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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"

24153 results found.

  1. IceCube Alert 260825A: Global MASTER-Net observations report
  2. IceCube-Cascade 260824A: Upper limits from a search for additional neutrino events in IceCube
  3. GRB 260825A: Fermi GBM Final Real-time Localization
  4. IceCube-260825A - IceCube observation of a high-energy neutrino candidate track-like event
  5. GRB 260822A: PRIME near-infrared upper limits from multiple epochs
  6. GRB 260822A: EP/FXT follow-up observations
  7. GRB 260822A: the candidate optical afterglow is an unrelated type-Ia SN
  8. GRB 260818A: further EP-FXT observations and X-ray afterglow confirmation
  9. GRB 260822A: SVOM/VT optical detection of COLIBRÍ candidate
  10. GRB 260822A: LCO optical upper limits
  11. The EP-WXT trigger 01709287395 is likely a flaring star
  12. GRB260822B: Fermi GBM Final Localization
  13. GRB 260822A: GROWTH-India Telescope Upper Limits
  14. GRB 260822A: GOTO optical upper limit
  15. GRB 260822A: SVOM detection of a short burst
  16. Fermi-LAT Gamma-ray Observations of IceCube-260821A
  17. Fermi-LAT Gamma-ray Observations of IceCube-260807A
  18. IceCube-260821A: Upper limits from a search for additional neutrino events in IceCube
  19. GRB 260818B: SVOM/C-GFT optical upper limit
  20. EP260731a: SVOM/ECLAIRs detection through offline targeted search
  21. IceCube Alert 260821A: Global MASTER-Net observations report
  22. The EP-WXT trigger 01709286204 is likely a flaring star
  23. IceCube-260821A - IceCube observation of a high-energy neutrino candidate track-like event
  24. GRB 260818B: SVOM/GRM observation
  25. EP detected a brightening of LMXB 1ES 1735-26.9
  26. GRB260820A: Fermi GBM Final Real-Time Localization
  27. GRB 260818B: EP-FXT follow-up observation
  28. GRB 260818B: SVOM/ECLAIRs refined analysis
  29. GRB 260818A: SVOM/ECLAIRs refined analysis
  30. GRB 260810A: SVOM/GRM observation
  31. GRB260818A: EP-FXT follow-up observation
  32. GRB 260818B: LCO optical upper limits
  33. GRB 260818B: SVOM detection of a short burst
  34. GRB 260818A: LCO optical upper limits
  35. GRB 260818A: SVOM possible detection of a long and faint GRB
  36. EP260806a: SVOM/ECLAIRs detection through targeted search
  37. The EP-WXT trigger 01709281429 is likely a flaring star
  38. The EP-WXT trigger 01709280562 is likely a flaring star
  39. The EP-WXT trigger 01709279838 is likely a flaring star
  40. GRB 260805D: SVOM/GRM detection of a possible magnetar burst
  41. GRB 260808B: GTC/OSIRIS+ spectroscopic redshift z = 1.295
  42. GRB 260813A: BALROG localization (Fermi Trigger 808341387 / GRB 260813803)
  43. GRB 260813A: Fermi GBM Final Real-time Localization
  44. EP260812a: NOT and Liverpool Telescope upper limits:
  45. EP260812b: Liverpool Telescope observations
  46. EP260812b: GOTO detection of the optical counterpart
  47. EP260812a: refined analysis of the EP-WXT and autonomous EP-FXT observation
  48. EP260812a: SVOM/C-GFT optical upper limit
  49. EP260812b: SVOM/VT optical observation
  50. GRB 260808A: SVOM/GRM observation
  51. Fermi GBM Sub-Threshold Detection of GRB 260809A
  52. GRB 260808B: SVOM/VT optical re-brightening at day 3
  53. GRB 260317A: SVOM/ECLAIRs detection through offline targeted search and its possible association to magnetar 1E 1841-04.5
  54. GRB 260806A: CALET Gamma-Ray Burst Monitor detection
  55. GRB 260807A: SVOM/ECLAIRs refined analysis
  56. IceCube-260807A: Upper limits from a search for additional neutrino events in IceCube
  57. GRB 250607A: SVOM/ECLAIRs detection through offline targeted search
  58. EP260809a: VLT/X-shooter spectroscopic redshift z = 3.07
  59. GRB 260808A: CALET Gamma-Ray Burst Monitor detection
  60. GRB 260805C: CALET Gamma-Ray Burst Monitor detection
  61. GRB 260804A: CALET Gamma-Ray Burst Monitor detection
  62. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  63. The EP-WXT trigger 01709278015 is likely a flaring star
  64. IceCube-260805A: Upper limits from a search for additional neutrino events in IceCube
  65. GRB 260809A: SVOM/VT optical counterpart
  66. GRB 260808B: SVOM/ECLAIRs refined analysis
  67. EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation
  68. GRB 260809A: SVOM detection of a faint burst
  69. GRB 260808B: NOT optical observations
  70. GRB 260808B: LCO optical observations
  71. GRB 260808A: NuSTAR detection of prompt emission
  72. EP260809a: LCO optical observation
  73. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  74. GRB 260808B: SVOM/VT optical afterglow confirmation
  75. GRB 260808C: Fermi GBM Final Real-time Localization
  76. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  77. GRB 260808B: SVOM/VT optical candidate from VHF data
  78. GRB 260808B: SVOM detection of a faint burst
  79. GRB 260808A: BALROG localization (Fermi Trigger 807850307 / GRB 260808119)
  80. Fermi GRB 260808A: Global MASTER-Net observations report
  81. GRB 260808A: Fermi GBM Final Real-time Localization
  82. IceCube Alert 260807A: Global MASTER-Net observations report
  83. IceCube-260805A: One candidate from the Zwicky Transient Facility
  84. GRB 260807A: SVOM possible detection of a faint burst
  85. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  86. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  87. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  88. EP260806a: LCO likely optical counterpart
  89. GRB 260715A: cubesat Avion detection
  90. GRB 260709A: cubesat Avion detection
  91. GRB 260708A: cubesat Avion detection
  92. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
  93. Fermi GRB 260805A: Global MASTER-Net observations report
  94. GRB 260805B: Fermi GBM Final Localization
  95. GRB 260805B: BALROG localization (Fermi Trigger 807622617 / GRB 260805484)
  96. GRB 260805A: Fermi GBM Final Localization
  97. AT 2026wki: EP/FXT follow-up observations
  98. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  99. IceCube-Cascade 260801A: Upper limits from a search for additional neutrino events in IceCube
  100. GRB 260804A: Fermi GBM Final Real-time Localization

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