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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. EP241021a: Optical and NIR observations of counterpart with the Fraunhofer Telescope at Wendelstein Observatory
  2. EP 241021a: Swift-XRT observations
  3. EP241021a: optical follow-up observations with the Liverpool Telescope
  4. Fermi GRB 241025A: Global MASTER-Net observations report
  5. Swift GRB 241025A: Global MASTER-Net observations report
  6. EP241025a (GRB 241025A): EP observations update
  7. GRB 241025A : SVOM/VT optical afterglow observations
  8. EP 241021A: Swift ToO observations
  9. EP241021a: Liverpool Telescope optical follow-up observations
  10. GRB 241025A: Enhanced Swift-XRT position
  11. GRB 241001A: JWST spectroscopic identification of a supernova counterpart
  12. GRB 241025A: NOT spectroscopic redshift of z = 4.20
  13. GRB 241025A: DDOTI Afterglow detection
  14. EP241025a (GRB 241025A): EP on-board trigger and autonomous follow-up observation
  15. GRB 241025A: SVOM/GRM observation
  16. GRB 241025A: TRT optical afterglow observation
  17. Fermi GRB 241024B: Global MASTER-Net observations report
  18. GRB 241025A: Fermi GBM Final Real-time Localization
  19. GRB 241025A: Swift detection of a burst with an optical counterpart
  20. EP241021a: GTC OSIRIS+ spectroscopy of the optical counterpart
  21. GRB 241001A: ATCA radio observations
  22. GRB 241024B: Fermi GBM Final Localization
  23. EP241021a: No Detection in Fermi-GBM Observation
  24. GRB 241010A: VIRT Optical Upper Limit
  25. GRB 241024A: Fermi GBM Final Localisation
  26. EP241021a: VLT/FORS2 redshift z = 0.75
  27. Fermi trigger No 751449953: Global MASTER-Net observations report
  28. EP241021a: SAO RAS optical observations
  29. EP241021a: KAIT optical observations
  30. EP241021a: EP-FXT follow-up observation update
  31. IPN triangulation of GRB 241021A (long)
  32. EP241021a: Optical counterpart observations with the Liverpool Telescope
  33. EP241021a: 1.3m DFOT Optical observations
  34. EP241021a: GSP detects optical candidate counterpart
  35. EP241021a: Optical upper limits with Kinder observations
  36. EP241021a: TRT optical observations
  37. GRB 241018A: SVOM/C-GFT optical observations
  38. EP241021a: NOT likely optical counterpart
  39. EP EP241021a: Global MASTER-Net observations report
  40. GRB241017A: 1.3m DFOT optical upper limit
  41. GRB 241018A: 1.3m DFOT Optical upper limit
  42. GRB 241018A: EP-FXT afterglow detection
  43. EP241021a: GOTO optical upper limits
  44. EP241021a: EP detection of a fast X-ray transient
  45. IceCube-Cascade 241019A: Upper limits from a search for additional neutrino events in IceCube
  46. Konus-Wind detection of GRB 241018A
  47. GRB 241018A: SVOM/GRM observation
  48. GRB 241018A/sb24101802: Mephisto optical upper limit
  49. GRB 241017A/sb24101702: Mephisto optical upper limit
  50. GRB 241018A: BOOTES-4/MET optical upper limit
  51. GRB 241018A: Mondy optical upper limit
  52. GRB 241018A: SVOM/VT further analysis and counterpart confirmed
  53. GRB 241018A: GROWTH-India telescope optical upper limit
  54. GRB241018A: XingLong Optical Upper Limit
  55. GRB 241018A: Swift-XRT observations
  56. GRB 241018A: REM optical/NIR upper limits
  57. GRB 241018A: NOT optical observations
  58. GRB 241017A: SVOM/VT follow-up and optical upper limit
  59. GRB 241018A: SVOM/VT follow-up and optical candidate
  60. GRB 241018A: LCO/0.4m optical upper limits
  61. GRB 241018A: Swift ToO observations
  62. GRB 241006A: VIRT Optical Upper Limit
  63. GRB 240727A: VIRT Optical Upper Limit
  64. GRB 241018A: X-ray afterglow candidate observed by MXT
  65. GRB 241016B: Fermi GBM Observations
  66. GRB 241018A: Detection of a bright long GRB by SVOM
  67. GRB 241017A: Swift-XRT observations
  68. GRB241017a: Liverpool Telescope observations of XRT uncatalogued sources
  69. GRB 241001A: EP-FXT afterglow detection
  70. GRB 241017A: GROWTH-India Telescope optical upper limit
  71. GRB241017A: TOO Observations by SVOM/MXT
  72. GRB 241016B: Swift/BAT-GUANO localization skymap of a short burst
  73. GRB 241017A: J-band upper limit from WINTER
  74. Fermi trigger No 750788395: Global MASTER-Net observations report
  75. GRB 241016B: SVOM/GRM observation
  76. GRB241016C: Fermi GBM Final Localization
  77. Fermi Gamma-ray Burst Monitor trigger 750792698/241016730 is not a GRB
  78. GRB 241017A: Swift ToO observations
  79. GRB 241017A : Detection of a weak and soft long duration GRB by SVOM/ECLAIRs
  80. Fermi GRB 241016B: Global MASTER-Net observations report
  81. GRB 241016B: Fermi GBM Final Localization
  82. Fermi GRB 241016A: Global MASTER-Net observations report
  83. GRB 241016A: Fermi GBM Final Real-time Localization
  84. IceCube alert 139977_2910365 retraction
  85. IceCube Alert 241016.04: Global MASTER-Net observations report
  86. GRB 241010A: Swift-BAT refined analysis
  87. GRB 241013B: Fermi GBM Observation
  88. GRB 241013B: Swift/BAT-GUANO localization skymap of a burst
  89. GRB 241013A: Fermi GBM Observation
  90. GRB 240916A: radio detection with the VLA
  91. GRB241013A: REM observations
  92. GRB 241009A: LCO optical upper limits
  93. GRB 241013B: SVOM/GRM observation
  94. Fermi GRB 241013B: Global MASTER-Net observations report
  95. Integral GRB241013.04: Global MASTER-Net observations report
  96. GRB 241013B: Fermi GBM Final Real-time Localization
  97. GRB 241013A: a long GRB detected by INTEGRAL
  98. GRB 241013A: Fermi GBM Final Real-time Localization
  99. LIGO/Virgo/KAGRA S241009em: Updated Sky localization
  100. LIGO/Virgo/KAGRA S241011k: Updated Sky localization

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