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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"

32501 results found.

  1. EP260812b: Einstein Probe detection of an X-ray transient
  2. Fermi GBM Sub-Threshold Detection of GRB 260809A
  3. GRB 260810A: Glowbug gamma-ray detection
  4. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical rebrightening
  5. GRB 260809A: SAO RAS optical observations
  6. GRB 260808B: SAO RAS optical observations
  7. GRB 260808B: SVOM/VT optical re-brightening at day 3
  8. GRB 260317A: SVOM/ECLAIRs detection through offline targeted search and its possible association to magnetar 1E 1841-04.5
  9. GRB 260806A: CALET Gamma-Ray Burst Monitor detection
  10. GRB 260808A: GECAM-B observation
  11. GRB 260807A: SVOM/ECLAIRs refined analysis
  12. EP260806a: MAO/AZT-22 optical observations
  13. IceCube-260807A: Upper limits from a search for additional neutrino events in IceCube
  14. GRB260808B: MAO/AZT-22 optical observations
  15. GRB 250607A: SVOM/ECLAIRs detection through offline targeted search
  16. GRB 260809A: J-band upper limit with WINTER
  17. EP260809a: VLT/X-shooter spectroscopic redshift z = 3.07
  18. GRB 260808A: CALET Gamma-Ray Burst Monitor detection
  19. GRB 260805C: CALET Gamma-Ray Burst Monitor detection
  20. GRB 260804A: CALET Gamma-Ray Burst Monitor detection
  21. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  22. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  23. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  24. GRB 260809A: NOT optical observations
  25. GRB260809A: MAO/AZT-22 optical observations
  26. GRB260809A: OHP/T193 optical observations
  27. IceCube-260805A: Upper limits from a search for additional neutrino events in IceCube
  28. GRB 260809A: SVOM/VT optical counterpart
  29. EP260809a: J-band upper limit with WINTER
  30. GRB 260808B: J-band upper limit with WINTER
  31. GRB 260808B: SVOM/ECLAIRs refined analysis
  32. EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation
  33. GRB 260808B: Liverpool Telescope optical observations
  34. GRB 260808B: NOT optical observations
  35. GRB 260808B: LCO optical observations
  36. GRB 260808A: NuSTAR detection of prompt emission
  37. EP260809a: COLIBRÍ optical observations
  38. EP260809a: LCO optical observation
  39. GRB260808B: OHP/T193 optical observations
  40. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  41. GRB 260808B: SVOM/VT optical afterglow confirmation
  42. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  43. GRB 260808B: SVOM/VT optical candidate from VHF data
  44. Fermi GRB 260808A: Global MASTER-Net observations report
  45. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  46. IceCube-260805A: One candidate from the Zwicky Transient Facility
  47. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  48. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  49. EP260806a: COLIBRÍ optical observations
  50. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  51. EP260806a: SVOM/VT optical observation
  52. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  53. EP260806a: OSIRIS+/GTC redshift z=0.089
  54. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  55. EP260806a: LCO likely optical counterpart
  56. GRB 260715A: cubesat Avion detection
  57. GRB 260709A: cubesat Avion detection
  58. GRB 260708A: cubesat Avion detection
  59. SN 2026stf / GRB 260708A: ATLAS forced photometry
  60. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
  61. GRB 260730B: Glowbug gamma-ray detection
  62. GRB 260805B: Glowbug gamma-ray detection
  63. Fermi GRB 260805A: Global MASTER-Net observations report
  64. GRB 260804A: Glowbug gamma-ray detection
  65. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  66. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  67. GRB 260708A: LCO further optical observations show supernova features
  68. Fermi GRB 260802B: Global MASTER-Net observations report
  69. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  70. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  71. GRB 260802A: SVOM/VT optical upper limits from VHF data
  72. GRB 260802A: LCO optical upper limits
  73. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  74. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  75. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  76. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  77. GRB 260730B: AstroSat CZTI detection
  78. EP260731a: COLIBRÍ optical upper limit
  79. EP260731a: NOT optical upper limit
  80. GRB 260730B: NuSTAR detection of prompt emission
  81. GRB 260727A: SVOM/ECLAIRs refined analysis
  82. GRB 260726A: SVOM/ECLAIRs refined analysis
  83. EP260728a: COLIBRÍ optical upper limit
  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. EP260727a: SAO RAS optical observations
  88. GRB 260727A: AbAO and SAO RAS optical observations
  89. EP260728a: EP-FXT follow-up observation
  90. GRB 260726A: EP-FXT follow-up observations
  91. GRB 260727A: SVOM/GRM observation
  92. GRB 260726A: Fermi GBM Observation
  93. EP260727a: 1.5m OSN optical counterpart detection
  94. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  95. EP260727a: OHP/T193 optical observations
  96. Konus-Wind detection of GRB 260727A
  97. GRB 260726A: Liverpool Telescope optical observations
  98. GRB 260727A: Liverpool Telescope optical upper limits
  99. EP260727a: Liverpool Telescope confirmation of optical counterpart
  100. EP260727a: NUTTELA-TAO Early Optical Limits

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