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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"

20514 results found.

  1. Fermi trigger No 766148493: Global MASTER-Net observations report
  2. Fermi trigger No 766173972: Global MASTER-Net observations report
  3. GRB 250411A: DDOTI Optical Observations
  4. Fermi GRB 250411A: Global MASTER-Net observations report
  5. GRB 250407A: Continued KAIT/Nickel optical observations
  6. GRB 250314A: e-MERLIN observations
  7. GRB 250407A: Mondy and AbAO Optical Observations
  8. EP250227a: Further NOT optical observations
  9. IceCube-250406A: Swift-XRT observations
  10. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-250409A
  11. EP250407a: Global MASTER-Net observations report
  12. GRB 250407A: LCO detection of a fading optical counterpart
  13. Fermi-LAT gamma-ray observations of IceCube-250406A
  14. EP250407a: Swift-XRT observations
  15. EP250407a: EP-WXT detection of a fast X-ray transient
  16. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  17. GRB 250407A: KAIT Optical Afterglow Candidate
  18. IceCube-250406A: No candidates from the Zwicky Transient Facility
  19. GRB 250407A: Swift-XRT afterglow detection
  20. Fermi GRB 250407A: Global MASTER-Net observations report
  21. GRB 250407A: Swift ToO observations
  22. IceCube 250406A: DDOTI Optical Observations of the Refined Position
  23. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  24. IceCube 250406.951: DDOTI Optical Observations
  25. IceCube Alert 250406.95: Global MASTER-Net observations report
  26. Fermi trigger No 765663719: Global MASTER-Net observations report
  27. EP250404a: Multi-band Optical Observations from UCAS-70 and XL-C14
  28. Fermi GRB 250406A: Global MASTER-Net observations report
  29. GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  30. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  31. Fermi trigger No 765619921: Global MASTER-Net observations report
  32. GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
  33. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  34. GRB 250404A / EP250404a: Mondy optical observations
  35. EP250404a: refined analysis of the EP-WXT and EP-FXT observations
  36. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  37. GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  38. EP250402a: Optical upper limit with PD 1.3m observations
  39. GRB 250404A / EP250404a: NOT optical observations
  40. GRB 250331D: Swift-XRT afterglow detection
  41. EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  42. EP250404a: REM optical/NIR observations
  43. EP250404a: Seimei/TriCCS optical counterpart detection
  44. EP250404A: COLIBRÍ/DDRAGO Optical Observations
  45. EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection
  46. EP250404a: LCO optical counterpart detection
  47. Fermi GRB 250404A: Global MASTER-Net observations report
  48. EP250404a: Xinglong decaying optical counterpart
  49. GRB 250403A: Montarrenti Observatory optical detection
  50. EP250404a: Global MASTER-Net observations report
  51. GRB 250403A: KAIT optical observations
  52. EP250404a: AKO Optical Afterglow Detection
  53. EP250404a: LAST detection of optical counterpart
  54. GRB 250403A: Fermi GBM observations
  55. EP250404a: Mephisto multi-band optical detection
  56. EP250321A: J band upper limit by SYSU 80cm telescope
  57. EP250404a: Nanshan/HMT optical counterpart detection
  58. GRB 250402A: Mondy optical observations
  59. EP250402a: Optical upper limit with Kinder observations
  60. GRB 250403A: REM NIR afterglow detection
  61. GRB 250403A: LCO optical counterpart detection
  62. GRB 250403A: JinShan optical observations
  63. GRB 250403A: Optical counterpart detection by LCO.
  64. EP250402a: EP-FXT follow-up observations
  65. GRB 250403A: Swift-XRT observations
  66. GRB 250322A: 10 GHz VLA radio upper limits
  67. Fermi GRB 250403A: Global MASTER-Net observations report
  68. GRB 250403A: GOTO optical counterpart follow-up observations
  69. GRB 250402A: NUTTelA-TAO Early Optical Limits
  70. GRB 250403A: 1.6m Mephisto multi-band optical detection
  71. GRB 250403A: SVOM/C-GFT optical observations
  72. GRB 250403A: GOTO detection of the optical afterglow
  73. GRB 250402A: Swift-XRT observations
  74. GRB 250225B: VLT host galaxy redshift z = 0.950
  75. GRB250402A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  76. GRB 250402A: VLT/FORS2 spectroscopic redshift z = 2.823
  77. GRB 250402A: REM optical/NIR upper limits
  78. GRB 250402A: LCO optical counterpart detection
  79. GRB 250402A: refined SVOM/MXT data analysis
  80. EP250402a: Einstein Probe detection of a fast X-ray transient
  81. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  82. GRB 250314A: ALMA detection
  83. GRB 250329B: Swift/UVOT Upper Limit
  84. GRB 250329A: Swift/UVOT Upper Limit
  85. GRB 250327B: Swift/UVOT Detection
  86. GRB 250327A: Swift/UVOT Upper Limits
  87. GRB 250327B: Kilonova-Catcher Observations
  88. GRB250331D: AbAO optical observations
  89. GRB 250331C: Swift/UVOT Upper Limits
  90. GRB 250331B: Swift/UVOT Upper Limits
  91. GRB 250328A: AbAO AS-32 Optical Observations
  92. GRB 250219A: NOT candidate host galaxy detection
  93. GRB 250331D: Swift-XRT observations
  94. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
  95. Fermi GRB 250331E: Global MASTER-Net observations report
  96. Fermi GRB 250331D: Global MASTER-Net observations report
  97. Fermi trigger No 765078057: Global MASTER-Net observations report
  98. GRB 250331D: Swift ToO observations
  99. Swift GRB 250331C: Global MASTER-Net observations report
  100. Swift GRB 250331B: Global MASTER-Net observations report

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