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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 200801C: BOOTES-1 and BOOTES-2 optical limits
  2. Fermi GRB 200801A: Global MASTER-Net observations report
  3. Swift Detection of an SGR-like flare from AX J1846.4-0258
  4. Swift GRB200801.84: Global MASTER-Net observations report
  5. GRB 200801B: BALROG localization (Fermi Trigger 617988951 / GRB 200801650)
  6. GRB 200801B: Fermi GBM Final Real-time Localization
  7. GRB 200801A: Fermi GBM Final Real-time Localization
  8. GRB 200729A: RT-22 observations at 36.8 GHz
  9. GRB 200729A: VLA Observations
  10. GRB 200729A: Nanshan/NEXT optical upper limit
  11. GRB 200729A: Swift-BAT refined analysis
  12. GRB 200729A: further analysis of the NOT data
  13. GRB 200729A: Swift/UVOT Upper Limits
  14. GRB 200729A: Swift-XRT refined Analysis
  15. GRB 200729A: HST imaging
  16. Fermi-GBM Sub-Threshold candidate for GRB 200729A
  17. GRB 200729A: IceCube neutrino search
  18. GRB 200729A: Pan-STARRS pre-explosion source detection
  19. GRB 200729A: Spitzer archival source detection
  20. GRB 200729A: TNG NIR upper limits
  21. GRB 200729A: NOT optical upper limits
  22. GRB 200729A: Enhanced Swift-XRT position
  23. GRB200729A: BOOTES-1 optical upper limit
  24. Swift GRB 200729A: Global MASTER-Net observations report
  25. GRB 200729A: Swift detection of a burst
  26. IceCube Alert 200728.35: Global MASTER-Net observations report
  27. IceCube GCN Notice 134327_10548129 retraction
  28. Baksan Neutrino Observatory Alert 200726.66: Global MASTER-Net observations report
  29. GRB 200723A: ATLAS observations of GOTO candidate AT2020qer
  30. GRB 200723A: Swift ToO observations
  31. GRB 200723A: GOTO candidate afterglow and host galaxy
  32. GRB 200724A: Fermi GBM Final Real-time Localization
  33. Fermi GRB 200723A: Global MASTER-Net observations report
  34. GRB 200723A: BALROG localization (Fermi Trigger 617214929 / GRB 200723691)
  35. GRB 200723A: Fermi GBM Final Real-time Localization
  36. GRB 200716C: Kitab optical observations
  37. GRB 200722A: BALROG localization (Fermi Trigger 617076900 / GRB 200722094)
  38. GRB 200716C: CAHA optical observation // Anomalous light curve behavior?
  39. GRB 200716C: CrAO, Terskol, Assy-Turgen optical observations
  40. GRB 200714E: Swift-XRT afterglow detection
  41. GRB 200716C: FRAM-ORM afterglow detection
  42. Konus-Wind observation of GRB 200716C: correction to GCN 28147
  43. Konus-Wind observation of GRB 200716C
  44. GRB 200716C: VIRT optical detection.
  45. GRB 200716C: Insight-HXMT/HE detection
  46. AMON IC_HAWC 170720: Correction to ANTARES GCN 28142
  47. Fermi GRB 200718A: Global MASTER-Net observations report
  48. AMON IC_HAWC 170720: No Neutrino Counterpart detected with ANTARES
  49. Fermi GBM trigger 616776657/200718619 is not a GRB
  50. GRB 200718A: Fermi GBM Final Real-time Localization
  51. GRB 200716C: CALET Gamma-Ray Burst Monitor detection
  52. GRB 200716C: Optical observations from HCT
  53. GRB 200716B: Insight-HXMT/HE detection
  54. GRB 200716C: Swift-BAT refined analysis
  55. GRB 200716C: Fermi GBM detection
  56. Fermi GRB 200716A: Global MASTER-Net observations report
  57. GRB 200716C: AGILE/MCAL detection
  58. GRB 200716C: possible host galaxy from the SDSS
  59. GRB 200716C: Swift-XRT refined analysis correction
  60. GRB 200716C: Fermi-LAT detection
  61. GRB 200716C: Swift-XRT refined Analysis
  62. GRB 200716C: Enhanced Swift-XRT position
  63. GRB 200522A: HST NIR counterpart confirmation
  64. GRB200716C: BOOTES-1 optical afterglow detection
  65. Swift GRB200716C: Global MASTER-Net OT detection
  66. GRB 200716C: Swift detection of a burst with an optical counterpart
  67. GRB 200716C: Fermi GBM Final Real-time Localization
  68. Swift GRB200716.96: Global MASTER-Net observations report
  69. IPN triangulation of GRB 200716A
  70. GRB 200716A: Fermi GBM detection
  71. Fermi GRB 200716B: Global MASTER-Net observations report
  72. GRB 200716B: AstroSat CZTI detection
  73. GRB 200716A: AstroSat CZTI detection
  74. GRB 200716A: AGILE detection
  75. GRB 200715A: Swift-XRT afterglow detection
  76. GRB 200716B: BALROG localization (Fermi Trigger 616577673 / GRB 200716316)
  77. GRB 200716B: Fermi GBM Final Real-time Localization
  78. GRB 200716A: BALROG localization (Fermi Trigger 616555602 / GRB 200716060)
  79. GRB 200715A: Swift ToO observations
  80. GRB 200715A : A long GRB detected by INTEGRAL
  81. GRB 200716A: Fermi GBM Final Real-time Localization
  82. GRB 200714E: Fermi GBM observation
  83. GRB 200714E: Swift-XRT observations
  84. Fermi GRB 200714E: Global MASTER-Net observations report
  85. GRB 200714E: AGILE detection
  86. GRB 200714E: Swift ToO observations
  87. GRB 200714E: Swift/BAT-GUANO detection and arcminute localization
  88. Fermi GRB 200714D: Global MASTER-Net observations report
  89. Fermi GRB 200714A: Global MASTER-Net observations report
  90. GRB 200522A: Candidate Optical/nIR Counterpart from Gemini and HST Imaging
  91. GRB 200714E: BALROG localization (Fermi Trigger 616444510 / GRB 200714774)
  92. GRB 200714E: Fermi GBM Final Real-time Localization
  93. GRB 200714D: Fermi GBM Final Real-time Localization
  94. GRB 200713A: Swift-BAT refined analysis
  95. GRB 200714C: Fermi GBM Final Real-time Localization
  96. GRB 200711A: Insight-HXMT/HE detection
  97. GRB 200714B: Fermi GBM Final Real-time Localization
  98. GRB 200713A: Swift-XRT refined Analysis
  99. GRB 200714A: Fermi GBM Final Real-time Localization
  100. Fermi trigger No 616370565: Global MASTER-Net observations report

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