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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: HST Observations reveal an intermediate-time multicolor
  2. GRB011121, possible supernova association
  3. GRB011130 (XRF011130) Second Epoch Chandra Observations
  4. GRB020305: Subaru Optical Observations
  5. GRB 020305: Optical observations
  6. XRF/GRB 011030 Images
  7. XRF/GRB 011030: Detection of the Probable Host Galaxy
  8. GRB 020305: Candidate optical afterglow
  9. Type Ic SN2002bl (SN/GRB?) Radio Observations
  10. GRB020305, optical observations
  11. GRB020305: Optical Observations
  12. IPN triangulation of GRB020305 (HETE 1939)
  13. GRB020305 (=H1939): Localization of a GRB by HETE
  14. GRB 020305: Optical observations
  15. HST Imaging of the afterglow and host of GRB 011121
  16. GRB 010921: HST Observations
  17. IPN detection and localization of Cygnus X-1 flares
  18. GRB020127: Further VLA Observations of Possible Counterparts
  19. RXTE Observations of SGR 1900+14
  20. IPN detection of further SGR1900+14 activity
  21. SGR1900+14 activity
  22. IPN/HETE Detection of Bursts from SGR1900+14
  23. IPN Upper Limits to a GRB Associated With SN2002ap
  24. GRB020124 BVRI field photometry
  25. GRB020127: Palomar and VLA Observations of Possible Counterparts
  26. GRB020127: Comparison of Chandra Epochs and Identification of Possible Counterparts
  27. SN2002ap (SN/GRB?) Echelle spectra
  28. SN2002ap (SN/GRB?) optical spectrographic observations
  29. GRB020127, WSRT radio observations
  30. GRB020127 Optical Observations
  31. SN 2002ap (SN/GRB?)
  32. SN 2002ap in M74
  33. SN2002ap (SN/GRB?) UBVRI Field Photometry
  34. GRB020127: Chandra Observations and Prospective Counterparts
  35. pre-SN2002ap (SN/GRB?) imaging of M74
  36. SN 2002ap (hypernova / GRB ??): special list on VSNET
  37. Type Ib/c SN2002ap (SN/GRB?)
  38. Type Ib/c SN2002ap (SN/GRB?) Radio Observations
  39. GRB020124, optical observations
  40. GRB020127: Optical observations
  41. GRB 020127, I-band observations starting 3.14-hr after the event
  42. IPN detection of further activity from SGR1806-20
  43. IPN triangulation of GRB020127 (=H1902)
  44. GRB020127 Optical Observations -- Erratum to GCN 1230
  45. GRB010921 Optical Observations
  46. GRB020127(=H1902): Localization of a Double-Peaked GRB by HETE
  47. GRB020124: Optical observations
  48. VLT observations of GRB 020124: The fading optical/near-infrared afterglow
  49. GRB020124: Optical observations
  50. GRB 020124: Optical observations
  51. GRB 020124 Optical Observations
  52. IPN triangulation of GRB020124 (HETE 1896)
  53. IPN observations of SGR1806-20
  54. GRB 020124: Optical afterglow
  55. GRB020124(=H1896): Localization of a Long GRB by HETE
  56. HETE 1896: Optical observations
  57. GRB optical counterpart candidate in GCN 1217 is M dwarf
  58. Possible optical counterpart to a GRB
  59. GRB011212, Optical Observations
  60. GRB011211: BeppoSAX/GRBM data
  61. Optical polarization observations for GRB011211
  62. GRB 011211: Detection of the Probable Host Galaxy
  63. GRB 011130 and GRB 011212 - Milagro GeV/TeV Observations
  64. Color indices of the afterglow of GRB011211
  65. GRB011212: Optical observations at Gunma
  66. GRB 011211, spectrum and optical photometry
  67. GRB 011130: Optical Observations of X-ray and Radio Sources
  68. GRB 011130, Radio/X-ray Comparison
  69. GRB011212: Optical observations
  70. GRB 011212: optical observation at Asiago
  71. GRB 011211: Evidence for an Optical Break
  72. GRB 011211: TNG Spectroscopic Observations
  73. optical follow-up of GRB(XRF) 011211
  74. GRB 011212: optical observation at Oslo (relayed)
  75. GRB 011211: Optical Spectroscopy
  76. GRB 011211, Optical Observations
  77. GRB011212, BVRI field photometry
  78. GRB011211, BVRI field photometry
  79. GRB011212: Optical observations
  80. GRB 011211: BVRi-band photometry
  81. GRB011212 (=H10001): An X-Ray Rich GRB Detected by HETE
  82. Fading of the optical source associated of XRF 011211
  83. XMM-Newton observation of GRB011211
  84. GRB 011211 Optical Observations: Likely Afterglow
  85. GRB011130 (=XRF011130): Further analysis of Chandra Target of
  86. GRB011211(=XRF011211): BeppoSAX refined positions
  87. BeppoSAX Alert: GRB011211(=XRF011211)
  88. GRB 011130: Optical Observations of Chandra Sources
  89. GRB 011130: Optical Observations of Chandra sources
  90. GRB011130 (XRF011130) Chandra Observations
  91. GRB011130 (=XRF011130): Scheduled Target of Opportunity
  92. GRB 011130: Magellan spectroscopy
  93. Sub-mm and Centimeter Detections of the Host Galaxy of GRB000418
  94. GRB011130, optical observations
  95. GRB 011130, K band observations
  96. GRB011130, optical observations
  97. GRB011130 (=XRF011130): Second Revised Localization by HETE
  98. GRB 011130 I-band Observation
  99. GRB011130 (XRF011130) optical observations
  100. GRB011130 (XRF011130) SDSS PT i-band observations

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