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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"

45483 results found.

  1. EP260809a: COLIBRÍ optical observations
  2. EP260809a: LCO optical observation
  3. EP260809a: OHP/T193 optical observations
  4. GRB260808B: OHP/T193 optical observations
  5. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  6. EP260809a: Einstein Probe detection of an X-ray transient
  7. GRB 260808B: SVOM/VT optical afterglow confirmation
  8. GRB 260808C: Fermi GBM Final Real-time Localization
  9. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  10. GRB 260808B: SVOM/VT optical candidate from VHF data
  11. GRB 260808B: SVOM detection of a faint burst
  12. GRB 260808A: BALROG localization (Fermi Trigger 807850307 / GRB 260808119)
  13. Fermi GRB 260808A: Global MASTER-Net observations report
  14. GRB 260808A: Fermi GBM Final Real-time Localization
  15. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  16. IceCube Alert 260807A: Global MASTER-Net observations report
  17. IceCube-260805A: One candidate from the Zwicky Transient Facility
  18. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  19. GRB 260807A: SVOM possible detection of a faint burst
  20. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  21. EP260806a: COLIBRÍ optical observations
  22. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  23. EP260806a: SVOM/VT optical observation
  24. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  25. EP260806a: OSIRIS+/GTC redshift z=0.089
  26. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  27. EP260806a: LCO likely optical counterpart
  28. EP260806a: Einstein Probe detection of an X-ray transient
  29. GRB 260715A: cubesat Avion detection
  30. GRB 260709A: cubesat Avion detection
  31. GRB 260708A: cubesat Avion detection
  32. SN 2026stf / GRB 260708A: ATLAS forced photometry
  33. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
  34. GRB 260730B: Glowbug gamma-ray detection
  35. GRB 260805C: Glowbug gamma-ray detection
  36. GRB 260805B: Glowbug gamma-ray detection
  37. Fermi GRB 260805A: Global MASTER-Net observations report
  38. GRB 260805B: Fermi GBM Final Localization
  39. GRB 260804A: Glowbug gamma-ray detection
  40. GRB 260805B: BALROG localization (Fermi Trigger 807622617 / GRB 260805484)
  41. GRB 260805A: Fermi GBM Final Localization
  42. AT 2026wki: EP/FXT follow-up observations
  43. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  44. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  45. IceCube-Cascade 260801A: Upper limits from a search for additional neutrino events in IceCube
  46. GRB 260804A: Fermi GBM Final Real-time Localization
  47. GRB 260708A: LCO further optical observations show supernova features
  48. GRB 260803A: Fermi GBM Final Real-time Localization
  49. Fermi GRB 260802B: Global MASTER-Net observations report
  50. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  51. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  52. GRB 260802A: SVOM/VT optical upper limits from VHF data
  53. GRB 260802A: LCO optical upper limits
  54. GRB 260802B: Fermi GBM Final Localization
  55. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  56. The EP-WXT trigger 01709277420 is likely a flaring star
  57. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  58. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  59. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  60. GRB 260731A: AstroSat CZTI detection of a long burst
  61. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  62. GRB 260730B: AstroSat CZTI detection
  63. EP260731a: COLIBRÍ optical upper limit
  64. EP260731a: NOT optical upper limit
  65. GRB 260730B: NuSTAR detection of prompt emission
  66. EP260731a: Einstein Probe detection of an X-ray transient
  67. GRB 260727A: SVOM/ECLAIRs refined analysis
  68. GRB 260726A: SVOM/ECLAIRs refined analysis
  69. GRB260730A: Fermi GBM Final Localization
  70. EP260728a: COLIBRÍ optical upper limit
  71. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  72. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  73. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  74. EP260729a: Einstein Probe detection of an X-ray transient
  75. EP260727a: SAO RAS optical observations
  76. GRB 260727A: AbAO and SAO RAS optical observations
  77. EP260728a: EP-FXT follow-up observation
  78. GRB 260726A: EP-FXT follow-up observations
  79. EP260728a: Einstein Probe detection of a fast X-ray transient
  80. GRB 260727A: SVOM/GRM observation
  81. GRB 260726A: Fermi GBM Observation
  82. EP260727a: 1.5m OSN optical counterpart detection
  83. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  84. EP260727a: OHP/T193 optical observations
  85. Konus-Wind detection of GRB 260727A
  86. GRB 260726A: Liverpool Telescope optical observations
  87. GRB 260727A: Liverpool Telescope optical upper limits
  88. EP260727a: Liverpool Telescope confirmation of optical counterpart
  89. EP260727a: NUTTELA-TAO Early Optical Limits
  90. GRB 260728A: Fermi GBM Final Localization
  91. GRB 260727A: EP/FXT follow-up observations
  92. EP260727a: Einstein Probe detection of an X-ray transient
  93. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  94. GRB 260727A: Glowbug gamma-ray detection
  95. GRB 260726A: J-band upper limit with WINTER
  96. GRB 260727A: J-band upper limit with WINTER
  97. GRB 260726A: SVOM/VT optical candidate
  98. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  99. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  100. EP260723a: SVOM/ECLAIRs Upper Limit

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