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

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