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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"

20955 results found.

  1. GRB 250419A: Optical Observations via Virtual Telescope Project
  2. EP250421a: REM optical upper limit
  3. EP250421a: Swift/XRT counterpart detection
  4. EP250421A: COLIBRÍ Optical Upper Limit
  5. GRB 250419A: Mondy Continued Optical Observations
  6. Fermi GRB 250421A: Global MASTER-Net observations report
  7. EP250421a: Global MASTER-Net observations report
  8. EP250421a: Mephisto optical counterpart confirmation
  9. IceCube Alert 250421.71: Global MASTER-Net observations report
  10. EP250421a: JinShan likely optical counterpart
  11. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  12. GRB 250419A: Liverpool Telescope observations
  13. GRB 250419A: LCO optical observation
  14. GRB 250419A: JinShan optical observations
  15. GRB 250419A: SVOM/VT optical continuous observations
  16. GRB 250419A: SVOM/C-GFT optical observations
  17. GRB 250419A: Swift/UVOT Follow up
  18. GRB 250419A: LCO optical afterglow multi-band observations
  19. GRB 250419A: Mondy and AbAO Optical Observations
  20. GRB 250419A: Liverpool Telescope observations
  21. GRB 250419A: AKO Optical Afterglow Detection
  22. GRB 250419A: MASTER optical afterglow observation
  23. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  24. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  25. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  26. GRB 250419A: GOTO optical counterpart detection
  27. GRB 250419A: KAIT optical afterglow observations
  28. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  29. EP250416a: Swift/XRT counterpart fading
  30. EP250416a: refined EP-WXT and EP-FXT analysis
  31. EP20250416a: Swift/XRT counterpart detection
  32. GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
  33. IceCube-250416A: DDOTI Optical Observations
  34. EP250416a: Gemini South-GMOS optical counterpart
  35. EP250225a: SVOM/VT optical brightening
  36. EP250416a: GSP optical upper limit
  37. EP250416a: Global MASTER-Net observations report
  38. IceCube-250416A: Global MASTER-Net observations report
  39. IceCube 250414.324: DDOTI Optical Observations
  40. EP250304a: ATCA radio observations
  41. EP250404a: Nanshan 0.43m Telescope optical observatios
  42. Fermi trigger No 766148493: Global MASTER-Net observations report
  43. Fermi trigger No 766173972: Global MASTER-Net observations report
  44. GRB 250411A: DDOTI Optical Observations
  45. Fermi GRB 250411A: Global MASTER-Net observations report
  46. GRB 250407A: Continued KAIT/Nickel optical observations
  47. GRB 250314A: e-MERLIN observations
  48. GRB 250407A: Mondy and AbAO Optical Observations
  49. EP250227a: Further NOT optical observations
  50. IceCube-250406A: Swift-XRT observations
  51. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-250409A
  52. EP250407a: Global MASTER-Net observations report
  53. GRB 250407A: LCO detection of a fading optical counterpart
  54. Fermi-LAT gamma-ray observations of IceCube-250406A
  55. EP250407a: Swift-XRT observations
  56. EP250407a: EP-WXT detection of a fast X-ray transient
  57. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  58. GRB 250407A: KAIT Optical Afterglow Candidate
  59. IceCube-250406A: No candidates from the Zwicky Transient Facility
  60. GRB 250407A: Swift-XRT afterglow detection
  61. Fermi GRB 250407A: Global MASTER-Net observations report
  62. GRB 250407A: Swift ToO observations
  63. IceCube 250406A: DDOTI Optical Observations of the Refined Position
  64. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  65. IceCube 250406.951: DDOTI Optical Observations
  66. IceCube Alert 250406.95: Global MASTER-Net observations report
  67. Fermi trigger No 765663719: Global MASTER-Net observations report
  68. EP250404a: Multi-band Optical Observations from UCAS-70 and XL-C14
  69. Fermi GRB 250406A: Global MASTER-Net observations report
  70. GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  71. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  72. Fermi trigger No 765619921: Global MASTER-Net observations report
  73. GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
  74. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  75. GRB 250404A / EP250404a: Mondy optical observations
  76. EP250404a: refined analysis of the EP-WXT and EP-FXT observations
  77. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  78. GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  79. EP250402a: Optical upper limit with PD 1.3m observations
  80. GRB 250404A / EP250404a: NOT optical observations
  81. GRB 250331D: Swift-XRT afterglow detection
  82. EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  83. EP250404a: REM optical/NIR observations
  84. EP250404a: Seimei/TriCCS optical counterpart detection
  85. EP250404A: COLIBRÍ/DDRAGO Optical Observations
  86. EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection
  87. EP250404a: LCO optical counterpart detection
  88. Fermi GRB 250404A: Global MASTER-Net observations report
  89. EP250404a: Xinglong decaying optical counterpart
  90. GRB 250403A: Montarrenti Observatory optical detection
  91. EP250404a: Global MASTER-Net observations report
  92. GRB 250403A: KAIT optical observations
  93. EP250404a: AKO Optical Afterglow Detection
  94. EP250404a: LAST detection of optical counterpart
  95. GRB 250403A: Fermi GBM observations
  96. EP250404a: Mephisto multi-band optical detection
  97. EP250321A: J band upper limit by SYSU 80cm telescope
  98. EP250404a: Nanshan/HMT optical counterpart detection
  99. GRB 250402A: Mondy optical observations
  100. EP250402a: Optical upper limit with Kinder observations

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