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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"

39197 results found.

  1. GRB 241030A: ULL-ASTRO-MASTER detection of a bright optical counterpart with the LCOGT 40-cm telescope at McDonald Observatory
  2. GRB 241030A: COLIBRÍ Detection of the Bright Optical Counterpart
  3. GRB 241030A: Swift detection of a burst with a bright optical counterpart
  4. GRB 241030A: Fermi GBM Final Real-time Localization
  5. GRB 241029A: SAO RAS optical observations
  6. GRB 241026A: SAO RAS optical observations
  7. EP240919a / GRB 240919A: ATCA Detection of Radio Counterpart
  8. EP241021a: SAO RAS observations of rebrightening
  9. GRB 241029A: GTC/OSIRIS+ spectroscopic redshift z=1.072
  10. MISTRAL@OHP photometric and spectroscopic observations of GRB 241029A
  11. GRB 241026A: Swift/UVOT Upper Limits
  12. GRB 241029A: Swift-XRT observations
  13. GRB 241029A: Fermi GBM Observation
  14. GRB 241029A: AKO Optical Afterglow Detection
  15. GRB 241029A: GOTO optical afterglow detection
  16. GRB 241029A: MASTER early optical counterpart detection
  17. GRB 241029A: Xinglong-2.16m optical afterglow confirmation
  18. GRB 241029A: Mephisto observations
  19. EP 241026b: LBT possible optical counterpart (brightening source)
  20. GRB 241029A: TRT optical afterglow candidate detection
  21. GRB 241029A: Swift ToO observations
  22. GRB 241029A: SVOM/GRM observation
  23. GRB 241029A : Detection and localization of a bright long GRB by SVOM/ECLAIRs
  24. Fermi trigger No 751861204: Global MASTER-Net observations report
  25. GRB 241029A: Fermi GBM Final Real-time Localization
  26. GRB 240821A: Keck/LRIS spectroscopic observations
  27. GRB 241026A: the 100th GRB detected by GRBAlpha
  28. GRB 241026A: TNOT optical counterpart detection
  29. Konus-Wind detection of GRB 241025A
  30. GRB 241025A (EP241025a): Optical afterglow observations with the Tsinghua-Nanshan Optical Telescope
  31. GRB 241026A: LBT redshift confirmation
  32. GRB 241026A: GECAM detection
  33. GRB 241025A: further SAO RAS optical observations
  34. GRB 241026A: BTA and Zeiss-1000 optical observations
  35. GRB 241026A: SVOM/GRM observation
  36. EP241026B: GROWTH-India Telescope optical upper limit
  37. GRB 241025A: Swift/UVOT Detection
  38. GRB 241026A: GROWTH-India Telescope optical observations
  39. GRB 241026A Fermi GBM Analysis
  40. GRB 241026A: BTA redshift identification of z = 2.79
  41. GRB 241026A: J-band observations with WINTER
  42. GRB 241025A: SAO RAS optical observations
  43. GRB 241026A: Las Cumbres optical detection
  44. GRB 241025A: Mondy optical observations
  45. EP241021a: further SAO RAS optical observations
  46. EP241026a (GRB 241026A): EP on-board trigger and follow-up observation
  47. GRB 241026A: Swift-XRT refined Analysis
  48. EP 241026b: LBT optical observations
  49. EP EP241026b: Global MASTER-Net observations report
  50. GRB 241026A: Enhanced Swift-XRT position
  51. GRB 241026A: KAIT optical observations
  52. Fermi trigger No 751616906: Global MASTER-Net observations report
  53. GRB 241026A: COLIBRÍ Detection of the Optical Counterpart
  54. GRB 241026A: SAO RAS observations of possible optical afterglow
  55. Fermi GRB 241026A: Global MASTER-Net observations report
  56. GRB 241026A: Prompt enhanced Swift-XRT position
  57. GRB 241026A: Swift detection of a burst
  58. Swift GRB241026.95: Global MASTER-Net observations report
  59. GRB 241026A: Fermi GBM Final Real-time Localization
  60. GRB241025A: 1.3m DFOT optical afterglow detection
  61. ​GRB 241025A: optical photometry from Konkoly
  62. GRB 241025A: GROWTH-India Telescope optical observations
  63. GRB 241025A: COLIBRÍ Detection of the Afterglow
  64. GRB 241025A: Swift-XRT refined Analysis
  65. GRB 241025C: Fermi GBM Detection
  66. GRB 241025A: Fermi GBM Observation
  67. IPN triangulation of GRB 241022A (short/hard)
  68. LIGO/Virgo/KAGRA S241009l: Upper limits from Swift/BAT-GUANO
  69. GRB 241025C: Fermi GBM Final Localization
  70. GRB 241025A: GRANDMA and Kilonova-Catcher optical afterglow detections and upperlimits
  71. GRB 241025B: Fermi GBM Final Localization
  72. Fermi trigger No 751563375: Global MASTER-Net observations report
  73. Fermi trigger No 751554401: Global MASTER-Net observations report
  74. EP 241021a: Swift-XRT observations
  75. Fermi GRB 241025A: Global MASTER-Net observations report
  76. Swift GRB 241025A: Global MASTER-Net observations report
  77. EP241025a (GRB 241025A): EP observations update
  78. GRB 241025A : SVOM/VT optical afterglow observations
  79. EP 241021A: Swift ToO observations
  80. GRB 241025A: Enhanced Swift-XRT position
  81. GRB 241001A: JWST spectroscopic identification of a supernova counterpart
  82. GRB 241025A: NOT spectroscopic redshift of z = 4.20
  83. GRB 241025A: DDOTI Afterglow detection
  84. EP241025a (GRB 241025A): EP on-board trigger and autonomous follow-up observation
  85. GRB 241025A: SVOM/GRM observation
  86. GRB 241025A: TRT optical afterglow observation
  87. Fermi GRB 241024B: Global MASTER-Net observations report
  88. GRB 241025A: Fermi GBM Final Real-time Localization
  89. GRB 241025A: Swift detection of a burst with an optical counterpart
  90. GRB 241001A: ATCA radio observations
  91. GRB 241024B: Fermi GBM Final Localization
  92. EP241021a: No Detection in Fermi-GBM Observation
  93. GRB 241010A: VIRT Optical Upper Limit
  94. GRB 241024A: Fermi GBM Final Localisation
  95. EP241021a: VLT/FORS2 redshift z = 0.75
  96. Fermi trigger No 751449953: Global MASTER-Net observations report
  97. EP241021a: SAO RAS optical observations
  98. EP241021a: KAIT optical observations
  99. IPN triangulation of GRB 241021A (long)
  100. EP241021a: 1.3m DFOT Optical observations

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