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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 200219C: VLA Detection
  2. GRB 200303A: Swift detection of a burst
  3. Swift GRB200303.11: Global MASTER-Net observations report
  4. Fermi trigger No 604895668: Global MASTER-Net observations report
  5. GRB 200303A: Fermi GBM Final Real-time Localization
  6. LIGO/Virgo S200224ca: No counterpart candidates in TOROS observations
  7. LIGO/Virgo S200302c: Updated Sky Localization
  8. LIGO/Virgo S200302c: No significant counterpart candidates in Fermi-LAT observations
  9. LIGO/Virgo S200302c: No counterpart candidates in KAIT observations
  10. LIGO/Virgo S200302c: no counterpart candidates in the Swift/BAT observations
  11. LIGO/Virgo S200224ca: Transient found in Swift/UVOT counterpart search
  12. LIGO/Virgo S200302c: No counterpart candidates in HAWC observations
  13. LIGO/Virgo S200302c: Upper limits from Fermi-GBM Observations
  14. LIGO/Virgo S200302c: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  15. LIGO/Virgo S200302c : no neutrino counterpart candidate in ANTARES search
  16. LIGO/Virgo S200302c: upper limits from AGILE/MCAL observations
  17. LIGO/Virgo S200225q: AstroSat CZTI upper limits
  18. LIGO/Virgo S200219ac: AstroSat CZTI upper limits
  19. LIGO/Virgo S200302c: Coverage and upper limits from MAXI/GSC observations
  20. LIGO/Virgo S200302c: Upper limits from IceCube neutrino searches
  21. LIGO/Virgo S200302c: Identification of a GW compact binary merger candidate
  22. LIGO/Virgo S200302c: Global MASTER-Net observations report
  23. GRB 200228B: Mondy, TSHAO, AbAO and CrAO optical observations, afterglow candidate
  24. LIGO/Virgo S200225q : No significant candidates in TAROT - FRAM - GRANDMA observations.
  25. GRB 200228B: LCO Optical Upper Limit
  26. GRB 200228B: Swift-BAT refined analysis
  27. GRB 200228B: RATIR Optical Observations
  28. GRB 200228B: Liverpool Telescope imaging
  29. GRB 200228B: Swift-XRT refined Analysis
  30. Swift GRB 200228B: Global MASTER-Net observations report
  31. GRB 200228B: Swift/UVOT Upper Limits
  32. GRB 200228B: RATIR Optical Observations
  33. GRB 200228B: Fermi GBM observation
  34. GRB 200227A: RATIR Optical Observations
  35. IceCube-200227A: Upper limits from a search for additional neutrino events in IceCube
  36. GRB 200228B: KAIT Optical Upper Limit
  37. LIGO/Virgo S200224ca: Updated Sky Localization and EM Bright Classification
  38. GRB 200228C: Insight-HXMT/HE detection
  39. GRB 200228A: Fermi GBM observation
  40. GRB 200228A: Swift/BAT detection and arcminute localization from GUANO
  41. LIGO/Virgo S200213t: No significant EM counterparts identified from continued GECKO observation of host galaxy candidates
  42. GRB 200227A: Mondy optical upper limit
  43. GRB 200228B: Enhanced Swift-XRT position
  44. Fermi-LAT Gamma-ray Observations of IceCube-200227A
  45. GRB 200228B: Swift detection of a burst
  46. GRB 200228B: Fermi GBM Final Real-time Localization
  47. Fermi trigger No 604565918: Global MASTER-Net observations report
  48. GRB 200227A: Insight-HXMT/HE detection
  49. IceCube-200227A : Upper limits from Insight-HXMT/HE observations
  50. GRB 200227A: Swift-XRT refined Analysis
  51. GRB 200228A: BALROG localization (Fermi Trigger 604565918 / GRB 200228291)
  52. GRB 200228A: Fermi GBM Final Real-time Localization
  53. GRB 200227A: Swift-BAT refined analysis
  54. GRB 200219A: ATCA 5/9 GHz radio observations
  55. GRB 200227A: Swift/UVOT Upper Limits
  56. GRB 200227A: Enhanced Swift-XRT position
  57. HAWC-200216A: No Neutrino Counterpart in ANTARES Search
  58. IceCube-200227A: Upper limits from Fermi-GBM Observations
  59. GRB 200224A: Mondy optical upper limit
  60. GRB 200227A: Fermi GBM observation
  61. LIGO/Virgo S200224ca : No significant candidates in TAROT - FRAM - GRANDMA observations
  62. IceCube-200227A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  63. GRB 200227A: MITSuME Akeno optical upper limit
  64. IceCube-200227A: IceCube observation of a high-energy neutrino candidate event
  65. GRB 200227A: Swift detection of a burst
  66. GRB 200227A: Fermi GBM Final Real-time Localization
  67. LIGO/Virgo S200225q: Not observable by CALET
  68. LIGO/Virgo S200224ca: Upper limits from CALET observations.
  69. LIGO/Virgo S200224car: GRAWITA VST-ESO PARANAL observations.
  70. LIGO/Virgo S200225q: Updated Sky Localization
  71. Konus-Wind observation of GRB 200219C
  72. LIGO/Virgo S200224ca: DESGW Optical counterpart candidates from DECam
  73. Konus-Wind observation of GRB 200219A
  74. LIGO/Virgo S200219ac: Upper limits from Konus-Wind observations
  75. LIGO/Virgo S200213t: Upper limits from Konus-Wind observations
  76. LIGO/Virgo S200208q: Upper limits from Konus-Wind observations
  77. GRB 200224A: Calar Alto 2.2m optical afterglow detection
  78. LIGO/Virgo S200225q: no counterpart candidate in SVOM/GWAC observations
  79. LIGO/Virgo S200225q: Upper limits from Insight-HXMT/HE observations
  80. LIGO/Virgo S200224ca: Upper limits from Insight-HXMT/HE observations
  81. GRB 200219A: Chandra rapid ToO upper limit
  82. LIGO/Virgo S200225q: no counterpart candidates in the Swift/BAT observations
  83. LIGO/Virgo S200224ca: no counterpart candidates in the Swift/BAT observations
  84. GRB 200224B: DDOTI/OAN optical observations report
  85. LIGO/Virgo S200219ac: Updated Sky Localization
  86. LIGO/Virgo S200224ca: No counterpart candidates in KAIT observations
  87. LIGO/Virgo S200224ca: No Counterparts in DDOTI/OAN Optical Observations
  88. LIGO/Virgo S200224ca: GRAWITA-Campo Imperatore observations.
  89. IPN triangulation of GRB 200221A (short)
  90. LIGO/Virgo S200225q: Upper limits from Fermi-GBM Observations
  91. Fermi trigger No 604231129: Global MASTER-Net observations report
  92. LIGO/Virgo S200225q: No counterpart candidates in Fermi-LAT observations
  93. LIGO/Virgo S200225q: upper limits from AGILE/GRID observations
  94. LIGO/Virgo S200224ca: Subaru/Hyper Suprime-Cam follow-up observations
  95. LIGO/Virgo S200225q: upper limits from AGILE/MCAL observations
  96. LIGO/Virgo S200225q: Upper limits from IceCube neutrino searches
  97. LIGO/Virgo S200225q: No counterpart candidates in HAWC observations
  98. LIGO/Virgo S200225q : no neutrino counterpart candidate in ANTARES search
  99. LIGO/Virgo S200225q: Global MASTER-Net observations report
  100. LIGO/Virgo S200224ca: No counterpart candidates in Fermi-LAT observations

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