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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. 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"

35938 results found.

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

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