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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"

43933 results found.

  1. GRB 250407A: VZLUSAT-2 detection
  2. Fermi-LAT Gamma-ray Observations of IceCube-250429A
  3. GRB 250502B: DDOTI Optical Observations
  4. GRB 250430A: Swift-XRT refined Analysis
  5. GRB 250502A: Early optical counterpart detection by LCO.
  6. GRB 250502A: SVOM/VT optical bump
  7. GRB 250502A: TRT optical afterglow confirmation
  8. GRB 250430A: Enhanced Swift-XRT position
  9. Fermi GRB 250502B: Global MASTER-Net observations report
  10. GRB 250430A: Optical Observations via Virtual Telescope Project, Italy
  11. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  12. GRB 250502B: Fermi GBM Final Real-time Localization
  13. GRB 250502A: SVOM detection of a burst
  14. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  15. GRB 250430A: SVOM/VT optical observations
  16. GRB 250430A: KAIT optical observations
  17. EP250428b: Pan-STARRS follow-up, upper limit on the optical counterpart, and possible host galaxy.
  18. GRB 250430A / EP250430a: J-band upper limits with WINTER
  19. GRB 250430A: NUTTelA-TAO Early Measurements
  20. EP250427a / GRB 250427A: OHP/T193 photometric observations: third visit
  21. GRB 250430A: DDOTI Optical Observations
  22. GRB 250430A: Leavitt Observatory optical upper limit
  23. GRB 250430A: Bassano Bresciano Observatory upper limit
  24. GRB 250430A : MITSuME Akeno optical upper limits
  25. GRB 250430A / EP250430a: VLT/X-shooter spectroscopic redshift z = 0.767
  26. SVOM/sb25043004: EP-FXT observations
  27. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  28. GRB 250424A: CALET Gamma-Ray Burst Monitor detection
  29. IceCube-250429A: Upper limits from a search for additional neutrino events in IceCube
  30. IceCube-250426A: Upper limits from a search for additional neutrino events in IceCube
  31. GRB 250430A: AKO Optical Afterglow Detection
  32. GRB 250430A: Kanata optical upper limit
  33. EP 250427A: Optical counterpart detection by LCO.
  34. GRB 250430A: Swift detection of a burst with optical counterpart
  35. Swift GRB250430.73: Global MASTER-Net observations report
  36. EP250428b: FTW optical and NIR observations
  37. EP250427a/GRB250427A: HCT optical follow-up
  38. EP250427a / GRB 250427A: OHP/T193 continued photometric observations
  39. SVOM/sb25043004: SVOM detection of a X-ray transient
  40. Fermi trigger No 767623859: Global MASTER-Net observations report
  41. EP250428b: refined analysis of the EP-FXT follow-up observation
  42. EP250428b: GROWTH-India telescope optical upper limit
  43. EP250428b: SVOM/VT upper limit
  44. EP250428b: SAO RAS optical upper limit
  45. EP250428b: LAST optical upper limit
  46. IceCube-250429A - IceCube observation of a high-energy neutrino candidate track-like event
  47. GRB 250427A: Swift/UVOT Detection
  48. EP250428b: Global MASTER-Net observations report
  49. EP250428b: Einstein Probe detection of a fast X-ray transient
  50. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  51. EP250427a / GRB 250427A: OHP/T193 photometric observations
  52. EP250427a: EP-FXT follow-up observations
  53. EP250427a/GRB 250427A: FTW optical and NIR observations of the counterpart
  54. EP250427A: COLIBRÍ Continuing Optical Observations
  55. GRB250427A/EP250427a GIT optical afterglow detection:
  56. EP250427a: LT optical counterpart detection
  57. GRB 250427A: Swift-XRT refined Analysis
  58. EP250427a / GRB 250427A: LCO optical counterpart detection
  59. EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
  60. EP250427A/GRB250427A: Keck/LRIS redshift
  61. EP250427a: REM optical/NIR afterglow detection
  62. GRB 250424A: LCO optical observation
  63. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  64. EP250427A: COLIBRÍ Optical Detection
  65. EP250427a: TRT optical counterpart detection
  66. EP 250427a: BOOTES-7 optical afterglow candidate
  67. EP250427a: Global MASTER-Net observations report
  68. EP250427a: Einstein Probe detection of a fast X-ray transient
  69. IceCube Alert 250426.74: Global MASTER-Net observations report
  70. GRB 250424A: Swift-BAT refined analysis
  71. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event (duplicate submission)
  72. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event
  73. GRB 250424A: SVOM/GRM observation of a long burst
  74. GRB 250424A: PRIME near-infrared detection
  75. GRB 250424A: WINTER J-band detection
  76. GRB 250424A: EIRSAT-1 GMOD Detection
  77. IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
  78. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  79. GRB 250424A: SVOM/VT optical observation
  80. GRB 250419A: Mondy Optical Observations
  81. GRB 250424A: Swift/UVOT Detection
  82. Konus-Wind detection of GRB 250424A
  83. Fermi-LAT gamma-ray observations of IceCube-250421A
  84. GRB 250424A: Skynet Optical Observations
  85. GRB 250424A: Kilonova-Catcher optical afterglow detection
  86. GRB 250419a: Continued Liverpool Telescope observations
  87. GRB 250419A: Liverpool Telescope optical upper limit
  88. GRB 250407A: GRBAlpha detection
  89. GRB 250404A / EP250404a: GRBAlpha detection
  90. GRB 250330B: GRBAlpha detection
  91. GRB 250419A: SVOM/ECLAIRs refined analysis
  92. GRB 250424A: Swift-XRT refined Analysis
  93. GRB 250424A: Enhanced Swift-XRT position
  94. GRB 250424A: AstroSat CZTI detection of a bright long burst
  95. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  96. GRB 250424A: BlackGEM optical afterglow detection
  97. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  98. GRB 250424A: likely host galaxy
  99. GRB 250424A: DDOTI Afterglow Detection
  100. GRB 250424A: REM optical/NIR afterglow detection

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