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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"

41682 results found.

  1. GRB260809A: MAO/AZT-22 optical observations
  2. GRB260809A: OHP/T193 optical observations
  3. IceCube-260805A: Upper limits from a search for additional neutrino events in IceCube
  4. GRB 260809A: SVOM/VT optical counterpart
  5. EP260809a: J-band upper limit with WINTER
  6. GRB 260808B: J-band upper limit with WINTER
  7. GRB 260808B: SVOM/ECLAIRs refined analysis
  8. EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation
  9. GRB 260809A: SVOM detection of a faint burst
  10. GRB 260808B: Liverpool Telescope optical observations
  11. GRB 260808B: NOT optical observations
  12. GRB 260808B: LCO optical observations
  13. GRB 260808A: NuSTAR detection of prompt emission
  14. EP260809a: COLIBRÍ optical observations
  15. EP260809a: LCO optical observation
  16. EP260809a: OHP/T193 optical observations
  17. GRB260808B: OHP/T193 optical observations
  18. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  19. EP260809a: Einstein Probe detection of an X-ray transient
  20. GRB 260808B: SVOM/VT optical afterglow confirmation
  21. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  22. GRB 260808B: SVOM/VT optical candidate from VHF data
  23. GRB 260808B: SVOM detection of a faint burst
  24. Fermi GRB 260808A: Global MASTER-Net observations report
  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 260804A: Glowbug gamma-ray detection
  49. GRB 260805A: Fermi GBM Final Localization
  50. AT 2026wki: EP/FXT follow-up observations
  51. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  52. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  53. IceCube-Cascade 260801A: Upper limits from a search for additional neutrino events in IceCube
  54. GRB 260708A: LCO further optical observations show supernova features
  55. Fermi GRB 260802B: Global MASTER-Net observations report
  56. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  57. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  58. GRB 260802A: SVOM/VT optical upper limits from VHF data
  59. GRB 260802A: LCO optical upper limits
  60. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  61. The EP-WXT trigger 01709277420 is likely a flaring star
  62. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  63. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  64. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  65. GRB 260731A: AstroSat CZTI detection of a long burst
  66. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  67. GRB 260730B: AstroSat CZTI detection
  68. EP260731a: COLIBRÍ optical upper limit
  69. EP260731a: NOT optical upper limit
  70. GRB 260730B: NuSTAR detection of prompt emission
  71. EP260731a: Einstein Probe detection of an X-ray transient
  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. EP260729a: Einstein Probe detection of an X-ray transient
  79. EP260727a: SAO RAS optical observations
  80. GRB 260727A: AbAO and SAO RAS optical observations
  81. EP260728a: EP-FXT follow-up observation
  82. GRB 260726A: EP-FXT follow-up observations
  83. EP260728a: Einstein Probe detection of a fast X-ray transient
  84. GRB 260727A: SVOM/GRM observation
  85. GRB 260726A: Fermi GBM Observation
  86. EP260727a: 1.5m OSN optical counterpart detection
  87. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  88. EP260727a: OHP/T193 optical observations
  89. Konus-Wind detection of GRB 260727A
  90. GRB 260726A: Liverpool Telescope optical observations
  91. GRB 260727A: Liverpool Telescope optical upper limits
  92. EP260727a: Liverpool Telescope confirmation of optical counterpart
  93. EP260727a: NUTTELA-TAO Early Optical Limits
  94. GRB 260727A: EP/FXT follow-up observations
  95. EP260727a: Einstein Probe detection of an X-ray transient
  96. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  97. GRB 260727A: Glowbug gamma-ray detection
  98. GRB 260726A: J-band upper limit with WINTER
  99. GRB 260727A: J-band upper limit with WINTER
  100. GRB 260726A: SVOM/VT optical candidate

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