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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"

25840 results found.

  1. The EP-WXT trigger 01709251871 is likely a flaring star
  2. GRB 260120B: Swift-XRT refined Analysis
  3. EP260116a: COLIBRÍ further observations
  4. GRB 260120B: Fermi GBM Observation
  5. EP260105a: GTC/HiPERCAM optical observations
  6. GRB 260120B: Swift/UVOT Detection
  7. GRB 260120B: COLIBRÍ optical upper limits
  8. GRB 260120B: Enhanced Swift-XRT position
  9. GRB 260120B: SVOM/C-GFT optical counterpart detection
  10. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  11. GRB 260120B: Swift detection of a burst
  12. EP260119A: Mondy I-Band Observations
  13. GRB 260114A: Swift/UVOT Upper Limits
  14. EP260119a: Liverpool Telescope optical follow-up observations
  15. GRB 251202A: further radio observations with the VLA
  16. EP260119a: KAIT optical observations
  17. EP260119a: SVOM/VT optical observation
  18. EP260119a: update of EP-FXT follow-up 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: preliminary result from the EP-FXT observation
  30. GRB 260110A: SVOM detection of a burst through offline search
  31. EP260119a: EP-WXT detection of a fast X-ray transient
  32. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  33. Fermi-LAT Gamma-ray Observations of IceCube-260115A
  34. Swift trigger on the HMXB 1A 1118-61
  35. GRB 260117A: SVOM/C-GFT upper limit
  36. GRB 260117A: Swift-XRT observations
  37. GRB 260117A: SVOM detection of a long faint burst
  38. EP 260116a: COLIBRÍ optical upper limit
  39. Swift triggered on the HMXB 1A 1118-61
  40. GRB 260115A: GECAM-B observation
  41. FRB 20251229A: COLIBRÍ further inspection of the updated localization
  42. EP260116a: Liverpool Telescope upper limits
  43. EP260116A: 1.3m DFOT optical upper limit
  44. GRB 260114A: VLT/MUSE spectroscopic observations
  45. IceCube-260115A: Upper limits from a search for additional neutrino events in IceCube
  46. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  47. EP260116a: Xinglong optical upper limit
  48. EP260116a: Einstein Probe detection of an X-ray transient
  49. GRB 260114A: VLT/HAWK-I further near-infrared upper limits
  50. IceCube-260115A - IceCube observation of a high-energy neutrino candidate track-like event
  51. IceCube: GCN Notices for high-energy track alerts now streamed via Kafka
  52. GRB 251222A: radio detection with the VLA
  53. GRB 260114A: VLT/HAWK-I near-infrared upper limits
  54. Konus-Wind detection of GRB 260114A
  55. GRB 260114A: Swift-XRT refined Analysis
  56. GRB 260114A: VLT/X-shooter redshift of the putative host galaxy
  57. GRB 260114A : MITSuME Akeno optical upper limits
  58. GRB 260114A: COLIBRÍ optical upper limits
  59. GRB 260114A: TNG NIR upper limit
  60. GRB 260114A: NOT optical observations
  61. Konus-Wind detection of GRB 251230A / EP251230a
  62. GRB 260114A: SVOM/GRM observation of a short burst
  63. GRB 260114A: GECAM-B observation of a short burst
  64. GRB 260114A: Mondy optical observations
  65. GRB 260114A: Fermi GBM observation
  66. GRB 260114A: GMG Optical Observation
  67. Fermi-LAT Gamma-ray Observations of IceCube-260111A
  68. GRB 260114A: Swift detection of a short burst
  69. EP-WXT trigger 01709251266: SVOM/C-GFT confirmation of a stellar flare
  70. IceCube-260111A: Upper limits from a search for additional neutrino events in IceCube
  71. EP260110a: NOT and GTC Optical and Near-Infrared Observations
  72. EP260110a: TRT optical upper limits
  73. Konus-Wind detection of GRB 260101A
  74. GRB 260111A: Swift-XRT observations
  75. Swift Trigger 1439093: is probably not GRB 260113A
  76. GRB 260111A: COLIBRÍ optical afterglow candidate
  77. GRB 260111A: Fermi GBM Observation
  78. The EP-WXT trigger 01709251266 is likely a flaring star
  79. GRB 251230A: Mondy Optical Observations
  80. Swift trigger 1436759 is not an astrophysical event
  81. EP260110a: KAIT optical upper limit
  82. EP260110a: refined analysis of the EP-WXT and EP-FXT observations
  83. EP 260110a: COLIBRÍ optical observations
  84. EP260110a: SVOM/C-GFT upper limit
  85. EP260110a: Einstein Probe detection of an X-ray transient
  86. GRB 260109C: LCO optical upper limits
  87. GRB 260109C: Kilonova-Catcher optical upper limit
  88. Swift Trigger 1434591: possible GRB 260109C
  89. GRB 260102A: Swift-XRT afterglow detection
  90. GRB 260102A: AbAO optical observations
  91. EP260105b/EP-WXT trigger 01709251028: Einstein Probe detection of an X-ray transient
  92. The EP-WXT trigger 01709251112 is likely a flaring star
  93. GRB 260105B: Fermi GBM Detection
  94. GRB 260105A: SVOM/GRM observation
  95. GRB 260105B: SVOM/GRM observation
  96. The EP-WXT trigger 01709251028 is likely a flaring star
  97. FRB 20251229A: COLIBRÍ optical upper limits
  98. EP260105a: refined analysis of the EP-WXT and EP-FXT observations
  99. EP260105a: LCO Optical Upper limit
  100. EP260104a: Einstein Probe detection of a fast X-ray transient

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