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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"

27015 results found.

  1. GRB 260805C: CALET Gamma-Ray Burst Monitor detection
  2. GRB 260804A: CALET Gamma-Ray Burst Monitor detection
  3. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  4. The EP-WXT trigger 01709278015 is likely a flaring star
  5. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  6. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  7. GRB 260809A: NOT optical observations
  8. GRB260809A: MAO/AZT-22 optical observations
  9. GRB260809A: OHP/T193 optical observations
  10. GRB 260809A: SVOM/VT optical counterpart
  11. EP260809a: J-band upper limit with WINTER
  12. GRB 260808B: J-band upper limit with WINTER
  13. GRB 260808B: SVOM/ECLAIRs refined analysis
  14. EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation
  15. GRB 260809A: SVOM detection of a faint burst
  16. GRB 260808B: Liverpool Telescope optical observations
  17. GRB 260808B: NOT optical observations
  18. GRB 260808B: LCO optical observations
  19. EP260809a: COLIBRÍ optical observations
  20. EP260809a: LCO optical observation
  21. EP260809a: OHP/T193 optical observations
  22. GRB260808B: OHP/T193 optical observations
  23. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  24. EP260809a: Einstein Probe detection of an X-ray transient
  25. GRB 260808B: SVOM/VT optical afterglow confirmation
  26. GRB 260808C: Fermi GBM Final Real-time Localization
  27. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  28. GRB 260808B: SVOM/VT optical candidate from VHF data
  29. GRB 260808B: SVOM detection of a faint burst
  30. GRB 260808A: BALROG localization (Fermi Trigger 807850307 / GRB 260808119)
  31. Fermi GRB 260808A: Global MASTER-Net observations report
  32. GRB 260808A: Fermi GBM Final Real-time Localization
  33. IceCube Alert 260807A: Global MASTER-Net observations report
  34. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  35. GRB 260807A: SVOM possible detection of a faint burst
  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: OSIRIS+/GTC redshift z=0.089
  40. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  41. EP260806a: LCO likely optical counterpart
  42. EP260806a: Einstein Probe detection of an X-ray transient
  43. SN 2026stf / GRB 260708A: ATLAS forced photometry
  44. Fermi GRB 260805A: Global MASTER-Net observations report
  45. GRB 260805B: Fermi GBM Final Localization
  46. GRB 260805B: BALROG localization (Fermi Trigger 807622617 / GRB 260805484)
  47. GRB 260805A: Fermi GBM Final Localization
  48. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  49. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  50. GRB 260804A: Fermi GBM Final Real-time Localization
  51. GRB 260708A: LCO further optical observations show supernova features
  52. GRB 260803A: Fermi GBM Final Real-time Localization
  53. Fermi GRB 260802B: Global MASTER-Net observations report
  54. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  55. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  56. GRB 260802A: SVOM/VT optical upper limits from VHF data
  57. GRB 260802A: LCO optical upper limits
  58. GRB 260802B: Fermi GBM Final Localization
  59. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  60. The EP-WXT trigger 01709277420 is likely a flaring star
  61. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  62. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  63. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  64. GRB 260731A: AstroSat CZTI detection of a long burst
  65. EP260731a: COLIBRÍ optical upper limit
  66. EP260731a: NOT optical upper limit
  67. EP260731a: Einstein Probe detection of an X-ray transient
  68. GRB 260727A: SVOM/ECLAIRs refined analysis
  69. GRB 260726A: SVOM/ECLAIRs refined analysis
  70. GRB260730A: Fermi GBM Final Localization
  71. EP260728a: COLIBRÍ optical upper limit
  72. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  73. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  74. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  75. EP260729a: Einstein Probe detection of an X-ray transient
  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. GRB 260726A: Liverpool Telescope optical observations
  86. GRB 260727A: Liverpool Telescope optical upper limits
  87. EP260727a: NUTTELA-TAO Early Optical Limits
  88. GRB 260728A: Fermi GBM Final Localization
  89. GRB 260727A: EP/FXT follow-up observations
  90. EP260727a: Einstein Probe detection of an X-ray transient
  91. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  92. GRB 260726A: J-band upper limit with WINTER
  93. GRB 260727A: J-band upper limit with WINTER
  94. GRB 260726A: SVOM/VT optical candidate
  95. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  96. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  97. EP260723a: SVOM/ECLAIRs Upper Limit
  98. GRB 260727A: GOTO early optical upper limit
  99. GRB 260727A: Kilonova-Catcher optical upper limit
  100. GRB 260727A: LCO optical upper limits

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