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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"

19551 results found.

  1. GRB 260120B: SVOM/GRM observation
  2. EP260119a: Assy AZT-20 optical observations
  3. EP260119a: Mondy and SAO RAS optical upper limits
  4. EP260119a: Xinglong optical upper limit
  5. EP260116a: COLIBRÍ further observations
  6. EP260105a: GTC/HiPERCAM optical observations
  7. GRB 260120B: Swift/UVOT Detection
  8. GRB 260120B: COLIBRÍ optical upper limits
  9. GRB 260120B: Enhanced Swift-XRT position
  10. GRB 260120B: SVOM/C-GFT optical counterpart detection
  11. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  12. GRB 260120B: Swift detection of a burst
  13. EP260119A: Mondy I-Band Observations
  14. GRB 260114A: Swift/UVOT Upper Limits
  15. EP260119a: Liverpool Telescope optical follow-up observations
  16. GRB 251202A: further radio observations with the VLA
  17. EP260119a: KAIT optical observations
  18. EP260119a: SVOM/VT optical observation
  19. EP260119a: NOT optical observations
  20. EP260119a: SAO RAS optical observations
  21. EP260116a: COLIBRÍ detection of a fading optical source
  22. GRB 251208D: SVOM/ECLAIRs refined analysis
  23. GRB 251208D: SVOM/ECLAIRs refined analysis
  24. GRB 260117A: Swift-XRT afterglow detection
  25. EP260119a: COLIBRÍ photometric redshift z ≈ 5.6
  26. EP260119a: LCO optical observations
  27. GRB 260117A: ZTSh optical upper limit
  28. EP260119a: COLIBRÍ optical counterpart candidate
  29. EP260119a: EP-WXT detection of a fast X-ray transient
  30. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  31. Swift trigger on the HMXB 1A 1118-61
  32. GRB 260117A: SVOM/C-GFT upper limit
  33. GRB 260117A: Swift ToO observations
  34. EP 260116a: COLIBRÍ optical upper limit
  35. Swift triggered on the HMXB 1A 1118-61
  36. FRB 20251229A: COLIBRÍ further inspection of the updated localization
  37. EP260116a: Liverpool Telescope upper limits
  38. EP260116A: 1.3m DFOT optical upper limit
  39. GRB 260114A: VLT/MUSE spectroscopic observations
  40. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  41. EP260116a: Xinglong optical upper limit
  42. EP260116a: Einstein Probe detection of an X-ray transient
  43. GRB 260114A: VLT/HAWK-I further near-infrared upper limits
  44. GRB 251222A: radio detection with the VLA
  45. GRB 260114A: VLT/HAWK-I near-infrared upper limits
  46. GRB 260114A: Swift-XRT refined Analysis
  47. GRB 260114A: VLT/X-shooter redshift of the putative host galaxy
  48. GRB 260114A : MITSuME Akeno optical upper limits
  49. GRB 260114A: COLIBRÍ optical upper limits
  50. GRB 260114A: TNG NIR upper limit
  51. GRB 260114A: NOT optical observations
  52. GRB 260114A: SVOM/GRM observation of a short burst
  53. GRB 260114A: Mondy optical observations
  54. GRB 260114A: GMG Optical Observation
  55. GRB 260114A: Swift detection of a short burst
  56. EP-WXT trigger 01709251266: SVOM/C-GFT confirmation of a stellar flare
  57. EP260110a: NOT and GTC Optical and Near-Infrared Observations
  58. EP260110a: TRT optical upper limits
  59. Swift Trigger 1439093: is probably not GRB 260113A
  60. GRB 260111A: COLIBRÍ optical afterglow candidate
  61. GRB 260111A: Swift ToO observations
  62. GRB 251230A: Mondy Optical Observations
  63. Swift trigger 1436759 is not an astrophysical event
  64. EP260110a: KAIT optical upper limit
  65. EP260110a: refined analysis of the EP-WXT and EP-FXT observations
  66. EP 260110a: COLIBRÍ optical observations
  67. EP260110a: SVOM/C-GFT upper limit
  68. EP260110a: Einstein Probe detection of an X-ray transient
  69. GRB 260109C: LCO optical upper limits
  70. GRB 260109C: Kilonova-Catcher optical upper limit
  71. Swift Trigger 1434591: possible GRB 260109C
  72. GRB 260102A: Swift-XRT afterglow detection
  73. GRB 260102A: AbAO optical observations
  74. EP260105b/EP-WXT trigger 01709251028: Einstein Probe detection of an X-ray transient
  75. GRB 260105B: Fermi GBM Detection
  76. GRB 260105A: SVOM/GRM observation
  77. GRB 260105B: SVOM/GRM observation
  78. FRB 20251229A: COLIBRÍ optical upper limits
  79. EP260105a: refined analysis of the EP-WXT and EP-FXT observations
  80. EP260105a: LCO Optical Upper limit
  81. EP260104a: Einstein Probe detection of a fast X-ray transient
  82. GRB 260101A: COLIBRÍ optical upper limits
  83. EP260105a: Einstein Probe detection of an X-ray transient
  84. GRB 260104A: COLIBRÍ optical upper limits
  85. GRB 251230A/EP-WXT trigger 01709250693: Mephisto optical upper limits
  86. GRB 260104A: Enhanced Swift-XRT position
  87. GRB 260101A: Swift/UVOT Detection
  88. GRB 260104A: Swift detection of a burst
  89. GRB 260101A: COLIBRÍ optical observations
  90. GRB 260102A: LCO optical upper limits
  91. GRB 260102A: SVOM/COLIBRÍ (FM-GFT) optical observations
  92. GRB 260102A: Swift ToO observations
  93. EP260101a: refined analysis of the EP-WXT and EP-FXT observations
  94. GRB 260102A: SVOM detection of a burst
  95. GRB 260101A: SVOM/GRM observation
  96. GRB 260101A: Enhanced Swift-XRT position
  97. EP260101a: Einstein Probe detection of an X-ray transient
  98. GRB 260101A: LCO detection of the optical counterpart
  99. GRB 260101A: Swift detection of a burst with an optical counterpart
  100. GRB 251230A: GRANDMA/TAROT Early Detection

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