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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"

3089 results found.

  1. GRB 260818B: Further EP-FXT observation
  2. The EP-WXT trigger 01709291839 is likely the known LMXB 4U 1745-203
  3. IceCube-260825A: No transient candidates from the Zwicky Transient Facility
  4. IceCube Alert 260825A: Global MASTER-Net observations report
  5. GRB 260822A: SVOM/VT optical detection of COLIBRÍ candidate
  6. EP260806a: SAO RAS multicolor optical observations
  7. GRB 260813A: Fermi GBM Final Real-time Localization
  8. GRB 260808B: SAO RAS optical observations
  9. GRB 260809A: NOT optical observations
  10. GRB 260809A: SVOM/VT optical counterpart
  11. IceCube-260805A: One candidate from the Zwicky Transient Facility
  12. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  13. Fermi GRB 260805A: Global MASTER-Net observations report
  14. Fermi GRB 260802B: Global MASTER-Net observations report
  15. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  16. EP260729a: Einstein Probe detection of an X-ray transient
  17. GRB 260726A: SVOM/VT optical candidate
  18. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  19. GRB 260727A: GOTO early optical upper limit
  20. Fermi GRB 260726A: Global MASTER-Net observations report
  21. EP260723a: further EP-FXT follow-up observation
  22. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
  23. GRB 260718A : GRANDMA and KNC upper limits
  24. IceCube-260712A: No candidates with the Zwicky Transient Facility (ZTF)
  25. GRB 260714B: Fermi GBM Detection
  26. IceCube-260708A: One candidate from the Zwicky Transient Facility
  27. GRB 260704A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  28. IceCube-260704A: No candidates from the Zwicky Transient Facility
  29. IPN triangulation of GRB 260627A
  30. Fermi GRB 260703A: Global MASTER-Net observations report
  31. GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
  32. Fermi trigger No 804552016: Global MASTER-Net observations report
  33. Konus-Wind detection of GRB 260623B / EP260623a
  34. EP260618a: EP-FXT follow-up observation
  35. GRB 260616C: GECAM-B observation of a burst
  36. GRB 260617A: Fermi GBM Detection
  37. GRB260616C: MAXI/GSC detection
  38. GRB 260614B: SVOM detection of a burst
  39. IceCube-260610A: No candidates from the Zwicky Transient Facility
  40. EP260610b: SVOM/VT optical confirmation with blue color
  41. EP260610a: SVOM/VT optical upper limits
  42. GRB 260608C: Fermi GBM Final Real-time Localization
  43. GRB 260607B: Fermi GBM Observation
  44. GRB 260604C: LAST detection of optical counterpart candidate
  45. EP260602a: EP-FXT follow-up observation
  46. EP260601a/GRB 260601B: EP-FXT follow-up observation
  47. Fermi GRB 260602B: Global MASTER-Net observations report
  48. Fermi GRB 260602B: Global MASTER-Net observations report
  49. GRB 260601A: Fermi GBM Observation
  50. Fermi trigger No 801900520: Global MASTER-Net observations report
  51. GRB 260531A: MAXI/GSC detection
  52. EP260527a/GRB 260527A: further FTW optical and NIR observations
  53. GRB 260527A / EP260527a: VLA radio detection
  54. GRB 260523A: Fermi GBM Final Real-time Localization
  55. Fermi GRB 260516C: Global MASTER-Net observations report
  56. GRB 260516B: Fermi GBM Final Real-time Localization
  57. SVOM GRB 260515A: Global MASTER-Net observations report
  58. SVOM GRB 260515A: MASTER OT J151044.43+243321.7 optical counterpart detection
  59. IceCube-260504A: No Candidate Transients from the Zwicky Transient Facility
  60. EP260514a: Global MASTER-Net observations report
  61. GRB 260511B: Mephisto multi-band optical followup
  62. GRB 260511B: LCO optical counterpart detection
  63. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) further optical observations
  64. EP260509a: LCO optical upper limits
  65. GRB 260510C: SVOM/VT optical upper limits
  66. SVOM GRB 260509A: MASTER-OAFA optical observation
  67. GRB 260509A: SVOM/VT optical candidate with VHF data
  68. GRB 260509A: GOTO optical counterpart candidate
  69. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  70. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  71. EP260507a: Kinder optical counterpart candidate
  72. EP260507a: LCO optical counterpart
  73. EP260507a: Einstein Probe detection of an X-ray transient
  74. Fermi GRB 260506A: Global MASTER-Net observations report
  75. GRB 260430B: AstroSat CZTI detection of a long burst
  76. SVOM GRB 260504B: MASTER-OAFA optical observations
  77. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  78. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  79. GRB 260429A: Fermi GBM Detection
  80. Fermi GRB 260429A: Global MASTER-Net observations report
  81. EP260430a: Global MASTER-Net observations report
  82. EP260430a: Einstein Probe detection of an X-ray transient
  83. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  84. IPN triangulation of GRB 260424B (short)
  85. IceCube Alert 260425A: Global MASTER-Net observations report
  86. GRB 260419A: AstroSat CZTI detection
  87. GRB 260310A: Late-time Chandra X-ray Detection
  88. Fermi GRB 260421B: Global MASTER-Net observations report
  89. Fermi GRB 260421A: Global MASTER-Net observations report
  90. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  91. GRB 260419B: Fermi GBM Final Real-time Localization
  92. Fermi GRB 260417A: Global MASTER-Net observations report
  93. EP260416a: WFST optical observations and rebrightening
  94. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  95. EP260416a: Global MASTER-Net observations report
  96. EP260321a: CMO SAI J,K observations
  97. GRB 260414A: Fermi GBM Final Real-time Localization
  98. Fermi GRB 260412A: Global MASTER-Net observations report
  99. GRB 260410B: Fermi GBM Observation
  100. GRB 260411B: Fermi GBM Final Real-time Localization

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