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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"
  1. GRB 260909A: SVOM/VT optical upper limits
  2. GRB 260909A: SVOM/GRM observation
  3. GRB 260909A: Mondy optical observations and afterglow candidate
  4. GRB 260909A: Xinglong 2.16m optical upper limit
  5. GRB 260909A: SVOM/C-GFT optical upper limit
  6. GRB 260909A: SVOM detection of a burst
  7. The EP-WXT trigger 01709306297 is likely the known LMXB 4U 1745-203
  8. Fermi trigger No 810554827: Global MASTER-Net observations report
  9. EP Alert 260908.60: Global MASTER-Net observations report
  10. GRB 260907A: Glowbug gamma-ray detection of a likely short burst
  11. GRB 260903A: Swift ToO observations
  12. Fermi GRB 260907B: Global MASTER-Net observations report
  13. GRB 260903A: SAO RAS optical upper limit
  14. The EP-WXT trigger 01709305715 is likely a flaring star
  15. GRB 260907B: Fermi GBM Final Real-time Localization
  16. Fermi GRB 260907A: Global MASTER-Net observations report
  17. GRB 260907A: Fermi GBM Final Real-time Localization
  18. EP260903a: EP-FXT follow-up observation
  19. EP Alert 260905.11: Global MASTER-Net observations report
  20. The EP-WXT trigger 01709302592 is likely a flaring star
  21. GRB 260903A: J-band upper limit with WINTER
  22. EP Alert 260903.47: Global MASTER-Net observations report
  23. GRB 260903A: SVOM/ECLAIRs refined analysis
  24. GRB260903A: Liverpool Telescope optical observations
  25. GRB 260903A: SAO RAS optical observations
  26. GRB 260830A: GECAM-B detection of a burst
  27. EP260903a: EP-WXT detection of a fast X-ray transient
  28. EP Alert 260903.62: Global MASTER-Net observations report
  29. GRB 260830A: Insight-HXMT/HE detection
  30. GRB 260903A: EP-FXT follow-up observation
  31. GRB 260903A: OHP/T193 optical afterglow detection
  32. GRB 260903A: NOT optical observations and afterglow fading
  33. NuSTAR Transient 260828: SOAR Optical Upper Limits
  34. SVOM GRB260903A: Global MASTER-Net observations report
  35. GRB 260903A: LCO optical observations
  36. GRB 260903A: SVOM/VT optical candidate
  37. GRB 260903A: Retraction of optical counterpart of GCN 45501
  38. GRB 260831A: GECAM-B observation
  39. GRB 260903A: LCO optical counterpart detection
  40. GRB 260827A: Insight-HXMT/HE detection
  41. GRB 260903A: SVOM detection of a soft faint burst
  42. EP260901a: SVOM/VT optical upper limits
  43. EP260901a: EP-FXT follow-up observation
  44. Konus-Wind detection of GRB 260829A
  45. GRB 260829A: SVOM/GRM observation
  46. GRB 260818A: ATCA detection of a candidate radio counterpart
  47. EP260830a: EP-FXT follow-up observation
  48. EP260901a: Global MASTER-Net observations report
  49. IceCube-260827A: No transient candidates from the Zwicky Transient Facility
  50. GRB 260831B / sb26083106: SVOM/GWAC-F60A/B confirmation of optical variation of nova V* GK Per
  51. GRB 260831B / sb26083106: SVOM/VT optical variability of V* GK Per
  52. NuSTAR Transient 260828: LCO Optical Upper Limits
  53. EP260901a: EP-WXT detection of a fast X-ray transient
  54. SVOM trigger sb26083106 is not a GRB
  55. GRB 260829A: AstroSat CZTI detection
  56. GRB 260831B: EP-FXT follow-up observation
  57. GRB 260830A: NuSTAR detection of prompt emission
  58. GRB 260831B: LCO optical upper limits
  59. EP260830a: Global MASTER-Net observations report
  60. EP260830a: EP-WXT detection of a fast X-ray transient
  61. GRB 260827A: SVOM/GRM observation
  62. NuSTAR 260828: a 1100s hard X-ray transient
  63. GRB 260831B: SVOM detection of a possible burst
  64. IPN triangulation of GRB 260829A
  65. GRB 260827A: Glowbug gamma-ray detection
  66. EP260727a: ATCA 10 GHz detection
  67. GRB 260831A: Fermi GBM Final Real-time Localization
  68. Fermi-LAT Gamma-ray Observations of IceCube-260827A
  69. Fermi-LAT Gamma-ray Observations of IceCube-260825A
  70. GRB 260829A: GECAM-B observation of a long burst
  71. GRB 260825A: SVOM/GRM observation of a long burst
  72. GRB 260825A: GECAM-B observation
  73. GRB 260829A: Fermi GBM Detection
  74. GRB 260825A: AstroSat CZTI detection
  75. GRB 260829A: BALROG localization (Fermi Trigger 809676494 / GRB 260829256)
  76. GRB 260829A: Fermi GBM Final Real-time Localization
  77. IceCube-260827A: Upper limits from a search for additional neutrino events in IceCube
  78. IceCube-260825A: Upper limits from a search for additional neutrino events in IceCube
  79. IceCube-260825A: Upper limits from a search for additional neutrino events in IceCube
  80. Fermi GBM trigger 809666623/260829141 is not a GRB
  81. GRB 260818B: Further EP-FXT observation
  82. GRB 260818B: VLT optical and nIR observations
  83. GRB 260818B: TNG NIR observations
  84. MAXI GRB260827.40: Global MASTER-Net observations report
  85. IceCube-260827A - IceCube observation of a high-energy neutrino candidate track-like event
  86. The EP-WXT trigger 01709291839 is likely the known LMXB 4U 1745-203
  87. GRB 260827A: Fermi GBM Final Real-time Localization
  88. GRB 260818B: 6 GHz VLA observations
  89. GRB 260818B: SVOM/VT optical upper limit and continuous observations
  90. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  91. GRB 260808B: SAO RAS observations of the optical rebrightening
  92. EP260822a: Global MASTER-Net observations report
  93. EP Alert 260820.31: Global MASTER-Net observations report
  94. IceCube-260825A: No transient candidates from the Zwicky Transient Facility
  95. GRB 260807A: EP-FXT follow-up observations
  96. GRB 260822A: SVOM/ECLAIRs refined analysis
  97. GRB 260809A: SVOM/ECLAIRs refined analysis
  98. GRB 260822A: SVOM/VT optical upper limits
  99. IceCube Alert 260825A: Global MASTER-Net observations report
  100. IceCube-Cascade 260824A: Upper limits from a search for additional neutrino events in IceCube

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