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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 200306C: BOOTES-1 detection of the optical afterglow
  2. GRB 200306C: FRAM-ORM afterglow detection
  3. Swift GRB200306.95: Global MASTER-Net observations report
  4. GRB 200306C: Swift detection of a burst with an optical counterpart
  5. Swift GRB200306.95: Global MASTER-Net OT detection
  6. Swift GRB200306.95: Global MASTER-Net OT detection
  7. GRB 200306B: Fermi GBM Final Real-time Localization
  8. LIGO/Virgo S200302c : No significant candidates in FRAM - TAROT - GRANDMA observations.
  9. GRB 200306A: Potential LCO Optical Afterglow Detection
  10. GRB 200306A: Swift detection of a burst
  11. Swift GRB200306.01: Global MASTER-Net observations report
  12. GRB 200228B: continued optical observations
  13. LIGO/Virgo S200225q: No notable candidates in GOTO imaging
  14. Konus-Wind observation of GRB200303A
  15. LIGO/Virgo S200302c: AstroSat CZTI upper limits
  16. GRB 200303A: Fermi GBM observation
  17. GRB200210A AstroSat observations
  18. GRB 200303A: Swift-XRT refined Analysis
  19. GRB 200303A: Swift-BAT refined analysis
  20. LIGO/Virgo S200302c: Upper limits from Insight-HXMT/HE observations
  21. GRB 200303A: NOT optical observations
  22. GRB 200303A: Swift/UVOT Upper Limits
  23. GRB 200303A: FRAM-ORM optical limit
  24. LIGO/Virgo S200303ba: Retraction of GW compact binary merger candidate
  25. GRB 200219A: AstroSat CZTI detection
  26. GRB 200303A: GOTO observations upper limit
  27. GRB 200303A: Optical limit from CAHA
  28. GRB 200228A: AstroSat CZTI detection
  29. GRB 200303A: CALET Gamma-Ray Burst Monitor detection
  30. GRB 200303A: Enhanced Swift-XRT position
  31. LIGO/Virgo S200302c: No transient candidates in CALET observations
  32. GRB 200219C: VLA Detection
  33. GRB 200303A: Swift detection of a burst
  34. Swift GRB200303.11: Global MASTER-Net observations report
  35. Fermi trigger No 604895668: Global MASTER-Net observations report
  36. GRB 200303A: Fermi GBM Final Real-time Localization
  37. LIGO/Virgo S200224ca: No counterpart candidates in TOROS observations
  38. LIGO/Virgo S200302c: Updated Sky Localization
  39. LIGO/Virgo S200302c: No significant counterpart candidates in Fermi-LAT observations
  40. LIGO/Virgo S200302c: No counterpart candidates in KAIT observations
  41. LIGO/Virgo S200302c: no counterpart candidates in the Swift/BAT observations
  42. LIGO/Virgo S200224ca: Transient found in Swift/UVOT counterpart search
  43. LIGO/Virgo S200302c: No counterpart candidates in HAWC observations
  44. LIGO/Virgo S200302c: Upper limits from Fermi-GBM Observations
  45. LIGO/Virgo S200302c: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  46. LIGO/Virgo S200302c : no neutrino counterpart candidate in ANTARES search
  47. LIGO/Virgo S200302c: upper limits from AGILE/MCAL observations
  48. LIGO/Virgo S200225q: AstroSat CZTI upper limits
  49. LIGO/Virgo S200219ac: AstroSat CZTI upper limits
  50. LIGO/Virgo S200302c: Coverage and upper limits from MAXI/GSC observations
  51. LIGO/Virgo S200302c: Upper limits from IceCube neutrino searches
  52. LIGO/Virgo S200302c: Identification of a GW compact binary merger candidate
  53. LIGO/Virgo S200302c: Global MASTER-Net observations report
  54. GRB 200228B: Mondy, TSHAO, AbAO and CrAO optical observations, afterglow candidate
  55. LIGO/Virgo S200225q : No significant candidates in TAROT - FRAM - GRANDMA observations.
  56. GRB 200228B: LCO Optical Upper Limit
  57. GRB 200228B: Swift-BAT refined analysis
  58. GRB 200228B: RATIR Optical Observations
  59. GRB 200228B: Liverpool Telescope imaging
  60. GRB 200228B: Swift-XRT refined Analysis
  61. Swift GRB 200228B: Global MASTER-Net observations report
  62. GRB 200228B: Swift/UVOT Upper Limits
  63. GRB 200228B: RATIR Optical Observations
  64. GRB 200228B: Fermi GBM observation
  65. GRB 200227A: RATIR Optical Observations
  66. IceCube-200227A: Upper limits from a search for additional neutrino events in IceCube
  67. GRB 200228B: KAIT Optical Upper Limit
  68. LIGO/Virgo S200224ca: Updated Sky Localization and EM Bright Classification
  69. GRB 200228C: Insight-HXMT/HE detection
  70. GRB 200228A: Fermi GBM observation
  71. GRB 200228A: Swift/BAT detection and arcminute localization from GUANO
  72. LIGO/Virgo S200213t: No significant EM counterparts identified from continued GECKO observation of host galaxy candidates
  73. GRB 200227A: Mondy optical upper limit
  74. GRB 200228B: Enhanced Swift-XRT position
  75. Fermi-LAT Gamma-ray Observations of IceCube-200227A
  76. GRB 200228B: Swift detection of a burst
  77. GRB 200228B: Fermi GBM Final Real-time Localization
  78. Fermi trigger No 604565918: Global MASTER-Net observations report
  79. GRB 200227A: Insight-HXMT/HE detection
  80. IceCube-200227A : Upper limits from Insight-HXMT/HE observations
  81. GRB 200227A: Swift-XRT refined Analysis
  82. GRB 200228A: BALROG localization (Fermi Trigger 604565918 / GRB 200228291)
  83. GRB 200228A: Fermi GBM Final Real-time Localization
  84. GRB 200227A: Swift-BAT refined analysis
  85. GRB 200219A: ATCA 5/9 GHz radio observations
  86. GRB 200227A: Swift/UVOT Upper Limits
  87. GRB 200227A: Enhanced Swift-XRT position
  88. HAWC-200216A: No Neutrino Counterpart in ANTARES Search
  89. IceCube-200227A: Upper limits from Fermi-GBM Observations
  90. GRB 200224A: Mondy optical upper limit
  91. GRB 200227A: Fermi GBM observation
  92. LIGO/Virgo S200224ca : No significant candidates in TAROT - FRAM - GRANDMA observations
  93. IceCube-200227A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  94. GRB 200227A: MITSuME Akeno optical upper limit
  95. IceCube-200227A: IceCube observation of a high-energy neutrino candidate event
  96. GRB 200227A: Swift detection of a burst
  97. GRB 200227A: Fermi GBM Final Real-time Localization
  98. LIGO/Virgo S200225q: Not observable by CALET
  99. LIGO/Virgo S200224ca: Upper limits from CALET observations.
  100. LIGO/Virgo S200224car: GRAWITA VST-ESO PARANAL observations.

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