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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. GRB 041219: Infrared Afterglow Candidate
  2. GRB041219, BVRcIc field calibration
  3. GRB 041219: Infrared Afterglow Candidate
  4. GRB041218, BVRcIc field calibration
  5. GRB041219: Prompt Optical Observations from ROTSE-IIIb
  6. GRB041219: P60 Optical Observations
  7. GRB 041219 - A long GRB detected by INTEGRAL
  8. GRB 041219: PAIRITEL IR Observations, < 3 minutes after trigger
  9. GRB 041217: PROMPT Observations
  10. GRB041218: optical observations
  11. GRB041217: optical limit 30 min after GRB
  12. GRB 041218; optical candidate
  13. GRB 041218: Optical observations
  14. GRB 041217: LCO40 Optical Observations and Possible Candidates
  15. GRB 041218 - A long GRB detected by integral
  16. GRB041217: Optical Observations
  17. GRB041217: NIR and optical observations with REM
  18. GRB041217: P60 Optical Observations
  19. GRB041217: Infrared Observations
  20. GRB041217: The First GRB Located On-Board Swift
  21. GRB041211: Faulkes Telescope continued optical monitoring
  22. Optical Transient in Lynx not a GRB
  23. Optical transient (GRB?) in Lynx
  24. Optical transient (GRB?) in Lynx, UT Dec 11.4436
  25. GRB041211: Continued P60 Observations
  26. GRB041211: RAPTOR observations
  27. GRB041211: Ashra Prototype optical observation
  28. GRB041211, Faulkes Telescope optical observation
  29. GRB041211, BVRcIc field calibration
  30. GRB041211,optical observation
  31. GRB 041211: Infrared Observations
  32. GRB 041211: KAIT observations
  33. GRB 041211: Optical follow-up in East Asian region
  34. GRB 041211(=H3622): A Long GRB Localized by the HETE WXM and SXC
  35. GRB041211: P60 optical imaging
  36. GRB970815: Discovery of Optical Afterglow
  37. Distribution of IBAS Alerts for NON-GRB sources
  38. Triangulation of short GRB 041116 (large error box)
  39. GRB041015: Near-Infrared observations
  40. GRB 040924: Afterglow Color
  41. GRB 041006: GETS Optical Afterglow Observation
  42. Summary of the recent bursts from SGR 1806-20
  43. GRB 041006: Optical Observations
  44. GRB041006, late-time optical photometry
  45. GRB041015, optical observation in CrAO
  46. IBAS GRB Alert # 2034
  47. GRB041006: RTT150 Optical Observations
  48. GRB041015 : Multi epoch optical observations
  49. HST Observations: XRF 040701 and 040812
  50. Bright bursts from SGR1806-20
  51. GRB 041016: BOOTES-2 simultaneous observation
  52. GRB041006: RTT150 Optical Observations
  53. GRB041016,optical observation
  54. GRB 041016: Optical limits
  55. GRB 041016: Optical limits in V, R, I
  56. GRB 041016:Optical limit during first minute
  57. GRB041016: MASTER: Optical observations
  58. GRB 041015: Optical Observations at Rikubetsu
  59. GRB041006: Near Infrared observations
  60. GRB 041016: Optical limit
  61. GRB 041015 R band observations
  62. GRB040924, BVRcIc field calibration
  63. GRB041015: MASTER: Optical observations
  64. GRB041015,optical observation
  65. GRB041006: Fading X-ray Afterglow Observed with Chandra
  66. GRB 041015: Optical limit at Osaka University
  67. GRB041015 : Optical follow-up at Kiso
  68. GRB 041015 - A long GRB detected by INTEGRAL
  69. GRB 041006 R observations in Loiano
  70. GRB041006: VLT observations of the afterglow and host galaxy
  71. GRB041006: Optical observations and Potential host galaxy
  72. GRB041006, BVRcIc field calibration
  73. GRB 040924: VLT spectroscopy
  74. GRB 041006: SARA afterglow observations
  75. GRB041006, optical observation in CrAO
  76. Search for SN light in XRF 040912 with MEGACAM
  77. GRB 040916: Afterglow Color at Early Times
  78. GRB 041006 Optical afterglow observations
  79. IBAS GRB Alert # 2010
  80. GRB 041006: BR observations with VATT
  81. GRB 041006: Redshift confirmed
  82. GRB041006: Liverpool Telescope optical observations
  83. GRB 041006: Colour measurement
  84. GRB041006: break in the light curve
  85. GRB 041006: Radio Observations
  86. GRB041006, further submilllimetre observations
  87. GRB 041006 : optical follow-up observation at Lulin Observatory
  88. SUBJECT: GRB 041006 : Optical follow-up observation at TAROT
  89. GRB041006: Optical photometry and spectroscopy at TNG
  90. GRB 041006: presice astrometry
  91. GRB041006 (= H3570): Chandra Observations In Progress
  92. GRB 041006 : optical observation at Bisei
  93. GRB041006, optical I observation
  94. GRB041006 (=HETE3570): optical observations
  95. ROTSE-IIIa Observations of GRB 041006
  96. GRB041006, optical observation
  97. GRB041006, submillimetre observations
  98. GRB041006: MASTER optical observations
  99. GRB041006,optical observation
  100. GRB 041006: Optical decay

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