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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"

3101 results found.

  1. GRB 260917A: Fermi GBM Final Real-time Localization
  2. Fermi trigger No 811264269: Global MASTER-Net observations report
  3. GRB 260916A: MAXI/GSC detection
  4. EP Alert 260914.53: Global MASTER-Net observations report
  5. GRB 260909A: SVOM/ECLAIRs refined analysis
  6. EP Alert 260909.53: Global MASTER-Net observations report
  7. GRB 260909A: Mondy optical observations and afterglow candidate
  8. The EP-WXT trigger 01709306297 is likely the known LMXB 4U 1745-203
  9. Fermi GRB 260907A: Global MASTER-Net observations report
  10. EP260901a: Global MASTER-Net observations report
  11. IceCube-260827A: No transient candidates from the Zwicky Transient Facility
  12. GRB 260825A: SVOM/GRM observation of a long burst
  13. GRB 260818B: Further EP-FXT observation
  14. The EP-WXT trigger 01709291839 is likely the known LMXB 4U 1745-203
  15. IceCube-260825A: No transient candidates from the Zwicky Transient Facility
  16. IceCube Alert 260825A: Global MASTER-Net observations report
  17. GRB 260822A: SVOM/VT optical detection of COLIBRÍ candidate
  18. EP260806a: SAO RAS multicolor optical observations
  19. GRB 260813A: Fermi GBM Final Real-time Localization
  20. GRB 260808B: SAO RAS optical observations
  21. GRB 260809A: NOT optical observations
  22. GRB 260809A: SVOM/VT optical counterpart
  23. IceCube-260805A: One candidate from the Zwicky Transient Facility
  24. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  25. Fermi GRB 260805A: Global MASTER-Net observations report
  26. Fermi GRB 260802B: Global MASTER-Net observations report
  27. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  28. EP260729a: Einstein Probe detection of an X-ray transient
  29. GRB 260726A: SVOM/VT optical candidate
  30. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  31. GRB 260727A: GOTO early optical upper limit
  32. Fermi GRB 260726A: Global MASTER-Net observations report
  33. EP260723a: further EP-FXT follow-up observation
  34. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
  35. GRB 260718A : GRANDMA and KNC upper limits
  36. IceCube-260712A: No candidates with the Zwicky Transient Facility (ZTF)
  37. GRB 260714B: Fermi GBM Detection
  38. IceCube-260708A: One candidate from the Zwicky Transient Facility
  39. GRB 260704A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  40. IceCube-260704A: No candidates from the Zwicky Transient Facility
  41. IPN triangulation of GRB 260627A
  42. Fermi GRB 260703A: Global MASTER-Net observations report
  43. GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
  44. Fermi trigger No 804552016: Global MASTER-Net observations report
  45. Konus-Wind detection of GRB 260623B / EP260623a
  46. EP260618a: EP-FXT follow-up observation
  47. GRB 260616C: GECAM-B observation of a burst
  48. GRB 260617A: Fermi GBM Detection
  49. GRB260616C: MAXI/GSC detection
  50. GRB 260614B: SVOM detection of a burst
  51. IceCube-260610A: No candidates from the Zwicky Transient Facility
  52. EP260610b: SVOM/VT optical confirmation with blue color
  53. EP260610a: SVOM/VT optical upper limits
  54. GRB 260608C: Fermi GBM Final Real-time Localization
  55. GRB 260607B: Fermi GBM Observation
  56. GRB 260604C: LAST detection of optical counterpart candidate
  57. EP260602a: EP-FXT follow-up observation
  58. EP260601a/GRB 260601B: EP-FXT follow-up observation
  59. Fermi GRB 260602B: Global MASTER-Net observations report
  60. Fermi GRB 260602B: Global MASTER-Net observations report
  61. GRB 260601A: Fermi GBM Observation
  62. Fermi trigger No 801900520: Global MASTER-Net observations report
  63. GRB 260531A: MAXI/GSC detection
  64. EP260527a/GRB 260527A: further FTW optical and NIR observations
  65. GRB 260527A / EP260527a: VLA radio detection
  66. GRB 260523A: Fermi GBM Final Real-time Localization
  67. Fermi GRB 260516C: Global MASTER-Net observations report
  68. GRB 260516B: Fermi GBM Final Real-time Localization
  69. SVOM GRB 260515A: Global MASTER-Net observations report
  70. SVOM GRB 260515A: MASTER OT J151044.43+243321.7 optical counterpart detection
  71. IceCube-260504A: No Candidate Transients from the Zwicky Transient Facility
  72. EP260514a: Global MASTER-Net observations report
  73. GRB 260511B: Mephisto multi-band optical followup
  74. GRB 260511B: LCO optical counterpart detection
  75. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) further optical observations
  76. EP260509a: LCO optical upper limits
  77. GRB 260510C: SVOM/VT optical upper limits
  78. SVOM GRB 260509A: MASTER-OAFA optical observation
  79. GRB 260509A: SVOM/VT optical candidate with VHF data
  80. GRB 260509A: GOTO optical counterpart candidate
  81. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  82. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  83. EP260507a: Kinder optical counterpart candidate
  84. EP260507a: LCO optical counterpart
  85. EP260507a: Einstein Probe detection of an X-ray transient
  86. Fermi GRB 260506A: Global MASTER-Net observations report
  87. GRB 260430B: AstroSat CZTI detection of a long burst
  88. SVOM GRB 260504B: MASTER-OAFA optical observations
  89. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  90. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  91. GRB 260429A: Fermi GBM Detection
  92. Fermi GRB 260429A: Global MASTER-Net observations report
  93. EP260430a: Global MASTER-Net observations report
  94. EP260430a: Einstein Probe detection of an X-ray transient
  95. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  96. IPN triangulation of GRB 260424B (short)
  97. IceCube Alert 260425A: Global MASTER-Net observations report
  98. GRB 260419A: AstroSat CZTI detection
  99. GRB 260310A: Late-time Chandra X-ray Detection
  100. Fermi GRB 260421B: Global MASTER-Net observations report

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