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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"
  1. Fermi trigger No 751563375: Global MASTER-Net observations report
  2. Fermi trigger No 751554401: Global MASTER-Net observations report
  3. EP241021a: Optical and NIR observations of counterpart with the Fraunhofer Telescope at Wendelstein Observatory
  4. EP241021a: Optical and NIR observations of counterpart with the Fraunhofer Telescope at Wendelstein Observatory
  5. EP 241021a: Swift-XRT observations
  6. EP241021a: optical follow-up observations with the Liverpool Telescope
  7. Fermi GRB 241025A: Global MASTER-Net observations report
  8. Swift GRB 241025A: Global MASTER-Net observations report
  9. EP241025a (GRB 241025A): EP observations update
  10. GRB 241025A : SVOM/VT optical afterglow observations
  11. EP 241021A: Swift ToO observations
  12. EP241021a: Liverpool Telescope optical follow-up observations
  13. GRB 241025A: Enhanced Swift-XRT position
  14. GRB 241001A: JWST spectroscopic identification of a supernova counterpart
  15. GRB 241025A: NOT spectroscopic redshift of z = 4.20
  16. GRB 241025A: DDOTI Afterglow detection
  17. EP241025a (GRB 241025A): EP on-board trigger and autonomous follow-up observation
  18. GRB 241025A: SVOM/GRM observation
  19. GRB 241025A: TRT optical afterglow observation
  20. Fermi GRB 241024B: Global MASTER-Net observations report
  21. GRB 241025A: Fermi GBM Final Real-time Localization
  22. GRB 241025A: Swift detection of a burst with an optical counterpart
  23. EP241021a: GTC OSIRIS+ spectroscopy of the optical counterpart
  24. GRB 241001A: ATCA radio observations
  25. GRB 241024B: Fermi GBM Final Localization
  26. EP241021a: No Detection in Fermi-GBM Observation
  27. GRB 241010A: VIRT Optical Upper Limit
  28. GRB 241024A: Fermi GBM Final Localisation
  29. EP241021a: VLT/FORS2 redshift z = 0.75
  30. Fermi trigger No 751449953: Global MASTER-Net observations report
  31. EP241021a: SAO RAS optical observations
  32. EP241021a: KAIT optical observations
  33. EP241021a: EP-FXT follow-up observation update
  34. IPN triangulation of GRB 241021A (long)
  35. EP241021a: Optical counterpart observations with the Liverpool Telescope
  36. EP241021a: 1.3m DFOT Optical observations
  37. EP241021a: GSP detects optical candidate counterpart
  38. EP241021a: Optical upper limits with Kinder observations
  39. EP241021a: TRT optical observations
  40. GRB 241018A: SVOM/C-GFT optical observations
  41. EP241021a: NOT likely optical counterpart
  42. EP EP241021a: Global MASTER-Net observations report
  43. GRB241017A: 1.3m DFOT optical upper limit
  44. GRB 241018A: 1.3m DFOT Optical upper limit
  45. GRB 241018A: EP-FXT afterglow detection
  46. EP241021a: GOTO optical upper limits
  47. EP241021a: EP detection of a fast X-ray transient
  48. IceCube-Cascade 241019A: Upper limits from a search for additional neutrino events in IceCube
  49. Konus-Wind detection of GRB 241018A
  50. GRB 241018A: SVOM/GRM observation
  51. GRB 241018A/sb24101802: Mephisto optical upper limit
  52. GRB 241017A/sb24101702: Mephisto optical upper limit
  53. GRB 241018A: BOOTES-4/MET optical upper limit
  54. GRB 241018A: Mondy optical upper limit
  55. GRB 241018A: SVOM/VT further analysis and counterpart confirmed
  56. GRB 241018A: GROWTH-India telescope optical upper limit
  57. GRB241018A: XingLong Optical Upper Limit
  58. GRB 241018A: Swift-XRT observations
  59. GRB 241018A: REM optical/NIR upper limits
  60. GRB 241018A: NOT optical observations
  61. GRB 241017A: SVOM/VT follow-up and optical upper limit
  62. GRB 241018A: SVOM/VT follow-up and optical candidate
  63. GRB 241018A: LCO/0.4m optical upper limits
  64. GRB 241018A: Swift ToO observations
  65. GRB 241006A: VIRT Optical Upper Limit
  66. GRB 240727A: VIRT Optical Upper Limit
  67. GRB 241018A: X-ray afterglow candidate observed by MXT
  68. GRB 241016B: Fermi GBM Observations
  69. GRB 241018A: Detection of a bright long GRB by SVOM
  70. GRB 241017A: Swift-XRT observations
  71. GRB241017a: Liverpool Telescope observations of XRT uncatalogued sources
  72. GRB 241001A: EP-FXT afterglow detection
  73. GRB 241017A: GROWTH-India Telescope optical upper limit
  74. GRB241017A: TOO Observations by SVOM/MXT
  75. GRB 241016B: Swift/BAT-GUANO localization skymap of a short burst
  76. GRB 241017A: J-band upper limit from WINTER
  77. Fermi trigger No 750788395: Global MASTER-Net observations report
  78. GRB 241016B: SVOM/GRM observation
  79. GRB241016C: Fermi GBM Final Localization
  80. Fermi Gamma-ray Burst Monitor trigger 750792698/241016730 is not a GRB
  81. GRB 241017A: Swift ToO observations
  82. GRB 241017A : Detection of a weak and soft long duration GRB by SVOM/ECLAIRs
  83. Fermi GRB 241016B: Global MASTER-Net observations report
  84. GRB 241016B: Fermi GBM Final Localization
  85. Fermi GRB 241016A: Global MASTER-Net observations report
  86. GRB 241016A: Fermi GBM Final Real-time Localization
  87. IceCube alert 139977_2910365 retraction
  88. IceCube Alert 241016.04: Global MASTER-Net observations report
  89. GRB 241010A: Swift-BAT refined analysis
  90. GRB 241013B: Fermi GBM Observation
  91. GRB 241013B: Swift/BAT-GUANO localization skymap of a burst
  92. GRB 241013A: Fermi GBM Observation
  93. GRB 240916A: radio detection with the VLA
  94. GRB241013A: REM observations
  95. GRB 241009A: LCO optical upper limits
  96. GRB 241013B: SVOM/GRM observation
  97. Fermi GRB 241013B: Global MASTER-Net observations report
  98. Integral GRB241013.04: Global MASTER-Net observations report
  99. GRB 241013B: Fermi GBM Final Real-time Localization
  100. GRB 241013A: a long GRB detected by INTEGRAL

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