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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"

32497 results found.

  1. GRB 260809A: SAO RAS optical observations
  2. GRB 260808B: SAO RAS optical observations
  3. GRB 260808B: SVOM/VT optical re-brightening at day 3
  4. GRB 260317A: SVOM/ECLAIRs detection through offline targeted search and its possible association to magnetar 1E 1841-04.5
  5. GRB 260806A: CALET Gamma-Ray Burst Monitor detection
  6. GRB 260808A: GECAM-B observation
  7. GRB 260807A: SVOM/ECLAIRs refined analysis
  8. EP260806a: MAO/AZT-22 optical observations
  9. IceCube-260807A: Upper limits from a search for additional neutrino events in IceCube
  10. GRB260808B: MAO/AZT-22 optical observations
  11. GRB 250607A: SVOM/ECLAIRs detection through offline targeted search
  12. GRB 260809A: J-band upper limit with WINTER
  13. EP260809a: VLT/X-shooter spectroscopic redshift z = 3.07
  14. GRB 260808A: CALET Gamma-Ray Burst Monitor detection
  15. GRB 260805C: CALET Gamma-Ray Burst Monitor detection
  16. GRB 260804A: CALET Gamma-Ray Burst Monitor detection
  17. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  18. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  19. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  20. GRB 260809A: NOT optical observations
  21. GRB260809A: MAO/AZT-22 optical observations
  22. GRB260809A: OHP/T193 optical observations
  23. IceCube-260805A: Upper limits from a search for additional neutrino events in IceCube
  24. GRB 260809A: SVOM/VT optical counterpart
  25. EP260809a: J-band upper limit with WINTER
  26. GRB 260808B: J-band upper limit with WINTER
  27. GRB 260808B: SVOM/ECLAIRs refined analysis
  28. EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation
  29. GRB 260808B: Liverpool Telescope optical observations
  30. GRB 260808B: NOT optical observations
  31. GRB 260808B: LCO optical observations
  32. GRB 260808A: NuSTAR detection of prompt emission
  33. EP260809a: COLIBRÍ optical observations
  34. EP260809a: LCO optical observation
  35. GRB260808B: OHP/T193 optical observations
  36. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  37. GRB 260808B: SVOM/VT optical afterglow confirmation
  38. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  39. GRB 260808B: SVOM/VT optical candidate from VHF data
  40. Fermi GRB 260808A: Global MASTER-Net observations report
  41. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  42. IceCube-260805A: One candidate from the Zwicky Transient Facility
  43. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  44. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  45. EP260806a: COLIBRÍ optical observations
  46. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  47. EP260806a: SVOM/VT optical observation
  48. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  49. EP260806a: OSIRIS+/GTC redshift z=0.089
  50. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  51. EP260806a: LCO likely optical counterpart
  52. GRB 260715A: cubesat Avion detection
  53. GRB 260709A: cubesat Avion detection
  54. GRB 260708A: cubesat Avion detection
  55. SN 2026stf / GRB 260708A: ATLAS forced photometry
  56. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
  57. GRB 260730B: Glowbug gamma-ray detection
  58. GRB 260805B: Glowbug gamma-ray detection
  59. Fermi GRB 260805A: Global MASTER-Net observations report
  60. GRB 260804A: Glowbug gamma-ray detection
  61. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  62. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  63. GRB 260708A: LCO further optical observations show supernova features
  64. Fermi GRB 260802B: Global MASTER-Net observations report
  65. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  66. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  67. GRB 260802A: SVOM/VT optical upper limits from VHF data
  68. GRB 260802A: LCO optical upper limits
  69. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  70. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  71. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  72. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  73. GRB 260730B: AstroSat CZTI detection
  74. EP260731a: COLIBRÍ optical upper limit
  75. EP260731a: NOT optical upper limit
  76. GRB 260730B: NuSTAR detection of prompt emission
  77. GRB 260727A: SVOM/ECLAIRs refined analysis
  78. GRB 260726A: SVOM/ECLAIRs refined analysis
  79. EP260728a: COLIBRÍ optical upper limit
  80. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  81. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  82. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  83. EP260727a: SAO RAS optical observations
  84. GRB 260727A: AbAO and SAO RAS optical observations
  85. EP260728a: EP-FXT follow-up observation
  86. GRB 260726A: EP-FXT follow-up observations
  87. GRB 260727A: SVOM/GRM observation
  88. GRB 260726A: Fermi GBM Observation
  89. EP260727a: 1.5m OSN optical counterpart detection
  90. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  91. EP260727a: OHP/T193 optical observations
  92. Konus-Wind detection of GRB 260727A
  93. GRB 260726A: Liverpool Telescope optical observations
  94. GRB 260727A: Liverpool Telescope optical upper limits
  95. EP260727a: Liverpool Telescope confirmation of optical counterpart
  96. EP260727a: NUTTELA-TAO Early Optical Limits
  97. GRB 260727A: EP/FXT follow-up observations
  98. EP260727a: Einstein Probe detection of an X-ray transient
  99. GRB 260727A: Glowbug gamma-ray detection
  100. GRB 260726A: J-band upper limit with WINTER

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