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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"

15556 results found.

  1. EP 260116a: COLIBRÍ optical upper limit
  2. EP260116a: Liverpool Telescope upper limits
  3. EP260116A: 1.3m DFOT optical upper limit
  4. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  5. EP260116a: Xinglong optical upper limit
  6. GRB260114A: STEP/T80S optical limits
  7. GRB 251222A: radio detection with the VLA
  8. GRB 260114A : MITSuME Akeno optical upper limits
  9. GRB 260114A: COLIBRÍ optical upper limits
  10. GRB 260114A: TNG NIR upper limit
  11. GRB 260114A: NOT optical observations
  12. GRB 260114A: SVOM/GRM observation of a short burst
  13. GRB 260114A: Mondy optical observations
  14. GRB 260114A: GMG Optical Observation
  15. EP260110a: NOT and GTC Optical and Near-Infrared Observations
  16. EP260110a: TRT optical upper limits
  17. GRB 260111A: Swift-XRT observations
  18. GRB 260111A: COLIBRÍ optical afterglow candidate
  19. GRB 260111A: GOTO optical upper limits
  20. GRB 251230A: Mondy Optical Observations
  21. EP260110a: SVOM/VT optical upper limits
  22. EP260110a: KAIT optical upper limit
  23. EP260110a: refined analysis of the EP-WXT and EP-FXT observations
  24. EP 260110a: COLIBRÍ optical observations
  25. EP260110a: BOOTES-5/JGU optical upper limit
  26. GRB 260109C: LCO optical upper limits
  27. GRB 260109C: Kilonova-Catcher optical upper limit
  28. Swift GRB 251230A: Global MASTER-Net OT detection
  29. GRB 260102A: AbAO optical observations
  30. EP260105a: FTW optical observations
  31. EP260104a: FTW optical observations
  32. GRB 260105A: SVOM/GRM observation
  33. GRB 260105B: SVOM/GRM observation
  34. FRB 20251229A: COLIBRÍ optical upper limits
  35. EP260105a: SVOM/VT optical upperlimit
  36. EP260105a: refined analysis of the EP-WXT and EP-FXT observations
  37. EP260105a: LCO Optical Upper limit
  38. GRB 260101A: COLIBRÍ optical upper limits
  39. GRB 260104A: COLIBRÍ optical upper limits
  40. GRB 251230A/EP-WXT trigger 01709250693: Mephisto optical upper limits
  41. GRB 260101A: COLIBRÍ optical observations
  42. GRB 260102A: EP-FXT follow-up observation
  43. GRB 260102A: LCO optical upper limits
  44. GRB 260102A: Swift-XRT observations
  45. GRB 260102A: SVOM/COLIBRÍ (FM-GFT) optical observations
  46. GRB 260102A: SVOM/VT optical counterpart
  47. GRB 260101A: NOT spectroscopic observations
  48. GRB 260101A: SVOM/GRM observation
  49. GRB 260101A: OSIRIS+ redshift z = 2.623 for the new year burst
  50. GRB 260101A: LCO detection of the optical counterpart
  51. GRB 260101A: Swift detection of a burst with an optical counterpart
  52. GRB 251230A / EP251230a: SVOM/VT optical continued observations and upper limit
  53. GRB 251230A: GRANDMA/TAROT Early Detection
  54. GRB 251230A / EP251230a: further NOT optical observations revealing shallower decay or possible rebrightening
  55. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  56. EP251229a: Optical upper limit with Kinder observations
  57. GRB 251230A: 1.3m DFOT optical upper limit
  58. GRB 251222A: Mondy Optical Observations
  59. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  60. GRB 251230A: Swift/UVOT detection
  61. GRB251230A: 7DT optical upper limits
  62. GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
  63. EP251229a: BOOTES-2 early optical upper limit
  64. GRB 251230A: GOTO optical upper limit
  65. EP251229a: NOT optical upper limits
  66. GRB 251230A / EP251230a: SVOM/VT optical observation
  67. EP251229a: refined analysis of the EP-WXT and EP-FXT observations
  68. GRB 251230A: Early optical counterpart detection by LCO.
  69. EP-WXT trigger 01709250662 Mephisto and 50cm telescope follow-up
  70. GRB 251230A: Optical Observations via Virtual Telescope Project, Italy
  71. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  72. GRB 251230A/EP#01709250693 (likely EP251230a): FTW optical and NIR observations
  73. The EP-WXT trigger 01709250693/GRB 251230A: Las Cumbres detection of the optical counterpart
  74. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  75. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  76. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  77. GRB 251226A: SVOM/GRM observation
  78. GRB 251222A: NUTTelA-TAO Early Measurements
  79. GRB 251222A/EP251222b: Optical detection with Kinder observations
  80. EP251222a: Optical upper limit with Kinder observations
  81. GRB 251222A/EP251222b: FTW optical and NIR observations
  82. EP251222a: FTW optical and NIR observations
  83. GRB 251205A: Kilonova-Catcher optical afterglow detection
  84. GRB 251222A: AbAO optical observations
  85. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  86. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  87. EP251222a: VLT/FORS2 spectroscopic redshift z = 0.505
  88. GRB 251222A: ZTSH BVRI optical observations
  89. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  90. GRB 251222A: Continued 1.3m DFOT optical observation
  91. EP251220a: 3.6m DOT optical afterglow detection
  92. EP251220a: CrAO ZTSh optical observations
  93. EP251221a: Liverpool Telescope upper limits
  94. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  95. EP251222a: NTT/ULTRACAM optical observations
  96. EP251222a: GOTO optical upper limit
  97. GRB 251222A / EP251222b: GOTO optical counterpart detection
  98. GRB 251222A / EP251222b: LCO optical observations
  99. GRB 251222A: 1.3m DFOT optical detection
  100. GRB251221A: 7DT optical upper limits

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