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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 241026A: GROWTH-India Telescope optical observations
  2. GRB 241026A Fermi GBM Analysis
  3. GRB 241026A: BTA redshift identification of z = 2.79
  4. GRB 241026A: J-band observations with WINTER
  5. GRB 241025A: SAO RAS optical observations
  6. GRB 241026A: Las Cumbres optical detection
  7. GRB 241025A: Mondy optical observations
  8. EP241021a: SOAR observations of the optical counterpart
  9. EP241021a: further SAO RAS optical observations
  10. EP241026a (GRB 241026A): EP on-board trigger and follow-up observation
  11. GRB 241026A: Swift-XRT refined Analysis
  12. EP 241026b: LBT optical observations
  13. EP241021a: e-MERLIN radio observation
  14. EP EP241026b: Global MASTER-Net observations report
  15. GRB 241026A: Enhanced Swift-XRT position
  16. GRB 241026A: KAIT optical observations
  17. EP241026b: EP detection of a fast X-ray transient
  18. Fermi trigger No 751616906: Global MASTER-Net observations report
  19. GRB 241026A: COLIBRÍ Detection of the Optical Counterpart
  20. GRB 241026A: SAO RAS observations of possible optical afterglow
  21. Fermi GRB 241026A: Global MASTER-Net observations report
  22. GRB 241026A: Prompt enhanced Swift-XRT position
  23. GRB 241026A: Swift detection of a burst
  24. Swift GRB241026.95: Global MASTER-Net observations report
  25. GRB 241026A: Fermi GBM Final Real-time Localization
  26. GRB241025A: 1.3m DFOT optical afterglow detection
  27. EP241021a: optical follow-up observations with Xinglong Observatory
  28. ​GRB 241025A: optical photometry from Konkoly
  29. GRB 241025A: GROWTH-India Telescope optical observations
  30. GRB 241025A: COLIBRÍ Detection of the Afterglow
  31. GRB 241025A: Swift-XRT refined Analysis
  32. GRB 241025C: Fermi GBM Detection
  33. GRB 241025A: Fermi GBM Observation
  34. IPN triangulation of GRB 241022A (short/hard)
  35. LIGO/Virgo/KAGRA S241009l: Upper limits from Swift/BAT-GUANO
  36. GRB 241025C: Fermi GBM Final Localization
  37. GRB 241025A: GRANDMA and Kilonova-Catcher optical afterglow detections and upperlimits
  38. GRB 241025B: Fermi GBM Final Localization
  39. Fermi trigger No 751563375: Global MASTER-Net observations report
  40. Fermi trigger No 751554401: Global MASTER-Net observations report
  41. EP241021a: Optical and NIR observations of counterpart with the Fraunhofer Telescope at Wendelstein Observatory
  42. EP241021a: Optical and NIR observations of counterpart with the Fraunhofer Telescope at Wendelstein Observatory
  43. EP 241021a: Swift-XRT observations
  44. EP241021a: optical follow-up observations with the Liverpool Telescope
  45. Fermi GRB 241025A: Global MASTER-Net observations report
  46. Swift GRB 241025A: Global MASTER-Net observations report
  47. EP241025a (GRB 241025A): EP observations update
  48. GRB 241025A : SVOM/VT optical afterglow observations
  49. EP 241021A: Swift ToO observations
  50. EP241021a: Liverpool Telescope optical follow-up observations
  51. GRB 241025A: Enhanced Swift-XRT position
  52. GRB 241001A: JWST spectroscopic identification of a supernova counterpart
  53. GRB 241025A: NOT spectroscopic redshift of z = 4.20
  54. GRB 241025A: DDOTI Afterglow detection
  55. EP241025a (GRB 241025A): EP on-board trigger and autonomous follow-up observation
  56. GRB 241025A: SVOM/GRM observation
  57. GRB 241025A: TRT optical afterglow observation
  58. Fermi GRB 241024B: Global MASTER-Net observations report
  59. GRB 241025A: Fermi GBM Final Real-time Localization
  60. GRB 241025A: Swift detection of a burst with an optical counterpart
  61. EP241021a: GTC OSIRIS+ spectroscopy of the optical counterpart
  62. GRB 241001A: ATCA radio observations
  63. GRB 241024B: Fermi GBM Final Localization
  64. EP241021a: No Detection in Fermi-GBM Observation
  65. GRB 241010A: VIRT Optical Upper Limit
  66. GRB 241024A: Fermi GBM Final Localisation
  67. EP241021a: VLT/FORS2 redshift z = 0.75
  68. Fermi trigger No 751449953: Global MASTER-Net observations report
  69. EP241021a: SAO RAS optical observations
  70. EP241021a: KAIT optical observations
  71. EP241021a: EP-FXT follow-up observation update
  72. IPN triangulation of GRB 241021A (long)
  73. EP241021a: Optical counterpart observations with the Liverpool Telescope
  74. EP241021a: 1.3m DFOT Optical observations
  75. EP241021a: GSP detects optical candidate counterpart
  76. EP241021a: Optical upper limits with Kinder observations
  77. EP241021a: TRT optical observations
  78. GRB 241018A: SVOM/C-GFT optical observations
  79. EP241021a: NOT likely optical counterpart
  80. EP EP241021a: Global MASTER-Net observations report
  81. GRB241017A: 1.3m DFOT optical upper limit
  82. GRB 241018A: 1.3m DFOT Optical upper limit
  83. GRB 241018A: EP-FXT afterglow detection
  84. EP241021a: GOTO optical upper limits
  85. EP241021a: EP detection of a fast X-ray transient
  86. IceCube-Cascade 241019A: Upper limits from a search for additional neutrino events in IceCube
  87. Konus-Wind detection of GRB 241018A
  88. GRB 241018A: SVOM/GRM observation
  89. GRB 241018A/sb24101802: Mephisto optical upper limit
  90. GRB 241017A/sb24101702: Mephisto optical upper limit
  91. GRB 241018A: BOOTES-4/MET optical upper limit
  92. GRB 241018A: Mondy optical upper limit
  93. GRB 241018A: SVOM/VT further analysis and counterpart confirmed
  94. GRB 241018A: GROWTH-India telescope optical upper limit
  95. GRB241018A: XingLong Optical Upper Limit
  96. GRB 241018A: Swift-XRT observations
  97. GRB 241018A: REM optical/NIR upper limits
  98. GRB 241018A: NOT optical observations
  99. GRB 241017A: SVOM/VT follow-up and optical upper limit
  100. GRB 241018A: SVOM/VT follow-up and optical candidate

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