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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"

21769 results found.

  1. EP260119A: Mondy I-Band Observations
  2. GRB 260114A: Swift/UVOT Upper Limits
  3. EP260119a: Liverpool Telescope optical follow-up observations
  4. GRB 251202A: further radio observations with the VLA
  5. EP260119a: KAIT optical observations
  6. EP260119a: SVOM/VT optical observation
  7. EP260119a: NOT optical observations
  8. EP260119a: SAO RAS optical observations
  9. EP260116a: COLIBRÍ detection of a fading optical source
  10. GRB 260117A: Swift-XRT afterglow detection
  11. EP260119a: COLIBRÍ photometric redshift z ≈ 5.6
  12. EP260119a: LCO optical observations
  13. GRB 260117A: ZTSh optical upper limit
  14. EP260119a: COLIBRÍ optical counterpart candidate
  15. GRB 260110A: SVOM detection of a burst through offline search
  16. EP260119a: EP-WXT detection of a fast X-ray transient
  17. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  18. Swift trigger on the HMXB 1A 1118-61
  19. GRB 260117A: SVOM/C-GFT upper limit
  20. GRB 260117A: SVOM detection of a long faint burst
  21. EP 260116a: COLIBRÍ optical upper limit
  22. Swift triggered on the HMXB 1A 1118-61
  23. FRB 20251229A: COLIBRÍ further inspection of the updated localization
  24. EP260116a: Liverpool Telescope upper limits
  25. EP260116A: 1.3m DFOT optical upper limit
  26. GRB 260114A: VLT/MUSE spectroscopic observations
  27. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  28. EP260116a: Xinglong optical upper limit
  29. EP260116a: Einstein Probe detection of an X-ray transient
  30. GRB 260114A: VLT/HAWK-I further near-infrared upper limits
  31. GRB 251222A: radio detection with the VLA
  32. GRB 260114A: VLT/HAWK-I near-infrared upper limits
  33. Konus-Wind detection of GRB 260114A
  34. GRB 260114A: Swift-XRT refined Analysis
  35. GRB 260114A: VLT/X-shooter redshift of the putative host galaxy
  36. GRB 260114A : MITSuME Akeno optical upper limits
  37. GRB 260114A: COLIBRÍ optical upper limits
  38. GRB 260114A: TNG NIR upper limit
  39. GRB 260114A: NOT optical observations
  40. Konus-Wind detection of GRB 251230A / EP251230a
  41. GRB 260114A: SVOM/GRM observation of a short burst
  42. GRB 260114A: Mondy optical observations
  43. GRB 260114A: GMG Optical Observation
  44. GRB 260114A: Swift detection of a short burst
  45. EP-WXT trigger 01709251266: SVOM/C-GFT confirmation of a stellar flare
  46. EP260110a: NOT and GTC Optical and Near-Infrared Observations
  47. EP260110a: TRT optical upper limits
  48. Swift Trigger 1439093: is probably not GRB 260113A
  49. GRB 260111A: COLIBRÍ optical afterglow candidate
  50. GRB 260111A: GOTO optical upper limits
  51. GRB 251230A: Mondy Optical Observations
  52. GRB 260111A: Swift/BAT-GUANO arcminute localization of a burst
  53. Swift trigger 1436759 is not an astrophysical event
  54. EP260110a: KAIT optical upper limit
  55. EP260110a: refined analysis of the EP-WXT and EP-FXT observations
  56. EP 260110a: COLIBRÍ optical observations
  57. EP260110a: SVOM/C-GFT upper limit
  58. EP260110a: BOOTES-5/JGU optical upper limit
  59. EP260110a: Einstein Probe detection of an X-ray transient
  60. GRB 260109C: LCO optical upper limits
  61. GRB 260109C: Kilonova-Catcher optical upper limit
  62. Swift Trigger 1434591: possible GRB 260109C
  63. GRB 260102A: Swift-XRT afterglow detection
  64. Swift GRB 251230A: Global MASTER-Net OT detection
  65. GRB 260102A: AbAO optical observations
  66. EP260105b/EP-WXT trigger 01709251028: Einstein Probe detection of an X-ray transient
  67. GRB 260105A: SVOM/GRM observation
  68. GRB 260105B: SVOM/GRM observation
  69. FRB 20251229A: COLIBRÍ optical upper limits
  70. GRB 260105B: Fermi GBM Final Real-time Localization
  71. GRB 260105A: Fermi GBM Final Real-time Localization
  72. FRB 20251229A: A potentially hyperactive repeating fast radio burst source
  73. EP260105a: refined analysis of the EP-WXT and EP-FXT observations
  74. EP260105a: LCO Optical Upper limit
  75. EP260104a: Einstein Probe detection of a fast X-ray transient
  76. GRB 260101A: COLIBRÍ optical upper limits
  77. EP260105a: Einstein Probe detection of an X-ray transient
  78. GRB 260104A: COLIBRÍ optical upper limits
  79. GRB 251230A/EP-WXT trigger 01709250693: Mephisto optical upper limits
  80. GRB 260104A: Enhanced Swift-XRT position
  81. GRB 260101A: Swift/UVOT Detection
  82. GRB 260104A: Swift detection of a burst
  83. GRB 260101A: COLIBRÍ optical observations
  84. GRB 260102A: LCO optical upper limits
  85. GRB 260102A: SVOM/COLIBRÍ (FM-GFT) optical observations
  86. EP260101a: refined analysis of the EP-WXT and EP-FXT observations
  87. GRB 260102A: SVOM detection of a burst
  88. GRB 260101A: SVOM/GRM observation
  89. GRB 260101A: Enhanced Swift-XRT position
  90. EP260101a: Einstein Probe detection of an X-ray transient
  91. GRB 260101A: LCO detection of the optical counterpart
  92. GRB 260101A: Swift detection of a burst with an optical counterpart
  93. GRB 251230A: GRANDMA/TAROT Early Detection
  94. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  95. EP251229a: Optical upper limit with Kinder observations
  96. GRB 251230A: 1.3m DFOT optical upper limit
  97. GRB 251222A: Mondy Optical Observations
  98. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  99. GRB 251230A: Swift/UVOT detection
  100. GRB251230A: 7DT optical upper limits

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