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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 200629A: AstroSat CZTI detection
  2. GRB 200630A: Enhanced Swift-XRT position
  3. GRB 200630A: Swift detection of a burst
  4. Fermi trigger No 615174580: Global MASTER-Net observations report
  5. Fermi GRB 200629A: Global MASTER-Net observations report
  6. GRB 200629A: Fermi GBM Final Real-time Localization
  7. GRB 200629A: BALROG localization (Fermi Trigger 615127794 / GRB 200629535)
  8. GRB 200522A: Gemini North spectroscopy of the putative host galaxy
  9. Konus-Wind detection of short/hard GRB 200623B
  10. GRB 200623A: Further MMTCam Observations of XRT Source #3
  11. GRB 200625A: Fermi-LAT detection is likely a flare from PKS 1127-14
  12. GRB 200623A: LBT optical observations
  13. GRB 200623A : SMA observations at Swift/XRT Source #3
  14. Fermi GRB 200626A: Global MASTER-Net observations report
  15. GRB 200625A: Swift ToO observations
  16. GRB 200626A: Fermi GBM Final Real-time Localization
  17. Fermi GRB 200625A: Global MASTER-Net observations report
  18. GRB 200625A: Fermi GBM Final Real-time Localization
  19. Updated catalog of X-ray bursts of SGR J1935+2154 from Insight-HXMT observations
  20. GRB 200623A: MMT observations at XRT Source #3
  21. GRB 200623A: Swift/UVOT Upper Limits
  22. IPN triangulation of GRB 200623B (short)
  23. GRB 200623A: Swift-XRT observations
  24. GRB 200623A: OAJ deep multi-color imaging, XRT #2 is pre-detected
  25. GRB 200623A: TNG optical observations
  26. GRB 200623A: AbAO afterglow candidate within XRT #2
  27. GRB 200623A: Fermi GBM observation
  28. Fermi GRB 200623B: Global MASTER-Net observations report
  29. GRB 200623B: Fermi GBM Final Real-time Localization
  30. GRB 200623A: Correction to GCN 28013
  31. GRB 200623A: Swift ToO observations
  32. IceCube-200620A: No significant detection in HAWC
  33. GRB 200623A: Swift/BAT-GUANO detection and arcminute localization of a short GRB
  34. Fermi GRB 200623A: Global MASTER-Net observations report
  35. GRB 200623A: Fermi GBM Final Real-time Localization
  36. IceCube-200620A: Upper limits from a search for additional neutrino events in IceCube
  37. IceCube-200620A: INTEGRAL was inactive at the time of the event
  38. GRB 200622A: Fermi GBM Final Real-time Localization
  39. IceCube-200620A: MASTER previous detection of ZTF20abgvabi/AT2020ncr
  40. IceCube-200620A: not observable by Fermi-GBM
  41. IceCube-200620A: One Candidate Counterpart from the Zwicky Transient Facility
  42. Fermi-LAT Gamma-ray Observations of IceCube-200620A
  43. GRB 200613A: Continued CrAO optical observations
  44. IceCube-200620A: No ANTARES neutrino counterpart
  45. IceCube Alert 200620.13: Global MASTER-Net observations report
  46. GRB 200613A: CrAO optical observations
  47. GRB 200613A: R-band observations from HCT
  48. GRB 200613A: Further Liverpool Telescope observations
  49. IceCube-200620A - IceCube observation of a high-energy neutrino candidate track-like event
  50. GRB 200619C: Fermi GBM Final Real-time Localization
  51. Fermi GRB 200619B: Global MASTER-Net observations report
  52. GRB 200619B: AstroSat CZTI detection
  53. GRB 200619A: Fermi GBM observation
  54. Fermi trigger No 614239407: Global MASTER-Net observations report
  55. GRB 200619A: AGILE detection
  56. LIGO/Virgo MS200618aq: Retraction of a test binary neutron star candidate
  57. LIGO/Virgo MS200619bf: Retraction of a test binary neutron star candidate
  58. LIGO/Virgo MS200618bx: Retraction of a test binary neutron star candidate
  59. LIGO/Virgo MS200618bq: Retraction of a test binary neutron star candidate
  60. GRB 200619B: Fermi GBM Final Real-time Localization
  61. GRB 200619A: Insight-HXMT/HE detection
  62. Fermi trigger No 614226976: Global MASTER-Net observations report
  63. GRB 200613A: continued Kitab optical observations
  64. GRB 200613A: SAO RAS optical observations
  65. GRB 200617A: Insight-HXMT/HE detection
  66. IceCube-200530A - SN2020lls likely unrelated
  67. Swift/UVOT Observations of IceCube 200615A
  68. GRB 200613A: Mondy optical observations
  69. LIGO/Virgo MS200614ct: Identification of a test binary black hole candidate
  70. Fermi trigger No 614103490: Global MASTER-Net observations report
  71. Baksan Neutrino Observatory Alert 200617.47: Global MASTER-Net observations report
  72. GRB 200615B: CALET Gamma-Ray Burst Monitor detection
  73. Swift-XRT observations of IceCube 200615A
  74. IceCube-200615A: No significant detection in HAWC
  75. GRB 200613A: Jet-break from Xinglong-2.16m optical observations
  76. Fermi-LAT Gamma-ray Observations of IceCube-200615A
  77. IceCube-200614A: No significant detection in HAWC
  78. IceCube-200615A: Upper limits from a search for additional neutrino events in IceCube
  79. GRB 200616B: Fermi GBM Final Real-time Localization
  80. Fermi-LAT Gamma-ray Observations of IceCube-200614A and detection of a new gamma-ray source, Fermi J0202.8+3132
  81. LIGO/Virgo MS200615ce: Identification of a test binary black hole candidate
  82. GRB 200613A: CALET Gamma-Ray Burst Monitor detection
  83. LIGO/Virgo MS200614bz: Test Identification of a binary neutron star candidate
  84. GRB 200613A: MITSuME Akeno optical upper limits
  85. Fermi GRB 200616A: Global MASTER-Net observations report
  86. GRB 200615B: MAXI/GSC detection
  87. GRB 200616A: Fermi GBM Final Real-time Localization
  88. GRB 200613A: continued AbAO optical afterglow observations
  89. IceCube-200615A: Upper limits from Fermi-GBM Observations
  90. IceCube-200614A: Upper limits from a search for additional neutrino events in IceCube
  91. IceCube-200614A: not observable by Fermi-GBM
  92. IceCube-200615A: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  93. IceCube Alert 200615.62: Global MASTER-Net observations report
  94. IceCube-200614A: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  95. LIGO/Virgo MS200615h: Retraction of a test binary neutron star candidate
  96. IceCube-200615A: IceCube observation of a high-energy neutrino candidate event
  97. GRB 200613A: Continued Xinglong-2.16m optical observations
  98. Fermi GRB 200615A: Global MASTER-Net observations report
  99. GRB 200615A: Fermi GBM Final Real-time Localization
  100. Baksan Neutrino Observatory Alert 200614.34: Global MASTER-Net observations report

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