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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"

24818 results found.

  1. Chandra observations of GW170817 at 2.5 years since merger (All epochs 4 of 4)
  2. GW170817: Continued X-ray emission detected with Chandra at 940 days post-merger
  3. LIGO/Virgo S200316bj : No significant candidates in TAROT - FRAM - GRANDMA observations.
  4. LIGO/Virgo S200316bj: Upper limits from Insight-HXMT/HE observations
  5. Konus-Wind observation of GRB 200313B
  6. LIGO/Virgo S200316bj: no counterpart candidate in SVOM/GWAC observations
  7. LIGO/Virgo S200316bj: No neutrino candidates at Pierre Auger Observatory
  8. LIGO/Virgo S200316bj: No counterpart candidates in Fermi-LAT observations
  9. LIGO/Virgo S200316bj: No Counterparts in DDOTI/OAN Optical Observations
  10. LIGO/Virgo S200316bj: no counterpart candidates in the Swift/BAT observations
  11. LIGO/Virgo S200213t: Continued Swift UVOT and XRT observations of ZTF20aamvmzj (AT2020cja)
  12. LIGO/Virgo S200316bj: No counterpart candidates in INTEGRAL SPI-ACS, and IBIS prompt observation
  13. LIGO/Virgo S200316bj: upper limits from AGILE/GRID observations
  14. LIGO/Virgo S200316bj: upper limits from AGILE/MCAL observations
  15. LIGO/Virgo S200316bj: Upper limits from Fermi-GBM Observations
  16. LIGO/Virgo S200316bj: Coverage and upper limits from MAXI/GSC observations
  17. LIGO/Virgo S200316bj : no neutrino counterpart candidate in ANTARES search
  18. LIGO/Virgo S200316bj: Upper limits from IceCube neutrino searches
  19. LIGO/Virgo S200316bj: Identification of a GW compact binary merger candidate
  20. SGR Swift J1818.0-1607: Swift-BAT refined analysis
  21. GRB 200313A: Fermi GBM detection
  22. LIGO/Virgo S200311bg: Updated Sky Localization and EM Bright Classification
  23. GRB 200313A: BALROG localization (Fermi Trigger 605756501 / GRB 200313071)
  24. Swift GRB200312.89: Global MASTER-Net observations report
  25. Swift-BAT trigger 960986: Swift detection of a new SGR Swift J1818.0-1607
  26. LIGO/Virgo S200311bg: No significant counterpart candidates in Fermi-LAT observations
  27. IPN triangulation of GRB 200307A (short)
  28. LIGO/Virgo S200311bg: Coverage and upper limits from MAXI/GSC observations
  29. LIGO/Virgo S200311bg: No counterpart candidates in INTEGRAL SPI-ACS,prompt observation
  30. LIGO/Virgo S200311bg: Upper limits from IceCube neutrino searches
  31. LIGO/Virgo S200311bg: Identification of a GW compact binary merger candidate
  32. Chandra observations of GW170817 ~ 2.5 years since merger (epoch 1 of 4)
  33. GRB 200307A: Updated localization from Fermi/GBM and Swift/BAT-GUANO
  34. GRB 200310A: MAXI/GSC detection
  35. GRB 200306C: Swift-BAT refined analysis
  36. GRB 200306C: Swift/UVOT Detection
  37. GRB 200306A: Swift/UVOT Upper Limits
  38. GRB 200306C: Calar Alto 2.2m upper limit
  39. GRB 200306A: Swift-BAT refined analysis
  40. GRB 200306C: Swift-XRT refined Analysis
  41. GRB 200306A: RATIR Optical Observations
  42. GRB 200306C: Enhanced Swift-XRT position
  43. GRB 200306C: VIRT optical upper limits
  44. GRB200306C: First Hour Liverpool Telescope Observations
  45. GRB 200306C: LCO Optical Upper Limits
  46. GRB 200306C: SAO RAS observations of OT
  47. GRB 200306C: GOTO upper limits
  48. GRB 200306A: Swift-XRT refined Analysis
  49. LIGO/Virgo S200302c: No notable candidates in GOTO imaging
  50. GRB 200306C: BOOTES-1 detection of the optical afterglow
  51. GRB 200306C: Swift detection of a burst with an optical counterpart
  52. Swift GRB200306.95: Global MASTER-Net OT detection
  53. Swift GRB200306.95: Global MASTER-Net OT detection
  54. LIGO/Virgo S200302c : No significant candidates in FRAM - TAROT - GRANDMA observations.
  55. GRB 200306A: Potential LCO Optical Afterglow Detection
  56. GRB 200306A: Swift detection of a burst
  57. LIGO/Virgo S200225q: No notable candidates in GOTO imaging
  58. LIGO/Virgo S200302c: AstroSat CZTI upper limits
  59. GRB 200303A: Fermi GBM observation
  60. GRB200210A AstroSat observations
  61. GRB 200303A: Swift-XRT refined Analysis
  62. GRB 200303A: Swift-BAT refined analysis
  63. LIGO/Virgo S200302c: Upper limits from Insight-HXMT/HE observations
  64. GRB 200303A: Swift/UVOT Upper Limits
  65. GRB 200303A: GOTO observations upper limit
  66. GRB 200303A: Optical limit from CAHA
  67. GRB 200303A: Enhanced Swift-XRT position
  68. GRB 200303A: Swift detection of a burst
  69. LIGO/Virgo S200302c: Updated Sky Localization
  70. LIGO/Virgo S200302c: No significant counterpart candidates in Fermi-LAT observations
  71. LIGO/Virgo S200302c: no counterpart candidates in the Swift/BAT observations
  72. LIGO/Virgo S200224ca: Transient found in Swift/UVOT counterpart search
  73. LIGO/Virgo S200302c: No counterpart candidates in HAWC observations
  74. LIGO/Virgo S200302c: Upper limits from Fermi-GBM Observations
  75. LIGO/Virgo S200302c: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  76. LIGO/Virgo S200302c : no neutrino counterpart candidate in ANTARES search
  77. LIGO/Virgo S200302c: upper limits from AGILE/MCAL observations
  78. LIGO/Virgo S200225q: AstroSat CZTI upper limits
  79. LIGO/Virgo S200219ac: AstroSat CZTI upper limits
  80. LIGO/Virgo S200302c: Coverage and upper limits from MAXI/GSC observations
  81. LIGO/Virgo S200302c: Upper limits from IceCube neutrino searches
  82. LIGO/Virgo S200302c: Identification of a GW compact binary merger candidate
  83. GRB 200228B: Mondy, TSHAO, AbAO and CrAO optical observations, afterglow candidate
  84. LIGO/Virgo S200225q : No significant candidates in TAROT - FRAM - GRANDMA observations.
  85. GRB 200228B: LCO Optical Upper Limit
  86. GRB 200228B: Swift-BAT refined analysis
  87. GRB 200228B: RATIR Optical Observations
  88. GRB 200228B: Liverpool Telescope imaging
  89. GRB 200228B: Swift-XRT refined Analysis
  90. GRB 200228B: Swift/UVOT Upper Limits
  91. GRB 200228B: RATIR Optical Observations
  92. GRB 200228B: Fermi GBM observation
  93. GRB 200227A: RATIR Optical Observations
  94. IceCube-200227A: Upper limits from a search for additional neutrino events in IceCube
  95. LIGO/Virgo S200224ca: Updated Sky Localization and EM Bright Classification
  96. GRB 200228C: Insight-HXMT/HE detection
  97. GRB 200228A: Fermi GBM observation
  98. GRB 200227A: Mondy optical upper limit
  99. GRB 200228B: Enhanced Swift-XRT position
  100. Fermi-LAT Gamma-ray Observations of IceCube-200227A

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