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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"

24279 results found.

  1. GRB 260808C: Fermi GBM Final Real-time Localization
  2. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  3. GRB 260808B: SVOM/VT optical candidate from VHF data
  4. GRB 260808B: SVOM detection of a faint burst
  5. GRB 260808A: BALROG localization (Fermi Trigger 807850307 / GRB 260808119)
  6. Fermi GRB 260808A: Global MASTER-Net observations report
  7. GRB 260808A: Fermi GBM Final Real-time Localization
  8. IceCube Alert 260807A: Global MASTER-Net observations report
  9. IceCube-260805A: One candidate from the Zwicky Transient Facility
  10. GRB 260807A: SVOM possible detection of a faint burst
  11. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  12. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  13. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  14. EP260806a: LCO likely optical counterpart
  15. GRB 260715A: cubesat Avion detection
  16. GRB 260709A: cubesat Avion detection
  17. GRB 260708A: cubesat Avion detection
  18. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
  19. Fermi GRB 260805A: Global MASTER-Net observations report
  20. GRB 260805B: Fermi GBM Final Localization
  21. GRB 260805B: BALROG localization (Fermi Trigger 807622617 / GRB 260805484)
  22. GRB 260805A: Fermi GBM Final Localization
  23. AT 2026wki: EP/FXT follow-up observations
  24. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  25. IceCube-Cascade 260801A: Upper limits from a search for additional neutrino events in IceCube
  26. GRB 260804A: Fermi GBM Final Real-time Localization
  27. GRB 260708A: LCO further optical observations show supernova features
  28. GRB 260803A: Fermi GBM Final Real-time Localization
  29. Fermi GRB 260802B: Global MASTER-Net observations report
  30. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  31. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  32. GRB 260802A: SVOM/VT optical upper limits from VHF data
  33. GRB 260802A: LCO optical upper limits
  34. GRB 260802B: Fermi GBM Final Localization
  35. The EP-WXT trigger 01709277420 is likely a flaring star
  36. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  37. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  38. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  39. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  40. EP260731a: COLIBRÍ optical upper limit
  41. EP260731a: NOT optical upper limit
  42. GRB 260730B: NuSTAR detection of prompt emission
  43. GRB 260727A: SVOM/ECLAIRs refined analysis
  44. GRB 260726A: SVOM/ECLAIRs refined analysis
  45. GRB260730A: Fermi GBM Final Localization
  46. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  47. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  48. EP260728a: EP-FXT follow-up observation
  49. GRB 260726A: EP-FXT follow-up observations
  50. GRB 260727A: SVOM/GRM observation
  51. GRB 260726A: Fermi GBM Observation
  52. EP260727a: 1.5m OSN optical counterpart detection
  53. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  54. Konus-Wind detection of GRB 260727A
  55. EP260727a: NUTTELA-TAO Early Optical Limits
  56. GRB 260728A: Fermi GBM Final Localization
  57. GRB 260727A: EP/FXT follow-up observations
  58. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  59. GRB 260727A: J-band upper limit with WINTER
  60. GRB 260726A: SVOM/VT optical candidate
  61. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  62. GRB 260727A: LCO optical upper limits
  63. GRB 260727B: Fermi GBM Final Real-time Localization
  64. Fermi GRB 260726A: Global MASTER-Net observations report
  65. GRB 260727A: SVOM detection of a bright long burst
  66. GRB 260726A: SVOM detection of a burst
  67. GRB 260726A: Fermi GBM Final Real-time Localization
  68. EP260723a: further EP-FXT follow-up observation
  69. EP260725a: EP-WXT detection of an X-ray transient
  70. GRB 260616A: cubesat Avion detection
  71. GRB 260602B: cubesat Avion detection
  72. GRB 260601A: cubesat Avion detection
  73. EP260723a: EP-FXT follow-up observation
  74. IPN triangulation of GRB 260706B
  75. GRB 260718A: SVOM/ECLAIRs refined analysis
  76. EP260723a: SVOM/VT optical observation
  77. EP260723a: NOT optical conterpart confirmation
  78. GRB 260723A: Fermi GBM Final Localization
  79. IceCube-260722A: Upper limits from a search for additional neutrino events in IceCube
  80. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
  81. IceCube Alert 260722A: Global MASTER-Net observations report
  82. Konus-Wind detection of GRB 260721A
  83. GRB 260722A: Fermi GBM Final Real-time Localization
  84. IceCube-260722A - IceCube observation of a high-energy neutrino candidate track-like event
  85. GRB 260721A: NuSTAR detection of prompt emission
  86. Konus-Wind detection of GRB 260714B
  87. GRB 260718A: EP-FXT follow-up observation
  88. Fermi trigger No 806104130: Global MASTER-Net observations report
  89. Fermi GRB 260718A: Global MASTER-Net observations report
  90. GRB 260718A: LCO optical upper limits
  91. GRB 260710A: SVOM/GRM observation
  92. GRB 260718A: Fermi GBM Observation
  93. GRB 260718A : GRANDMA and KNC upper limits
  94. GRB 260718A: SVOM/VT optical upper limits
  95. GRB 260718A: SVOM/VT optical upper limits from VHF data
  96. GRB 260718A: SVOM detection of a burst
  97. GRB 260714B: SVOM/GRM observation
  98. GRB 260310A / AT2026fgk: Late-time Chandra Detection
  99. GRB 260714B: GECAM-B observation of a burst
  100. GRB 260618B: EP-FXT follow-up observation upper limit

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