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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 241024A: Fermi GBM Final Localisation
  2. EP241021a: VLT/FORS2 redshift z = 0.75
  3. Fermi trigger No 751449953: Global MASTER-Net observations report
  4. EP241021a: SAO RAS optical observations
  5. EP241021a: KAIT optical observations
  6. EP241021a: EP-FXT follow-up observation update
  7. IPN triangulation of GRB 241021A (long)
  8. EP241021a: Optical counterpart observations with the Liverpool Telescope
  9. EP241021a: 1.3m DFOT Optical observations
  10. EP241021a: GSP detects optical candidate counterpart
  11. EP241021a: Optical upper limits with Kinder observations
  12. EP241021a: TRT optical observations
  13. GRB 241018A: SVOM/C-GFT optical observations
  14. EP241021a: NOT likely optical counterpart
  15. EP EP241021a: Global MASTER-Net observations report
  16. GRB241017A: 1.3m DFOT optical upper limit
  17. GRB 241018A: 1.3m DFOT Optical upper limit
  18. GRB 241018A: EP-FXT afterglow detection
  19. EP241021a: GOTO optical upper limits
  20. EP241021a: EP detection of a fast X-ray transient
  21. IceCube-Cascade 241019A: Upper limits from a search for additional neutrino events in IceCube
  22. Konus-Wind detection of GRB 241018A
  23. GRB 241018A: SVOM/GRM observation
  24. GRB 241018A/sb24101802: Mephisto optical upper limit
  25. GRB 241017A/sb24101702: Mephisto optical upper limit
  26. GRB 241018A: BOOTES-4/MET optical upper limit
  27. GRB 241018A: Mondy optical upper limit
  28. GRB 241018A: SVOM/VT further analysis and counterpart confirmed
  29. GRB 241018A: GROWTH-India telescope optical upper limit
  30. GRB241018A: XingLong Optical Upper Limit
  31. GRB 241018A: Swift-XRT observations
  32. GRB 241018A: REM optical/NIR upper limits
  33. GRB 241018A: NOT optical observations
  34. GRB 241017A: SVOM/VT follow-up and optical upper limit
  35. GRB 241018A: SVOM/VT follow-up and optical candidate
  36. GRB 241018A: LCO/0.4m optical upper limits
  37. GRB 241018A: Swift ToO observations
  38. GRB 241006A: VIRT Optical Upper Limit
  39. GRB 240727A: VIRT Optical Upper Limit
  40. GRB 241018A: X-ray afterglow candidate observed by MXT
  41. GRB 241016B: Fermi GBM Observations
  42. GRB 241018A: Detection of a bright long GRB by SVOM
  43. GRB 241017A: Swift-XRT observations
  44. GRB241017a: Liverpool Telescope observations of XRT uncatalogued sources
  45. GRB 241001A: EP-FXT afterglow detection
  46. GRB 241017A: GROWTH-India Telescope optical upper limit
  47. GRB241017A: TOO Observations by SVOM/MXT
  48. GRB 241016B: Swift/BAT-GUANO localization skymap of a short burst
  49. GRB 241017A: J-band upper limit from WINTER
  50. Fermi trigger No 750788395: Global MASTER-Net observations report
  51. GRB 241016B: SVOM/GRM observation
  52. GRB241016C: Fermi GBM Final Localization
  53. Fermi Gamma-ray Burst Monitor trigger 750792698/241016730 is not a GRB
  54. GRB 241017A: Swift ToO observations
  55. GRB 241017A : Detection of a weak and soft long duration GRB by SVOM/ECLAIRs
  56. Fermi GRB 241016B: Global MASTER-Net observations report
  57. GRB 241016B: Fermi GBM Final Localization
  58. Fermi GRB 241016A: Global MASTER-Net observations report
  59. GRB 241016A: Fermi GBM Final Real-time Localization
  60. IceCube alert 139977_2910365 retraction
  61. IceCube Alert 241016.04: Global MASTER-Net observations report
  62. GRB 241010A: Swift-BAT refined analysis
  63. GRB 241013B: Fermi GBM Observation
  64. GRB 241013B: Swift/BAT-GUANO localization skymap of a burst
  65. GRB 241013A: Fermi GBM Observation
  66. GRB 240916A: radio detection with the VLA
  67. GRB241013A: REM observations
  68. GRB 241009A: LCO optical upper limits
  69. GRB 241013B: SVOM/GRM observation
  70. Fermi GRB 241013B: Global MASTER-Net observations report
  71. Integral GRB241013.04: Global MASTER-Net observations report
  72. GRB 241013B: Fermi GBM Final Real-time Localization
  73. GRB 241013A: a long GRB detected by INTEGRAL
  74. GRB 241013A: Fermi GBM Final Real-time Localization
  75. LIGO/Virgo/KAGRA S241009em: Updated Sky localization
  76. LIGO/Virgo/KAGRA S241011k: Updated Sky localization
  77. LIGO/Virgo/KAGRA S241011k: NED Galaxies in the Localization Volume
  78. LIGO/Virgo/KAGRA S241011k: Identification of a GW compact binary merger candidate
  79. Fermi Gamma-ray Burst Monitor GRB trigger 750372658/241011869 (GRB 241011A) is not a GRB
  80. GRB 241011A: Fermi GBM Final Real-time Localization
  81. GRB 241009A: GRANDMA optical upper limits
  82. GRB 241009A: Swift-XRT afterglow detection
  83. GRB 241010A: JinShan optical observations and potential host galaxy
  84. GRB 241006A: ATCA Radio Upper Limits
  85. GRB 241010A: Swift-XRT refined Analysis
  86. LIGO/Virgo/KAGRA S241007bw: Updated Sky localization
  87. Fermi trigger No 750211959: Global MASTER-Net observations report
  88. Fermi Gamma-ray Burst Monitor trigger 750303285/241011066 is not a GRB
  89. Fermi Gamma-ray Burst Monitor trigger 750291012/241010924 is not a GRB
  90. Swift GRB 241010A: Global MASTER-Net observations report
  91. Fermi trigger No 750291012: Global MASTER-Net observations report
  92. GRB 241010A: J-band observations with WINTER
  93. LIGO/Virgo/KAGRA S241009an: Updated Sky localization
  94. Fermi GRB 241010B: Global MASTER-Net observations report
  95. GRB 241010B: Fermi GBM Final Real-time Localization
  96. IceCube-241006A: Upper limits from a search for additional neutrino events in IceCube
  97. GRB 241010A: Enhanced Swift-XRT position
  98. GRB 241010A: LCO optical observations
  99. GRB 241010A: Swift detection of a burst with an optical counterpart
  100. Fermi-LAT Gamma-ray Observations of IceCube-241006A

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