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

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