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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"

32488 results found.

  1. GRB260808B: MAO/AZT-22 optical observations
  2. GRB 250607A: SVOM/ECLAIRs detection through offline targeted search
  3. GRB 260809A: J-band upper limit with WINTER
  4. EP260809a: VLT/X-shooter spectroscopic redshift z = 3.07
  5. GRB 260808A: CALET Gamma-Ray Burst Monitor detection
  6. GRB 260805C: CALET Gamma-Ray Burst Monitor detection
  7. GRB 260804A: CALET Gamma-Ray Burst Monitor detection
  8. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  9. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  10. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  11. GRB 260809A: NOT optical observations
  12. GRB260809A: MAO/AZT-22 optical observations
  13. GRB260809A: OHP/T193 optical observations
  14. IceCube-260805A: Upper limits from a search for additional neutrino events in IceCube
  15. GRB 260809A: SVOM/VT optical counterpart
  16. EP260809a: J-band upper limit with WINTER
  17. GRB 260808B: J-band upper limit with WINTER
  18. GRB 260808B: SVOM/ECLAIRs refined analysis
  19. EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation
  20. GRB 260808B: Liverpool Telescope optical observations
  21. GRB 260808B: NOT optical observations
  22. GRB 260808B: LCO optical observations
  23. GRB 260808A: NuSTAR detection of prompt emission
  24. EP260809a: COLIBRÍ optical observations
  25. EP260809a: LCO optical observation
  26. GRB260808B: OHP/T193 optical observations
  27. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  28. GRB 260808B: SVOM/VT optical afterglow confirmation
  29. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  30. GRB 260808B: SVOM/VT optical candidate from VHF data
  31. Fermi GRB 260808A: Global MASTER-Net observations report
  32. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  33. IceCube-260805A: One candidate from the Zwicky Transient Facility
  34. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  35. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  36. EP260806a: COLIBRÍ optical observations
  37. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  38. EP260806a: SVOM/VT optical observation
  39. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  40. EP260806a: OSIRIS+/GTC redshift z=0.089
  41. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  42. EP260806a: LCO likely optical counterpart
  43. GRB 260715A: cubesat Avion detection
  44. GRB 260709A: cubesat Avion detection
  45. GRB 260708A: cubesat Avion detection
  46. SN 2026stf / GRB 260708A: ATLAS forced photometry
  47. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
  48. GRB 260730B: Glowbug gamma-ray detection
  49. GRB 260805B: Glowbug gamma-ray detection
  50. Fermi GRB 260805A: Global MASTER-Net observations report
  51. GRB 260804A: Glowbug gamma-ray detection
  52. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  53. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  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. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  62. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  63. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  64. GRB 260730B: AstroSat CZTI detection
  65. EP260731a: COLIBRÍ optical upper limit
  66. EP260731a: NOT optical upper limit
  67. GRB 260730B: NuSTAR detection of prompt emission
  68. GRB 260727A: SVOM/ECLAIRs refined analysis
  69. GRB 260726A: SVOM/ECLAIRs refined analysis
  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. EP260727a: SAO RAS optical observations
  75. GRB 260727A: AbAO and SAO RAS optical observations
  76. EP260728a: EP-FXT follow-up observation
  77. GRB 260726A: EP-FXT follow-up observations
  78. GRB 260727A: SVOM/GRM observation
  79. GRB 260726A: Fermi GBM Observation
  80. EP260727a: 1.5m OSN optical counterpart detection
  81. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  82. EP260727a: OHP/T193 optical observations
  83. Konus-Wind detection of GRB 260727A
  84. GRB 260726A: Liverpool Telescope optical observations
  85. GRB 260727A: Liverpool Telescope optical upper limits
  86. EP260727a: Liverpool Telescope confirmation of optical counterpart
  87. EP260727a: NUTTELA-TAO Early Optical Limits
  88. GRB 260727A: EP/FXT follow-up observations
  89. EP260727a: Einstein Probe detection of an X-ray transient
  90. GRB 260727A: Glowbug gamma-ray detection
  91. GRB 260726A: J-band upper limit with WINTER
  92. GRB 260727A: J-band upper limit with WINTER
  93. GRB 260726A: SVOM/VT optical candidate
  94. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  95. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  96. EP260723a: SVOM/ECLAIRs Upper Limit
  97. GRB 260727A: GOTO early optical upper limit
  98. GRB 260727A: AstroSat CZTI detection
  99. GRB 260727A: Kilonova-Catcher optical upper limit
  100. GRB 260727A: LCO optical upper limits

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