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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"

21263 results found.

  1. EP260119a: NOT optical observations
  2. EP260119a: SAO RAS optical observations
  3. EP260116a: COLIBRÍ detection of a fading optical source
  4. GRB 260117A: Swift-XRT afterglow detection
  5. EP260119a: COLIBRÍ photometric redshift z ≈ 5.6
  6. EP260119a: LCO optical observations
  7. GRB 260117A: ZTSh optical upper limit
  8. EP260119a: COLIBRÍ optical counterpart candidate
  9. GRB 260110A: SVOM detection of a burst through offline search
  10. EP260119a: EP-WXT detection of a fast X-ray transient
  11. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  12. Swift trigger on the HMXB 1A 1118-61
  13. GRB 260117A: SVOM/C-GFT upper limit
  14. GRB 260117A: SVOM detection of a long faint burst
  15. EP 260116a: COLIBRÍ optical upper limit
  16. Swift triggered on the HMXB 1A 1118-61
  17. FRB 20251229A: COLIBRÍ further inspection of the updated localization
  18. EP260116a: Liverpool Telescope upper limits
  19. EP260116A: 1.3m DFOT optical upper limit
  20. GRB 260114A: VLT/MUSE spectroscopic observations
  21. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  22. EP260116a: Xinglong optical upper limit
  23. EP260116a: Einstein Probe detection of an X-ray transient
  24. GRB 260114A: VLT/HAWK-I further near-infrared upper limits
  25. GRB 251222A: radio detection with the VLA
  26. GRB 260114A: VLT/HAWK-I near-infrared upper limits
  27. Konus-Wind detection of GRB 260114A
  28. GRB 260114A: Swift-XRT refined Analysis
  29. GRB 260114A: VLT/X-shooter redshift of the putative host galaxy
  30. GRB 260114A : MITSuME Akeno optical upper limits
  31. GRB 260114A: COLIBRÍ optical upper limits
  32. GRB 260114A: TNG NIR upper limit
  33. GRB 260114A: NOT optical observations
  34. Konus-Wind detection of GRB 251230A / EP251230a
  35. GRB 260114A: SVOM/GRM observation of a short burst
  36. GRB 260114A: Mondy optical observations
  37. GRB 260114A: GMG Optical Observation
  38. GRB 260114A: Swift detection of a short burst
  39. EP-WXT trigger 01709251266: SVOM/C-GFT confirmation of a stellar flare
  40. EP260110a: NOT and GTC Optical and Near-Infrared Observations
  41. EP260110a: TRT optical upper limits
  42. Swift Trigger 1439093: is probably not GRB 260113A
  43. GRB 260111A: COLIBRÍ optical afterglow candidate
  44. GRB 260111A: GOTO optical upper limits
  45. GRB 251230A: Mondy Optical Observations
  46. GRB 260111A: Swift/BAT-GUANO arcminute localization of a burst
  47. Swift trigger 1436759 is not an astrophysical event
  48. EP260110a: KAIT optical upper limit
  49. EP260110a: refined analysis of the EP-WXT and EP-FXT observations
  50. EP 260110a: COLIBRÍ optical observations
  51. EP260110a: SVOM/C-GFT upper limit
  52. EP260110a: BOOTES-5/JGU optical upper limit
  53. EP260110a: Einstein Probe detection of an X-ray transient
  54. GRB 260109C: LCO optical upper limits
  55. GRB 260109C: Kilonova-Catcher optical upper limit
  56. Swift Trigger 1434591: possible GRB 260109C
  57. GRB 260102A: Swift-XRT afterglow detection
  58. Swift GRB 251230A: Global MASTER-Net OT detection
  59. GRB 260102A: AbAO optical observations
  60. EP260105b/EP-WXT trigger 01709251028: Einstein Probe detection of an X-ray transient
  61. GRB 260105A: SVOM/GRM observation
  62. GRB 260105B: SVOM/GRM observation
  63. FRB 20251229A: COLIBRÍ optical upper limits
  64. GRB 260105B: Fermi GBM Final Real-time Localization
  65. GRB 260105A: Fermi GBM Final Real-time Localization
  66. FRB 20251229A: A potentially hyperactive repeating fast radio burst source
  67. EP260105a: refined analysis of the EP-WXT and EP-FXT observations
  68. EP260105a: LCO Optical Upper limit
  69. EP260104a: Einstein Probe detection of a fast X-ray transient
  70. GRB 260101A: COLIBRÍ optical upper limits
  71. EP260105a: Einstein Probe detection of an X-ray transient
  72. GRB 260104A: COLIBRÍ optical upper limits
  73. GRB 251230A/EP-WXT trigger 01709250693: Mephisto optical upper limits
  74. GRB 260104A: Enhanced Swift-XRT position
  75. GRB 260101A: Swift/UVOT Detection
  76. GRB 260104A: Swift detection of a burst
  77. GRB 260101A: COLIBRÍ optical observations
  78. GRB 260102A: LCO optical upper limits
  79. GRB 260102A: SVOM/COLIBRÍ (FM-GFT) optical observations
  80. EP260101a: refined analysis of the EP-WXT and EP-FXT observations
  81. GRB 260102A: SVOM detection of a burst
  82. GRB 260101A: SVOM/GRM observation
  83. GRB 260101A: Enhanced Swift-XRT position
  84. EP260101a: Einstein Probe detection of an X-ray transient
  85. GRB 260101A: LCO detection of the optical counterpart
  86. GRB 260101A: Swift detection of a burst with an optical counterpart
  87. GRB 251230A: GRANDMA/TAROT Early Detection
  88. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  89. EP251229a: Optical upper limit with Kinder observations
  90. GRB 251230A: 1.3m DFOT optical upper limit
  91. GRB 251222A: Mondy Optical Observations
  92. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  93. GRB 251230A: Swift/UVOT detection
  94. GRB251230A: 7DT optical upper limits
  95. GRB 251230A: GOTO optical upper limit
  96. EP251229a: NOT optical upper limits
  97. GRB 251230A / EP251230a: SVOM/VT optical observation
  98. EP251229a: refined analysis of the EP-WXT and EP-FXT observations
  99. GRB 251230A: Enhanced Swift-XRT position
  100. GRB 251230A: Early optical counterpart detection by LCO.

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