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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"

42561 results found.

  1. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  2. The EP-WXT trigger 01709278015 is likely a flaring star
  3. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  4. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  5. GRB 260809A: NOT optical observations
  6. GRB260809A: MAO/AZT-22 optical observations
  7. GRB260809A: OHP/T193 optical observations
  8. IceCube-260805A: Upper limits from a search for additional neutrino events in IceCube
  9. GRB 260809A: SVOM/VT optical counterpart
  10. EP260809a: J-band upper limit with WINTER
  11. GRB 260808B: J-band upper limit with WINTER
  12. GRB 260808B: SVOM/ECLAIRs refined analysis
  13. EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation
  14. GRB 260809A: SVOM detection of a faint burst
  15. GRB 260808B: Liverpool Telescope optical observations
  16. GRB 260808B: NOT optical observations
  17. GRB 260808B: LCO optical observations
  18. GRB 260808A: NuSTAR detection of prompt emission
  19. EP260809a: COLIBRÍ optical observations
  20. EP260809a: LCO optical observation
  21. EP260809a: OHP/T193 optical observations
  22. GRB260808B: OHP/T193 optical observations
  23. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  24. EP260809a: Einstein Probe detection of an X-ray transient
  25. GRB 260808B: SVOM/VT optical afterglow confirmation
  26. GRB 260808C: Fermi GBM Final Real-time Localization
  27. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  28. GRB 260808B: SVOM/VT optical candidate from VHF data
  29. GRB 260808B: SVOM detection of a faint burst
  30. Fermi GRB 260808A: Global MASTER-Net observations report
  31. GRB 260808A: Fermi GBM Final Real-time Localization
  32. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  33. IceCube Alert 260807A: Global MASTER-Net observations report
  34. IceCube-260805A: One candidate from the Zwicky Transient Facility
  35. GRB 260807A: SVOM possible detection of a faint burst
  36. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  37. EP260806a: COLIBRÍ optical observations
  38. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  39. EP260806a: SVOM/VT optical observation
  40. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  41. EP260806a: OSIRIS+/GTC redshift z=0.089
  42. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  43. EP260806a: LCO likely optical counterpart
  44. EP260806a: Einstein Probe detection of an X-ray transient
  45. GRB 260715A: cubesat Avion detection
  46. GRB 260709A: cubesat Avion detection
  47. GRB 260708A: cubesat Avion detection
  48. SN 2026stf / GRB 260708A: ATLAS forced photometry
  49. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
  50. GRB 260730B: Glowbug gamma-ray detection
  51. GRB 260805C: Glowbug gamma-ray detection
  52. GRB 260805B: Glowbug gamma-ray detection
  53. Fermi GRB 260805A: Global MASTER-Net observations report
  54. GRB 260805B: Fermi GBM Final Localization
  55. GRB 260804A: Glowbug gamma-ray detection
  56. GRB 260805A: Fermi GBM Final Localization
  57. AT 2026wki: EP/FXT follow-up observations
  58. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  59. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  60. IceCube-Cascade 260801A: Upper limits from a search for additional neutrino events in IceCube
  61. GRB 260804A: Fermi GBM Final Real-time Localization
  62. GRB 260708A: LCO further optical observations show supernova features
  63. GRB 260803A: Fermi GBM Final Real-time Localization
  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 260802B: Fermi GBM Final Localization
  70. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  71. The EP-WXT trigger 01709277420 is likely a flaring star
  72. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  73. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  74. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  75. GRB 260731A: AstroSat CZTI detection of a long burst
  76. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  77. GRB 260730B: AstroSat CZTI detection
  78. EP260731a: NOT optical upper limit
  79. GRB 260730B: NuSTAR detection of prompt emission
  80. EP260731a: Einstein Probe detection of an X-ray transient
  81. GRB 260727A: SVOM/ECLAIRs refined analysis
  82. GRB 260726A: SVOM/ECLAIRs refined analysis
  83. GRB260730A: Fermi GBM Final Localization
  84. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  85. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  86. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  87. EP260729a: Einstein Probe detection of an X-ray transient
  88. EP260727a: SAO RAS optical observations
  89. GRB 260727A: AbAO and SAO RAS optical observations
  90. EP260728a: EP-FXT follow-up observation
  91. GRB 260726A: EP-FXT follow-up observations
  92. EP260728a: Einstein Probe detection of a fast X-ray transient
  93. GRB 260727A: SVOM/GRM observation
  94. GRB 260726A: Fermi GBM Observation
  95. EP260727a: 1.5m OSN optical counterpart detection
  96. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  97. EP260727a: OHP/T193 optical observations
  98. Konus-Wind detection of GRB 260727A
  99. GRB 260726A: Liverpool Telescope optical observations
  100. GRB 260727A: Liverpool Telescope optical upper limits

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