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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. EP260221a: Global MASTER-Net observations report
  2. EP260221a: EP-FXT follow-up observation
  3. Fermi GRB 260221B: Global MASTER-Net observations report
  4. EP-WXT01709258519: Xinglong optical upper limit
  5. EP260221a: Xinglong optical upper limit
  6. Fermi GRB 260221A: Global MASTER-Net observations report
  7. EP260221a: GOTO optical upper limit
  8. EP260221a: COLIBRÍ optical upper limit
  9. SVOM alert sb26021801: LCO optical upper limit
  10. IceCube-260217A: Upper limits from a search for additional neutrino events in IceCube
  11. Fermi GRB 260219A: Global MASTER-Net observations report
  12. SVOM alert sb26021801: LAST optical upper limit
  13. sb26021801: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  14. IceCube Alert 260217A: Global MASTER-Net observations report
  15. Fermi-LAT Gamma-ray Observations of IceCube-260217A
  16. EP-WXT 01709258455: NOT optical upper limits
  17. EP260214b: 1.3m DFOT optical upper limit
  18. EP260210a: Mondy optical upper limits
  19. Konus-Wind detection of GRB 260212A
  20. GRB 260208A: AbAO and Terskol optical upper limits
  21. EP260214b: Optical upper limit with Kinder observations
  22. EP260214a: Optical upper limits with Kinder observations
  23. EP260214b: GROWTH-India Telescope optical upper limit
  24. EP260214a: NOT optical upper limits
  25. EP260214a: COLIBRÍ optical upper limits
  26. EP260214a: SVOM/VT optical upper limits
  27. EP260214a: Global MASTER-Net observations report
  28. EP260213a: Liverpool Telescope optical upper limits
  29. EP260213a: Global MASTER-Net observations report
  30. EP260213a: COLIBRÍ optical upper limits
  31. EP260213a: Optical upper limits with Kinder observations
  32. EP260213a: SVOM/VT optical upper limit
  33. EP260213a: Mondy R-band optical upper limit
  34. EP260213a: NUTTelA-TAO Early Optical Limits
  35. EP260213a: SVOM/C-GFT upper limit
  36. EP/WXT 01709258378: NOT optical upper limits
  37. GRB 260211A: GOTO optical upper limit
  38. Fermi GRB 260212A: Global MASTER-Net observations report
  39. GRB 260211A: LAST optical upper limit
  40. Konus-Wind detection of GRB 260207B
  41. GRB 260211A: LCO optical upper limits
  42. GRB 260211A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  43. Fermi trigger No 792537871: Global MASTER-Net observations report
  44. Konus-Wind detection of GRB 260209B
  45. GRB 260208A: Swift UVOT detection
  46. EP260209a: COLIBRÍ optical upper limit
  47. Fermi GRB 260210C: Global MASTER-Net observations report
  48. EP260209a: LCO optical upper limits
  49. EP260210a: Global MASTER-Net observations report
  50. EP260209a: Global MASTER-Net observations report
  51. EP260210a: Optical upper limits with Kinder observations
  52. EP260210a: SVOM/VT optical upper limit
  53. EP260210a: COLIBRÍ optical upper limit
  54. EP260210a: SVOM/C-GFT upper limit
  55. GRB 260204A: Swift-XRT afterglow detection
  56. Fermi GRB 260209A: Global MASTER-Net observations report
  57. GRB 260208B: Swift-XRT observations
  58. GRB 260204A: Swift/UVOT Upper Limits
  59. Fermi GRB 260208C: Global MASTER-Net observations report
  60. Fermi GRB 260208D: Global MASTER-Net observations report
  61. GRB 260208A: Swift-XRT observations
  62. LAT GRB 260208B: Global MASTER-Net observations report
  63. Fermi GRB 260208A: Global MASTER-Net observations report
  64. Fermi GRB 260207B: Global MASTER-Net observations report
  65. GRB 260206A: Swift-XRT observations
  66. Fermi trigger No 792135758: Global MASTER-Net observations report
  67. GRB 260206A (or XRB from 4U 0513-40): MAXI/GSC detection
  68. GRB 260204A: Swift-XRT observations
  69. GRB 260204A: LCO optical afterglow detection
  70. GRB 260204A : MASTER Global robotic net optical observations
  71. GRB 260204A: GOTO optical upper limit
  72. GRB 260204A: LCO optical upper limits
  73. EP260110a: Late GTC/EMIR near-infrared observations
  74. GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
  75. GRB 260131A/B: EP/FXT X-ray afterglow detection
  76. GRB 260131A: NOT spectroscopic redshift z = 1.434
  77. EP260131a: Liverpool Telescope optical upper limits
  78. EP260131a: Xinglong optical upper limit
  79. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  80. GRB 260131B: MAXI/GSC detection
  81. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  82. Fermi GRB 260130A: Global MASTER-Net observations report
  83. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
  84. Fermi GRB 260129A: Global MASTER-Net observations report
  85. GRB 260128B: LCO optical upper limits
  86. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  87. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  88. GRB 260127B: Swift-XRT observations
  89. EP260128a: Liverpool Telescope optical observations and possible counterpart
  90. EP260128a: LCO optical upper limits
  91. EP260128a: Global MASTER-Net observations report
  92. Fermi GRB 260127A: Global MASTER-Net observations report
  93. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  94. GRB 260127A: COLIBRÍ optical observations
  95. EP260126a: Seimei/TriCCS optical upper limit
  96. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  97. GRB 260127A: SVOM/C-GFT optical observations
  98. Fermi GRB 260127B: Global MASTER-Net observations report
  99. Swift GRB 260127A: Global MASTER-Net observations report
  100. GRB 260125A: Swift-XRT observations

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