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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"

21770 results found.

  1. GRB 260120B: Swift detection of a burst
  2. EP260119A: Mondy I-Band Observations
  3. GRB 260114A: Swift/UVOT Upper Limits
  4. EP260119a: Liverpool Telescope optical follow-up observations
  5. GRB 251202A: further radio observations with the VLA
  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 260110A: SVOM detection of a burst through offline search
  17. EP260119a: EP-WXT detection of a fast X-ray transient
  18. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  19. Swift trigger on the HMXB 1A 1118-61
  20. GRB 260117A: SVOM/C-GFT upper limit
  21. GRB 260117A: SVOM detection of a long faint burst
  22. EP 260116a: COLIBRÍ optical upper limit
  23. Swift triggered on the HMXB 1A 1118-61
  24. FRB 20251229A: COLIBRÍ further inspection of the updated localization
  25. EP260116a: Liverpool Telescope upper limits
  26. EP260116A: 1.3m DFOT optical upper limit
  27. GRB 260114A: VLT/MUSE spectroscopic observations
  28. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  29. EP260116a: Xinglong optical upper limit
  30. EP260116a: Einstein Probe detection of an X-ray transient
  31. GRB 260114A: VLT/HAWK-I further near-infrared upper limits
  32. GRB 251222A: radio detection with the VLA
  33. GRB 260114A: VLT/HAWK-I near-infrared upper limits
  34. Konus-Wind detection of GRB 260114A
  35. GRB 260114A: Swift-XRT refined Analysis
  36. GRB 260114A: VLT/X-shooter redshift of the putative host galaxy
  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. Konus-Wind detection of GRB 251230A / EP251230a
  42. GRB 260114A: SVOM/GRM observation of a short burst
  43. GRB 260114A: Mondy optical observations
  44. GRB 260114A: GMG Optical Observation
  45. GRB 260114A: Swift detection of a short burst
  46. EP-WXT trigger 01709251266: SVOM/C-GFT confirmation of a stellar flare
  47. EP260110a: NOT and GTC Optical and Near-Infrared Observations
  48. EP260110a: TRT optical upper limits
  49. Swift Trigger 1439093: is probably not GRB 260113A
  50. GRB 260111A: COLIBRÍ optical afterglow candidate
  51. GRB 260111A: GOTO optical upper limits
  52. GRB 251230A: Mondy Optical Observations
  53. GRB 260111A: Swift/BAT-GUANO arcminute localization of a burst
  54. Swift trigger 1436759 is not an astrophysical event
  55. EP260110a: KAIT optical upper limit
  56. EP260110a: refined analysis of the EP-WXT and EP-FXT observations
  57. EP 260110a: COLIBRÍ optical observations
  58. EP260110a: SVOM/C-GFT upper limit
  59. EP260110a: BOOTES-5/JGU optical upper limit
  60. EP260110a: Einstein Probe detection of an X-ray transient
  61. GRB 260109C: LCO optical upper limits
  62. GRB 260109C: Kilonova-Catcher optical upper limit
  63. Swift Trigger 1434591: possible GRB 260109C
  64. GRB 260102A: Swift-XRT afterglow detection
  65. Swift GRB 251230A: Global MASTER-Net OT detection
  66. GRB 260102A: AbAO optical observations
  67. EP260105b/EP-WXT trigger 01709251028: Einstein Probe detection of an X-ray transient
  68. GRB 260105A: SVOM/GRM observation
  69. GRB 260105B: SVOM/GRM observation
  70. FRB 20251229A: COLIBRÍ optical upper limits
  71. GRB 260105B: Fermi GBM Final Real-time Localization
  72. GRB 260105A: Fermi GBM Final Real-time Localization
  73. FRB 20251229A: A potentially hyperactive repeating fast radio burst source
  74. EP260105a: refined analysis of the EP-WXT and EP-FXT observations
  75. EP260105a: LCO Optical Upper limit
  76. EP260104a: Einstein Probe detection of a fast X-ray transient
  77. GRB 260101A: COLIBRÍ optical upper limits
  78. EP260105a: Einstein Probe detection of an X-ray transient
  79. GRB 260104A: COLIBRÍ optical upper limits
  80. GRB 251230A/EP-WXT trigger 01709250693: Mephisto optical upper limits
  81. GRB 260104A: Enhanced Swift-XRT position
  82. GRB 260101A: Swift/UVOT Detection
  83. GRB 260104A: Swift detection of a burst
  84. GRB 260101A: COLIBRÍ optical observations
  85. GRB 260102A: LCO optical upper limits
  86. GRB 260102A: SVOM/COLIBRÍ (FM-GFT) optical observations
  87. EP260101a: refined analysis of the EP-WXT and EP-FXT observations
  88. GRB 260102A: SVOM detection of a burst
  89. GRB 260101A: SVOM/GRM observation
  90. GRB 260101A: Enhanced Swift-XRT position
  91. EP260101a: Einstein Probe detection of an X-ray transient
  92. GRB 260101A: LCO detection of the optical counterpart
  93. GRB 260101A: Swift detection of a burst with an optical counterpart
  94. GRB 251230A: GRANDMA/TAROT Early Detection
  95. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  96. EP251229a: Optical upper limit with Kinder observations
  97. GRB 251230A: 1.3m DFOT optical upper limit
  98. GRB 251222A: Mondy Optical Observations
  99. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  100. GRB 251230A: Swift/UVOT detection

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