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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"

12318 results found.

  1. EP260707a (by EP-FXT): NOT optical upper limit
  2. EP260707a: LCOGT Optical Upper Limit
  3. EP260707a: TRT optical upper limit
  4. GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
  5. GRB 260706A: LCO optical upper limit
  6. IceCube-260704A: Upper limits from a search for additional neutrino events in IceCube
  7. GRB 260705A: LCO optical upper limits
  8. GRB 260704A: NOT optical upper limits
  9. EP260703a: EP-FXT follow-up observation
  10. Fermi trigger No 804738310: Global MASTER-Net observations report
  11. Fermi GRB 260703A: Global MASTER-Net observations report
  12. GRB 260614B: ATCA Radio Upper Limits
  13. Fermi trigger No 804552016: Global MASTER-Net observations report
  14. Fermi-LAT Gamma-ray Observations of IceCube-260622A
  15. EP260628a: EP-FXT follow-up observation
  16. Fermi GRB 260628A: Global MASTER-Net observations report
  17. EP260626a: further Liverpool Telescope optical upper limits
  18. EP260626a: COLIBRÍ optical upper limit
  19. EP260626a: Liverpool Telescope upper limits
  20. Konus-Wind detection of GRB 260618B
  21. IceCube-260622A: Upper limits from a search for additional neutrino events in IceCube
  22. IceCube-Cascade 260618A: Upper limits from a search for additional neutrino events in IceCube
  23. Fermi-LAT Gamma-ray Observations of IceCube-260610A
  24. GRB 260619A: Kilonova-Catcher optical upper limit
  25. IceCube-260610A: Upper limits from a search for additional neutrino events in IceCube
  26. Konus-Wind detection of GRB 260616B/EP260616a
  27. EP260616a/GRB260616B: COLIBRÍ optical upper limit
  28. EP260605a: COLIBRÍ optical upper limits
  29. EP260610b: Liverpool Telescope optical upper limits
  30. IceCube-260610A: EP-FXT follow-up observation
  31. EP260610b: GTC likely spectroscopic redshift z = 1.10
  32. GRB 260610B / AT2026owq: Early ATLAS observations
  33. EP260610a: SVOM/VT optical upper limits
  34. Konus-Wind detection of GRB 260601A
  35. EP260610a: COLIBRÍ optical upper limits
  36. GRB 260604C: SVOM/C-GFT upper limit
  37. GRB 260604C: 6 GHz VLA observations
  38. EP260603a: COLIBRÍ optical upper limit
  39. GRB 260604C: LCO optical upper limit
  40. EP260602d: EP-FXT follow-up observation
  41. EP260602c: EP-FXT follow-up observation
  42. GRB 260527A/EP260527a: 6 GHz VLA observations
  43. EP260602d: J-band upper limit with WINTER
  44. EP260602b: J-band upper limit with WINTER
  45. Fermi GRB 260604C: Global MASTER-Net observations report
  46. Fermi GRB 260604C: Global MASTER-Net observations report
  47. SVOM GRB260604.85: Global MASTER-Net observations report
  48. GRB 260515A: SVOM/VT optical detection at about 18 days post trigger
  49. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  50. EP260603a: Global MASTER-Net observations report
  51. EP260602d: Optical Upper limits with kinder observations
  52. EP260602b: Liverpool Telescope observations
  53. EP260602a: Liverpool Telescope optical upper limits
  54. GRB 260601B / EP260601a: Mondy optical upper limit
  55. GRB 260603A: Kilonova-Catcher optical upper limit
  56. Fermi trigger No 802141998: Global MASTER-Net observations report
  57. SVOM GRB260603.23: Global MASTER-Net observations report
  58. Fermi GRB 260602B: Global MASTER-Net observations report
  59. Fermi GRB 260602B: Global MASTER-Net observations report
  60. GRB 260601B/EP260601a: J-band upper limit with WINTER
  61. EP260602a: Optical upper limits with Kinder observations
  62. Fermi GRB 260601A: Global MASTER-Net observations report
  63. Fermi trigger No 801900520: Global MASTER-Net observations report
  64. GRB 260531A: MAXI/GSC detection
  65. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  66. Fermi GRB 260529A: Global MASTER-Net observations report
  67. EP260526a: SVOM/VT optical upper limits
  68. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  69. Fermi trigger No 801580882: Global MASTER-Net observations report
  70. EP260526a: LCO optical upper limits
  71. EP260526.405: COLIBRÍ optical upper limits
  72. Fermi GRB 260526A: Global MASTER-Net observations report
  73. EP01709266106 (EP260526a?): Liverpool Telescope upper limits
  74. EP-WXT 01709266106: NOT optical upper limits
  75. Fermi GRB 260525A: Global MASTER-Net observations report
  76. Fermi GRB 260523A: Global MASTER-Net observations report
  77. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  78. GRB 260522A: GOTO optical upper limit
  79. Fermi trigger No 801135305: Global MASTER-Net observations report
  80. Fermi GRB 260522A: Global MASTER-Net observations report
  81. GRB 260511A: iTelescope T-75 optical detection
  82. Konus-Wind detection of GRB 260519C
  83. Konus-Wind detection of GRB 260518A
  84. GRB 260509A: CrAO ZTSh optical upper limit (Duplicate Submission)
  85. GRB 260509A: CrAO ZTSh optical upper limit
  86. GRB 260516D: GROWTH-India Telescope optical detection
  87. Fermi GRB 260516C: Global MASTER-Net observations report
  88. SVOM GRB260516D: Global MASTER-Net observations report
  89. Fermi GRB 260516B: Global MASTER-Net observations report
  90. EP260514a: COLIBRÍ optical upper limits
  91. SVOM GRB 260515A: Global MASTER-Net observations report
  92. SVOM GRB 260515A: MASTER OT J151044.43+243321.7 optical counterpart detection
  93. EP260514a: GROWTH-India Telescope optical upper limit
  94. GRB 260511B: GMG Optical Upper Limit
  95. EP260514a: Global MASTER-Net observations report
  96. EP260512a: LCO optical upper limits
  97. Fermi GRB 260514A: Global MASTER-Net observations report
  98. EP260512a: EP-FXT follow-up observation
  99. EP260512a: Global MASTER-Net observations report
  100. Fermi GRB 260513A: Global MASTER-Net observations report

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