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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"

32479 results found.

  1. GRB 260809A: NOT optical observations
  2. GRB260809A: MAO/AZT-22 optical observations
  3. GRB260809A: OHP/T193 optical observations
  4. IceCube-260805A: Upper limits from a search for additional neutrino events in IceCube
  5. GRB 260809A: SVOM/VT optical counterpart
  6. EP260809a: J-band upper limit with WINTER
  7. GRB 260808B: J-band upper limit with WINTER
  8. GRB 260808B: SVOM/ECLAIRs refined analysis
  9. EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation
  10. GRB 260808B: Liverpool Telescope optical observations
  11. GRB 260808B: NOT optical observations
  12. GRB 260808B: LCO optical observations
  13. GRB 260808A: NuSTAR detection of prompt emission
  14. EP260809a: COLIBRÍ optical observations
  15. EP260809a: LCO optical observation
  16. GRB260808B: OHP/T193 optical observations
  17. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  18. GRB 260808B: SVOM/VT optical afterglow confirmation
  19. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  20. GRB 260808B: SVOM/VT optical candidate from VHF data
  21. Fermi GRB 260808A: Global MASTER-Net observations report
  22. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  23. IceCube-260805A: One candidate from the Zwicky Transient Facility
  24. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  25. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  26. EP260806a: COLIBRÍ optical observations
  27. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  28. EP260806a: SVOM/VT optical observation
  29. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  30. EP260806a: OSIRIS+/GTC redshift z=0.089
  31. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  32. EP260806a: LCO likely optical counterpart
  33. GRB 260715A: cubesat Avion detection
  34. GRB 260709A: cubesat Avion detection
  35. GRB 260708A: cubesat Avion detection
  36. SN 2026stf / GRB 260708A: ATLAS forced photometry
  37. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
  38. GRB 260730B: Glowbug gamma-ray detection
  39. GRB 260805B: Glowbug gamma-ray detection
  40. Fermi GRB 260805A: Global MASTER-Net observations report
  41. GRB 260804A: Glowbug gamma-ray detection
  42. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  43. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  44. GRB 260708A: LCO further optical observations show supernova features
  45. Fermi GRB 260802B: Global MASTER-Net observations report
  46. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  47. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  48. GRB 260802A: SVOM/VT optical upper limits from VHF data
  49. GRB 260802A: LCO optical upper limits
  50. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  51. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  52. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  53. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  54. GRB 260730B: AstroSat CZTI detection
  55. EP260731a: COLIBRÍ optical upper limit
  56. EP260731a: NOT optical upper limit
  57. GRB 260730B: NuSTAR detection of prompt emission
  58. GRB 260727A: SVOM/ECLAIRs refined analysis
  59. GRB 260726A: SVOM/ECLAIRs refined analysis
  60. EP260728a: COLIBRÍ optical upper limit
  61. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  62. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  63. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  64. EP260727a: SAO RAS optical observations
  65. GRB 260727A: AbAO and SAO RAS optical observations
  66. EP260728a: EP-FXT follow-up observation
  67. GRB 260726A: EP-FXT follow-up observations
  68. GRB 260727A: SVOM/GRM observation
  69. GRB 260726A: Fermi GBM Observation
  70. EP260727a: 1.5m OSN optical counterpart detection
  71. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  72. EP260727a: OHP/T193 optical observations
  73. Konus-Wind detection of GRB 260727A
  74. GRB 260726A: Liverpool Telescope optical observations
  75. GRB 260727A: Liverpool Telescope optical upper limits
  76. EP260727a: Liverpool Telescope confirmation of optical counterpart
  77. EP260727a: NUTTELA-TAO Early Optical Limits
  78. GRB 260727A: EP/FXT follow-up observations
  79. EP260727a: Einstein Probe detection of an X-ray transient
  80. GRB 260727A: Glowbug gamma-ray detection
  81. GRB 260726A: J-band upper limit with WINTER
  82. GRB 260727A: J-band upper limit with WINTER
  83. GRB 260726A: SVOM/VT optical candidate
  84. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  85. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  86. EP260723a: SVOM/ECLAIRs Upper Limit
  87. GRB 260727A: GOTO early optical upper limit
  88. GRB 260727A: AstroSat CZTI detection
  89. GRB 260727A: Kilonova-Catcher optical upper limit
  90. GRB 260727A: LCO optical upper limits
  91. Fermi GRB 260726A: Global MASTER-Net observations report
  92. GRB 260726A: SVOM detection of a burst
  93. IceCube-260722A: Classification of ZTF26abjbxfs/SN 2026vts as a Type Ia Supernova
  94. EP260723a: further EP-FXT follow-up observation
  95. EP260725a: EP-FXT follow-up observation and association with a bright flaring star
  96. GRB 260616A: cubesat Avion detection
  97. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  98. GRB 260602B: cubesat Avion detection
  99. GRB 260601A: cubesat Avion detection
  100. EP260723a: EP-FXT follow-up observation

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