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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 011121: Fourth Epoch of HST Imaging
  2. GRB020317: optical observations
  3. GRB020321 optical observations
  4. GRB020321: BeppoSAX/NFI Observations
  5. GRB020321: a faint BeppoSAX detection
  6. GRB020305: NIR observations
  7. GRB 020317 : KISO Optical Observations
  8. BeppoSAX ALERT: GRB020321, the "Springtime Burst"
  9. GRB020317 (=H1959): Localization by HETE of a Low Fluence GRB
  10. GRB 020305: Optical Observations
  11. GRB020317, optical observations
  12. GRB 020317: Optical observations
  13. GRB 011121: Third HST Epoch
  14. GRB020305: Properties of the Candidate Optical Afterglow
  15. GRB 011121: HST Observations reveal an intermediate-time multicolor
  16. GRB011121, possible supernova association
  17. GRB011130 (XRF011130) Second Epoch Chandra Observations
  18. GRB020305: Subaru Optical Observations
  19. GRB 020305: Optical observations
  20. XRF/GRB 011030 Images
  21. XRF/GRB 011030: Detection of the Probable Host Galaxy
  22. GRB 020305: Candidate optical afterglow
  23. Type Ic SN2002bl (SN/GRB?) Radio Observations
  24. GRB020305, optical observations
  25. GRB020305: Optical Observations
  26. IPN triangulation of GRB020305 (HETE 1939)
  27. GRB020305 (=H1939): Localization of a GRB by HETE
  28. GRB 020305: Optical observations
  29. HST Imaging of the afterglow and host of GRB 011121
  30. GRB 010921: HST Observations
  31. IPN detection and localization of Cygnus X-1 flares
  32. GRB020127: Further VLA Observations of Possible Counterparts
  33. RXTE Observations of SGR 1900+14
  34. IPN detection of further SGR1900+14 activity
  35. SGR1900+14 activity
  36. IPN/HETE Detection of Bursts from SGR1900+14
  37. IPN Upper Limits to a GRB Associated With SN2002ap
  38. GRB020124 BVRI field photometry
  39. GRB020127: Palomar and VLA Observations of Possible Counterparts
  40. GRB020127: Comparison of Chandra Epochs and Identification of Possible Counterparts
  41. SN2002ap (SN/GRB?) Echelle spectra
  42. SN2002ap (SN/GRB?) optical spectrographic observations
  43. GRB020127, WSRT radio observations
  44. GRB020127 Optical Observations
  45. SN 2002ap (SN/GRB?)
  46. SN 2002ap in M74
  47. SN2002ap (SN/GRB?) UBVRI Field Photometry
  48. GRB020127: Chandra Observations and Prospective Counterparts
  49. pre-SN2002ap (SN/GRB?) imaging of M74
  50. SN 2002ap (hypernova / GRB ??): special list on VSNET
  51. Type Ib/c SN2002ap (SN/GRB?)
  52. Type Ib/c SN2002ap (SN/GRB?) Radio Observations
  53. GRB020124, optical observations
  54. GRB020127: Optical observations
  55. GRB 020127, I-band observations starting 3.14-hr after the event
  56. IPN detection of further activity from SGR1806-20
  57. IPN triangulation of GRB020127 (=H1902)
  58. GRB020127 Optical Observations -- Erratum to GCN 1230
  59. GRB010921 Optical Observations
  60. GRB020127(=H1902): Localization of a Double-Peaked GRB by HETE
  61. GRB020124: Optical observations
  62. VLT observations of GRB 020124: The fading optical/near-infrared afterglow
  63. GRB020124: Optical observations
  64. GRB 020124: Optical observations
  65. GRB 020124 Optical Observations
  66. IPN triangulation of GRB020124 (HETE 1896)
  67. IPN observations of SGR1806-20
  68. GRB 020124: Optical afterglow
  69. GRB020124(=H1896): Localization of a Long GRB by HETE
  70. HETE 1896: Optical observations
  71. GRB optical counterpart candidate in GCN 1217 is M dwarf
  72. Possible optical counterpart to a GRB
  73. GRB011212, Optical Observations
  74. GRB011211: BeppoSAX/GRBM data
  75. Optical polarization observations for GRB011211
  76. GRB 011211: Detection of the Probable Host Galaxy
  77. GRB 011130 and GRB 011212 - Milagro GeV/TeV Observations
  78. Color indices of the afterglow of GRB011211
  79. GRB011212: Optical observations at Gunma
  80. GRB 011211, spectrum and optical photometry
  81. GRB 011130: Optical Observations of X-ray and Radio Sources
  82. GRB 011130, Radio/X-ray Comparison
  83. GRB011212: Optical observations
  84. GRB 011212: optical observation at Asiago
  85. GRB 011211: Evidence for an Optical Break
  86. GRB 011211: TNG Spectroscopic Observations
  87. optical follow-up of GRB(XRF) 011211
  88. GRB 011212: optical observation at Oslo (relayed)
  89. GRB 011211: Optical Spectroscopy
  90. GRB 011211, Optical Observations
  91. GRB011212, BVRI field photometry
  92. GRB011211, BVRI field photometry
  93. GRB011212: Optical observations
  94. GRB 011211: BVRi-band photometry
  95. GRB011212 (=H10001): An X-Ray Rich GRB Detected by HETE
  96. Fading of the optical source associated of XRF 011211
  97. XMM-Newton observation of GRB011211
  98. GRB 011211 Optical Observations: Likely Afterglow
  99. GRB011130 (=XRF011130): Further analysis of Chandra Target of
  100. GRB011211(=XRF011211): BeppoSAX refined positions

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