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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"

36141 results found.

  1. GRB 250331D: Swift-XRT afterglow detection
  2. GRB 250404B: AstroSat CZTI detection of a short burst
  3. GRB 250403A: AstroSat CZTI detection
  4. EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  5. EP250404a: REM optical/NIR observations
  6. EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection
  7. EP250404a: LCO optical counterpart detection
  8. Fermi GRB 250404A: Global MASTER-Net observations report
  9. GRB 250403A: Montarrenti Observatory optical detection
  10. GRB 250404A: Fermi GBM Detection
  11. GRB 250403A: KAIT optical observations
  12. GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
  13. EP250404a: Xinglong-2.16m spectroscopic redshift
  14. GRB 250403A: Fermi GBM observations
  15. GRB 250327B: VIRT Optical Upper Limit
  16. GRB 250331C Swift-BAT refined analysis
  17. GRB 250331B Swift-BAT refined analysis
  18. GRB 250330A Swift-BAT refined analysis
  19. EP250404a: Nanshan/HMT optical counterpart detection
  20. EP250404a: Einstein Probe detection of an X-ray transient
  21. GRB 250404A: Fermi GBM Final Real-time Localization
  22. GRB 250402A: Mondy optical observations
  23. GRB 250403A: Swift/UVOT Detection
  24. GRB 250402A: Swift/UVOT Upper Limits
  25. GRB 250403A: SVOM/VT optical observation
  26. GRB 250403A: REM NIR afterglow detection
  27. GRB 250403A: LCO optical counterpart detection
  28. GRB 250403A: JinShan optical observations
  29. GRB 250402A: EP-FXT afterglow detection
  30. GRB 250403A: Optical counterpart detection by LCO.
  31. GRB 250403A: Swift-XRT observations
  32. GRB 250322A: 10 GHz VLA radio upper limits
  33. Fermi GRB 250403A: Global MASTER-Net observations report
  34. GRB 250403A: GOTO optical counterpart follow-up observations
  35. GRB 250402A: NUTTelA-TAO Early Optical Limits
  36. GRB 250403A: GMG Optical Observation
  37. GRB 250403A: 1.6m Mephisto multi-band optical detection
  38. GRB 250402A: Fermi GBM Observation
  39. GRB 250403A: SVOM/C-GFT optical observations
  40. GRB 250403A: GOTO detection of the optical afterglow
  41. GRB 250402A: Swift-XRT observations
  42. GRB 250403A : SVOM detection of a burst
  43. GRB 250403A: Fermi GBM Final Real-time Localization
  44. GRB 250225B: VLT host galaxy redshift z = 0.950
  45. GRB250402A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  46. GRB 250402A: VLT/FORS2 spectroscopic redshift z = 2.823
  47. GRB 250402A: REM optical/NIR upper limits
  48. GRB 250402A: LCO optical counterpart detection
  49. GRB 250402A: refined SVOM/MXT data analysis
  50. GRB 250402B: AstroSat CZTI detection of a short burst
  51. GRB 250402A: SVOM/VT optical counterpart
  52. GRB 250402A: SVOM detection of a burst
  53. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  54. GRB 250314A: ALMA detection
  55. GRB 250329B: Swift/UVOT Upper Limit
  56. GRB 250329A: Swift/UVOT Upper Limit
  57. GRB 250327B: Swift/UVOT Detection
  58. GRB 250327A: Swift/UVOT Upper Limits
  59. GRB 250331E: SVOM/GRM observation
  60. GRB 250327B: Kilonova-Catcher Observations
  61. GRB250331D: AbAO optical observations
  62. GRB 250331D: Fermi GBM observation
  63. GRB 250331C: Swift/UVOT Upper Limits
  64. GRB 250331B: Swift/UVOT Upper Limits
  65. GRB 250328A: AbAO AS-32 Optical Observations
  66. GRB 250219A: NOT candidate host galaxy detection
  67. GRB 250322B: GRBAlpha detection
  68. GRB 250331D: Swift-XRT observations
  69. GRB 250331C: Swift-XRT refined Analysis
  70. GRB 250331B: Swift-XRT refined Analysis
  71. GRB 250331B: Swift-XRT refined Analysis
  72. GRB 250322B possible detection by the AstroSat Satellite
  73. GRB 250330B: SVOM/GRM observation of a short burst
  74. Fermi GRB 250331E: Global MASTER-Net observations report
  75. Fermi GRB 250331D: Global MASTER-Net observations report
  76. GRB 250330B: EIRSAT-1 GMOD Detection
  77. GRB 250331E: Fermi GBM Final Real-time Localization
  78. GRB 250327A Swift-BAT refined analysis
  79. GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
  80. GRB 250329B: CAHA 2.2m telescope optical limit
  81. GRB 250331D: Swift ToO observations
  82. Swift GRB 250331C: Global MASTER-Net observations report
  83. Swift GRB 250331B: Global MASTER-Net observations report
  84. GRB 250331D: Swift/BAT-GUANO arcminute localization of a burst during slew
  85. Konus-Wind detection of GRB 250327B
  86. GRB 250331C: Enhanced Swift-XRT position
  87. GRB 250331B: Enhanced Swift-XRT position
  88. GRB 250320C : SVOM detection of a burst through offline search
  89. GRB 250329B: Swift-XRT confirmation of fading
  90. GRB 250330A: VLT/FORS2 Afterglow Detection
  91. GRB20250327B: 45th Parallel Observatory upper limit
  92. GRB 250328A: Swift/UVOT Detection
  93. GRB 250328A: Swift-XRT refined Analysis
  94. GRB 250330A: Fermi GBM Observation
  95. GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
  96. GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
  97. GRB 250331D: Fermi GBM Final Real-time Localization
  98. GRB 250331C: Prompt enhanced Swift-XRT position
  99. GRB 250331C: Swift detection of a burst
  100. GRB 250331B: Swift detection of a burst

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