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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"

16158 results found.

  1. GRB 260120B: SVOM/C-GFT optical counterpart detection
  2. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  3. GRB 260114A: Swift/UVOT Upper Limits
  4. EP260119a: Liverpool Telescope optical follow-up observations
  5. EP260119A: GTC/OSIRIS+ spectroscopic redshift z = 5.47
  6. EP260119a: KAIT optical observations
  7. EP260119a: SVOM/VT optical observation
  8. EP260119a: NOT optical observations
  9. EP260119a: SAO RAS optical observations
  10. EP260116a: COLIBRÍ detection of a fading optical source
  11. GRB 260117A: Swift-XRT afterglow detection
  12. EP260119a: COLIBRÍ photometric redshift z ≈ 5.6
  13. EP260119a: LCO optical observations
  14. GRB 260117A: ZTSh optical upper limit
  15. EP260119a: COLIBRÍ optical counterpart candidate
  16. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  17. GRB 260117A: SVOM/VT optical candidate
  18. GRB 260117A: SVOM detection of a long faint burst
  19. EP 260116a: COLIBRÍ optical upper limit
  20. EP260116a: Liverpool Telescope upper limits
  21. EP260116A: 1.3m DFOT optical upper limit
  22. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  23. EP260116a: Xinglong optical upper limit
  24. GRB260114A: STEP/T80S optical limits
  25. GRB 251222A: radio detection with the VLA
  26. GRB 260114A : MITSuME Akeno optical upper limits
  27. GRB 260114A: COLIBRÍ optical upper limits
  28. GRB 260114A: TNG NIR upper limit
  29. GRB 260114A: NOT optical observations
  30. GRB 260114A: SVOM/GRM observation of a short burst
  31. GRB 260114A: Mondy optical observations
  32. GRB 260114A: GMG Optical Observation
  33. EP260110a: NOT and GTC Optical and Near-Infrared Observations
  34. EP260110a: TRT optical upper limits
  35. GRB 260111A: Swift-XRT observations
  36. GRB 260111A: COLIBRÍ optical afterglow candidate
  37. GRB 260111A: GOTO optical upper limits
  38. GRB 251230A: Mondy Optical Observations
  39. EP260110a: SVOM/VT optical upper limits
  40. EP260110a: KAIT optical upper limit
  41. EP260110a: refined analysis of the EP-WXT and EP-FXT observations
  42. EP 260110a: COLIBRÍ optical observations
  43. EP260110a: BOOTES-5/JGU optical upper limit
  44. GRB 260109C: LCO optical upper limits
  45. GRB 260109C: Kilonova-Catcher optical upper limit
  46. Swift GRB 251230A: Global MASTER-Net OT detection
  47. GRB 260102A: AbAO optical observations
  48. EP260105a: FTW optical observations
  49. EP260104a: FTW optical observations
  50. GRB 260105A: SVOM/GRM observation
  51. GRB 260105B: SVOM/GRM observation
  52. FRB 20251229A: COLIBRÍ optical upper limits
  53. EP260105a: SVOM/VT optical upperlimit
  54. EP260105a: refined analysis of the EP-WXT and EP-FXT observations
  55. EP260105a: LCO Optical Upper limit
  56. GRB 260101A: COLIBRÍ optical upper limits
  57. GRB 260104A: COLIBRÍ optical upper limits
  58. GRB 251230A/EP-WXT trigger 01709250693: Mephisto optical upper limits
  59. GRB 260101A: COLIBRÍ optical observations
  60. GRB 260102A: EP-FXT follow-up observation
  61. GRB 260102A: LCO optical upper limits
  62. GRB 260102A: Swift-XRT observations
  63. GRB 260102A: SVOM/COLIBRÍ (FM-GFT) optical observations
  64. GRB 260102A: SVOM/VT optical counterpart
  65. GRB 260101A: NOT spectroscopic observations
  66. GRB 260101A: SVOM/GRM observation
  67. GRB 260101A: OSIRIS+ redshift z = 2.623 for the new year burst
  68. GRB 260101A: LCO detection of the optical counterpart
  69. GRB 260101A: Swift detection of a burst with an optical counterpart
  70. GRB 251230A / EP251230a: SVOM/VT optical continued observations and upper limit
  71. GRB 251230A: GRANDMA/TAROT Early Detection
  72. GRB 251230A / EP251230a: further NOT optical observations revealing shallower decay or possible rebrightening
  73. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  74. EP251229a: Optical upper limit with Kinder observations
  75. GRB 251230A: 1.3m DFOT optical upper limit
  76. GRB 251222A: Mondy Optical Observations
  77. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  78. GRB 251230A: Swift/UVOT detection
  79. GRB251230A: 7DT optical upper limits
  80. GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
  81. EP251229a: BOOTES-2 early optical upper limit
  82. GRB 251230A: GOTO optical upper limit
  83. EP251229a: NOT optical upper limits
  84. GRB 251230A / EP251230a: SVOM/VT optical observation
  85. EP251229a: refined analysis of the EP-WXT and EP-FXT observations
  86. GRB 251230A: Early optical counterpart detection by LCO.
  87. EP-WXT trigger 01709250662 Mephisto and 50cm telescope follow-up
  88. GRB 251230A: Optical Observations via Virtual Telescope Project, Italy
  89. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  90. GRB 251230A/EP#01709250693 (likely EP251230a): FTW optical and NIR observations
  91. LIGO/Virgo/KAGRA S251112cm: Candidates from the NSF-DOE Vera C. Rubin Observatory
  92. The EP-WXT trigger 01709250693/GRB 251230A: Las Cumbres detection of the optical counterpart
  93. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  94. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  95. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  96. GRB 251226A: SVOM/GRM observation
  97. GRB 251222A: NUTTelA-TAO Early Measurements
  98. GRB 251222A/EP251222b: Optical detection with Kinder observations
  99. EP251222a: Optical upper limit with Kinder observations
  100. GRB 251222A/EP251222b: FTW optical and NIR observations

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