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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"

15983 results found.

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

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