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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"

37072 results found.

  1. GRB 260915A: EP-FXT follow-up observation
  2. GRB 260915A: REM optical/NIR observations
  3. GRB 260914A: REM optical/NIR observations
  4. GRB 260914A: VLT/X-shooter observations and redshift confirmation
  5. GRB 260915A: SVOM/VT optical upper limits
  6. GRB 260915A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  7. GRB 260914A: VLT/X-shooter spectroscopic redshift z = 0.778
  8. GRB 260915A: 10.4m GTC deep optical limits
  9. GRB 260915A: NOT optical upper limit
  10. GRB 260915A: SVOM/VT optical upper limits from VHF data
  11. Fermi GBM Sub-Threshold Detection of GRB 260915A
  12. GRB 260915A: LCO optical upper limits
  13. GRB 260914A: EP-FXT follow-up observation
  14. GRB 260915A: SVOM detection of a burst
  15. Fermi GBM Sub-Threshold Detection of GRB 260914A
  16. GRB 260914A: LCO optical observation
  17. GRB 260914A: SVOM/C-GFT optical observations
  18. GRB 260914A: SVOM/VT optical counterpart confirmation
  19. GRB 260914A: SVOM/VT optical observation from VHF data
  20. GRB 260914A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  21. GRB 260914A: SVOM detection of a burst
  22. GRB 260913A: SVOM trigger sb26091302 is not an astrophysical event
  23. GRB 260818A: Continued ATCA observations
  24. GRB 260913A: SVOM/C-GFT optical upper limit
  25. GRB 260913A: SVOM detection of a faint burst
  26. GRB 260909A: OSN 1.5m, CAHA 2.2m and GTC 10.4m optical upper limits
  27. GRB 260907A: SVOM/GRM observation
  28. GRB 260909A: CrAO and AbAO optical upper limits
  29. GRB 260909A: SVOM/ECLAIRs refined analysis
  30. GRB 260910B: GOTO tentative optical counterpart candidates
  31. GRB 260909A: Swift ToO observations
  32. GRB 260910B: Fermi GBM Final Real-time Localization
  33. GRB 260909A: KAIT optical upper limit
  34. GRB 260903A: Swift-XRT observations
  35. GRB 260909A: OHP/T193 z-band upper limit
  36. GRB 260909A: VLT optical and near-infrared upper limits
  37. GRB 260909A: EP-FXT follow-up observation
  38. GRB 260910A: Fermi GBM Final Real-time Localization
  39. EP260623a: NOEMA detections
  40. GRB 260909A: SVOM/VT optical upper limits
  41. GRB 260909A: SVOM/GRM observation
  42. GRB 260909A: Mondy optical observations and afterglow candidate
  43. GRB 260909A: Xinglong 2.16m optical upper limit
  44. GRB 260909A: SVOM/C-GFT optical upper limit
  45. GRB 260909A: SVOM detection of a burst
  46. GRB 260907A: Glowbug gamma-ray detection of a likely short burst
  47. GRB 260903A: Swift ToO observations
  48. Fermi GRB 260907B: Global MASTER-Net observations report
  49. GRB 260903A: SAO RAS optical upper limit
  50. GRB 260907B: Fermi GBM Final Real-time Localization
  51. Fermi GRB 260907A: Global MASTER-Net observations report
  52. GRB 260907A: Fermi GBM Final Real-time Localization
  53. GRB 260903A: J-band upper limit with WINTER
  54. GRB 260903A: SVOM/ECLAIRs refined analysis
  55. GRB260903A: Liverpool Telescope optical observations
  56. GRB 260903A: SAO RAS optical observations
  57. GRB 260830A: GECAM-B detection of a burst
  58. GRB 260830A: Insight-HXMT/HE detection
  59. GRB 260903A: EP-FXT follow-up observation
  60. GRB 260903A: OHP/T193 optical afterglow detection
  61. GRB 260903A: NOT optical observations and afterglow fading
  62. GRB 260903A: LCO optical observations
  63. GRB 260903A: SVOM/VT optical candidate
  64. GRB 260903A: Retraction of optical counterpart of GCN 45501
  65. GRB 260831A: GECAM-B observation
  66. GRB 260903A: LCO optical counterpart detection
  67. GRB 260827A: Insight-HXMT/HE detection
  68. GRB 260903A: SVOM detection of a soft faint burst
  69. Konus-Wind detection of GRB 260829A
  70. GRB 260829A: SVOM/GRM observation
  71. GRB 260818A: ATCA detection of a candidate radio counterpart
  72. GRB 260831B / sb26083106: SVOM/GWAC-F60A/B confirmation of optical variation of nova V* GK Per
  73. GRB 260831B / sb26083106: SVOM/VT optical variability of V* GK Per
  74. SVOM trigger sb26083106 is not a GRB
  75. GRB 260829A: AstroSat CZTI detection
  76. GRB 260831B: EP-FXT follow-up observation
  77. GRB 260830A: NuSTAR detection of prompt emission
  78. GRB 260831B: LCO optical upper limits
  79. GRB 260827A: SVOM/GRM observation
  80. NuSTAR 260828: a 1100s hard X-ray transient
  81. GRB 260831B: SVOM detection of a possible burst
  82. IPN triangulation of GRB 260829A
  83. GRB 260827A: Glowbug gamma-ray detection
  84. GRB 260831A: Fermi GBM Final Real-time Localization
  85. GRB 260829A: GECAM-B observation of a long burst
  86. GRB 260825A: SVOM/GRM observation of a long burst
  87. GRB 260825A: GECAM-B observation
  88. GRB 260829A: Fermi GBM Detection
  89. GRB 260825A: AstroSat CZTI detection
  90. GRB 260829A: BALROG localization (Fermi Trigger 809676494 / GRB 260829256)
  91. GRB 260829A: Fermi GBM Final Real-time Localization
  92. Fermi GBM trigger 809666623/260829141 is not a GRB
  93. GRB 260818B: Further EP-FXT observation
  94. GRB 260818B: VLT optical and nIR observations
  95. GRB 260818B: TNG NIR observations
  96. GRB 260827A: Fermi GBM Final Real-time Localization
  97. GRB 260818B: 6 GHz VLA observations
  98. GRB 260818B: SVOM/VT optical upper limit and continuous observations
  99. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  100. GRB 260808B: SAO RAS observations of the optical rebrightening

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