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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 260915A: SVOM/VT optical upper limits
  2. GRB 260915A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  3. GRB 260914A: VLT/X-shooter spectroscopic redshift z = 0.778
  4. GRB 260915A: 10.4m GTC deep optical limits
  5. GRB 260915A: NOT optical upper limit
  6. SVOM GRB260915.05: Global MASTER-Net observations report
  7. GRB 260915A: SVOM/VT optical upper limits from VHF data
  8. Fermi GBM Sub-Threshold Detection of GRB 260915A
  9. GRB 260915A: LCO optical upper limits
  10. EP Alert 260914.53: Global MASTER-Net observations report
  11. GRB 260914A: EP-FXT follow-up observation
  12. GRB 260915A: SVOM detection of a burst
  13. Fermi GBM Sub-Threshold Detection of GRB 260914A
  14. GRB 260914A: LCO optical observation
  15. GRB 260914A: SVOM/C-GFT optical observations
  16. GRB 260914A: SVOM/VT optical counterpart confirmation
  17. GRB 260914A: SVOM/VT optical observation from VHF data
  18. GRB 260914A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  19. SVOM GRB260914.47: Global MASTER-Net observations report
  20. GRB 260914A: SVOM detection of a burst
  21. GRB 260913A: SVOM trigger sb26091302 is not an astrophysical event
  22. GRB 260818A: Continued ATCA observations
  23. SVOM GRB260913.32: Global MASTER-Net observations report
  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. EP260806a: VLA+ALMA radio detections
  36. GRB 260909A: OHP/T193 z-band upper limit
  37. GRB 260909A: VLT optical and near-infrared upper limits
  38. EP Alert 260909.53: Global MASTER-Net observations report
  39. GRB 260909A: EP-FXT follow-up observation
  40. GRB 260910A: Fermi GBM Final Real-time Localization
  41. EP260806a: NOEMA detection
  42. EP260623a: NOEMA detections
  43. GRB 260909A: SVOM/VT optical upper limits
  44. GRB 260909A: SVOM/GRM observation
  45. GRB 260909A: Mondy optical observations and afterglow candidate
  46. GRB 260909A: Xinglong 2.16m optical upper limit
  47. GRB 260909A: SVOM/C-GFT optical upper limit
  48. GRB 260909A: SVOM detection of a burst
  49. The EP-WXT trigger 01709306297 is likely the known LMXB 4U 1745-203
  50. Fermi trigger No 810554827: Global MASTER-Net observations report
  51. EP Alert 260908.60: Global MASTER-Net observations report
  52. GRB 260907A: Glowbug gamma-ray detection of a likely short burst
  53. GRB 260903A: Swift ToO observations
  54. Fermi GRB 260907B: Global MASTER-Net observations report
  55. GRB 260903A: SAO RAS optical upper limit
  56. The EP-WXT trigger 01709305715 is likely a flaring star
  57. GRB 260907B: Fermi GBM Final Real-time Localization
  58. Fermi GRB 260907A: Global MASTER-Net observations report
  59. GRB 260907A: Fermi GBM Final Real-time Localization
  60. EP260903a: EP-FXT follow-up observation
  61. EP Alert 260905.11: Global MASTER-Net observations report
  62. The EP-WXT trigger 01709302592 is likely a flaring star
  63. GRB 260903A: J-band upper limit with WINTER
  64. EP Alert 260903.47: Global MASTER-Net observations report
  65. GRB 260903A: SVOM/ECLAIRs refined analysis
  66. GRB260903A: Liverpool Telescope optical observations
  67. GRB 260903A: SAO RAS optical observations
  68. GRB 260830A: GECAM-B detection of a burst
  69. EP260903a: EP-WXT detection of a fast X-ray transient
  70. EP Alert 260903.62: Global MASTER-Net observations report
  71. GRB 260830A: Insight-HXMT/HE detection
  72. GRB 260903A: EP-FXT follow-up observation
  73. GRB 260903A: OHP/T193 optical afterglow detection
  74. GRB 260903A: NOT optical observations and afterglow fading
  75. NuSTAR Transient 260828: SOAR Optical Upper Limits
  76. SVOM GRB260903A: Global MASTER-Net observations report
  77. GRB 260903A: LCO optical observations
  78. GRB 260903A: SVOM/VT optical candidate
  79. GRB 260903A: Retraction of optical counterpart of GCN 45501
  80. GRB 260831A: GECAM-B observation
  81. GRB 260903A: LCO optical counterpart detection
  82. GRB 260827A: Insight-HXMT/HE detection
  83. GRB 260903A: SVOM detection of a soft faint burst
  84. EP260901a: SVOM/VT optical upper limits
  85. EP260901a: EP-FXT follow-up observation
  86. Konus-Wind detection of GRB 260829A
  87. GRB 260829A: SVOM/GRM observation
  88. GRB 260818A: ATCA detection of a candidate radio counterpart
  89. EP260830a: EP-FXT follow-up observation
  90. EP260901a: Global MASTER-Net observations report
  91. IceCube-260827A: No transient candidates from the Zwicky Transient Facility
  92. GRB 260831B / sb26083106: SVOM/GWAC-F60A/B confirmation of optical variation of nova V* GK Per
  93. GRB 260831B / sb26083106: SVOM/VT optical variability of V* GK Per
  94. NuSTAR Transient 260828: LCO Optical Upper Limits
  95. EP260901a: EP-WXT detection of a fast X-ray transient
  96. SVOM trigger sb26083106 is not a GRB
  97. GRB 260829A: AstroSat CZTI detection
  98. GRB 260831B: EP-FXT follow-up observation
  99. GRB 260830A: NuSTAR detection of prompt emission
  100. GRB 260831B: LCO optical upper limits

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