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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"

35258 results found.

  1. GRB 250407A: Fermi GBM Final Real-time Localization
  2. GRB 250406A: AstroSat CZTI detection
  3. Fermi GRB 250406A: Global MASTER-Net observations report
  4. GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  5. GRB 250406A: Fermi GBM Final Real-time Localization
  6. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  7. Fermi Gamma-ray Burst Monitor trigger 765619921/250406342 is not a GRB
  8. GRB 250404A / EP250404a: RC500 INASAN-Kislovodsk optical upper limit
  9. GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
  10. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  11. Konus-Wind detection of GRB 250404A / EP250404a
  12. GRB 250404A / EP250404a: Mondy optical observations
  13. GRB 250404A / EP250404a: GMG spectroscopic redshift at z ~ 2.627
  14. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  15. GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  16. GRB 250404A / EP250404a: NOT optical observations
  17. GRB 250331D: Swift-XRT afterglow detection
  18. GRB 250404B: AstroSat CZTI detection of a short burst
  19. GRB 250403A: AstroSat CZTI detection
  20. EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  21. EP250404a: REM optical/NIR observations
  22. EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection
  23. EP250404a: LCO optical counterpart detection
  24. Fermi GRB 250404A: Global MASTER-Net observations report
  25. GRB 250403A: Montarrenti Observatory optical detection
  26. GRB 250404A: Fermi GBM Detection
  27. GRB 250403A: KAIT optical observations
  28. GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
  29. EP250404a: Xinglong-2.16m spectroscopic redshift
  30. GRB 250403A: Fermi GBM observations
  31. GRB 250327B: VIRT Optical Upper Limit
  32. GRB 250331C Swift-BAT refined analysis
  33. GRB 250331B Swift-BAT refined analysis
  34. GRB 250330A Swift-BAT refined analysis
  35. EP250404a: Nanshan/HMT optical counterpart detection
  36. EP250404a: Einstein Probe detection of an X-ray transient
  37. GRB 250404A: Fermi GBM Final Real-time Localization
  38. GRB 250402A: Mondy optical observations
  39. GRB 250403A: Swift/UVOT Detection
  40. GRB 250402A: Swift/UVOT Upper Limits
  41. GRB 250403A: SVOM/VT optical observation
  42. GRB 250403A: REM NIR afterglow detection
  43. GRB 250403A: LCO optical counterpart detection
  44. GRB 250403A: JinShan optical observations
  45. GRB 250402A: EP-FXT afterglow detection
  46. GRB 250403A: Optical counterpart detection by LCO.
  47. GRB 250403A: Swift-XRT observations
  48. GRB 250322A: 10 GHz VLA radio upper limits
  49. Fermi GRB 250403A: Global MASTER-Net observations report
  50. GRB 250403A: GOTO optical counterpart follow-up observations
  51. GRB 250402A: NUTTelA-TAO Early Optical Limits
  52. GRB 250403A: GMG Optical Observation
  53. GRB 250403A: 1.6m Mephisto multi-band optical detection
  54. GRB 250402A: Fermi GBM Observation
  55. GRB 250403A: SVOM/C-GFT optical observations
  56. GRB 250403A: GOTO detection of the optical afterglow
  57. GRB 250402A: Swift-XRT observations
  58. GRB 250403A : SVOM detection of a burst
  59. GRB 250403A: Fermi GBM Final Real-time Localization
  60. GRB 250225B: VLT host galaxy redshift z = 0.950
  61. GRB250402A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  62. GRB 250402A: VLT/FORS2 spectroscopic redshift z = 2.823
  63. GRB 250402A: REM optical/NIR upper limits
  64. GRB 250402A: LCO optical counterpart detection
  65. GRB 250402A: refined SVOM/MXT data analysis
  66. GRB 250402B: AstroSat CZTI detection of a short burst
  67. GRB 250402A: SVOM/VT optical counterpart
  68. GRB 250402A: SVOM detection of a burst
  69. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  70. GRB 250314A: ALMA detection
  71. GRB 250329B: Swift/UVOT Upper Limit
  72. GRB 250329A: Swift/UVOT Upper Limit
  73. GRB 250327B: Swift/UVOT Detection
  74. GRB 250327A: Swift/UVOT Upper Limits
  75. GRB 250331E: SVOM/GRM observation
  76. GRB 250327B: Kilonova-Catcher Observations
  77. GRB250331D: AbAO optical observations
  78. GRB 250331D: Fermi GBM observation
  79. GRB 250331C: Swift/UVOT Upper Limits
  80. GRB 250331B: Swift/UVOT Upper Limits
  81. GRB 250328A: AbAO AS-32 Optical Observations
  82. GRB 250219A: NOT candidate host galaxy detection
  83. GRB 250322B: GRBAlpha detection
  84. GRB 250331D: Swift-XRT observations
  85. GRB 250331C: Swift-XRT refined Analysis
  86. GRB 250331B: Swift-XRT refined Analysis
  87. GRB 250331B: Swift-XRT refined Analysis
  88. GRB 250322B possible detection by the AstroSat Satellite
  89. GRB 250330B: SVOM/GRM observation of a short burst
  90. Fermi GRB 250331E: Global MASTER-Net observations report
  91. Fermi GRB 250331D: Global MASTER-Net observations report
  92. GRB 250330B: EIRSAT-1 GMOD Detection
  93. GRB 250331E: Fermi GBM Final Real-time Localization
  94. GRB 250327A Swift-BAT refined analysis
  95. GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
  96. GRB 250329B: CAHA 2.2m telescope optical limit
  97. GRB 250331D: Swift ToO observations
  98. Swift GRB 250331C: Global MASTER-Net observations report
  99. Swift GRB 250331B: Global MASTER-Net observations report
  100. GRB 250331D: Swift/BAT-GUANO arcminute localization of a burst during slew

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