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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. EP260327a: Xinglong optical upper limit
  2. GRB 260330B: SVOM/VT optical upper limits
  3. Konus-Wind detection of GRB 260320A
  4. GRB 260321A: SVOM/ECLAIRs refined analysis
  5. EP260329b: J-band upper limits with WINTER
  6. EP260329a: J-band upper limit with WINTER
  7. GRB 260330B: LCO optical upper limits
  8. EP260329a: COLIBRÍ optical upper limit
  9. EP260329a: EP-FXT follow up observation
  10. EP260329b: Global MASTER-Net observations report
  11. Fermi trigger No 796485221: Global MASTER-Net observations report
  12. EP260329b: Optical follow-up with Kinder observations
  13. EP260329a: Optical upper limit with Kinder observations
  14. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  15. EP260327a: SVOM/VT optical upper limits
  16. GRB 260307B: ATCA Radio Upper Limits
  17. EP260327a: WINTER J-band upper limit
  18. EP260327a: COLIBRÍ optical upper limits
  19. EP260327a: Gemini-North optical upper limits
  20. EP260327a: Global MASTER-Net observations report
  21. EP260321a: Upper limits from a neutrino search with IceCube
  22. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  23. Fermi GRB 260323A: Global MASTER-Net observations report
  24. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  25. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  26. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  27. EP260321a: further Kinder optical observations
  28. GRB 260321A: SVOM/VT optical upper limits
  29. EP260321a: Las Cumbres upper limit
  30. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  31. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  32. EP260321a: SVOM/VT optical upper limit
  33. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  34. EP260321a: Global MASTER-Net observations report
  35. Fermi GRB 260318A: Global MASTER-Net observations report
  36. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  37. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  38. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  39. EP260316a: Xinglong optical upper limit
  40. EP260316a: optical upper limit with Kinder observations
  41. EP260314a: Xinglong optical upper limit
  42. EP260314a: optical upper limit with Kinder observations
  43. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  44. EP260314a: COLIBRÍ optical upper limit
  45. EP260314a: BOOTES-6/DPR optical upper limits at early times
  46. EP260314a: Global MASTER-Net observations report
  47. Fermi trigger No 795185313: Global MASTER-Net observations report
  48. IceCube Alert 260315A: Global MASTER-Net observations report
  49. The EP-WXT trigger 01709258851: Las Cumbres upper limit
  50. GRB 260310A/AT2026fgk: radio detection at 15GHz
  51. Fermi GRB 260314A: Global MASTER-Net observations report
  52. Fermi GRB 260313A: Global MASTER-Net observations report
  53. GRB 260310A: NOT optical polarimetry
  54. Fermi GRB 260312B: Global MASTER-Net observations report
  55. Fermi GRB 260311B: Global MASTER-Net observations report
  56. EP260306a: Mondy optical upper limit
  57. Fermi GRB 260310B: Global MASTER-Net observations report
  58. Fermi GRB 260310A: Global MASTER-Net observations report
  59. GRB 260307B: Mephisto optical upper limits
  60. GRB 260307B: SVOM/VT upper limit with X band data analysis
  61. Fermi GRB 260307A: Global MASTER-Net observations report
  62. GRB260307B: GROWTH-India Telescope optical upper limit
  63. GRB 260307B: SVOM/C-GFT upper limit
  64. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  65. EP260302a: Gemini-South redshift z = 1.535
  66. GRB 260303A: 1.3m DFOT optical upper limit (duplicate submission)
  67. GRB 260303A: 1.3m DFOT optical upper limit
  68. EP260214b: ATCA 6 GHz observations
  69. Fermi GRB 260305A: Global MASTER-Net observations report
  70. GRB 260303A: J-band observations with WINTER
  71. EP260302a: Global MASTER-Net observations report
  72. Fermi GRB 260303B: Global MASTER-Net observations report
  73. GRB 260228A: CAHA 2.2m telescope optical upper limit
  74. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  75. GRB 260228A: SVOM/VT optical upper limits
  76. GRB 260226A: Asiago r-band upper limit
  77. GRB 260225A: SVOM/VT optical continued observations and upper limit
  78. EP260227a: Global MASTER-Net observations report
  79. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  80. GRB 260225A: WINTER J-band upper limit
  81. GRB 260226A: COLIBRÍ optical upper limits
  82. GRB 260226A: LCOGT Optical Upper Limit
  83. GRB 260226A : GROWTH-India Telescope optical observations
  84. GRB 260226A: LAST optical upper limit
  85. LAT GRB260226.44: Global MASTER-Net observations report
  86. Fermi GRB 260226A: Global MASTER-Net observations report
  87. EP260224a: LCO optical upper limits
  88. GRB 260225A: SVOM/VT optical upper limits
  89. EP260223a: Liverpool Telescope upper limits
  90. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  91. EP260223a: Xinglong optical upper limit
  92. EP260213a: Mephisto optical upper limits
  93. EP260223a: EP-FXT follow-up observation
  94. sb26021801: SVOM/VT optical upper limits
  95. sb26021801: SVOM/C-GFT upper limit
  96. EP260223a: COLIBRÍ optical upper limits
  97. EP260221a: Optical upper limit with Kinder observations
  98. Fermi GRB 260223A: Global MASTER-Net observations report
  99. EP260221a: Liverpool Telescope detection of COLIBRÍ counterpart candidate
  100. EP260221a: Gemini South z-band upper limit

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