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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. EP241026b: EP-FXT follow-up observation
  2. GRB 241030A: Multiband optical detection with Mephisto
  3. GRB 241030A: SVOM/VT optical afterglow observations
  4. GRB 241025A: The discovery of a BdHN I from data of Swift, Fermi, SVOM and Einstein Probe telescopes
  5. GRB 241030A : MITSuME Akeno optical afterglow detection
  6. GRB 241030A: Enhanced Swift-XRT position
  7. GRB 241029A: GROWTH-India Telescope optical follow up
  8. GRB 241030A: TRT optical observations
  9. GRB 241030A: Keck/LRIS spectroscopic redshift z = 1.411
  10. GRB 241030A: ULL-ASTRO-MASTER detection of a bright optical counterpart with the LCOGT 40-cm telescope at McDonald Observatory
  11. GRB 241030A: COLIBRÍ Detection of the Bright Optical Counterpart
  12. GRB 241030A: Swift detection of a burst with a bright optical counterpart
  13. GRB 241030A: Fermi GBM Final Real-time Localization
  14. GRB 241029A: SAO RAS optical observations
  15. GRB 241026A: SAO RAS optical observations
  16. EP240919a / GRB 240919A: ATCA Detection of Radio Counterpart
  17. EP241021a: SAO RAS observations of rebrightening
  18. GRB 241029A: GTC/OSIRIS+ spectroscopic redshift z=1.072
  19. EP241021a: ATCA radio observations
  20. MISTRAL@OHP photometric and spectroscopic observations of GRB 241029A
  21. GRB 241026A: Swift/UVOT Upper Limits
  22. GRB 241029A: Swift-XRT observations
  23. GRB 241029A: Fermi GBM Observation
  24. GRB 241029A: AKO Optical Afterglow Detection
  25. GRB 241029A: GOTO optical afterglow detection
  26. EP241021a: continued SOAR observations confirm optical rebrightening
  27. GRB 241029A: MASTER early optical counterpart detection
  28. GRB 241029A: Xinglong-2.16m optical afterglow confirmation
  29. GRB 241029A: Mephisto observations
  30. EP 241026b: LBT possible optical counterpart (brightening source)
  31. GRB 241029A: TRT optical afterglow candidate detection
  32. GRB 241029A: Swift ToO observations
  33. GRB 241029A: SVOM/GRM observation
  34. GRB 241029A : Detection and localization of a bright long GRB by SVOM/ECLAIRs
  35. Fermi trigger No 751861204: Global MASTER-Net observations report
  36. GRB 241029A: Fermi GBM Final Real-time Localization
  37. GRB 240821A: Keck/LRIS spectroscopic observations
  38. EP241021a: Gemini-South detection of optical rebrightening
  39. GRB 241026A: the 100th GRB detected by GRBAlpha
  40. GRB 241026A: TNOT optical counterpart detection
  41. Konus-Wind detection of GRB 241025A
  42. GRB 241025A (EP241025a): Optical afterglow observations with the Tsinghua-Nanshan Optical Telescope
  43. GRB 241026A: LBT redshift confirmation
  44. GRB 241026A: GECAM detection
  45. GRB 241025A: further SAO RAS optical observations
  46. GRB 241026A: BTA and Zeiss-1000 optical observations
  47. GRB 241026A: SVOM/GRM observation
  48. EP241026B: GROWTH-India Telescope optical upper limit
  49. GRB 241025A: Swift/UVOT Detection
  50. GRB 241026A: GROWTH-India Telescope optical observations
  51. GRB 241026A Fermi GBM Analysis
  52. GRB 241026A: BTA redshift identification of z = 2.79
  53. GRB 241026A: J-band observations with WINTER
  54. GRB 241025A: SAO RAS optical observations
  55. GRB 241026A: Las Cumbres optical detection
  56. GRB 241025A: Mondy optical observations
  57. EP241021a: SOAR observations of the optical counterpart
  58. EP241021a: further SAO RAS optical observations
  59. EP241026a (GRB 241026A): EP on-board trigger and follow-up observation
  60. GRB 241026A: Swift-XRT refined Analysis
  61. EP 241026b: LBT optical observations
  62. EP241021a: e-MERLIN radio observation
  63. EP EP241026b: Global MASTER-Net observations report
  64. GRB 241026A: Enhanced Swift-XRT position
  65. GRB 241026A: KAIT optical observations
  66. EP241026b: EP detection of a fast X-ray transient
  67. Fermi trigger No 751616906: Global MASTER-Net observations report
  68. GRB 241026A: COLIBRÍ Detection of the Optical Counterpart
  69. GRB 241026A: SAO RAS observations of possible optical afterglow
  70. Fermi GRB 241026A: Global MASTER-Net observations report
  71. GRB 241026A: Prompt enhanced Swift-XRT position
  72. GRB 241026A: Swift detection of a burst
  73. Swift GRB241026.95: Global MASTER-Net observations report
  74. GRB 241026A: Fermi GBM Final Real-time Localization
  75. GRB241025A: 1.3m DFOT optical afterglow detection
  76. EP241021a: optical follow-up observations with Xinglong Observatory
  77. ​GRB 241025A: optical photometry from Konkoly
  78. GRB 241025A: GROWTH-India Telescope optical observations
  79. GRB 241025A: COLIBRÍ Detection of the Afterglow
  80. GRB 241025A: Swift-XRT refined Analysis
  81. GRB 241025C: Fermi GBM Detection
  82. GRB 241025A: Fermi GBM Observation
  83. IPN triangulation of GRB 241022A (short/hard)
  84. LIGO/Virgo/KAGRA S241009l: Upper limits from Swift/BAT-GUANO
  85. GRB 241025C: Fermi GBM Final Localization
  86. GRB 241025A: GRANDMA and Kilonova-Catcher optical afterglow detections and upperlimits
  87. GRB 241025B: Fermi GBM Final Localization
  88. Fermi trigger No 751563375: Global MASTER-Net observations report
  89. Fermi trigger No 751554401: Global MASTER-Net observations report
  90. EP241021a: Optical and NIR observations of counterpart with the Fraunhofer Telescope at Wendelstein Observatory
  91. EP241021a: Optical and NIR observations of counterpart with the Fraunhofer Telescope at Wendelstein Observatory
  92. EP 241021a: Swift-XRT observations
  93. EP241021a: optical follow-up observations with the Liverpool Telescope
  94. Fermi GRB 241025A: Global MASTER-Net observations report
  95. Swift GRB 241025A: Global MASTER-Net observations report
  96. EP241025a (GRB 241025A): EP observations update
  97. GRB 241025A : SVOM/VT optical afterglow observations
  98. EP 241021A: Swift ToO observations
  99. EP241021a: Liverpool Telescope optical follow-up observations
  100. GRB 241025A: Enhanced Swift-XRT position

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