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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"

27887 results found.

  1. GRB 260909A: KAIT optical upper limit
  2. GRB 260903A: Swift-XRT observations
  3. GRB 260909A: OHP/T193 z-band upper limit
  4. GRB 260909A: VLT optical and near-infrared upper limits
  5. EP Alert 260909.53: Global MASTER-Net observations report
  6. GRB 260909A: EP-FXT follow-up observation
  7. EP260806a: NOEMA detection
  8. EP260623a: NOEMA detections
  9. GRB 260909A: Mondy optical observations and afterglow candidate
  10. GRB 260909A: Xinglong 2.16m optical upper limit
  11. GRB 260909A: SVOM/C-GFT optical upper limit
  12. GRB 260909A: SVOM detection of a burst
  13. Fermi trigger No 810554827: Global MASTER-Net observations report
  14. EP Alert 260908.60: Global MASTER-Net observations report
  15. GRB 260907A: Glowbug gamma-ray detection of a likely short burst
  16. Fermi GRB 260907B: Global MASTER-Net observations report
  17. GRB 260903A: SAO RAS optical upper limit
  18. Fermi GRB 260907A: Global MASTER-Net observations report
  19. EP260903a: EP-FXT follow-up observation
  20. EP Alert 260905.11: Global MASTER-Net observations report
  21. GRB 260903A: J-band upper limit with WINTER
  22. EP Alert 260903.47: Global MASTER-Net observations report
  23. GRB260903A: Liverpool Telescope optical observations
  24. GRB 260903A: SAO RAS optical observations
  25. GRB 260830A: GECAM-B detection of a burst
  26. EP260903a: EP-WXT detection of a fast X-ray transient
  27. EP Alert 260903.62: Global MASTER-Net observations report
  28. GRB 260830A: Insight-HXMT/HE detection
  29. GRB 260903A: EP-FXT follow-up observation
  30. GRB 260903A: OHP/T193 optical afterglow detection
  31. NuSTAR Transient 260828: SOAR Optical Upper Limits
  32. SVOM GRB260903A: Global MASTER-Net observations report
  33. GRB 260903A: LCO optical counterpart detection
  34. GRB 260827A: Insight-HXMT/HE detection
  35. EP260901a: SVOM/VT optical upper limits
  36. EP260901a: EP-FXT follow-up observation
  37. GRB 260829A: SVOM/GRM observation
  38. GRB 260818A: ATCA detection of a candidate radio counterpart
  39. EP260830a: EP-FXT follow-up observation
  40. EP260901a: Global MASTER-Net observations report
  41. GRB 260831B / sb26083106: SVOM/GWAC-F60A/B confirmation of optical variation of nova V* GK Per
  42. NuSTAR Transient 260828: LCO Optical Upper Limits
  43. EP260901a: EP-WXT detection of a fast X-ray transient
  44. GRB 260830A: NuSTAR detection of prompt emission
  45. GRB 260831B: LCO optical upper limits
  46. EP260830a: Global MASTER-Net observations report
  47. EP260830a: EP-WXT detection of a fast X-ray transient
  48. GRB 260827A: SVOM/GRM observation
  49. NuSTAR 260828: a 1100s hard X-ray transient
  50. GRB 260831B: SVOM detection of a possible burst
  51. GRB 260827A: Glowbug gamma-ray detection
  52. Fermi-LAT Gamma-ray Observations of IceCube-260827A
  53. Fermi-LAT Gamma-ray Observations of IceCube-260825A
  54. GRB 260825A: SVOM/GRM observation of a long burst
  55. GRB 260829A: Fermi GBM Detection
  56. GRB 260825A: AstroSat CZTI detection
  57. GRB 260829A: BALROG localization (Fermi Trigger 809676494 / GRB 260829256)
  58. IceCube-260827A: Upper limits from a search for additional neutrino events in IceCube
  59. IceCube-260825A: Upper limits from a search for additional neutrino events in IceCube
  60. IceCube-260825A: Upper limits from a search for additional neutrino events in IceCube
  61. GRB 260818B: Further EP-FXT observation
  62. GRB 260818B: VLT optical and nIR observations
  63. GRB 260818B: TNG NIR observations
  64. MAXI GRB260827.40: Global MASTER-Net observations report
  65. GRB 260818B: 6 GHz VLA observations
  66. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  67. GRB 260808B: SAO RAS observations of the optical rebrightening
  68. EP260822a: Global MASTER-Net observations report
  69. EP Alert 260820.31: Global MASTER-Net observations report
  70. GRB 260807A: EP-FXT follow-up observations
  71. IceCube Alert 260825A: Global MASTER-Net observations report
  72. IceCube-Cascade 260824A: Upper limits from a search for additional neutrino events in IceCube
  73. GRB 260822A: PRIME near-infrared upper limits from multiple epochs
  74. GRB 260822A: the candidate optical afterglow is an unrelated type-Ia SN
  75. GRB 260818A: further EP-FXT observations and X-ray afterglow confirmation
  76. EP260822a: EP-FXT non-detection and upper limit
  77. GRB 260822A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  78. EP260822a: Einstein Probe detection of a fast X-ray transient
  79. GRB 260822A: LCO optical upper limits
  80. GRB 260822A: GROWTH-India Telescope Upper Limits
  81. Fermi-LAT Gamma-ray Observations of IceCube-260821A
  82. Fermi-LAT Gamma-ray Observations of IceCube-260807A
  83. IceCube-260821A: Upper limits from a search for additional neutrino events in IceCube
  84. GRB 260818B: VLA radio observations
  85. GRB 260818B: SVOM/C-GFT optical upper limit
  86. EP260731a: SVOM/ECLAIRs detection through offline targeted search
  87. IceCube Alert 260821A: Global MASTER-Net observations report
  88. GRB 260820A: Insight-HXMT/HE detection
  89. EP detected a brightening of LMXB 1ES 1735-26.9
  90. GRB 260818A: J-band observations with WINTER
  91. GRB 260818A: SVOM/ECLAIRs refined analysis
  92. GRB 260818B: NOT optical upper limits
  93. GRB 260810A: SVOM/GRM observation
  94. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  95. GRB 260818B: LCO optical upper limits
  96. GRB 260818B: SVOM detection of a short burst
  97. EP260806a: SAO RAS multicolor optical observations
  98. GRB 260818A: LCO optical upper limits
  99. EP260812a: AbAO optical upper limit
  100. GRB 260818A: SVOM/COLIBRÍ (FM-GFT) optical upper limit

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