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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 160101A: MITSuME Akeno optical upper limits
  2. LIGO/Virgo G211117: MASTER OTs 26.XII.2015 - 01.I.2016
  3. LIGO/Virgo G211117: CSS/CRTS observations on 29/30 Dec 2015 UT
  4. GRB 160102A: Tiled Swift observations
  5. GRB 160102A: MAXI/GSC detection
  6. LIGO/Virgo G211117: La Silla - QUEST observations 2015 Dec 28 - 30
  7. GRB 160101B: Fermi-LAT detection
  8. GRB 160101B: Fermi GBM detection
  9. GRB 160101A: Swift/UVOT Detection
  10. GRB 160101A: Fermi GBM observation
  11. GRB 160101A: Swift-XRT afterglow detection
  12. GRB 160101A: Tiled Swift observations
  13. GRB 160101A: MAXI/GSC detection
  14. GRB 151227B: CALET Gamma-Ray Burst Monitor detection
  15. LIGO/Virgo G211117: Liverpool Telescope classification of EM candidates
  16. LIGO/Virgo G211117: FLOYDS Classification of SMTJ13331687-1607330 as a Two-Week-Old Type Ia Supernova
  17. LIGO/Virgo G211117: LBT follow-up imaging of iPTF15fhq
  18. GRB 151231B: Fermi GBM observation
  19. GRB 151231A: Fermi GBM observation
  20. LIGO/Virgo G211117: 44 transients from Pan-STARRS data during 2015-12-28/30
  21. Trigger 668949: Swift detection of V 404 Cyg
  22. LIGO/Virgo G211117: MAXI/GSC observations
  23. MASTER-NET observations of V404Cyg Swift Trigger 668877
  24. LIGO/Virgo G211117: Liverpool Telescope followup of EM candidates
  25. Konus-Wind observation of GRB 151227B
  26. LIGO/Virgo G211117: VLA follow-up
  27. LIGO/Virgo G211117: LBT Follow-up of iPTF15fen
  28. Trigger 668879: Swift detection of V 404 Cyg again
  29. Trigger 668877: Swift detection of V 404 Cyg
  30. LIGO/Virgo G211117: MAGIC very-high energy gamma-ray observations
  31. LIGO/Virgo G211117: INAF TNG follow-up of MASTER OT J020906.21+013800.1
  32. LIGO/Virgo G211117: OAO-WFC NIR follow-up observations
  33. IPN Triangulation of GRB 151227B
  34. GRB 151228A: Correction to GCN 18770
  35. LIGO/Virgo G211117: SkyMapper observations and transient candidate
  36. GRB 151228A: Swift-XRT refined Analysis
  37. V404Cyg Swift Trigger 668097: CrAO RT-22 radio observations
  38. LIGO/Virgo G211117: MASTER Observations of the 3 iPTF candidates
  39. V404Cyg Swift Trigger 668097: AbAO optical observations
  40. GRB 151228B: Swift/UVOT Detection
  41. GRB 151229A: MITSuME Akeno optical upper limits
  42. LIGO/Virgo G211117: Optical Observations with Kiso Schmidt telescope and KWFC
  43. LIGO/Virgo G211117: List of near-term future observation regions by Project Mini-GWAC of SVOM
  44. LIGO/Virgo G211117: iPTF Optical Transient Candidates
  45. GRB 151229A: MITSuME Okayama upper limits
  46. GRB 151229A Swift-BAT Spectral lag analysis
  47. LIGO/Virgo G211117: La Silla - QUEST observations 2015 Dec 28, 29
  48. GRB 151228B: MITSuME Akeno optical upper limits
  49. GRB 151229A: Swift-XRT refined Analysis
  50. GRB 151229A: Fermi GBM observation
  51. GRB 151228B: Fermi GBM observation
  52. GRB 151228A: Swift-BAT refined analysis
  53. GRB 151229A: Swift/UVOT observations
  54. GRB 151228B: Swift-BAT refined analysis
  55. GRB 151229A: Swift-BAT refined analysis
  56. GRB 151229A: Enhanced Swift-XRT position
  57. GRB 151228B: Swift-XRT refined Analysis
  58. LIGO/Virgo G211117: Further Swift-XRT sources
  59. GRB 151228A: MITSuME Akeno optical upper limits
  60. GRB 151228A: T60 observations
  61. GRB 151229A: Swift detection of a short burst
  62. LIGO/Virgo G211117: DESGW program observations with DECam
  63. GRB 151228B: Enhanced Swift-XRT position
  64. LIGO/Virgo G211117: Optical NIR observation with Kanata telescope
  65. LIGO/Virgo G211117: Fermi GBM Observations
  66. LIGO/Virgo G211117: Optical follow-up with Kanata telescope
  67. GRB 151228B: Swift detection of a burst with an optical detection
  68. LIGO/Virgo G211117: MASTER Observations and Inspection + OT
  69. LIGO/Virgo G211117: INTEGRAL was inactive at the time of the event
  70. GRB 151228A: Fermi GBM observation
  71. LIGO/Virgo G211117: Pan-STARRS1 observations 2015-12-28
  72. LIGO/Virgo G211117: INAF VST-ESO PARANAL observations
  73. LIGO/Virgo G211117: Further Swift-XRT sources
  74. LIGO/Virgo G211117: Swift-XRT sources
  75. GRB 151228A: Swift detection of a short burst
  76. LIGO/Virgo G211117: SWASP optical observations
  77. LIGO/Virgo G211117: MASTER possible OT detection at the begining of inspection
  78. LIGO/Virgo G211117: Identification of a GW CBC Candidate
  79. GRB 151227B: Fermi GBM detection
  80. GRB 151227A: Fermi GBM detection
  81. GRB 151212A iTelescope observation
  82. GRB 151225A: CALET Gamma-Ray Burst Monitor detection of a possible short GRB
  83. Konus-Wind observation of GRB 151222A
  84. Fermi GBM trigger 472694170/151224997 is not a GRB
  85. V404Cyg Swift Trigger 668097: TSHAO optical observations
  86. IPN Triangulation of GRB 151222A (short/hard)
  87. Fermi GBM trigger 151221730 is not a GRB
  88. V404Cyg Swift Trigger 668097: MASTER-Tunka optical wake up detection
  89. V404Cyg Swift Trigger 668097:
  90. Trigger 668097: Swift detection of V 404 Cyg
  91. GRB 151222A: Fermi GBM detection
  92. Fermi GBM trigger 151221690 is not a GRB
  93. Fermi GBM trigger 472271765/151220108 is not a GRB
  94. IBAS Alert 7313 is SGR J1935+2154
  95. GRB 151221A: INTEGRAL detection of a short burst or possible SGR
  96. Fermi GBM trigger 472166503/151218890 is not a GRB
  97. LIGO/Virgo G184098: Fermi-LAT search for high-energy gamma-ray counterpart
  98. GRB 151215A: TSHAO optical observations
  99. GRB151215A: Continued P60 Observations
  100. GRB 151212B: CALET Gamma-Ray Burst Monitor detection

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