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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"

45292 results found.

  1. GRB 260808A: BALROG localization (Fermi Trigger 807850307 / GRB 260808119)
  2. Fermi GRB 260808A: Global MASTER-Net observations report
  3. GRB 260808A: Fermi GBM Final Real-time Localization
  4. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  5. IceCube Alert 260807A: Global MASTER-Net observations report
  6. IceCube-260805A: One candidate from the Zwicky Transient Facility
  7. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  8. GRB 260807A: SVOM possible detection of a faint burst
  9. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  10. EP260806a: COLIBRÍ optical observations
  11. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  12. EP260806a: SVOM/VT optical observation
  13. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  14. EP260806a: OSIRIS+/GTC redshift z=0.089
  15. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  16. EP260806a: LCO likely optical counterpart
  17. EP260806a: Einstein Probe detection of an X-ray transient
  18. GRB 260715A: cubesat Avion detection
  19. GRB 260709A: cubesat Avion detection
  20. GRB 260708A: cubesat Avion detection
  21. SN 2026stf / GRB 260708A: ATLAS forced photometry
  22. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
  23. GRB 260730B: Glowbug gamma-ray detection
  24. GRB 260805C: Glowbug gamma-ray detection
  25. GRB 260805B: Glowbug gamma-ray detection
  26. Fermi GRB 260805A: Global MASTER-Net observations report
  27. GRB 260805B: Fermi GBM Final Localization
  28. GRB 260804A: Glowbug gamma-ray detection
  29. GRB 260805B: BALROG localization (Fermi Trigger 807622617 / GRB 260805484)
  30. GRB 260805A: Fermi GBM Final Localization
  31. AT 2026wki: EP/FXT follow-up observations
  32. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  33. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  34. IceCube-Cascade 260801A: Upper limits from a search for additional neutrino events in IceCube
  35. GRB 260804A: Fermi GBM Final Real-time Localization
  36. GRB 260708A: LCO further optical observations show supernova features
  37. GRB 260803A: Fermi GBM Final Real-time Localization
  38. Fermi GRB 260802B: Global MASTER-Net observations report
  39. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  40. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  41. GRB 260802A: SVOM/VT optical upper limits from VHF data
  42. GRB 260802A: LCO optical upper limits
  43. GRB 260802B: Fermi GBM Final Localization
  44. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  45. The EP-WXT trigger 01709277420 is likely a flaring star
  46. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  47. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  48. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  49. GRB 260731A: AstroSat CZTI detection of a long burst
  50. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  51. GRB 260730B: AstroSat CZTI detection
  52. EP260731a: COLIBRÍ optical upper limit
  53. EP260731a: NOT optical upper limit
  54. GRB 260730B: NuSTAR detection of prompt emission
  55. EP260731a: Einstein Probe detection of an X-ray transient
  56. GRB 260727A: SVOM/ECLAIRs refined analysis
  57. GRB 260726A: SVOM/ECLAIRs refined analysis
  58. GRB260730A: Fermi GBM Final Localization
  59. EP260728a: COLIBRÍ optical upper limit
  60. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  61. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  62. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  63. EP260729a: Einstein Probe detection of an X-ray transient
  64. EP260727a: SAO RAS optical observations
  65. GRB 260727A: AbAO and SAO RAS optical observations
  66. EP260728a: EP-FXT follow-up observation
  67. GRB 260726A: EP-FXT follow-up observations
  68. EP260728a: Einstein Probe detection of a fast X-ray transient
  69. GRB 260727A: SVOM/GRM observation
  70. GRB 260726A: Fermi GBM Observation
  71. EP260727a: 1.5m OSN optical counterpart detection
  72. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  73. EP260727a: OHP/T193 optical observations
  74. Konus-Wind detection of GRB 260727A
  75. GRB 260726A: Liverpool Telescope optical observations
  76. GRB 260727A: Liverpool Telescope optical upper limits
  77. EP260727a: Liverpool Telescope confirmation of optical counterpart
  78. EP260727a: NUTTELA-TAO Early Optical Limits
  79. GRB 260728A: Fermi GBM Final Localization
  80. GRB 260727A: EP/FXT follow-up observations
  81. EP260727a: Einstein Probe detection of an X-ray transient
  82. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  83. GRB 260727A: Glowbug gamma-ray detection
  84. GRB 260726A: J-band upper limit with WINTER
  85. GRB 260727A: J-band upper limit with WINTER
  86. GRB 260726A: SVOM/VT optical candidate
  87. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  88. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  89. EP260723a: SVOM/ECLAIRs Upper Limit
  90. GRB 260727A: GOTO early optical upper limit
  91. GRB 260727A: AstroSat CZTI detection
  92. GRB 260727A: Kilonova-Catcher optical upper limit
  93. GRB 260727A: LCO optical upper limits
  94. GRB 260727B: Fermi GBM Final Real-time Localization
  95. Fermi GRB 260726A: Global MASTER-Net observations report
  96. GRB 260727A: SVOM detection of a bright long burst
  97. GRB 260726A: SVOM detection of a burst
  98. GRB 260726A: Fermi GBM Final Real-time Localization
  99. IceCube-260722A: Classification of ZTF26abjbxfs/SN 2026vts as a Type Ia Supernova
  100. EP260723a: further EP-FXT follow-up observation

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