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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"

32577 results found.

  1. GRB 250430A: Swift-BAT refined analysis
  2. GRB 250504A: VLT/X-shooter upper limits
  3. Fermi GRB 250505A: Global MASTER-Net observations report
  4. GRB 250504A: SVOM/VT upper limit
  5. GRB 250504A: REM optical/NIR observations
  6. GRB 250502A: REM optical/NIR observations
  7. GRB 250504A: MeerLICHT optical afterglow detection
  8. GRB 250504A: Fermi GBM Observation
  9. Fermi GRB 250504A: Global MASTER-Net observations report
  10. GRB 250502A: Swift/UVOT Follow up
  11. GRB 250502A: Mondy and Tien-Shan Optical Observations
  12. GRB 250502A: KAIT optical observations
  13. GRB 250502A: Montarrenti Observatory optical detection
  14. GRB 250502A: Swift-XRT afterglow detection
  15. GRB 250502A: NOT optical observations
  16. GRB 250502a: Liverpool Telescope optical follow-up
  17. GRB 250502B: AstroSat CZTI detection
  18. GRB 250502A: AKO Optical Afterglow Detection
  19. GRB 250502A: LCO optical counterpart detection
  20. GRB 250502A: Swift ToO observations
  21. GRB 250502A: Redshift from OSIRIS+/GTC z = 2.163
  22. GRB 250407A: VZLUSAT-2 detection
  23. Fermi-LAT Gamma-ray Observations of IceCube-250429A
  24. GRB 250502B: DDOTI Optical Observations
  25. GRB 250502A: Early optical counterpart detection by LCO.
  26. GRB 250430A: Swift/UVOT Detection
  27. GRB 250502A: SVOM/VT optical bump
  28. GRB 250502A: TRT optical afterglow confirmation
  29. Fermi GRB 250502B: Global MASTER-Net observations report
  30. GRB 250430A: Optical Observations via Virtual Telescope Project, Italy
  31. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  32. GRB 250430A: SVOM/VT optical observations
  33. GRB 250430A: KAIT optical observations
  34. EP250428b: Pan-STARRS follow-up, upper limit on the optical counterpart, and possible host galaxy.
  35. GRB 250430A / EP250430a: J-band upper limits with WINTER
  36. GRB 250430A: NUTTelA-TAO Early Measurements
  37. EP250427a / GRB 250427A: OHP/T193 photometric observations: third visit
  38. GRB 250430A: DDOTI Optical Observations
  39. GRB 250430A: Leavitt Observatory optical upper limit
  40. GRB 250430A: Bassano Bresciano Observatory upper limit
  41. GRB 250430A : MITSuME Akeno optical upper limits
  42. GRB 250430A / EP250430a: VLT/X-shooter spectroscopic redshift z = 0.767
  43. SVOM/sb25043004: EP-FXT observations
  44. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  45. GRB 250424A: CALET Gamma-Ray Burst Monitor detection
  46. IceCube-250429A: Upper limits from a search for additional neutrino events in IceCube
  47. IceCube-250426A: Upper limits from a search for additional neutrino events in IceCube
  48. GRB 250430A: AKO Optical Afterglow Detection
  49. GRB 250430A: Kanata optical upper limit
  50. EP 250427A: Optical counterpart detection by LCO.
  51. EP250428b: FTW optical and NIR observations
  52. EP250427a/GRB250427A: HCT optical follow-up
  53. EP250427a / GRB 250427A: OHP/T193 continued photometric observations
  54. EP250428b: refined analysis of the EP-FXT follow-up observation
  55. EP250428b: GROWTH-India telescope optical upper limit
  56. EP250428b: SVOM/VT upper limit
  57. EP250428b: SAO RAS optical upper limit
  58. EP250428b: LAST optical upper limit
  59. GRB 250427A: Swift/UVOT Detection
  60. EP250428b: Global MASTER-Net observations report
  61. EP250428b: Einstein Probe detection of a fast X-ray transient
  62. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  63. EP250427a / GRB 250427A: OHP/T193 photometric observations
  64. EP250427a: EP-FXT follow-up observations
  65. EP250427a/GRB 250427A: FTW optical and NIR observations of the counterpart
  66. EP250427a: Lesedi optical counterpart detection
  67. EP250427A: COLIBRÍ Continuing Optical Observations
  68. GRB250427A/EP250427a GIT optical afterglow detection:
  69. EP250427a: LT optical counterpart detection
  70. GRB 250427A: Swift-XRT refined Analysis
  71. EP250427a / GRB 250427A: LCO optical counterpart detection
  72. EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
  73. EP250427A/GRB250427A: Keck/LRIS redshift
  74. EP250427a: REM optical/NIR afterglow detection
  75. GRB 250424A: LCO optical observation
  76. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  77. EP250427A: COLIBRÍ Optical Detection
  78. EP250427a: TRT optical counterpart detection
  79. EP250427a: Global MASTER-Net observations report
  80. EP250427a: Einstein Probe detection of a fast X-ray transient
  81. GRB 250424A: Swift-BAT refined analysis
  82. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event (duplicate submission)
  83. GRB 250424A: SVOM/GRM observation of a long burst
  84. GRB 250424A: PRIME near-infrared detection
  85. GRB 250424A: WINTER J-band detection
  86. GRB 250424A: EIRSAT-1 GMOD Detection
  87. IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
  88. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  89. GRB 250424A: SVOM/VT optical observation
  90. GRB 250419A: Mondy Optical Observations
  91. GRB 250424A: Swift/UVOT Detection
  92. Konus-Wind detection of GRB 250424A
  93. Fermi-LAT gamma-ray observations of IceCube-250421A
  94. GRB 250424A: Skynet Optical Observations
  95. GRB 250424A: Kilonova-Catcher optical afterglow detection
  96. GRB 250419a: Continued Liverpool Telescope observations
  97. GRB 250419A: Liverpool Telescope optical upper limit
  98. GRB 250407A: GRBAlpha detection
  99. GRB 250404A / EP250404a: GRBAlpha detection
  100. GRB 250330B: GRBAlpha detection

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