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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. LIGO/Virgo S200114f: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  2. LIGO/Virgo S200114f : no neutrino counterpart candidate in ANTARES search
  3. LIGO/Virgo S200114f: Candidates from the Zwicky Transient Facility
  4. LIGO/Virgo S200112r: Upper limits from CALET observations
  5. LIGO/Virgo S200114f: Upper limits from Fermi-GBM Observations
  6. LIGO/Virgo S200114f: Coverage and upper limits from MAXI/GSC observations
  7. Fermi trigger No 600666048: Global MASTER-Net observations report
  8. GRB 200114A: BALROG localization (Fermi Trigger 600666048 / GRB 200114153)
  9. GRB 200114A: Fermi GBM Final Real-time Localization
  10. LIGO/Virgo S200114f: Identification of a GW unmodeled transient candidate
  11. LIGO/Virgo S200114f: No counterpart candidates in HAWC observations
  12. LIGO/Virgo S200114f: Upper limits from IceCube neutrino searches
  13. LIGO/Virgo S200114f: Global MASTER-Net observations report
  14. LIGO/Virgo S200112r: Upper limits from Insight-HXMT/HE observations
  15. GRB 200112A: AstroSat CZTI detection
  16. Fermi-LAT Gamma-ray Observations of IceCube-200109A and detection of a possible new gamma-ray source, Fermi J1055.8+1034
  17. LIGO/Virgo 200112r: No counterpart candidates in Fermi-LAT observations
  18. LIGO/Virgo S200112r: not observable by Fermi-GBM
  19. LIGO/Virgo S200112r: not observable by Fermi-GBM
  20. LIGO/Virgo S200112r: upper limits from AGILE/GRID observations
  21. LIGO/Virgo S200112r: Swift/BAT in the South Atlantic Anomaly
  22. LIGO/Virgo S200112r: upper limits from AGILE/MCAL observations
  23. LIGO/Virgo S200112r: INTEGRAL was inactive at the time of the event
  24. LIGO/Virgo S200112r: Coverage and upper limits from MAXI/GSC observations
  25. LIGO/Virgo S200112r: No counterpart candidates in HAWC observations
  26. LIGO/Virgo S200112r : no neutrino counterpart candidate in ANTARES search
  27. LIGO/Virgo S200112r: Global MASTER-Net observations report
  28. LIGO/Virgo S200112r: Upper limits from IceCube neutrino searches
  29. LIGO/Virgo S200112r: Identification of a GW compact binary merger candidate
  30. GRB 200111A: Insight-HXMT/HE detection
  31. GRB 200112A: BALROG localization (Fermi Trigger 600525396 / GRB 200112525)
  32. Fermi trigger No 600525396: Global MASTER-Net observations report
  33. GRB 200112A: Fermi GBM Final Real-time Localization
  34. GRB 200109A: Insight-HXMT/HE detection
  35. IceCube 200109A: No significant detection in HAWC
  36. Fermi-LAT ANTARES coincidence: No significant detection in HAWC
  37. IceCube-200109A: Upper limits from a search for additional neutrino events in IceCube
  38. Fermi trigger No 600448273: Global MASTER-Net observations report
  39. GRB 200111A: Fermi GBM Final Real-time Localization
  40. IceCube-200107A: Upper limits from a search for additional neutrino events in IceCube
  41. LIGO/Virgo S200105ae: AT2020pq, AT2020ps and AT2020pv 10.4m GTC spectroscopy
  42. LIGO/Virgo S200105ae: AT2020pp and AT2020py 10.4m GTC spectroscopy
  43. LIGO/Virgo S200105ae: AT2020oo 10.4m GTC spectroscopy
  44. IceCube-200109A: Swift-XRT and UVoT Follow-up Observations
  45. ANTARES 200108A: No detection by Swift-XRT
  46. IceCube-200109A: INTEGRAL was inactive at the time of the event
  47. IceCube-200109A: Upper limits from Fermi-GBM Observations
  48. IceCube-200109A: IceCube observation of a high-energy neutrino candidate event
  49. IceCube Alert 200109.99: Global MASTER-Net observations report
  50. IceCube Alert 200109.99: Global MASTER-Net observations report
  51. GRB 200107B: Swift/UVOT Observations
  52. GRB 200109A: Swift-BAT refined analysis
  53. Swift follow-up observations of IceCube-200107A: Identification of X-ray high state for 4FGL J0955.1+3551
  54. GRB 200109A: Swift/UVOT Upper Limits
  55. GRB 200109A: Fermi GBM observation
  56. LIGO/Virgo S200105ae: Updated Sky Localization and EM-Bright Probabilities
  57. LIGO/Virgo S200105ae : No significant candidates in TAROT - FRAM - GRANDMA observations.
  58. LIGO/Virgo S200105ae: Gaia Photometric Alerts transient candidate
  59. GRB 200107B: Swift-XRT refined Analysis
  60. Fermi-LAT ANTARES coincidence /ANTARES alert 200108.39: MASTER alert and inspect observation
  61. Fermi-LAT ANTARES coincidence: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  62. GRB 200109A: Swift-XRT refined Analysis
  63. GRB 200109A: Enhanced Swift-XRT position
  64. Fermi trigger No 600227156: Global MASTER-Net observations report
  65. Swift GRB200109.07: Global MASTER-Net observations report
  66. GRB 200109A: Swift detection of a burst
  67. GRB 200109A: Fermi GBM Final Real-time Localization
  68. Fermi-LAT ANTARES coincidence: Upper limits from Fermi-GBM Observations
  69. LIGO/Virgo S200105ae: GW data still under study
  70. Fermi-LAT ANTARES coincidence
  71. LIGO/Virgo S200105ae: Candidates from the Zwicky Transient Facility
  72. Swift GRB 200107B: Global MASTER-Net observations report
  73. GRB 200107B: Fermi GBM observation
  74. GRB 200107B: Swift-BAT refined analysis
  75. Fermi-LAT Gamma-ray Observations of IceCube-200107A
  76. IceCube-200107A: No significant detection in HAWC
  77. IceCube-200107A: No candidates from the Zwicky Transient Facility
  78. IceCube-200107A: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  79. LIGO/Virgo S200108v: Retraction of GW compact binary merger candidate
  80. LIGO/Virgo S200105ae: Upper limits from CALET observations.
  81. GRB 200101A: CALET Gamma-Ray Burst Monitor detection
  82. LIGO/Virgo S200105ae: Upper Limits from the Zwicky Transient Facility
  83. GRB 200107B: Swift detection of a burst
  84. Swift GRB200107.81: Global MASTER-Net OT detection
  85. GRB 200107B: Fermi GBM Final Real-time Localization
  86. Swift GRB200107.81: Global MASTER-Net observations report
  87. LIGO/Virgo S200105ae: Further study ongoing for GW compact binary merger candidate
  88. IceCube-200107A: Upper limits from Fermi-GBM Observations
  89. IceCube-200107A: IceCube observation of a high-energy neutrino candidate event
  90. LIGO/Virgo 200105ae: No counterpart candidates in Fermi-LAT observations
  91. GRB 191228A: FRAM-ORM optical limit
  92. LIGO/Virgo S200105ae: AstroSat CZTI upper limits
  93. LIGO/Virgo S200105ae: Coverage and upper limits from MAXI/GSC observations
  94. LIGO/Virgo S200105ae: No counterpart candidates in HAWC observations
  95. LIGO/Virgo S200105ae: no counterpart candidates in the Swift/BAT observations
  96. LIGO/Virgo S200105ae: Upper limits from IceCube neutrino searches
  97. LIGO/Virgo S200105ae: not observable by AGILE-MCAL
  98. LIGO/Virgo S200105ae: Global MASTER-Net observations report
  99. LIGO/Virgo S200105ae: Upper limits from Fermi-GBM Observations
  100. LIGO/Virgo S200105ae: No counterpart candidates in INTEGRAL SPI-ACS prompt observation

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