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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"

41676 results found.

  1. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  2. IceCube Alert 260807A: Global MASTER-Net observations report
  3. IceCube-260805A: One candidate from the Zwicky Transient Facility
  4. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  5. GRB 260807A: SVOM possible detection of a faint burst
  6. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  7. EP260806a: COLIBRÍ optical observations
  8. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  9. EP260806a: SVOM/VT optical observation
  10. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  11. EP260806a: OSIRIS+/GTC redshift z=0.089
  12. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  13. EP260806a: LCO likely optical counterpart
  14. EP260806a: Einstein Probe detection of an X-ray transient
  15. GRB 260715A: cubesat Avion detection
  16. SN 2026stf / GRB 260708A: ATLAS forced photometry
  17. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
  18. GRB 260730B: Glowbug gamma-ray detection
  19. GRB 260805C: Glowbug gamma-ray detection
  20. GRB 260805B: Glowbug gamma-ray detection
  21. Fermi GRB 260805A: Global MASTER-Net observations report
  22. GRB 260805B: Fermi GBM Final Localization
  23. GRB 260804A: Glowbug gamma-ray detection
  24. GRB 260805B: BALROG localization (Fermi Trigger 807622617 / GRB 260805484)
  25. GRB 260805A: Fermi GBM Final Localization
  26. AT 2026wki: EP/FXT follow-up observations
  27. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  28. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  29. IceCube-Cascade 260801A: Upper limits from a search for additional neutrino events in IceCube
  30. GRB 260804A: Fermi GBM Final Real-time Localization
  31. GRB 260708A: LCO further optical observations show supernova features
  32. GRB 260803A: Fermi GBM Final Real-time Localization
  33. Fermi GRB 260802B: Global MASTER-Net observations report
  34. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  35. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  36. GRB 260802A: SVOM/VT optical upper limits from VHF data
  37. GRB 260802A: LCO optical upper limits
  38. GRB 260802B: Fermi GBM Final Localization
  39. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  40. The EP-WXT trigger 01709277420 is likely a flaring star
  41. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  42. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  43. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  44. GRB 260731A: AstroSat CZTI detection of a long burst
  45. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  46. GRB 260730B: AstroSat CZTI detection
  47. EP260731a: COLIBRÍ optical upper limit
  48. EP260731a: NOT optical upper limit
  49. GRB 260730B: NuSTAR detection of prompt emission
  50. EP260731a: Einstein Probe detection of an X-ray transient
  51. GRB 260727A: SVOM/ECLAIRs refined analysis
  52. GRB 260726A: SVOM/ECLAIRs refined analysis
  53. GRB260730A: Fermi GBM Final Localization
  54. EP260728a: COLIBRÍ optical upper limit
  55. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  56. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  57. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  58. EP260729a: Einstein Probe detection of an X-ray transient
  59. EP260727a: SAO RAS optical observations
  60. GRB 260727A: AbAO and SAO RAS optical observations
  61. EP260728a: EP-FXT follow-up observation
  62. GRB 260726A: EP-FXT follow-up observations
  63. EP260728a: Einstein Probe detection of a fast X-ray transient
  64. GRB 260727A: SVOM/GRM observation
  65. GRB 260726A: Fermi GBM Observation
  66. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  67. EP260727a: OHP/T193 optical observations
  68. Konus-Wind detection of GRB 260727A
  69. GRB 260726A: Liverpool Telescope optical observations
  70. GRB 260727A: Liverpool Telescope optical upper limits
  71. EP260727a: Liverpool Telescope confirmation of optical counterpart
  72. EP260727a: NUTTELA-TAO Early Optical Limits
  73. GRB 260728A: Fermi GBM Final Localization
  74. GRB 260727A: EP/FXT follow-up observations
  75. EP260727a: Einstein Probe detection of an X-ray transient
  76. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  77. GRB 260727A: Glowbug gamma-ray detection
  78. GRB 260726A: J-band upper limit with WINTER
  79. GRB 260727A: J-band upper limit with WINTER
  80. GRB 260726A: SVOM/VT optical candidate
  81. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  82. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  83. EP260723a: SVOM/ECLAIRs Upper Limit
  84. GRB 260727A: GOTO early optical upper limit
  85. GRB 260727A: AstroSat CZTI detection
  86. GRB 260727A: Kilonova-Catcher optical upper limit
  87. GRB 260727A: LCO optical upper limits
  88. GRB 260727B: Fermi GBM Final Real-time Localization
  89. Fermi GRB 260726A: Global MASTER-Net observations report
  90. GRB 260727A: SVOM detection of a bright long burst
  91. GRB 260726A: SVOM detection of a burst
  92. GRB 260726A: Fermi GBM Final Real-time Localization
  93. IceCube-260722A: Classification of ZTF26abjbxfs/SN 2026vts as a Type Ia Supernova
  94. EP260723a: further EP-FXT follow-up observation
  95. EP260725a: EP-FXT follow-up observation and association with a bright flaring star
  96. EP260725a: EP-WXT detection of an X-ray transient
  97. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  98. GRB 260602B: cubesat Avion detection
  99. GRB 260601A: cubesat Avion detection
  100. EP260723a: EP-FXT follow-up observation

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