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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"

35255 results found.

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

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