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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. Baksan Neutrino Observatory Alert 200406.3: Global MASTER-Net observations report
  2. GRB 200407B: Fermi GBM Final Real-time Localization
  3. GRB 200407A: Fermi GBM Final Real-time Localization
  4. GRB 200405B: LCO Optical Upper Limits
  5. GRB 200405B: Swift-XRT observations
  6. GRB 200405B: Swift ToO observations
  7. Fermi GRB 200405A: Global MASTER-Net observations report
  8. GRB 200405B: Swift/BAT-GUANO detection and *possible* arcminute localization of a short GRB
  9. GRB 200405A: Fermi GBM Final Real-time Localization
  10. GRB 200404A: Fermi GBM Final Localization
  11. Fermi GRB 200403C: Global MASTER-Net observations report
  12. GRB 200404A: BALROG localization (Fermi Trigger 607712227 / GRB 200404706)
  13. GRB 200403A: AstroSat CZTI detection
  14. Fermi GRB 200403B: Global MASTER-Net observations report
  15. Fermi GRB 200403A: Global MASTER-Net observations report
  16. GRB 200403C: Fermi GBM Final Real-time Localization
  17. LIGO/Virgo S200316bj: Upper limits from Konus-Wind observations
  18. LIGO/Virgo S200311bg: Upper limits from Konus-Wind observations
  19. LIGO/Virgo S200302c: Upper limits from Konus-Wind observations
  20. LIGO/Virgo S200225q: Upper limits from Konus-Wind observations
  21. GRB 200403B: Fermi GBM Final Real-time Localization
  22. LIGO/Virgo S200224ca: Upper limits from Konus-Wind observations
  23. GRB 200403A: Fermi GBM Final Real-time Localization
  24. GRB 200325B: Mondy continued observations
  25. Fermi GRB 200402C: Global MASTER-Net observations report
  26. GRB 200402C: Fermi GBM Final Localization
  27. GRB 200402B: Fermi GBM Final Localization
  28. Fermi trigger No 607537834: Global MASTER-Net observations report
  29. GRB 200402B: BALROG localization (Fermi Trigger 607537834 / GRB 200402688)
  30. Fermi GRB 200402A: Global MASTER-Net observations report
  31. GRB 200402A: BALROG localization (Fermi Trigger 607513182 / GRB 200402403)
  32. GRB 200325B: Optical upper limit
  33. GRB 200402A: Fermi GBM Final Real-time Localization
  34. GRB 200325B: further Swift-XRT observations
  35. Fermi GRB 200401A: Global MASTER-Net observations report
  36. GRB 200401A: Fermi GBM Final Real-time Localization
  37. GRB 200325B: Mondy continued observations
  38. GRB 200325B: Mondy continued observations
  39. GRB 200327A: Fermi GBM detection
  40. GRB 200325B: Mondy continued observations
  41. GRB 200325B: Tautenburg observations
  42. IPN triangulation of GRB 200327A (short)
  43. GRB 200326B: AstroSat CZTI detection
  44. GRB 200327A: AGILE/MCAL observations
  45. GRB 200325B: Fermi GBM observation
  46. Fermi trigger No 607035413: Global MASTER-Net observations report
  47. GRB 200327A: Fermi GBM Final Real-time Localization
  48. GRB 200325B: Swift-XRT and UVOT observations
  49. GRB 200325B: LCO Optical Detection
  50. GRB 200325B: Mondy, CrAO, AbAO afterglow confirmation and refined photometry of MASTER OT J111012.51+274912.8
  51. GRB 200326B: AstroSat LAXPC detection
  52. GRB 200325A: Fermi GBM observation
  53. GRB 200325B: Mondy and CrAO observations, Master MASTER OT J111012.51+274912.8 confirmation
  54. Fermi trigger No 606918292: Global MASTER-Net observations report
  55. GRB 200325B: Swift ToO observations
  56. IPN triangulation of GRB 200325A (short)
  57. Fermi trigger No 606799116: Global MASTER-Net observations report
  58. GRB 200326A: Fermi GBM Final Real-time Localization
  59. GRB 200325B: MASTERt OT detection
  60. GRB 200324A: AROMA-N Optical Observation
  61. GRB 200325A: Swift/BAT detection and probable arcminute localization of a short GRB from GUANO
  62. GRB 200324A, Swift-BAT refined analysis
  63. Fermi trigger No 606840801: Global MASTER-Net observations report
  64. GRB 200325B: Fermi GBM Final Real-time Localization
  65. GRB 200324A:: TSHAO optical upper limit
  66. GRB 200324A: Swift/UVOT Upper Limits
  67. GRB 200325A: AstroSat CZTI detection
  68. GRB 200325A: AGILE/MCAL observations
  69. GRB 200324A: LCO Optical Upper Limit
  70. GRB 200324A: Swift-XRT refined Analysis
  71. GRB 200325A: Fermi GBM Final Real-time Localization
  72. GRB 200324A: Konkoly Obs. optical upper limit
  73. GRB 200324A: NOT optical upper limit
  74. GRB 200324A: Tautenburg observations
  75. GRB 200324A: Enhanced Swift-XRT position
  76. GRB 200324A:MITSuME Akeno optical upper limits
  77. GRB 200324A: Swift detection of a burst
  78. Swift GRB200324.69: Global MASTER-Net observations report
  79. GRB 200318A : AstroSat CZTI detection
  80. GRB 200317A: AstroSat CZTI detection
  81. Fermi trigger No 606681997: Global MASTER-Net observations report
  82. GRB 200323A: Fermi GBM detection
  83. GRB 200323A: Fermi GBM Final Real-time Localization
  84. LIGO/Virgo S200316bj: no counterpart candidate in SVOM/GWAC-F30 observations
  85. Fermi trigger No 606614927: Global MASTER-Net observations report
  86. LIGO/Virgo S200316bj: Updated Sky Localization and EM Bright Classification
  87. GRB 200320B: MAXI/GSC detection
  88. GRB 200320A: Fermi GBM Final Localization
  89. GRB 200319A: BALROG localization (Fermi Trigger 606296685 / GRB 200319323)
  90. GRB 200319A: Fermi GBM Final Real-time Localization
  91. Chandra observations of GW170817 at 2.5 years since merger (All epochs 4 of 4)
  92. Fermi trigger No 606263732: Global MASTER-Net observations report
  93. GRB 200318A: Fermi GBM Final Real-time Localization
  94. GW170817: Continued X-ray emission detected with Chandra at 940 days post-merger
  95. LIGO/Virgo S200316bj : No significant candidates in TAROT - FRAM - GRANDMA observations.
  96. LIGO/Virgo S200316bj: Upper limits from Insight-HXMT/HE observations
  97. Konus-Wind observation of GRB 200313B
  98. LIGO/Virgo S200316bj: no counterpart candidate in SVOM/GWAC observations
  99. LIGO/Virgo S200316bj: Upper limits from CALET observations
  100. LIGO/Virgo S200316bj: No neutrino candidates at Pierre Auger Observatory

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