767623859: Global MASTER-Net observations report
  49. EP250428b: refined analysis of the EP-FXT follow-up observation
  50. EP250428b: GROWTH-India telescope optical upper limit
  51. EP250428b: SVOM/VT upper limit
  52. EP250428b: SAO RAS optical upper limit
  53. EP250428b: LAST optical upper limit
  54. IceCube-250429A - IceCube observation of a high-energy neutrino candidate track-like event
  55. GRB 250427A: Swift/UVOT Detection
  56. EP250428b: Global MASTER-Net observations report
  57. EP250428b: Einstein Probe detection of a fast X-ray transient
  58. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  59. EP250427a / GRB 250427A: OHP/T193 photometric observations
  60. EP250427a: EP-FXT follow-up observations
  61. EP250427a/GRB 250427A: FTW optical and NIR observations of the counterpart
  62. EP250427A: COLIBRÍ Continuing Optical Observations
  63. GRB250427A/EP250427a GIT optical afterglow detection:
  64. EP250427a: LT optical counterpart detection
  65. GRB 250427A: Swift-XRT refined Analysis
  66. EP250427a / GRB 250427A: LCO optical counterpart detection
  67. EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
  68. EP250427A/GRB250427A: Keck/LRIS redshift
  69. EP250427a: REM optical/NIR afterglow detection
  70. GRB 250424A: LCO optical observation
  71. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  72. EP250427A: COLIBRÍ Optical Detection
  73. EP250427a: TRT optical counterpart detection
  74. EP 250427a: BOOTES-7 optical afterglow candidate
  75. EP250427a: Global MASTER-Net observations report
  76. EP250427a: Einstein Probe detection of a fast X-ray transient
  77. IceCube Alert 250426.74: Global MASTER-Net observations report
  78. GRB 250424A: Swift-BAT refined analysis
  79. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event (duplicate submission)
  80. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event
  81. GRB 250424A: SVOM/GRM observation of a long burst
  82. GRB 250424A: PRIME near-infrared detection
  83. GRB 250424A: WINTER J-band detection
  84. GRB 250424A: EIRSAT-1 GMOD Detection
  85. IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
  86. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  87. GRB 250424A: SVOM/VT optical observation
  88. GRB 250419A: Mondy Optical Observations
  89. GRB 250424A: Swift/UVOT Detection
  90. Konus-Wind detection of GRB 250424A
  91. Fermi-LAT gamma-ray observations of IceCube-250421A
  92. GRB 250424A: Skynet Optical Observations
  93. GRB 250424A: Kilonova-Catcher optical afterglow detection
  94. GRB 250419a: Continued Liverpool Telescope observations
  95. GRB 250419A: Liverpool Telescope optical upper limit
  96. GRB 250407A: GRBAlpha detection
  97. GRB 250404A / EP250404a: GRBAlpha detection
  98. GRB 250330B: GRBAlpha detection
  99. GRB 250419A: SVOM/ECLAIRs refined analysis
  100. GRB 250424A: Swift-XRT refined Analysis

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