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

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