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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"

32493 results found.

  1. GRB 260808A: GECAM-B observation
  2. GRB 260807A: SVOM/ECLAIRs refined analysis
  3. EP260806a: MAO/AZT-22 optical observations
  4. IceCube-260807A: Upper limits from a search for additional neutrino events in IceCube
  5. GRB260808B: MAO/AZT-22 optical observations
  6. GRB 250607A: SVOM/ECLAIRs detection through offline targeted search
  7. GRB 260809A: J-band upper limit with WINTER
  8. EP260809a: VLT/X-shooter spectroscopic redshift z = 3.07
  9. GRB 260808A: CALET Gamma-Ray Burst Monitor detection
  10. GRB 260805C: CALET Gamma-Ray Burst Monitor detection
  11. GRB 260804A: CALET Gamma-Ray Burst Monitor detection
  12. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  13. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  14. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  15. GRB 260809A: NOT optical observations
  16. GRB260809A: MAO/AZT-22 optical observations
  17. GRB260809A: OHP/T193 optical observations
  18. IceCube-260805A: Upper limits from a search for additional neutrino events in IceCube
  19. GRB 260809A: SVOM/VT optical counterpart
  20. EP260809a: J-band upper limit with WINTER
  21. GRB 260808B: J-band upper limit with WINTER
  22. GRB 260808B: SVOM/ECLAIRs refined analysis
  23. EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation
  24. GRB 260808B: Liverpool Telescope optical observations
  25. GRB 260808B: NOT optical observations
  26. GRB 260808B: LCO optical observations
  27. GRB 260808A: NuSTAR detection of prompt emission
  28. EP260809a: COLIBRÍ optical observations
  29. EP260809a: LCO optical observation
  30. GRB260808B: OHP/T193 optical observations
  31. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  32. GRB 260808B: SVOM/VT optical afterglow confirmation
  33. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  34. GRB 260808B: SVOM/VT optical candidate from VHF data
  35. Fermi GRB 260808A: Global MASTER-Net observations report
  36. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  37. IceCube-260805A: One candidate from the Zwicky Transient Facility
  38. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  39. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  40. EP260806a: COLIBRÍ optical observations
  41. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  42. EP260806a: SVOM/VT optical observation
  43. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  44. EP260806a: OSIRIS+/GTC redshift z=0.089
  45. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  46. EP260806a: LCO likely optical counterpart
  47. GRB 260715A: cubesat Avion detection
  48. GRB 260709A: cubesat Avion detection
  49. GRB 260708A: cubesat Avion detection
  50. SN 2026stf / GRB 260708A: ATLAS forced photometry
  51. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
  52. GRB 260730B: Glowbug gamma-ray detection
  53. GRB 260805B: Glowbug gamma-ray detection
  54. Fermi GRB 260805A: Global MASTER-Net observations report
  55. GRB 260804A: Glowbug gamma-ray detection
  56. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  57. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  58. GRB 260708A: LCO further optical observations show supernova features
  59. Fermi GRB 260802B: Global MASTER-Net observations report
  60. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  61. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  62. GRB 260802A: SVOM/VT optical upper limits from VHF data
  63. GRB 260802A: LCO optical upper limits
  64. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  65. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  66. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  67. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  68. GRB 260730B: AstroSat CZTI detection
  69. EP260731a: COLIBRÍ optical upper limit
  70. EP260731a: NOT optical upper limit
  71. GRB 260730B: NuSTAR detection of prompt emission
  72. GRB 260727A: SVOM/ECLAIRs refined analysis
  73. GRB 260726A: SVOM/ECLAIRs refined analysis
  74. EP260728a: COLIBRÍ optical upper limit
  75. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  76. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  77. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  78. EP260727a: SAO RAS optical observations
  79. GRB 260727A: AbAO and SAO RAS optical observations
  80. EP260728a: EP-FXT follow-up observation
  81. GRB 260726A: EP-FXT follow-up observations
  82. GRB 260727A: SVOM/GRM observation
  83. GRB 260726A: Fermi GBM Observation
  84. EP260727a: 1.5m OSN optical counterpart detection
  85. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  86. EP260727a: OHP/T193 optical observations
  87. Konus-Wind detection of GRB 260727A
  88. GRB 260726A: Liverpool Telescope optical observations
  89. GRB 260727A: Liverpool Telescope optical upper limits
  90. EP260727a: Liverpool Telescope confirmation of optical counterpart
  91. EP260727a: NUTTELA-TAO Early Optical Limits
  92. GRB 260727A: EP/FXT follow-up observations
  93. EP260727a: Einstein Probe detection of an X-ray transient
  94. GRB 260727A: Glowbug gamma-ray detection
  95. GRB 260726A: J-band upper limit with WINTER
  96. GRB 260727A: J-band upper limit with WINTER
  97. GRB 260726A: SVOM/VT optical candidate
  98. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  99. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  100. EP260723a: SVOM/ECLAIRs Upper Limit

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