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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: GTC/OSIRIS+ spectroscopic redshift z=1.072
  2. EP241021a: ATCA radio observations
  3. MISTRAL@OHP photometric and spectroscopic observations of GRB 241029A
  4. GRB 241026A: Swift/UVOT Upper Limits
  5. GRB 241029A: Swift-XRT observations
  6. GRB 241029A: Fermi GBM Observation
  7. GRB 241029A: AKO Optical Afterglow Detection
  8. GRB 241029A: GOTO optical afterglow detection
  9. EP241021a: continued SOAR observations confirm optical rebrightening
  10. GRB 241029A: MASTER early optical counterpart detection
  11. GRB 241029A: Xinglong-2.16m optical afterglow confirmation
  12. GRB 241029A: Mephisto observations
  13. EP 241026b: LBT possible optical counterpart (brightening source)
  14. GRB 241029A: TRT optical afterglow candidate detection
  15. GRB 241029A: Swift ToO observations
  16. GRB 241029A: SVOM/GRM observation
  17. GRB 241029A : Detection and localization of a bright long GRB by SVOM/ECLAIRs
  18. Fermi trigger No 751861204: Global MASTER-Net observations report
  19. GRB 241029A: Fermi GBM Final Real-time Localization
  20. GRB 240821A: Keck/LRIS spectroscopic observations
  21. EP241021a: Gemini-South detection of optical rebrightening
  22. GRB 241026A: the 100th GRB detected by GRBAlpha
  23. GRB 241026A: TNOT optical counterpart detection
  24. Konus-Wind detection of GRB 241025A
  25. GRB 241025A (EP241025a): Optical afterglow observations with the Tsinghua-Nanshan Optical Telescope
  26. GRB 241026A: LBT redshift confirmation
  27. GRB 241026A: GECAM detection
  28. GRB 241025A: further SAO RAS optical observations
  29. GRB 241026A: BTA and Zeiss-1000 optical observations
  30. GRB 241026A: SVOM/GRM observation
  31. EP241026B: GROWTH-India Telescope optical upper limit
  32. GRB 241025A: Swift/UVOT Detection
  33. GRB 241026A: GROWTH-India Telescope optical observations
  34. GRB 241026A Fermi GBM Analysis
  35. GRB 241026A: BTA redshift identification of z = 2.79
  36. GRB 241026A: J-band observations with WINTER
  37. GRB 241025A: SAO RAS optical observations
  38. GRB 241026A: Las Cumbres optical detection
  39. GRB 241025A: Mondy optical observations
  40. EP241021a: SOAR observations of the optical counterpart
  41. EP241021a: further SAO RAS optical observations
  42. EP241026a (GRB 241026A): EP on-board trigger and follow-up observation
  43. GRB 241026A: Swift-XRT refined Analysis
  44. EP 241026b: LBT optical observations
  45. EP241021a: e-MERLIN radio observation
  46. EP EP241026b: Global MASTER-Net observations report
  47. GRB 241026A: Enhanced Swift-XRT position
  48. GRB 241026A: KAIT optical observations
  49. EP241026b: EP detection of a fast X-ray transient
  50. Fermi trigger No 751616906: Global MASTER-Net observations report
  51. GRB 241026A: COLIBRÍ Detection of the Optical Counterpart
  52. GRB 241026A: SAO RAS observations of possible optical afterglow
  53. Fermi GRB 241026A: Global MASTER-Net observations report
  54. GRB 241026A: Prompt enhanced Swift-XRT position
  55. GRB 241026A: Swift detection of a burst
  56. Swift GRB241026.95: Global MASTER-Net observations report
  57. GRB 241026A: Fermi GBM Final Real-time Localization
  58. GRB241025A: 1.3m DFOT optical afterglow detection
  59. EP241021a: optical follow-up observations with Xinglong Observatory
  60. ​GRB 241025A: optical photometry from Konkoly
  61. GRB 241025A: GROWTH-India Telescope optical observations
  62. GRB 241025A: COLIBRÍ Detection of the Afterglow
  63. GRB 241025A: Swift-XRT refined Analysis
  64. GRB 241025C: Fermi GBM Detection
  65. GRB 241025A: Fermi GBM Observation
  66. IPN triangulation of GRB 241022A (short/hard)
  67. LIGO/Virgo/KAGRA S241009l: Upper limits from Swift/BAT-GUANO
  68. GRB 241025C: Fermi GBM Final Localization
  69. GRB 241025A: GRANDMA and Kilonova-Catcher optical afterglow detections and upperlimits
  70. GRB 241025B: Fermi GBM Final Localization
  71. Fermi trigger No 751563375: Global MASTER-Net observations report
  72. Fermi trigger No 751554401: Global MASTER-Net observations report
  73. EP241021a: Optical and NIR observations of counterpart with the Fraunhofer Telescope at Wendelstein Observatory
  74. EP241021a: Optical and NIR observations of counterpart with the Fraunhofer Telescope at Wendelstein Observatory
  75. EP 241021a: Swift-XRT observations
  76. EP241021a: optical follow-up observations with the Liverpool Telescope
  77. Fermi GRB 241025A: Global MASTER-Net observations report
  78. Swift GRB 241025A: Global MASTER-Net observations report
  79. EP241025a (GRB 241025A): EP observations update
  80. GRB 241025A : SVOM/VT optical afterglow observations
  81. EP 241021A: Swift ToO observations
  82. EP241021a: Liverpool Telescope optical follow-up observations
  83. GRB 241025A: Enhanced Swift-XRT position
  84. GRB 241001A: JWST spectroscopic identification of a supernova counterpart
  85. GRB 241025A: NOT spectroscopic redshift of z = 4.20
  86. GRB 241025A: DDOTI Afterglow detection
  87. EP241025a (GRB 241025A): EP on-board trigger and autonomous follow-up observation
  88. GRB 241025A: SVOM/GRM observation
  89. GRB 241025A: TRT optical afterglow observation
  90. Fermi GRB 241024B: Global MASTER-Net observations report
  91. GRB 241025A: Fermi GBM Final Real-time Localization
  92. GRB 241025A: Swift detection of a burst with an optical counterpart
  93. EP241021a: GTC OSIRIS+ spectroscopy of the optical counterpart
  94. GRB 241001A: ATCA radio observations
  95. GRB 241024B: Fermi GBM Final Localization
  96. EP241021a: No Detection in Fermi-GBM Observation
  97. GRB 241010A: VIRT Optical Upper Limit
  98. GRB 241024A: Fermi GBM Final Localisation
  99. EP241021a: VLT/FORS2 redshift z = 0.75
  100. Fermi trigger No 751449953: Global MASTER-Net observations report

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