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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"

26301 results found.

  1. GRB 260808B: SVOM/VT optical re-brightening at day 3
  2. GRB 260317A: SVOM/ECLAIRs detection through offline targeted search and its possible association to magnetar 1E 1841-04.5
  3. GRB 260806A: CALET Gamma-Ray Burst Monitor detection
  4. GRB 260808A: GECAM-B observation
  5. GRB 260807A: SVOM/ECLAIRs refined analysis
  6. EP260806a: MAO/AZT-22 optical observations
  7. GRB260808B: MAO/AZT-22 optical observations
  8. GRB 250607A: SVOM/ECLAIRs detection through offline targeted search
  9. GRB 260809A: J-band upper limit with WINTER
  10. GRB 260806A: Glowbug gamma-ray detection
  11. GRB 260808A: CALET Gamma-Ray Burst Monitor detection
  12. GRB 260805C: CALET Gamma-Ray Burst Monitor detection
  13. GRB 260804A: CALET Gamma-Ray Burst Monitor detection
  14. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  15. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  16. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  17. GRB 260809A: NOT optical observations
  18. GRB260809A: MAO/AZT-22 optical observations
  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 260809A: SVOM detection of a faint burst
  25. GRB 260808B: Liverpool Telescope optical observations
  26. GRB 260808B: NOT optical observations
  27. GRB 260808B: LCO optical observations
  28. GRB 260808A: NuSTAR detection of prompt emission
  29. EP260809a: COLIBRÍ optical observations
  30. EP260809a: LCO optical observation
  31. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  32. EP260809a: Einstein Probe detection of an X-ray transient
  33. GRB 260808B: SVOM/VT optical afterglow confirmation
  34. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  35. GRB 260808B: SVOM/VT optical candidate from VHF data
  36. GRB 260808B: SVOM detection of a faint burst
  37. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  38. IceCube-260805A: One candidate from the Zwicky Transient Facility
  39. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  40. GRB 260807A: SVOM possible detection of a faint burst
  41. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  42. EP260806a: COLIBRÍ optical observations
  43. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  44. EP260806a: SVOM/VT optical observation
  45. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  46. EP260806a: OSIRIS+/GTC redshift z=0.089
  47. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  48. EP260806a: LCO likely optical counterpart
  49. EP260806a: Einstein Probe detection of an X-ray transient
  50. GRB 260715A: cubesat Avion detection
  51. GRB 260709A: cubesat Avion detection
  52. GRB 260708A: cubesat Avion detection
  53. SN 2026stf / GRB 260708A: ATLAS forced photometry
  54. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
  55. GRB 260730B: Glowbug gamma-ray detection
  56. GRB 260805C: Glowbug gamma-ray detection
  57. GRB 260805B: Glowbug gamma-ray detection
  58. GRB 260804A: Glowbug gamma-ray detection
  59. GRB 260805A: Fermi GBM Final Localization
  60. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  61. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  62. GRB 260708A: LCO further optical observations show supernova features
  63. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  64. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  65. GRB 260802A: SVOM/VT optical upper limits from VHF data
  66. GRB 260802A: LCO optical upper limits
  67. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  68. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  69. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  70. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  71. GRB 260731A: AstroSat CZTI detection of a long burst
  72. GRB 260730B: AstroSat CZTI detection
  73. EP260731a: COLIBRÍ optical upper limit
  74. EP260731a: NOT optical upper limit
  75. GRB 260730B: NuSTAR detection of prompt emission
  76. EP260731a: Einstein Probe detection of an X-ray transient
  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. EP260729a: Einstein Probe detection of an X-ray transient
  84. EP260727a: SAO RAS optical observations
  85. GRB 260727A: AbAO and SAO RAS optical observations
  86. EP260728a: EP-FXT follow-up observation
  87. GRB 260726A: EP-FXT follow-up observations
  88. EP260728a: Einstein Probe detection of a fast X-ray transient
  89. GRB 260727A: SVOM/GRM observation
  90. GRB 260726A: Fermi GBM Observation
  91. EP260727a: 1.5m OSN optical counterpart detection
  92. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  93. Konus-Wind detection of GRB 260727A
  94. GRB 260726A: Liverpool Telescope optical observations
  95. GRB 260727A: Liverpool Telescope optical upper limits
  96. EP260727a: Liverpool Telescope confirmation of optical counterpart
  97. EP260727a: NUTTELA-TAO Early Optical Limits
  98. GRB 260727A: EP/FXT follow-up observations
  99. EP260727a: Einstein Probe detection of an X-ray transient
  100. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart

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