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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"

43624 results found.

  1. GRB 260710A: SVOM/GRM observation
  2. GRB 260718A: Fermi GBM Observation
  3. GRB 260718A : GRANDMA and KNC upper limits
  4. GRB 260718A: SVOM/VT optical upper limits
  5. GRB 260718A: SVOM/VT optical upper limits from VHF data
  6. GRB 260718A: SVOM detection of a burst
  7. GRB 260714B: SVOM/GRM observation
  8. GRB 260310A / AT2026fgk: Late-time Chandra Detection
  9. GRB 260714B: GECAM-B observation of a burst
  10. GRB 260618B: EP-FXT follow-up observation upper limit
  11. GRB 260714B: COLIBRÍ optical counterpart candidate
  12. IceCube-260708A: Follow-up studies of cosmic-ray origin of high-energy neutrino alert
  13. SVOM sb26071506: Global MASTER-Net observations report
  14. sb26071506: SVOM detection of a X-ray transient
  15. IceCube-260712A: No candidates with the Zwicky Transient Facility (ZTF)
  16. GRB 260715A: Fermi GBM Final Real-time Localization
  17. EP260703a: SVOM/ECLAIRs Upper Limit
  18. GRB 260710A: AstroSat CZTI detection
  19. GRB 260709A: AstroSat CZTI detection
  20. GRB 260714B: AstroSat CZTI detection
  21. GRB 260714B: Fermi-LAT detection
  22. GRB 260714B: Fermi GBM Detection
  23. GRB 260714B: BALROG localization (Fermi Trigger 805746211 / GRB 260714766)
  24. IceCube-260712A: Upper limits from a search for additional neutrino events in IceCube
  25. GRB 260714B: Fermi GBM Final Real-time Localization
  26. IceCube-260712A: LAST optical follow-up observations of the IceCube neutrino candidate
  27. GRB 260706A: ATCA detection of possible radio counterpart
  28. GRB 260705A: ATCA radio observations
  29. GRB 260714A: Fermi GBM Final Real-time Localization
  30. EP260713a: Einstein Probe detection of an X-ray transient
  31. GRB 260619A: SVOM/VT continuous optical observations
  32. GRB 260618B: SVOM/VT optical observations indicate shallow decay and reddening
  33. GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
  34. EP260623a: KAIT optical observations
  35. EP260711a: EP-FXT follow-up observation
  36. GRB 260708A: GRANDMA Optical Observations
  37. Fermi-LAT Gamma-ray Observations of IceCube-260712A
  38. Fermi-LAT Gamma-ray Observations of IceCube-260708A
  39. GRB 260710A: Insight-HXMT/HE detection
  40. Fermi-LAT Gamma-ray Observations of IceCube-260704A
  41. IceCube-260708A: Upper limits from a search for additional neutrino events in IceCube
  42. IceCube-260712A - IceCube observation of a high-energy neutrino candidate track-like event
  43. GRB 260708A: LCO optical observations
  44. EP260711a: Einstein Probe detection of an X-ray transient
  45. GRB 260710A: Fermi GBM Detection
  46. GRB 260709A: SVOM/GRM detection
  47. GRB 260709A: GECAM-B observation
  48. The EP-WXT trigger 01709274666 is likely a new outburst of the CV SS Cyg
  49. IceCube-260708A: Observations with the Vera C. Rubin Observatory
  50. EP-WXT trigger 0170924151 : RAPAS optical counterpart candidate detection
  51. GRB 260705C: AstroSat CZTI detection
  52. GRB 260710A: Fermi GBM Final Real-time Localization
  53. GRB 260708A: Glowbug gamma-ray detection
  54. GRB 260704A: SVOM/ECLAIRs refined analysis
  55. GRB 260706A : GRANDMA Upper limits
  56. GRB 260708A: Kilonova-Catcher optical afterglow detection
  57. GRB 260708A: GECAM-B observation of a burst
  58. IceCube-260708A: One candidate from the Zwicky Transient Facility
  59. GRB 260708A: Fermi-GBM observation
  60. Fermi LAT GRB 260708A: MASTER OT J150237.02-435307.7 optical counterpart detection
  61. IceCube Alert 260709A: Global MASTER-Net observations report
  62. GRB 260709A: Fermi GBM Final Real-time Localization
  63. IceCube-260708A - IceCube observation of a high-energy neutrino candidate track-like event
  64. LAT GRB260708.42: Global MASTER-Net observations report
  65. GRB260708B: MAXI/GSC detection
  66. GRB 260708A: Fermi-LAT detection
  67. GRB 260705B: SVOM/GRM observation
  68. GRB 260708A: Fermi-GBM detection
  69. GRB 260706A: Further EP-FXT follow-up observation
  70. GRB 260706A: SVOM/VT optical upper limits
  71. EP260707a (by EP-FXT): NOT optical upper limit
  72. EP260707a is not a real source
  73. EP260707a: LCOGT Optical Upper Limit
  74. EP260707a: TRT optical upper limit
  75. Fermi GBM trigger 805087514/260707142 (GRB 260707A) is not a GRB
  76. EP260707a: Einstein Probe detection of an X-ray transient
  77. Nova AT2026oyp (ASASSN-26dt): Pre-outburst Swift UVOT observation
  78. GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
  79. GRB 260705C: Glowbug gamma-ray detection of a short burst
  80. GRB 260706A: SVOM/ECLAIRs refined analysis
  81. GRB 260704A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  82. GRB 260706A: SVOM/GRM observation
  83. GRB 260706A: REM optical/NIR observations
  84. IceCube-260704A: No candidates from the Zwicky Transient Facility
  85. GRB 260706A: LCO optical upper limit
  86. GRB 260706A: EP-FXT follow-up observation
  87. GRB 260707A: Fermi GBM Final Real-time Localization
  88. The EP-WXT trigger 01709274151 is likely a flaring star
  89. The EP-WXT trigger 01709274141 is likely a flaring star
  90. GRB 260706A: Fermi GBM Observation
  91. IceCube-260704A: Upper limits from a search for additional neutrino events in IceCube
  92. IPN triangulation of GRB 260627A
  93. GRB 260705A: SVOM/ECLAIRs refined analysis
  94. GRB 260706A: SVOM detection of a burst
  95. GRB 260706A: Fermi GBM Final Real-time Localization
  96. The EP-WXT trigger 01709274014: KAIT confirmation of a stellar flare
  97. The EP-WXT trigger 01709274014 is likely a flaring star
  98. IceCube260704A: OHP/T193 optical observations
  99. GRB 260705A: LCO optical upper limits
  100. GRB 260704A: NOT optical upper limits

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