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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: TRT optical observations
  2. GRB 241030A: Keck/LRIS spectroscopic redshift z = 1.411
  3. GRB 241030A: ULL-ASTRO-MASTER detection of a bright optical counterpart with the LCOGT 40-cm telescope at McDonald Observatory
  4. GRB 241030A: COLIBRÍ Detection of the Bright Optical Counterpart
  5. GRB 241030A: Swift detection of a burst with a bright optical counterpart
  6. GRB 241030A: Fermi GBM Final Real-time Localization
  7. GRB 241029A: SAO RAS optical observations
  8. GRB 241026A: SAO RAS optical observations
  9. EP240919a / GRB 240919A: ATCA Detection of Radio Counterpart
  10. EP241021a: SAO RAS observations of rebrightening
  11. GRB 241029A: GTC/OSIRIS+ spectroscopic redshift z=1.072
  12. EP241021a: ATCA radio observations
  13. MISTRAL@OHP photometric and spectroscopic observations of GRB 241029A
  14. GRB 241026A: Swift/UVOT Upper Limits
  15. GRB 241029A: Swift-XRT observations
  16. GRB 241029A: Fermi GBM Observation
  17. GRB 241029A: AKO Optical Afterglow Detection
  18. GRB 241029A: GOTO optical afterglow detection
  19. EP241021a: continued SOAR observations confirm optical rebrightening
  20. GRB 241029A: MASTER early optical counterpart detection
  21. GRB 241029A: Xinglong-2.16m optical afterglow confirmation
  22. GRB 241029A: Mephisto observations
  23. EP 241026b: LBT possible optical counterpart (brightening source)
  24. GRB 241029A: TRT optical afterglow candidate detection
  25. GRB 241029A: Swift ToO observations
  26. GRB 241029A: SVOM/GRM observation
  27. GRB 241029A : Detection and localization of a bright long GRB by SVOM/ECLAIRs
  28. Fermi trigger No 751861204: Global MASTER-Net observations report
  29. GRB 241029A: Fermi GBM Final Real-time Localization
  30. GRB 240821A: Keck/LRIS spectroscopic observations
  31. EP241021a: Gemini-South detection of optical rebrightening
  32. GRB 241026A: the 100th GRB detected by GRBAlpha
  33. GRB 241026A: TNOT optical counterpart detection
  34. Konus-Wind detection of GRB 241025A
  35. GRB 241025A (EP241025a): Optical afterglow observations with the Tsinghua-Nanshan Optical Telescope
  36. GRB 241026A: LBT redshift confirmation
  37. GRB 241026A: GECAM detection
  38. GRB 241025A: further SAO RAS optical observations
  39. GRB 241026A: BTA and Zeiss-1000 optical observations
  40. GRB 241026A: SVOM/GRM observation
  41. EP241026B: GROWTH-India Telescope optical upper limit
  42. GRB 241025A: Swift/UVOT Detection
  43. GRB 241026A: GROWTH-India Telescope optical observations
  44. GRB 241026A Fermi GBM Analysis
  45. GRB 241026A: BTA redshift identification of z = 2.79
  46. GRB 241026A: J-band observations with WINTER
  47. GRB 241025A: SAO RAS optical observations
  48. GRB 241026A: Las Cumbres optical detection
  49. GRB 241025A: Mondy optical observations
  50. EP241021a: SOAR observations of the optical counterpart
  51. EP241021a: further SAO RAS optical observations
  52. EP241026a (GRB 241026A): EP on-board trigger and follow-up observation
  53. GRB 241026A: Swift-XRT refined Analysis
  54. EP 241026b: LBT optical observations
  55. EP241021a: e-MERLIN radio observation
  56. EP EP241026b: Global MASTER-Net observations report
  57. GRB 241026A: Enhanced Swift-XRT position
  58. GRB 241026A: KAIT optical observations
  59. EP241026b: EP detection of a fast X-ray transient
  60. Fermi trigger No 751616906: Global MASTER-Net observations report
  61. GRB 241026A: COLIBRÍ Detection of the Optical Counterpart
  62. GRB 241026A: SAO RAS observations of possible optical afterglow
  63. Fermi GRB 241026A: Global MASTER-Net observations report
  64. GRB 241026A: Prompt enhanced Swift-XRT position
  65. GRB 241026A: Swift detection of a burst
  66. Swift GRB241026.95: Global MASTER-Net observations report
  67. GRB 241026A: Fermi GBM Final Real-time Localization
  68. GRB241025A: 1.3m DFOT optical afterglow detection
  69. EP241021a: optical follow-up observations with Xinglong Observatory
  70. ​GRB 241025A: optical photometry from Konkoly
  71. GRB 241025A: GROWTH-India Telescope optical observations
  72. GRB 241025A: COLIBRÍ Detection of the Afterglow
  73. GRB 241025A: Swift-XRT refined Analysis
  74. GRB 241025C: Fermi GBM Detection
  75. GRB 241025A: Fermi GBM Observation
  76. IPN triangulation of GRB 241022A (short/hard)
  77. LIGO/Virgo/KAGRA S241009l: Upper limits from Swift/BAT-GUANO
  78. GRB 241025C: Fermi GBM Final Localization
  79. GRB 241025A: GRANDMA and Kilonova-Catcher optical afterglow detections and upperlimits
  80. GRB 241025B: Fermi GBM Final Localization
  81. Fermi trigger No 751563375: Global MASTER-Net observations report
  82. Fermi trigger No 751554401: Global MASTER-Net observations report
  83. EP241021a: Optical and NIR observations of counterpart with the Fraunhofer Telescope at Wendelstein Observatory
  84. EP241021a: Optical and NIR observations of counterpart with the Fraunhofer Telescope at Wendelstein Observatory
  85. EP 241021a: Swift-XRT observations
  86. EP241021a: optical follow-up observations with the Liverpool Telescope
  87. Fermi GRB 241025A: Global MASTER-Net observations report
  88. Swift GRB 241025A: Global MASTER-Net observations report
  89. EP241025a (GRB 241025A): EP observations update
  90. GRB 241025A : SVOM/VT optical afterglow observations
  91. EP 241021A: Swift ToO observations
  92. EP241021a: Liverpool Telescope optical follow-up observations
  93. GRB 241025A: Enhanced Swift-XRT position
  94. GRB 241001A: JWST spectroscopic identification of a supernova counterpart
  95. GRB 241025A: NOT spectroscopic redshift of z = 4.20
  96. GRB 241025A: DDOTI Afterglow detection
  97. EP241025a (GRB 241025A): EP on-board trigger and autonomous follow-up observation
  98. GRB 241025A: SVOM/GRM observation
  99. GRB 241025A: TRT optical afterglow observation
  100. Fermi GRB 241024B: Global MASTER-Net observations report

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