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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. Fermi trigger No 606799116: Global MASTER-Net observations report
  2. GRB 200326A: Fermi GBM Final Real-time Localization
  3. GRB 200325B: MASTERt OT detection
  4. GRB 200324A: AROMA-N Optical Observation
  5. GRB 200325A: Swift/BAT detection and probable arcminute localization of a short GRB from GUANO
  6. GRB 200324A, Swift-BAT refined analysis
  7. Fermi trigger No 606840801: Global MASTER-Net observations report
  8. GRB 200325B: Fermi GBM Final Real-time Localization
  9. GRB 200324A:: TSHAO optical upper limit
  10. GRB 200324A: Swift/UVOT Upper Limits
  11. GRB 200325A: AstroSat CZTI detection
  12. GRB 200325A: AGILE/MCAL observations
  13. GRB 200324A: LCO Optical Upper Limit
  14. GRB 200324A: Swift-XRT refined Analysis
  15. GRB 200325A: Fermi GBM Final Real-time Localization
  16. GRB 200324A: Konkoly Obs. optical upper limit
  17. GRB 200324A: NOT optical upper limit
  18. GRB 200324A: Tautenburg observations
  19. GRB 200324A: Enhanced Swift-XRT position
  20. GRB 200324A:MITSuME Akeno optical upper limits
  21. GRB 200324A: Swift detection of a burst
  22. Swift GRB200324.69: Global MASTER-Net observations report
  23. GRB 200318A : AstroSat CZTI detection
  24. GRB 200317A: AstroSat CZTI detection
  25. Fermi trigger No 606681997: Global MASTER-Net observations report
  26. GRB 200323A: Fermi GBM detection
  27. GRB 200323A: Fermi GBM Final Real-time Localization
  28. LIGO/Virgo S200316bj: no counterpart candidate in SVOM/GWAC-F30 observations
  29. Fermi trigger No 606614927: Global MASTER-Net observations report
  30. LIGO/Virgo S200316bj: Updated Sky Localization and EM Bright Classification
  31. GRB 200320B: MAXI/GSC detection
  32. GRB 200320A: Fermi GBM Final Localization
  33. GRB 200319A: BALROG localization (Fermi Trigger 606296685 / GRB 200319323)
  34. GRB 200319A: Fermi GBM Final Real-time Localization
  35. Chandra observations of GW170817 at 2.5 years since merger (All epochs 4 of 4)
  36. Fermi trigger No 606263732: Global MASTER-Net observations report
  37. GRB 200318A: Fermi GBM Final Real-time Localization
  38. GW170817: Continued X-ray emission detected with Chandra at 940 days post-merger
  39. LIGO/Virgo S200316bj : No significant candidates in TAROT - FRAM - GRANDMA observations.
  40. LIGO/Virgo S200316bj: Upper limits from Insight-HXMT/HE observations
  41. Konus-Wind observation of GRB 200313B
  42. LIGO/Virgo S200316bj: no counterpart candidate in SVOM/GWAC observations
  43. LIGO/Virgo S200316bj: Upper limits from CALET observations
  44. LIGO/Virgo S200316bj: No neutrino candidates at Pierre Auger Observatory
  45. LIGO/Virgo S200316bj: No counterpart candidates in Fermi-LAT observations
  46. LIGO/Virgo S200316bj: No Counterparts in DDOTI/OAN Optical Observations
  47. LIGO/Virgo S200316bj: no counterpart candidates in the Swift/BAT observations
  48. LIGO/Virgo S200213t: Continued Swift UVOT and XRT observations of ZTF20aamvmzj (AT2020cja)
  49. Konus-Wind observation of GRB 200313A
  50. Konus-Wind observation of GRB 200311A
  51. LIGO/Virgo S200316bj: No counterpart candidates in INTEGRAL SPI-ACS, and IBIS prompt observation
  52. LIGO/Virgo S200316bj: upper limits from AGILE/GRID observations
  53. LIGO/Virgo S200316bj: upper limits from AGILE/MCAL observations
  54. LIGO/Virgo S200316bj: Upper limits from Fermi-GBM Observations
  55. Fermi trigger No 606098435: Global MASTER-Net observations report
  56. GRB 200317A: Fermi GBM Final Real-time Localization
  57. LIGO/Virgo S200316bj: Coverage and upper limits from MAXI/GSC observations
  58. LIGO/Virgo S200316bj : no neutrino counterpart candidate in ANTARES search
  59. LIGO/Virgo S200316bj: Upper limits from IceCube neutrino searches
  60. LIGO/Virgo S200316bj: Identification of a GW compact binary merger candidate
  61. LIGO/Virgo S200316bj: Global MASTER-Net observations report
  62. IPN triangulation of GRB 200313B (short)
  63. IPN triangulation of GRB 200313A
  64. SGR Swift J1818.0-1607: Swift-BAT refined analysis
  65. GRB 200313A: Fermi GBM detection
  66. LIGO/Virgo S200311bg: Updated Sky Localization and EM Bright Classification
  67. IPN triangulation of GRB 200311A
  68. Fermi trigger No 605789837: Global MASTER-Net observations report
  69. GRB 200313B: Fermi GBM Final Real-time Localization
  70. SGR Swift J1818.0-1607: BOOTES-4/MET optical limit
  71. GRB 200313A: BALROG localization (Fermi Trigger 605756501 / GRB 200313071)
  72. Fermi trigger No 605756501: Global MASTER-Net observations report
  73. Swift GRB200312.89: Global MASTER-Net observations report
  74. GRB 200313A: Fermi GBM Final Real-time Localization
  75. Swift-BAT trigger 960986: Swift detection of a new SGR Swift J1818.0-1607
  76. LIGO/Virgo S200311bg: Not observable by CALET
  77. GRB 200311A: AstroSat CZTI detection
  78. Fermi trigger No 605632577: Global MASTER-Net observations report
  79. LIGO/Virgo S200311bg: Swift/BAT in the South Atlantic Anomaly
  80. LIGO/Virgo S200311bg: No significant counterpart candidates in Fermi-LAT observations
  81. IPN triangulation of GRB 200307A (short)
  82. LIGO/Virgo S200224ca: DESGW Summary of DECam Observations
  83. GRB 200311A: AGILE/MCAL and scientific ratemeters observations
  84. LIGO/Virgo S200311bg: not observable by Fermi GBM
  85. GRB 200311A: Fermi GBM Final Real-time Localization
  86. LIGO/Virgo S200311bg: Coverage and upper limits from MAXI/GSC observations
  87. LIGO/Virgo S200311bg: not observable by AGILE at the event time
  88. LIGO/Virgo S200311bg: No counterpart candidates in INTEGRAL SPI-ACS,prompt observation
  89. LIGO/Virgo S200311bg: Upper limits from IceCube neutrino searches
  90. LIGO/Virgo S200311bg: Identification of a GW compact binary merger candidate
  91. Chandra observations of GW170817 ~ 2.5 years since merger (epoch 1 of 4)
  92. GRB 200307A: Updated localization from Fermi/GBM and Swift/BAT-GUANO
  93. GRB 200310A: MAXI/GSC detection
  94. GRB 200306C: ALMA 3mm upper limit
  95. GRB 200306C: Swift-BAT refined analysis
  96. GRB 200306C: Swift/UVOT Detection
  97. GRB 200306A: Swift/UVOT Upper Limits
  98. GRB 200308A: Fermi GBM Final Real-time Localization
  99. Fermi trigger No 605309224: Global MASTER-Net observations report
  100. GRB 200306C: Calar Alto 2.2m upper limit

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