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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"

15985 results found.

  1. GRB 260125A: GOTO candidate optical counterpart
  2. GRB 260114A: SVOM/VT optical upper limits
  3. GRB 260120B: SVOM/GRM observation
  4. EP260119a: Assy AZT-20 optical observations
  5. EP260119a: Mondy and SAO RAS optical upper limits
  6. EP260119a: Xinglong optical upper limit
  7. GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765
  8. EP260105a: GTC/HiPERCAM optical observations
  9. GRB 260120B: Swift/UVOT Detection
  10. GRB 260120B: COLIBRÍ optical upper limits
  11. GRB 260120B: SVOM/C-GFT optical counterpart detection
  12. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  13. GRB 260114A: Swift/UVOT Upper Limits
  14. EP260119a: Liverpool Telescope optical follow-up observations
  15. EP260119A: GTC/OSIRIS+ spectroscopic redshift z = 5.47
  16. EP260119a: KAIT optical observations
  17. EP260119a: SVOM/VT optical observation
  18. EP260119a: update of EP-FXT follow-up observation
  19. EP260119a: NOT optical observations
  20. EP260119a: SAO RAS optical observations
  21. EP260116a: COLIBRÍ detection of a fading optical source
  22. GRB 260117A: Swift-XRT afterglow detection
  23. EP260119a: COLIBRÍ photometric redshift z ≈ 5.6
  24. EP260119a: LCO optical observations
  25. GRB 260117A: ZTSh optical upper limit
  26. EP260119a: COLIBRÍ optical counterpart candidate
  27. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  28. GRB 260117A: SVOM/VT optical candidate
  29. GRB 260117A: SVOM detection of a long faint burst
  30. EP 260116a: COLIBRÍ optical upper limit
  31. EP260116a: Liverpool Telescope upper limits
  32. EP260116A: 1.3m DFOT optical upper limit
  33. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  34. EP260116a: Xinglong optical upper limit
  35. GRB260114A: STEP/T80S optical limits
  36. GRB 251222A: radio detection with the VLA
  37. GRB 260114A : MITSuME Akeno optical upper limits
  38. GRB 260114A: COLIBRÍ optical upper limits
  39. GRB 260114A: TNG NIR upper limit
  40. GRB 260114A: NOT optical observations
  41. GRB 260114A: SVOM/GRM observation of a short burst
  42. GRB 260114A: Mondy optical observations
  43. GRB 260114A: GMG Optical Observation
  44. EP260110a: NOT and GTC Optical and Near-Infrared Observations
  45. EP260110a: TRT optical upper limits
  46. GRB 260111A: Swift-XRT observations
  47. GRB 260111A: COLIBRÍ optical afterglow candidate
  48. GRB 260111A: GOTO optical upper limits
  49. GRB 251230A: Mondy Optical Observations
  50. EP260110a: SVOM/VT optical upper limits
  51. EP260110a: KAIT optical upper limit
  52. EP260110a: refined analysis of the EP-WXT and EP-FXT observations
  53. EP 260110a: COLIBRÍ optical observations
  54. EP260110a: BOOTES-5/JGU optical upper limit
  55. GRB 260109C: LCO optical upper limits
  56. GRB 260109C: Kilonova-Catcher optical upper limit
  57. Swift GRB 251230A: Global MASTER-Net OT detection
  58. GRB 260102A: AbAO optical observations
  59. EP260105a: FTW optical observations
  60. EP260104a: FTW optical observations
  61. GRB 260105A: SVOM/GRM observation
  62. GRB 260105B: SVOM/GRM observation
  63. FRB 20251229A: COLIBRÍ optical upper limits
  64. EP260105a: SVOM/VT optical upperlimit
  65. EP260105a: refined analysis of the EP-WXT and EP-FXT observations
  66. EP260105a: LCO Optical Upper limit
  67. GRB 260101A: COLIBRÍ optical upper limits
  68. GRB 260104A: COLIBRÍ optical upper limits
  69. GRB 251230A/EP-WXT trigger 01709250693: Mephisto optical upper limits
  70. GRB 260101A: COLIBRÍ optical observations
  71. GRB 260102A: EP-FXT follow-up observation
  72. GRB 260102A: LCO optical upper limits
  73. GRB 260102A: Swift-XRT observations
  74. GRB 260102A: SVOM/COLIBRÍ (FM-GFT) optical observations
  75. GRB 260102A: SVOM/VT optical counterpart
  76. GRB 260101A: NOT spectroscopic observations
  77. GRB 260101A: SVOM/GRM observation
  78. GRB 260101A: OSIRIS+ redshift z = 2.623 for the new year burst
  79. GRB 260101A: LCO detection of the optical counterpart
  80. GRB 260101A: Swift detection of a burst with an optical counterpart
  81. GRB 251230A / EP251230a: SVOM/VT optical continued observations and upper limit
  82. GRB 251230A: GRANDMA/TAROT Early Detection
  83. GRB 251230A / EP251230a: further NOT optical observations revealing shallower decay or possible rebrightening
  84. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  85. EP251229a: Optical upper limit with Kinder observations
  86. GRB 251230A: 1.3m DFOT optical upper limit
  87. GRB 251222A: Mondy Optical Observations
  88. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  89. GRB 251230A: Swift/UVOT detection
  90. GRB251230A: 7DT optical upper limits
  91. GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
  92. EP251229a: BOOTES-2 early optical upper limit
  93. GRB 251230A: GOTO optical upper limit
  94. EP251229a: NOT optical upper limits
  95. GRB 251230A / EP251230a: SVOM/VT optical observation
  96. EP251229a: refined analysis of the EP-WXT and EP-FXT observations
  97. GRB 251230A: Early optical counterpart detection by LCO.
  98. EP-WXT trigger 01709250662 Mephisto and 50cm telescope follow-up
  99. GRB 251230A: Optical Observations via Virtual Telescope Project, Italy
  100. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient

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