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

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