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

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