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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 241029A: COLIBRI Detection of the Optical Counterpart
  2. GRB 241030B: Swift/UVOT Detection
  3. EP EP241030a: Global MASTER-Net observations report
  4. GRB 241029A: LCO optical detection
  5. Fermi trigger No 752006065: Global MASTER-Net observations report
  6. GRB 241030B: GTC/OSIRIS+ tentative spectroscopic redshift z = 2.82
  7. Swift GRB241030.77: Global MASTER-Net observations report
  8. GRB 241030B: SVOM/GRM observation
  9. GRB 241030B : MITSuME Akeno optical upper limits
  10. GRB 241030A: COLIBRI Continuing Detection of the Afterglow
  11. GRB 241030B: SVOM/VT optical afterglow observations
  12. GRB 241030B: COLIBRÍ Upper Limits on the Optical Counterpart
  13. EP241030a: EP detection of GRB 241030A X-ray Afterglow
  14. GRB241030B: Fermi GBM Observation
  15. GRB 241030B: BTA observations
  16. GRB 241029A: SVOM/VT optical afterglow observations
  17. GRB 241030A: detection of the bright optical counterpart in ATLAS forced photometry
  18. GRB 241030B: Enhanced Swift-XRT position
  19. GRB 241030B: optical observations from the INAF Asiago Observatory
  20. EP241021a: Swift-UVOT detection
  21. GRB241030B: GRANDMA/TAROT Upper Limit
  22. GRB 241030A: Swift-XRT refined Analysis
  23. GRB 241030B: SAO RAS optical observations
  24. GRB 241030B: AKO Optical Afterglow Detection
  25. GRB 241030B: Nanshan/HMT optical afterglow detection
  26. GRB 241030B: SVOM/ECLAIRs detection of a burst
  27. GRB 241030B: Prompt enhanced Swift-XRT position
  28. Konus-Wind detection of GRB 241030A
  29. GRB 241030B: Swift detection of a burst
  30. GRB 241030B: Fermi GBM Final Real-time Localization
  31. GRB 241030A: Fermi-LAT detection
  32. GRB 240912A: radio detection with the VLA
  33. Fermi GRB 241030A: Global MASTER-Net observations report
  34. GRB 241030A: AKO Optical Afterglow Detection
  35. Swift GRB 241030A: Global MASTER-Net observations report
  36. GRB 241030A: Swift/UVOT Detection
  37. EP 241021a: further Swift-XRT observations and X-ray counterpart detection
  38. GRB 241030A: SVOM/GRM observation
  39. GRB 241026A: Swift-BAT refined analysis
  40. GRB 241030A: SVOM/C-GFT optical observations
  41. GRB 241026A: LBT optical observations
  42. EP241021a: Optical rebrightening observations with Mephisto
  43. EP241026b: EP-FXT follow-up observation
  44. GRB 241030A: Multiband optical detection with Mephisto
  45. GRB 241030A: SVOM/VT optical afterglow observations
  46. GRB 241025A: The discovery of a BdHN I from data of Swift, Fermi, SVOM and Einstein Probe telescopes
  47. GRB 241030A : MITSuME Akeno optical afterglow detection
  48. GRB 241030A: Enhanced Swift-XRT position
  49. GRB 241029A: GROWTH-India Telescope optical follow up
  50. GRB 241030A: TRT optical observations
  51. GRB 241030A: Keck/LRIS spectroscopic redshift z = 1.411
  52. GRB 241030A: ULL-ASTRO-MASTER detection of a bright optical counterpart with the LCOGT 40-cm telescope at McDonald Observatory
  53. GRB 241030A: COLIBRÍ Detection of the Bright Optical Counterpart
  54. GRB 241030A: Swift detection of a burst with a bright optical counterpart
  55. GRB 241030A: Fermi GBM Final Real-time Localization
  56. GRB 241029A: SAO RAS optical observations
  57. GRB 241026A: SAO RAS optical observations
  58. EP240919a / GRB 240919A: ATCA Detection of Radio Counterpart
  59. EP241021a: SAO RAS observations of rebrightening
  60. GRB 241029A: GTC/OSIRIS+ spectroscopic redshift z=1.072
  61. EP241021a: ATCA radio observations
  62. MISTRAL@OHP photometric and spectroscopic observations of GRB 241029A
  63. GRB 241026A: Swift/UVOT Upper Limits
  64. GRB 241029A: Swift-XRT observations
  65. GRB 241029A: Fermi GBM Observation
  66. GRB 241029A: AKO Optical Afterglow Detection
  67. GRB 241029A: GOTO optical afterglow detection
  68. EP241021a: continued SOAR observations confirm optical rebrightening
  69. GRB 241029A: MASTER early optical counterpart detection
  70. GRB 241029A: Xinglong-2.16m optical afterglow confirmation
  71. GRB 241029A: Mephisto observations
  72. EP 241026b: LBT possible optical counterpart (brightening source)
  73. GRB 241029A: TRT optical afterglow candidate detection
  74. GRB 241029A: Swift ToO observations
  75. GRB 241029A: SVOM/GRM observation
  76. GRB 241029A : Detection and localization of a bright long GRB by SVOM/ECLAIRs
  77. Fermi trigger No 751861204: Global MASTER-Net observations report
  78. GRB 241029A: Fermi GBM Final Real-time Localization
  79. GRB 240821A: Keck/LRIS spectroscopic observations
  80. EP241021a: Gemini-South detection of optical rebrightening
  81. GRB 241026A: the 100th GRB detected by GRBAlpha
  82. GRB 241026A: TNOT optical counterpart detection
  83. Konus-Wind detection of GRB 241025A
  84. GRB 241025A (EP241025a): Optical afterglow observations with the Tsinghua-Nanshan Optical Telescope
  85. GRB 241026A: LBT redshift confirmation
  86. GRB 241026A: GECAM detection
  87. GRB 241025A: further SAO RAS optical observations
  88. GRB 241026A: BTA and Zeiss-1000 optical observations
  89. GRB 241026A: SVOM/GRM observation
  90. EP241026B: GROWTH-India Telescope optical upper limit
  91. GRB 241025A: Swift/UVOT Detection
  92. GRB 241026A: GROWTH-India Telescope optical observations
  93. GRB 241026A Fermi GBM Analysis
  94. GRB 241026A: BTA redshift identification of z = 2.79
  95. GRB 241026A: J-band observations with WINTER
  96. GRB 241025A: SAO RAS optical observations
  97. GRB 241026A: Las Cumbres optical detection
  98. GRB 241025A: Mondy optical observations
  99. EP241021a: SOAR observations of the optical counterpart
  100. EP241021a: further SAO RAS optical observations

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