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

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