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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"

27215 results found.

  1. GRB 250407A: LCO detection of a fading optical counterpart
  2. GRB 250407A: SVOM/GRM observation of a bright long burst
  3. GRB 250407A: EP-WXT afterglow detection
  4. EP250407a: EP-WXT detection of a fast X-ray transient
  5. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  6. GRB 250407A: Fermi GBM Detection
  7. Fermi GRB 250407A: Global MASTER-Net observations report
  8. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  9. IceCube 250406A: DDOTI Optical Observations of the Refined Position
  10. GRB 250407A: BALROG localization (Fermi Trigger 765733706 / GRB 250407659)
  11. GRB 250407A: Fermi GBM Final Real-time Localization
  12. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  13. IceCube 250406.951: DDOTI Optical Observations
  14. IceCube Alert 250406.95: Global MASTER-Net observations report
  15. Fermi trigger No 765663719: Global MASTER-Net observations report
  16. Fermi GRB 250406A: Global MASTER-Net observations report
  17. GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  18. GRB 250406A: Fermi GBM Final Real-time Localization
  19. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  20. Fermi trigger No 765619921: Global MASTER-Net observations report
  21. Fermi Gamma-ray Burst Monitor trigger 765619921/250406342 is not a GRB
  22. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  23. EP250404a: refined analysis of the EP-WXT and EP-FXT observations
  24. GRB 250404A / EP250404a: GMG spectroscopic redshift at z ~ 2.627
  25. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  26. EP250402a: Optical upper limit with PD 1.3m observations
  27. GRB 250404A / EP250404a: NOT optical observations
  28. EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  29. EP250404a: REM optical/NIR observations
  30. EP250404A: COLIBRÍ/DDRAGO Optical Observations
  31. EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection
  32. EP250404a: LCO optical counterpart detection
  33. Fermi GRB 250404A: Global MASTER-Net observations report
  34. EP250404a: Xinglong decaying optical counterpart
  35. GRB 250404A: Fermi GBM Detection
  36. EP250404a: Global MASTER-Net observations report
  37. GRB 250403A: KAIT optical observations
  38. EP250404a: AKO Optical Afterglow Detection
  39. GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
  40. GRB 250403A: Fermi GBM observations
  41. EP250404a: Mephisto multi-band optical detection
  42. GRB 250331C Swift-BAT refined analysis
  43. GRB 250331B Swift-BAT refined analysis
  44. GRB 250330A Swift-BAT refined analysis
  45. EP250321A: J band upper limit by SYSU 80cm telescope
  46. EP250404a: Nanshan/HMT optical counterpart detection
  47. EP250404a: Einstein Probe detection of an X-ray transient
  48. GRB 250404A: Fermi GBM Final Real-time Localization
  49. EP250402a: Optical upper limit with Kinder observations
  50. GRB 250403A: SVOM/VT optical observation
  51. GRB 250403A: REM NIR afterglow detection
  52. IceCube-250330A: MASTER detection of PKS 2032+107 blazar flare with Zhirkov effect
  53. GRB 250403A: JinShan optical observations
  54. GRB 250402A: EP-FXT afterglow detection
  55. GRB 250403A: Optical counterpart detection by LCO.
  56. EP250402a: EP-FXT follow-up observations
  57. GRB 250403A: Swift-XRT observations
  58. Fermi GRB 250403A: Global MASTER-Net observations report
  59. GRB 250402A: NUTTelA-TAO Early Optical Limits
  60. GRB 250403A: GMG Optical Observation
  61. GRB 250403A: 1.6m Mephisto multi-band optical detection
  62. GRB 250402A: Fermi GBM Observation
  63. GRB 250403A: SVOM/C-GFT optical observations
  64. GRB 250403A: GOTO detection of the optical afterglow
  65. GRB 250402A: Swift-XRT observations
  66. GRB 250403A : SVOM detection of a burst
  67. GRB 250403A: Fermi GBM Final Real-time Localization
  68. GRB 250225B: VLT host galaxy redshift z = 0.950
  69. GRB250402A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  70. GRB 250402A: VLT/FORS2 spectroscopic redshift z = 2.823
  71. GRB 250402A: REM optical/NIR upper limits
  72. GRB 250402A: LCO optical counterpart detection
  73. GRB 250402A: refined SVOM/MXT data analysis
  74. The EP-WXT trigger 01709133862 is a flaring star
  75. EP250402a: Einstein Probe detection of a fast X-ray transient
  76. GRB 250402A: SVOM/VT optical counterpart
  77. GRB 250402A: SVOM detection of a burst
  78. GRB 250329B: Swift/UVOT Upper Limit
  79. GRB 250329A: Swift/UVOT Upper Limit
  80. GRB 250327B: Swift/UVOT Detection
  81. GRB 250327A: Swift/UVOT Upper Limits
  82. GRB 250331E: SVOM/GRM observation
  83. GRB 250327B: Kilonova-Catcher Observations
  84. GRB 250331D: Fermi GBM observation
  85. GRB 250331C: Swift/UVOT Upper Limits
  86. GRB 250331B: Swift/UVOT Upper Limits
  87. GRB 250328A: AbAO AS-32 Optical Observations
  88. GRB 250331C: Swift-XRT refined Analysis
  89. GRB 250331B: Swift-XRT refined Analysis
  90. GRB 250331B: Swift-XRT refined Analysis
  91. GRB 250330B: SVOM/GRM observation of a short burst
  92. Fermi GRB 250331E: Global MASTER-Net observations report
  93. Fermi GRB 250331D: Global MASTER-Net observations report
  94. GRB 250331E: Fermi GBM Final Real-time Localization
  95. GRB 250327A Swift-BAT refined analysis
  96. Fermi trigger No 765078057: Global MASTER-Net observations report
  97. GRB 250329B: CAHA 2.2m telescope optical limit
  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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