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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"

5458 results found.

  1. EP260731a: COLIBRÍ optical upper limit
  2. EP260731a: NOT optical upper limit
  3. EP260727a: SAO RAS optical observations
  4. EP260727a: OHP/T193 optical observations
  5. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  6. GRB 260727B: Fermi GBM Final Real-time Localization
  7. GRB 260726A: SVOM detection of a burst
  8. GRB 260616A: cubesat Avion detection
  9. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  10. Fermi GBM trigger 806384210/260722151 is not a GRB
  11. GRB 260714B: COLIBRÍ optical counterpart candidate
  12. IceCube Alert 260709A: Global MASTER-Net observations report
  13. GRB260708B: MAXI/GSC detection
  14. Fermi GBM trigger 805087514/260707142 (GRB 260707A) is not a GRB
  15. GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
  16. GRB 260707A: Fermi GBM Final Real-time Localization
  17. IceCube-260704A: Upper limits from a search for additional neutrino events in IceCube
  18. GRB 260705A: LCO optical upper limits
  19. GRB 260703B: Fermi GBM Final Localization
  20. Fermi trigger No 804738310: Global MASTER-Net observations report
  21. Fermi GRB 260703A: Global MASTER-Net observations report
  22. GRB 260703A: Fermi GBM Final Localization
  23. GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
  24. Fermi trigger No 804552016: Global MASTER-Net observations report
  25. Fermi GRB 260628A: Global MASTER-Net observations report
  26. EP260623a: REM optical/NIR afterglow detection
  27. GRB 260616A: AstroSat CZTI detection
  28. GRB 260616A: SVOM/GRM observation
  29. EP260618a: COLIBRÍ optical counterpart candidate
  30. GRB 260616A: Fermi GBM Observation
  31. Konus-Wind detection of GRB 260616A
  32. GRB 260616A: Fermi-LAT detection
  33. The EP-WXT trigger 01709270148 is likely a flaring star
  34. GRB 260616A: BALROG localization (Fermi Trigger 803272919 / GRB 260616140)
  35. GRB 260616A: Fermi GBM Final Real-time Localization
  36. GRB 260603C: AstroSat CZTI detection
  37. GRB 260610B / AT2026owq: further SAO RAS optical observations
  38. GRB 260610B: IAC-80 Optical observations
  39. GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong
  40. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  41. Fermi GRB 260604C: Global MASTER-Net observations report
  42. Fermi GRB 260604C: Global MASTER-Net observations report
  43. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  44. GRB 260603B: Fermi GBM Final Localization
  45. EP260601a/GRB 260601B: EP-FXT follow-up observation
  46. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  47. Fermi trigger No 802141998: Global MASTER-Net observations report
  48. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  49. EP260602a: COLIBRÍ optical observations
  50. GRB260601B/EP260601a: NOT near-infrared observations
  51. SVOM GRB260603.23: Global MASTER-Net observations report
  52. Fermi GRB 260602B: Global MASTER-Net observations report
  53. Fermi GRB 260602B: Global MASTER-Net observations report
  54. EP260602a: SVOM/VT optical candidate
  55. Fermi trigger No 801900520: Global MASTER-Net observations report
  56. GRB 260531A: MAXI/GSC detection
  57. IPN triangulation of GRB 260527A / EP260527a
  58. GRB 260529A: GOTO tentative optical afterglow candidate
  59. Fermi GRB 260529A: Global MASTER-Net observations report
  60. Fermi trigger No 801580882: Global MASTER-Net observations report
  61. Fermi GRB 260526A: Global MASTER-Net observations report
  62. GRB 260522A: GOTO optical upper limit
  63. GRB 260307A: TERI Gamma-ray detection
  64. GRB 260519B: Fermi GBM Final Localization
  65. GRB 260516D: GOTO optical counterpart detection
  66. GRB 260516D: GTC/OSIRIS+ spectroscopic redshift z = 1.801
  67. Fermi GRB 260516C: Global MASTER-Net observations report
  68. EP260514a: SVOM/VT optical candidate
  69. Fermi GRB 260516B: Global MASTER-Net observations report
  70. EP260514a: COLIBRÍ optical upper limits
  71. SVOM GRB 260515A: Global MASTER-Net observations report
  72. SVOM GRB 260515A: MASTER OT J151044.43+243321.7 optical counterpart detection
  73. Fermi GRB 260512A: Global MASTER-Net observations report
  74. GRB 260511B: further SAO RAS optical observations
  75. GRB 260511B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  76. GRB 260511B: LCO optical counterpart detection
  77. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) further optical observations
  78. GRB 260511B: SVOM/COLIBRÍ (FM-GFT) optical observations
  79. GRB 260511B: SVOM detection of a burst
  80. GRB 260510C: EP-FXT follow-up observation
  81. Fermi GRB 260511A: Global MASTER-Net observations report
  82. GRB 260510C: MAXI/GSC detection
  83. SVOM GRB 260509A: MASTER-OAFA optical observation
  84. Fermi GRB 260510A: Global MASTER-Net observations report
  85. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  86. GRB 260509A: SVOM detection of a burst
  87. IceCube-260504A: Upper limits from a search for additional neutrino events in IceCube
  88. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  89. IPN triangulation of GRB 260428A
  90. SVOM GRB 260504B: MASTER-OAFA optical observations
  91. Fermi GRB 260504A: Global MASTER-Net observations report
  92. EP260430a: LCO optical upper limits
  93. EP260430a: Global MASTER-Net observations report
  94. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  95. Fermi trigger No 798737427: Global MASTER-Net observations report
  96. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  97. Fermi GRB 260421C: Global MASTER-Net observations report
  98. Fermi GRB 260421B: Global MASTER-Net observations report
  99. Fermi GRB 260421A: Global MASTER-Net observations report
  100. EP260416a: VLT/FORS2 spectroscopic redshift confirmation

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