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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"

12008 results found.

  1. GRB 260818A: further EP-FXT observations and X-ray afterglow confirmation
  2. GRB 260822A: LCO optical upper limits
  3. GRB260822B: Fermi GBM Final Localization
  4. Fermi-LAT Gamma-ray Observations of IceCube-260821A
  5. Fermi-LAT Gamma-ray Observations of IceCube-260807A
  6. IceCube-260821A: Upper limits from a search for additional neutrino events in IceCube
  7. GRB 260818B: VLA radio observations
  8. EP detected a brightening of LMXB 1ES 1735-26.9
  9. GRB260820A: Fermi GBM Final Real-Time Localization
  10. GRB 260818B: SVOM/ECLAIRs refined analysis
  11. EP260806a: SAO RAS multicolor optical observations
  12. EP260806a: SVOM/ECLAIRs detection through targeted search
  13. EP260812b: Optical upper limit with Kinder
  14. EP260812a: NOT and Liverpool Telescope upper limits:
  15. EP260812a: refined analysis of the EP-WXT and autonomous EP-FXT observation
  16. EP260812b: Einstein Probe detection of an X-ray transient
  17. EP trigger #01709278129 (EP260812b?): NOT optical counterpart
  18. GRB 260810A: AstroSat CZTI detection of a long burst
  19. EP260812a: Einstein Probe detection of an X-ray transient
  20. GRB 260809A: SAO RAS optical observations
  21. GRB 260807A: SVOM/ECLAIRs refined analysis
  22. GRB 250607A: SVOM/ECLAIRs detection through offline targeted search
  23. GRB 260808B: SVOM/ECLAIRs refined analysis
  24. EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation
  25. GRB 260808B: LCO optical observations
  26. GRB 260808A: NuSTAR detection of prompt emission
  27. EP260809a: COLIBRÍ optical observations
  28. EP260809a: Einstein Probe detection of an X-ray transient
  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. GRB 260808B: SVOM detection of a faint burst
  32. GRB 260807A: SVOM possible detection of a faint burst
  33. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  34. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  35. EP260806a: Einstein Probe detection of an X-ray transient
  36. SN 2026stf / GRB 260708A: ATLAS forced photometry
  37. Fermi GRB 260802B: Global MASTER-Net observations report
  38. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  39. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  40. GRB 260731A: AstroSat CZTI detection of a long burst
  41. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  42. GRB 260730B: AstroSat CZTI detection
  43. EP260731a: Einstein Probe detection of an X-ray transient
  44. EP260729a: Einstein Probe detection of an X-ray transient
  45. EP260727a: SAO RAS optical observations
  46. EP260728a: Einstein Probe detection of a fast X-ray transient
  47. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  48. Konus-Wind detection of GRB 260727A
  49. EP260727a: Einstein Probe detection of an X-ray transient
  50. GRB 260727A: AstroSat CZTI detection
  51. EP260723a: further EP-FXT follow-up observation
  52. EP260725a: EP-WXT detection of an X-ray transient
  53. EP260723a: EP-WXT detection of a fast X-ray transient
  54. Konus-Wind detection of GRB 260721A
  55. Konus-Wind detection of GRB 260714B
  56. GRB 260705A: Retraction of optical counterpart
  57. Fermi trigger No 806104130: Global MASTER-Net observations report
  58. Fermi GRB 260718A: Global MASTER-Net observations report
  59. GRB 260718A: SVOM detection of a burst
  60. sb26071506: SVOM detection of a X-ray transient
  61. GRB 260710A: AstroSat CZTI detection
  62. GRB 260709A: AstroSat CZTI detection
  63. GRB 260714B: AstroSat CZTI detection
  64. GRB 260714B: Fermi-LAT detection
  65. IceCube-260712A: LAST optical follow-up observations of the IceCube neutrino candidate
  66. EP260713a: Einstein Probe detection of an X-ray transient
  67. Fermi-LAT Gamma-ray Observations of IceCube-260712A
  68. Fermi-LAT Gamma-ray Observations of IceCube-260708A
  69. Fermi-LAT Gamma-ray Observations of IceCube-260704A
  70. EP-WXT trigger 0170924151 : RAPAS optical counterpart candidate detection
  71. GRB 260705C: AstroSat CZTI detection
  72. GRB 260706A : GRANDMA Upper limits
  73. IceCube-260708A: One candidate from the Zwicky Transient Facility
  74. GRB260708B: MAXI/GSC detection
  75. GRB 260708A: Fermi-LAT detection
  76. EP260707a: LCOGT Optical Upper Limit
  77. EP260707a: Einstein Probe detection of an X-ray transient
  78. GRB 260704A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  79. The EP-WXT trigger 01709274141 is likely a flaring star
  80. IPN triangulation of GRB 260627A
  81. GRB 260706A: SVOM detection of a burst
  82. GRB 260629A: AstroSat CZTI detection
  83. GRB 260704A: SVOM detection of a possible GRB
  84. EP260703a: EP-WXT detection of a fast X-ray transient
  85. EP260628b: EP-WXT detection of an X-ray transient and EP-FXT follow-up observation
  86. Fermi GRB 260703A: Global MASTER-Net observations report
  87. GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
  88. Fermi trigger No 804552016: Global MASTER-Net observations report
  89. Fermi-LAT Gamma-ray Observations of IceCube-260622A
  90. EP260628a: EP-WXT detection of a fast X-ray transient
  91. Konus-Wind detection of GRB 260623B / EP260623a
  92. EP260623a: FTW optical and NIR observations
  93. Konus-Wind detection of GRB 260618B
  94. EP260623a:refined analysis of the EP-WXT and EP-FXT observation
  95. EP260623a: Optical follow-up observations with Kinder
  96. EP260623a: FRAM-ORM detection of the optical afterglow rise, peak and decay
  97. EP260623a: Einstein Probe detection of an X-ray transient
  98. GRB 260618C: SVOM/ECLAIRs detection of a possible burst through on-ground search
  99. GRB 260618B: LCO optical observations
  100. GRB 260618B: Fermi GBM Observation

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