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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"

12316 results found.

  1. EP260901a: Global MASTER-Net observations report
  2. GRB 260831B / sb26083106: SVOM/GWAC-F60A/B confirmation of optical variation of nova V* GK Per
  3. GRB 260831B / sb26083106: SVOM/VT optical variability of V* GK Per
  4. NuSTAR Transient 260828: LCO Optical Upper Limits
  5. GRB 260831B: EP-FXT follow-up observation
  6. GRB 260831B: LCO optical upper limits
  7. EP260830a: Global MASTER-Net observations report
  8. Fermi-LAT Gamma-ray Observations of IceCube-260827A
  9. Fermi-LAT Gamma-ray Observations of IceCube-260825A
  10. IceCube-260827A: Upper limits from a search for additional neutrino events in IceCube
  11. IceCube-260825A: Upper limits from a search for additional neutrino events in IceCube
  12. IceCube-260825A: Upper limits from a search for additional neutrino events in IceCube
  13. MAXI GRB260827.40: Global MASTER-Net observations report
  14. GRB 260818B: SVOM/VT optical upper limit and continuous observations
  15. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  16. EP260822a: Global MASTER-Net observations report
  17. EP Alert 260820.31: Global MASTER-Net observations report
  18. GRB 260807A: EP-FXT follow-up observations
  19. GRB 260822A: SVOM/VT optical upper limits
  20. IceCube Alert 260825A: Global MASTER-Net observations report
  21. IceCube-Cascade 260824A: Upper limits from a search for additional neutrino events in IceCube
  22. GRB 260822A: PRIME near-infrared upper limits from multiple epochs
  23. EP260822a: EP-FXT non-detection and upper limit
  24. GRB 260822A: LCO optical upper limits
  25. GRB 260822A: GROWTH-India Telescope Upper Limits
  26. GRB 260822A: GOTO optical upper limit
  27. Fermi-LAT Gamma-ray Observations of IceCube-260821A
  28. Fermi-LAT Gamma-ray Observations of IceCube-260807A
  29. IceCube-260821A: Upper limits from a search for additional neutrino events in IceCube
  30. GRB 260818B: SVOM/C-GFT optical upper limit
  31. IceCube Alert 260821A: Global MASTER-Net observations report
  32. GRB 260818A: J-band observations with WINTER
  33. GRB 260818B: NOT optical upper limits
  34. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  35. GRB 260818B: LCO optical upper limits
  36. GRB 260818A: LCO optical upper limits
  37. EP260812a: AbAO optical upper limit
  38. GRB 260818A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  39. EP260812a: AZT-22 optical upper limit
  40. EP260812b: Optical upper limit with Kinder
  41. EP260812a: NOT and Liverpool Telescope upper limits:
  42. EP260812a: SVOM/C-GFT optical upper limit
  43. IceCube-260807A: Upper limits from a search for additional neutrino events in IceCube
  44. GRB 260809A: J-band upper limit with WINTER
  45. IceCube-260805A: Upper limits from a search for additional neutrino events in IceCube
  46. EP260809a: J-band upper limit with WINTER
  47. GRB 260808B: J-band upper limit with WINTER
  48. Fermi GRB 260808A: Global MASTER-Net observations report
  49. IceCube Alert 260807A: Global MASTER-Net observations report
  50. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  51. Fermi GRB 260805A: Global MASTER-Net observations report
  52. AT 2026wki: EP/FXT follow-up observations
  53. IceCube-Cascade 260801A: Upper limits from a search for additional neutrino events in IceCube
  54. Fermi GRB 260802B: Global MASTER-Net observations report
  55. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  56. GRB 260802A: SVOM/VT optical upper limits from VHF data
  57. GRB 260802A: LCO optical upper limits
  58. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  59. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  60. EP260731a: COLIBRÍ optical upper limit
  61. EP260731a: NOT optical upper limit
  62. EP260728a: COLIBRÍ optical upper limit
  63. GRB 260726A: EP-FXT follow-up observations
  64. Konus-Wind detection of GRB 260727A
  65. GRB 260727A: Liverpool Telescope optical upper limits
  66. EP260727a: Liverpool Telescope confirmation of optical counterpart
  67. EP260727a: NUTTELA-TAO Early Optical Limits
  68. GRB 260726A: J-band upper limit with WINTER
  69. GRB 260727A: J-band upper limit with WINTER
  70. GRB 260726A: SVOM/VT optical candidate
  71. EP260723a: SVOM/ECLAIRs Upper Limit
  72. GRB 260727A: GOTO early optical upper limit
  73. GRB 260727A: Kilonova-Catcher optical upper limit
  74. GRB 260727A: LCO optical upper limits
  75. Fermi GRB 260726A: Global MASTER-Net observations report
  76. EP260723a: Liverpool Telescope likely optical counterpart
  77. IceCube-260722A: Upper limits from a search for additional neutrino events in IceCube
  78. IceCube Alert 260722A: Global MASTER-Net observations report
  79. GRB 260705A: Retraction of optical counterpart
  80. Fermi trigger No 806104130: Global MASTER-Net observations report
  81. Fermi GRB 260718A: Global MASTER-Net observations report
  82. GRB 260718A: LCO optical upper limits
  83. GRB 260718A : GRANDMA and KNC upper limits
  84. GRB 260718A: SVOM/VT optical upper limits
  85. GRB 260718A: SVOM/VT optical upper limits from VHF data
  86. GRB 260618B: EP-FXT follow-up observation upper limit
  87. SVOM sb26071506: Global MASTER-Net observations report
  88. EP260703a: SVOM/ECLAIRs Upper Limit
  89. IceCube-260712A: Upper limits from a search for additional neutrino events in IceCube
  90. Fermi-LAT Gamma-ray Observations of IceCube-260712A
  91. Fermi-LAT Gamma-ray Observations of IceCube-260708A
  92. Fermi-LAT Gamma-ray Observations of IceCube-260704A
  93. IceCube-260708A: Upper limits from a search for additional neutrino events in IceCube
  94. GRB 260706A : GRANDMA Upper limits
  95. IceCube Alert 260709A: Global MASTER-Net observations report
  96. LAT GRB260708.42: Global MASTER-Net observations report
  97. GRB260708B: MAXI/GSC detection
  98. GRB 260706A: SVOM/VT optical upper limits
  99. EP260707a (by EP-FXT): NOT optical upper limit
  100. EP260707a: LCOGT Optical Upper Limit

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