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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"
  1. GRB 260825A: Fermi GBM Final Real-time Localization
  2. IceCube-260825A - IceCube observation of a high-energy neutrino candidate track-like event
  3. GRB 260822A: PRIME near-infrared upper limits from multiple epochs
  4. GRB 260822A: EP/FXT follow-up observations
  5. GRB 260822A: the candidate optical afterglow is an unrelated type-Ia SN
  6. GRB 260818A: further EP-FXT observations and X-ray afterglow confirmation
  7. EP260822a: EP-FXT non-detection and upper limit
  8. GRB 260822A: Retraction of GOTO optical counterpart detection GCN 45431
  9. GRB 260822A: GOTO optical counterpart detection
  10. GRB 260822A: SVOM/VT optical detection of COLIBRÍ candidate
  11. GRB 260822A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  12. EP260822a: Einstein Probe detection of a fast X-ray transient
  13. GRB 260822A: LCO optical upper limits
  14. The EP-WXT trigger 01709287395 is likely a flaring star
  15. GRB260822B: Fermi GBM Final Localization
  16. GRB 260822A: GROWTH-India Telescope Upper Limits
  17. GRB 260822A: GOTO optical upper limit
  18. GRB 260822A: SVOM detection of a short burst
  19. Fermi-LAT Gamma-ray Observations of IceCube-260821A
  20. Fermi-LAT Gamma-ray Observations of IceCube-260807A
  21. IceCube-260821A: Upper limits from a search for additional neutrino events in IceCube
  22. GRB 260818B: VLA radio observations
  23. GRB 260818B: SVOM/C-GFT optical upper limit
  24. EP260731a: SVOM/ECLAIRs detection through offline targeted search
  25. IceCube Alert 260821A: Global MASTER-Net observations report
  26. The EP-WXT trigger 01709286204 is likely a flaring star
  27. GRB 260820A: Insight-HXMT/HE detection
  28. IceCube-260821A - IceCube observation of a high-energy neutrino candidate track-like event
  29. GRB 260818B: SVOM/GRM observation
  30. EP detected a brightening of LMXB 1ES 1735-26.9
  31. GRB260820A: Fermi GBM Final Real-Time Localization
  32. GRB 260818B: Insight-HXMT detection
  33. GRB 260818B: EP-FXT follow-up observation
  34. GRB 260818A: J-band observations with WINTER
  35. GRB 260818B: SVOM/ECLAIRs refined analysis
  36. GRB 260818A: SVOM/ECLAIRs refined analysis
  37. GRB 260818B: NOT optical upper limits
  38. GRB 260810A: SVOM/GRM observation
  39. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  40. GRB260818A: EP-FXT follow-up observation
  41. GRB 260818B: LCO optical upper limits
  42. GRB 260818B: SVOM detection of a short burst
  43. SVOM trigger sb26081806 is not a GRB
  44. EP260806a: SAO RAS multicolor optical observations
  45. GRB 260818A: LCO optical upper limits
  46. EP260812a: AbAO optical upper limit
  47. GRB 260818A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  48. GRB 260810A: Insight-HXMT/HE detection
  49. GRB 260818A: SVOM possible detection of a long and faint GRB
  50. EP260806a: SVOM/ECLAIRs detection through targeted search
  51. EP260806a: NUTTELA-TAO optical observations
  52. The EP-WXT trigger 01709281429 is likely a flaring star
  53. EP260812a: AZT-22 optical upper limit
  54. EP260812b: GTC/OSIRIS+ tentative spectroscopic redshift z = 2.034
  55. EP260806a: WFST optical observations
  56. The EP-WXT trigger 01709280562 is likely a flaring star
  57. EP260812b: Optical upper limit with Kinder
  58. The EP-WXT trigger 01709279838 is likely a flaring star
  59. GRB 260805D: SVOM/GRM detection of a possible magnetar burst
  60. GRB 260808B: Liverpool Telescope further optical observations
  61. GRB 260808B: GTC/OSIRIS+ spectroscopic redshift z = 1.295
  62. GRB 260813A: BALROG localization (Fermi Trigger 808341387 / GRB 260813803)
  63. GRB 260813A: Fermi GBM Final Real-time Localization
  64. EP260812a: NOT and Liverpool Telescope upper limits:
  65. EP260812b: Liverpool Telescope observations
  66. EP260812b: GOTO detection of the optical counterpart
  67. EP260812a: refined analysis of the EP-WXT and autonomous EP-FXT observation
  68. EP260812a: SVOM/C-GFT optical upper limit
  69. EP260812b: COLIBRÍ optical observations
  70. EP260812b: SVOM/VT optical observation
  71. GRB 260808A: SVOM/GRM observation
  72. EP260812b: Einstein Probe detection of an X-ray transient
  73. EP trigger #01709278129 (EP260812b?): NOT optical counterpart
  74. Fermi GBM Sub-Threshold Detection of GRB 260809A
  75. GRB 260810A: Glowbug gamma-ray detection
  76. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical rebrightening
  77. GRB 260810A: AstroSat CZTI detection of a long burst
  78. EP260812a: Einstein Probe detection of an X-ray transient
  79. GRB 260809A: SAO RAS optical observations
  80. GRB 260808B: SAO RAS optical observations
  81. GRB 260808B: SVOM/VT optical re-brightening at day 3
  82. GRB 260317A: SVOM/ECLAIRs detection through offline targeted search and its possible association to magnetar 1E 1841-04.5
  83. GRB 260806A: CALET Gamma-Ray Burst Monitor detection
  84. GRB 260808A: GECAM-B observation
  85. GRB 260807A: SVOM/ECLAIRs refined analysis
  86. EP260806a: MAO/AZT-22 optical observations
  87. IceCube-260807A: Upper limits from a search for additional neutrino events in IceCube
  88. GRB260808B: MAO/AZT-22 optical observations
  89. GRB 250607A: SVOM/ECLAIRs detection through offline targeted search
  90. GRB 260809A: J-band upper limit with WINTER
  91. EP260809a: VLT/X-shooter spectroscopic redshift z = 3.07
  92. GRB 260806A: Glowbug gamma-ray detection
  93. GRB 260808A: CALET Gamma-Ray Burst Monitor detection
  94. GRB 260805C: CALET Gamma-Ray Burst Monitor detection
  95. GRB 260804A: CALET Gamma-Ray Burst Monitor detection
  96. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  97. The EP-WXT trigger 01709278015 is likely a flaring star
  98. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  99. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  100. GRB 260809A: NOT optical observations

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