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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"

12334 results found.

  1. GRB 260909A: Xinglong 2.16m optical upper limit
  2. GRB 260909A: SVOM/C-GFT optical upper limit
  3. Fermi trigger No 810554827: Global MASTER-Net observations report
  4. EP Alert 260908.60: Global MASTER-Net observations report
  5. Fermi GRB 260907B: Global MASTER-Net observations report
  6. GRB 260903A: SAO RAS optical upper limit
  7. Fermi GRB 260907A: Global MASTER-Net observations report
  8. EP Alert 260905.11: Global MASTER-Net observations report
  9. GRB 260903A: J-band upper limit with WINTER
  10. EP Alert 260903.47: Global MASTER-Net observations report
  11. GRB260903A: Liverpool Telescope optical observations
  12. EP Alert 260903.62: Global MASTER-Net observations report
  13. NuSTAR Transient 260828: SOAR Optical Upper Limits
  14. SVOM GRB260903A: Global MASTER-Net observations report
  15. EP260901a: SVOM/VT optical upper limits
  16. EP260901a: EP-FXT follow-up observation
  17. Konus-Wind detection of GRB 260829A
  18. EP260830a: EP-FXT follow-up observation
  19. EP260901a: Global MASTER-Net observations report
  20. GRB 260831B / sb26083106: SVOM/GWAC-F60A/B confirmation of optical variation of nova V* GK Per
  21. GRB 260831B / sb26083106: SVOM/VT optical variability of V* GK Per
  22. NuSTAR Transient 260828: LCO Optical Upper Limits
  23. GRB 260831B: EP-FXT follow-up observation
  24. GRB 260831B: LCO optical upper limits
  25. EP260830a: Global MASTER-Net observations report
  26. Fermi-LAT Gamma-ray Observations of IceCube-260827A
  27. Fermi-LAT Gamma-ray Observations of IceCube-260825A
  28. IceCube-260827A: Upper limits from a search for additional neutrino events in IceCube
  29. IceCube-260825A: Upper limits from a search for additional neutrino events in IceCube
  30. IceCube-260825A: Upper limits from a search for additional neutrino events in IceCube
  31. MAXI GRB260827.40: Global MASTER-Net observations report
  32. GRB 260818B: SVOM/VT optical upper limit and continuous observations
  33. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  34. EP260822a: Global MASTER-Net observations report
  35. EP Alert 260820.31: Global MASTER-Net observations report
  36. GRB 260807A: EP-FXT follow-up observations
  37. GRB 260822A: SVOM/VT optical upper limits
  38. IceCube Alert 260825A: Global MASTER-Net observations report
  39. IceCube-Cascade 260824A: Upper limits from a search for additional neutrino events in IceCube
  40. GRB 260822A: PRIME near-infrared upper limits from multiple epochs
  41. EP260822a: EP-FXT non-detection and upper limit
  42. GRB 260822A: LCO optical upper limits
  43. GRB 260822A: GROWTH-India Telescope Upper Limits
  44. GRB 260822A: GOTO optical upper limit
  45. Fermi-LAT Gamma-ray Observations of IceCube-260821A
  46. Fermi-LAT Gamma-ray Observations of IceCube-260807A
  47. IceCube-260821A: Upper limits from a search for additional neutrino events in IceCube
  48. GRB 260818B: SVOM/C-GFT optical upper limit
  49. IceCube Alert 260821A: Global MASTER-Net observations report
  50. GRB 260818A: J-band observations with WINTER
  51. GRB 260818B: NOT optical upper limits
  52. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  53. GRB 260818B: LCO optical upper limits
  54. GRB 260818A: LCO optical upper limits
  55. EP260812a: AbAO optical upper limit
  56. GRB 260818A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  57. EP260812a: AZT-22 optical upper limit
  58. EP260812b: Optical upper limit with Kinder
  59. EP260812a: NOT and Liverpool Telescope upper limits:
  60. EP260812a: SVOM/C-GFT optical upper limit
  61. IceCube-260807A: Upper limits from a search for additional neutrino events in IceCube
  62. GRB 260809A: J-band upper limit with WINTER
  63. IceCube-260805A: Upper limits from a search for additional neutrino events in IceCube
  64. EP260809a: J-band upper limit with WINTER
  65. GRB 260808B: J-band upper limit with WINTER
  66. Fermi GRB 260808A: Global MASTER-Net observations report
  67. IceCube Alert 260807A: Global MASTER-Net observations report
  68. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  69. Fermi GRB 260805A: Global MASTER-Net observations report
  70. AT 2026wki: EP/FXT follow-up observations
  71. IceCube-Cascade 260801A: Upper limits from a search for additional neutrino events in IceCube
  72. Fermi GRB 260802B: Global MASTER-Net observations report
  73. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  74. GRB 260802A: SVOM/VT optical upper limits from VHF data
  75. GRB 260802A: LCO optical upper limits
  76. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  77. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  78. EP260731a: COLIBRÍ optical upper limit
  79. EP260731a: NOT optical upper limit
  80. EP260728a: COLIBRÍ optical upper limit
  81. GRB 260726A: EP-FXT follow-up observations
  82. Konus-Wind detection of GRB 260727A
  83. GRB 260727A: Liverpool Telescope optical upper limits
  84. EP260727a: Liverpool Telescope confirmation of optical counterpart
  85. EP260727a: NUTTELA-TAO Early Optical Limits
  86. GRB 260726A: J-band upper limit with WINTER
  87. GRB 260727A: J-band upper limit with WINTER
  88. GRB 260726A: SVOM/VT optical candidate
  89. EP260723a: SVOM/ECLAIRs Upper Limit
  90. GRB 260727A: GOTO early optical upper limit
  91. GRB 260727A: Kilonova-Catcher optical upper limit
  92. GRB 260727A: LCO optical upper limits
  93. Fermi GRB 260726A: Global MASTER-Net observations report
  94. EP260723a: Liverpool Telescope likely optical counterpart
  95. IceCube-260722A: Upper limits from a search for additional neutrino events in IceCube
  96. IceCube Alert 260722A: Global MASTER-Net observations report
  97. GRB 260705A: Retraction of optical counterpart
  98. Fermi trigger No 806104130: Global MASTER-Net observations report
  99. Fermi GRB 260718A: Global MASTER-Net observations report
  100. GRB 260718A: LCO optical upper limits

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