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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. EP241030a: EP detection of GRB 241030A X-ray Afterglow
  2. GRB241030B: Fermi GBM Observation
  3. GRB 241030B: BTA observations
  4. GRB 241029A: SVOM/VT optical afterglow observations
  5. GRB 241030A: detection of the bright optical counterpart in ATLAS forced photometry
  6. GRB 241030B: Enhanced Swift-XRT position
  7. GRB 241030B: optical observations from the INAF Asiago Observatory
  8. EP241021a: Swift-UVOT detection
  9. GRB241030B: GRANDMA/TAROT Upper Limit
  10. GRB 241030A: Swift-XRT refined Analysis
  11. GRB 241030B: SAO RAS optical observations
  12. GRB 241030B: AKO Optical Afterglow Detection
  13. GRB 241030B: Nanshan/HMT optical afterglow detection
  14. GRB 241030B: SVOM/ECLAIRs detection of a burst
  15. GRB 241030B: Prompt enhanced Swift-XRT position
  16. Konus-Wind detection of GRB 241030A
  17. GRB 241030B: Swift detection of a burst
  18. GRB 241030B: Fermi GBM Final Real-time Localization
  19. GRB 241030A: Fermi-LAT detection
  20. GRB 240912A: radio detection with the VLA
  21. Fermi GRB 241030A: Global MASTER-Net observations report
  22. GRB 241030A: AKO Optical Afterglow Detection
  23. Swift GRB 241030A: Global MASTER-Net observations report
  24. GRB 241030A: Swift/UVOT Detection
  25. EP 241021a: further Swift-XRT observations and X-ray counterpart detection
  26. GRB 241030A: SVOM/GRM observation
  27. GRB 241026A: Swift-BAT refined analysis
  28. GRB 241030A: SVOM/C-GFT optical observations
  29. GRB 241026A: LBT optical observations
  30. EP241021a: Optical rebrightening observations with Mephisto
  31. EP241026b: EP-FXT follow-up observation
  32. GRB 241030A: Multiband optical detection with Mephisto
  33. GRB 241030A: SVOM/VT optical afterglow observations
  34. GRB 241025A: The discovery of a BdHN I from data of Swift, Fermi, SVOM and Einstein Probe telescopes
  35. GRB 241030A : MITSuME Akeno optical afterglow detection
  36. GRB 241030A: Enhanced Swift-XRT position
  37. GRB 241029A: GROWTH-India Telescope optical follow up
  38. GRB 241030A: TRT optical observations
  39. GRB 241030A: Keck/LRIS spectroscopic redshift z = 1.411
  40. GRB 241030A: ULL-ASTRO-MASTER detection of a bright optical counterpart with the LCOGT 40-cm telescope at McDonald Observatory
  41. GRB 241030A: COLIBRÍ Detection of the Bright Optical Counterpart
  42. GRB 241030A: Swift detection of a burst with a bright optical counterpart
  43. GRB 241030A: Fermi GBM Final Real-time Localization
  44. GRB 241029A: SAO RAS optical observations
  45. GRB 241026A: SAO RAS optical observations
  46. EP240919a / GRB 240919A: ATCA Detection of Radio Counterpart
  47. EP241021a: SAO RAS observations of rebrightening
  48. GRB 241029A: GTC/OSIRIS+ spectroscopic redshift z=1.072
  49. EP241021a: ATCA radio observations
  50. MISTRAL@OHP photometric and spectroscopic observations of GRB 241029A
  51. GRB 241026A: Swift/UVOT Upper Limits
  52. GRB 241029A: Swift-XRT observations
  53. GRB 241029A: Fermi GBM Observation
  54. GRB 241029A: AKO Optical Afterglow Detection
  55. GRB 241029A: GOTO optical afterglow detection
  56. EP241021a: continued SOAR observations confirm optical rebrightening
  57. GRB 241029A: MASTER early optical counterpart detection
  58. GRB 241029A: Xinglong-2.16m optical afterglow confirmation
  59. GRB 241029A: Mephisto observations
  60. EP 241026b: LBT possible optical counterpart (brightening source)
  61. GRB 241029A: TRT optical afterglow candidate detection
  62. GRB 241029A: Swift ToO observations
  63. GRB 241029A: SVOM/GRM observation
  64. GRB 241029A : Detection and localization of a bright long GRB by SVOM/ECLAIRs
  65. Fermi trigger No 751861204: Global MASTER-Net observations report
  66. GRB 241029A: Fermi GBM Final Real-time Localization
  67. GRB 240821A: Keck/LRIS spectroscopic observations
  68. EP241021a: Gemini-South detection of optical rebrightening
  69. GRB 241026A: the 100th GRB detected by GRBAlpha
  70. GRB 241026A: TNOT optical counterpart detection
  71. Konus-Wind detection of GRB 241025A
  72. GRB 241025A (EP241025a): Optical afterglow observations with the Tsinghua-Nanshan Optical Telescope
  73. GRB 241026A: LBT redshift confirmation
  74. GRB 241026A: GECAM detection
  75. GRB 241025A: further SAO RAS optical observations
  76. GRB 241026A: BTA and Zeiss-1000 optical observations
  77. GRB 241026A: SVOM/GRM observation
  78. EP241026B: GROWTH-India Telescope optical upper limit
  79. GRB 241025A: Swift/UVOT Detection
  80. GRB 241026A: GROWTH-India Telescope optical observations
  81. GRB 241026A Fermi GBM Analysis
  82. GRB 241026A: BTA redshift identification of z = 2.79
  83. GRB 241026A: J-band observations with WINTER
  84. GRB 241025A: SAO RAS optical observations
  85. GRB 241026A: Las Cumbres optical detection
  86. GRB 241025A: Mondy optical observations
  87. EP241021a: SOAR observations of the optical counterpart
  88. EP241021a: further SAO RAS optical observations
  89. EP241026a (GRB 241026A): EP on-board trigger and follow-up observation
  90. GRB 241026A: Swift-XRT refined Analysis
  91. EP 241026b: LBT optical observations
  92. EP241021a: e-MERLIN radio observation
  93. EP EP241026b: Global MASTER-Net observations report
  94. GRB 241026A: Enhanced Swift-XRT position
  95. GRB 241026A: KAIT optical observations
  96. EP241026b: EP detection of a fast X-ray transient
  97. Fermi trigger No 751616906: Global MASTER-Net observations report
  98. GRB 241026A: COLIBRÍ Detection of the Optical Counterpart
  99. GRB 241026A: SAO RAS observations of possible optical afterglow
  100. Fermi GRB 241026A: Global MASTER-Net observations report

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