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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"

45401 results found.

  1. GRB 260809A: SVOM/VT optical counterpart
  2. EP260809a: J-band upper limit with WINTER
  3. GRB 260808B: J-band upper limit with WINTER
  4. GRB 260808B: SVOM/ECLAIRs refined analysis
  5. EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation
  6. GRB 260809A: SVOM detection of a faint burst
  7. GRB 260808B: Liverpool Telescope optical observations
  8. GRB 260808B: NOT optical observations
  9. GRB 260808B: LCO optical observations
  10. GRB 260808A: NuSTAR detection of prompt emission
  11. EP260809a: COLIBRÍ optical observations
  12. EP260809a: LCO optical observation
  13. EP260809a: OHP/T193 optical observations
  14. GRB260808B: OHP/T193 optical observations
  15. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  16. EP260809a: Einstein Probe detection of an X-ray transient
  17. GRB 260808B: SVOM/VT optical afterglow confirmation
  18. GRB 260808C: Fermi GBM Final Real-time Localization
  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. GRB 260808B: SVOM detection of a faint burst
  22. GRB 260808A: BALROG localization (Fermi Trigger 807850307 / GRB 260808119)
  23. Fermi GRB 260808A: Global MASTER-Net observations report
  24. GRB 260808A: Fermi GBM Final Real-time Localization
  25. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  26. IceCube Alert 260807A: Global MASTER-Net observations report
  27. IceCube-260805A: One candidate from the Zwicky Transient Facility
  28. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  29. GRB 260807A: SVOM possible detection of a faint burst
  30. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  31. EP260806a: COLIBRÍ optical observations
  32. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  33. EP260806a: SVOM/VT optical observation
  34. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  35. EP260806a: OSIRIS+/GTC redshift z=0.089
  36. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  37. EP260806a: LCO likely optical counterpart
  38. EP260806a: Einstein Probe detection of an X-ray transient
  39. GRB 260715A: cubesat Avion detection
  40. GRB 260709A: cubesat Avion detection
  41. GRB 260708A: cubesat Avion detection
  42. SN 2026stf / GRB 260708A: ATLAS forced photometry
  43. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
  44. GRB 260730B: Glowbug gamma-ray detection
  45. GRB 260805C: Glowbug gamma-ray detection
  46. GRB 260805B: Glowbug gamma-ray detection
  47. Fermi GRB 260805A: Global MASTER-Net observations report
  48. GRB 260805B: Fermi GBM Final Localization
  49. GRB 260804A: Glowbug gamma-ray detection
  50. GRB 260805B: BALROG localization (Fermi Trigger 807622617 / GRB 260805484)
  51. GRB 260805A: Fermi GBM Final Localization
  52. AT 2026wki: EP/FXT follow-up observations
  53. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  54. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  55. IceCube-Cascade 260801A: Upper limits from a search for additional neutrino events in IceCube
  56. GRB 260804A: Fermi GBM Final Real-time Localization
  57. GRB 260708A: LCO further optical observations show supernova features
  58. GRB 260803A: Fermi GBM Final Real-time Localization
  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 260802B: Fermi GBM Final Localization
  65. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  66. The EP-WXT trigger 01709277420 is likely a flaring star
  67. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  68. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  69. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  70. GRB 260731A: AstroSat CZTI detection of a long burst
  71. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  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. GRB260730A: Fermi GBM Final Localization
  80. EP260728a: COLIBRÍ optical upper limit
  81. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  82. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  83. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  84. EP260729a: Einstein Probe detection of an X-ray transient
  85. EP260727a: SAO RAS optical observations
  86. GRB 260727A: AbAO and SAO RAS optical observations
  87. EP260728a: EP-FXT follow-up observation
  88. GRB 260726A: EP-FXT follow-up observations
  89. EP260728a: Einstein Probe detection of a fast X-ray transient
  90. GRB 260727A: SVOM/GRM observation
  91. GRB 260726A: Fermi GBM Observation
  92. EP260727a: 1.5m OSN optical counterpart detection
  93. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  94. EP260727a: OHP/T193 optical observations
  95. Konus-Wind detection of GRB 260727A
  96. GRB 260726A: Liverpool Telescope optical observations
  97. GRB 260727A: Liverpool Telescope optical upper limits
  98. EP260727a: Liverpool Telescope confirmation of optical counterpart
  99. EP260727a: NUTTELA-TAO Early Optical Limits
  100. GRB 260728A: Fermi GBM Final Localization

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