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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 030227: Kyoto optical observation
  2. GRB 030226, optical light curve
  3. GRB 030226 spectroscopy
  4. GRB030227: refined INTEGRAL position
  5. GRB030227 localized by INTEGRAL
  6. Possible break in the GRB 030226 light curve
  7. GRB 030226 : Predicted light curve
  8. GRB030226: optical observation
  9. IPN triangulation of GRB030225 (annulus)
  10. GRB 030226: Confirmed decay index
  11. GRB030226: ESI spectroscopy
  12. GRB030226 (=U10893): A Long GRB Localized by the HETE WXM and SXC
  13. GRB 030226 simultaneous optical observations
  14. Two absorption systems in GRB 030226
  15. GRB 030226, optical observations
  16. GRB030226: optical observations and refined redshift
  17. GRB030226: Optical decay index
  18. GRB 030226 Optical Spectra and R,I,z' Imaging
  19. GRB 030226, optical observations
  20. GRB 030226: Optical afterglow
  21. GRB030226: Candidate optical afterglow
  22. GRB 030217: Optical Observations at 4, 5, and 6 Days
  23. IPN triangulation of GRB030223 (annulus)
  24. IPN triangulation of GRB030220 (annulus)
  25. GRB: Non-Referencing of GCN Circulars.
  26. IPN triangulation of GRB030218 (annulus)
  27. GRB030217: optical observations
  28. IPN triangulation of GRB030217 (small error box)
  29. IPN triangulation of GRB030215C (annulus)
  30. IPN triangulation of GRB030217 (annulus)
  31. IPN triangulation of GRB030216 (annulus)
  32. IPN triangulation of GRB030215A and GRB030215B (annuli)
  33. GRB030115, WSRT radio observations - correction to GCN 1864
  34. GRB 030131: marginal optical detection
  35. GCN/INTEGRAL Mistake Fixed
  36. GRB030115, WSRT radio observations
  37. IPN triangulation of GRB030206 (annulus)
  38. IPN triangulation of GRB030208 (annulus)
  39. GRB 030204: Optical Observations
  40. GRB030204 field photometry
  41. GRB020819: Kiso R and I band observations
  42. GRB 030204: Correction to GCN 1856
  43. GRB030131: Candidate Optical Afterglow
  44. GRB 030115: Optical Observations
  45. GRB 030204, optical observations
  46. IPN triangulation of GRB030204 (small error box)
  47. IPN triangulation of GRB030202 (annulus)
  48. GRB 030131, optical observations
  49. GRB030131: Kiso optical limit for corrected position
  50. GRB030131: Optical limits for corrected position
  51. GRB 030131: afterglow candidate
  52. GRB 030115, late-time optical observations
  53. GRB030131: corrected INTEGRAL position
  54. Type Ic SN2003L (SN/GRB?), optical spectrum
  55. GRB030131: Kiso Observations
  56. GRB 020819: Host galaxy at Radio Position
  57. IPN triangulation of GRB030131 - CORRECTION
  58. GRB 020819: afterglow candidate
  59. IPN triangulation of GRB030131
  60. GRB030131: Optical limit
  61. GRB 030131 optical observations
  62. GRB030131: refined position
  63. GRB 030131 optical observations
  64. A long GRB detected by INTEGRAL
  65. GRB030115: 1.2 mm upper limits with MAMBO @ IRAM 30m
  66. Type Ic SN2003L (SN/GRB?) Radio Observations
  67. IPN triangulation of GRB030127 (annulus)
  68. GRB030115 submm upper limit
  69. IPN triangulation of GRB030119 (two large error boxes)
  70. GRB 030115: Further IR observations with IRSF/SIRIUS
  71. IPN triangulation of GRB030117 (two large error boxes)
  72. Publicizing GRB Discoveries - A Message from NASA HQ
  73. GRB 030115: Radio detection of IR candidate
  74. GRB 030115, simultaneous observations by BOOTES-1
  75. GRB 030115: IR observations with IRSF/SIRIUS
  76. IPN triangulation of GRB030115C (large error box)
  77. GRB030115: R-band counterpart of IR candidate
  78. GRB030115, afterglow candidate
  79. GRB 021211: R-band observations at late-time
  80. GRB030115: Optical Observations, Swiss Telescope at La Silla (ESO, Chile)
  81. IPN triangulation of GRB030115B (small error box)
  82. GRB 030115 : Possible IR counterpart
  83. GRB 030115: Radio Observations
  84. GRB030115 (=H2533): A Long GRB Localized by the HETE WXM and SXC
  85. Distribution of INTEGRAL SPI-ACS triggers for GRB bursts
  86. IPN triangulation of GRB030115B (annulus)
  87. ANNOUNCEMENT ON INTEGRAL GRB ALERTS
  88. Distribution of INTEGRAL SPI-ACS triggers
  89. GRB030115: R-band observations at Asiago
  90. GRB030115: TAROT optical observations
  91. GRB 021211: VLT spectrum
  92. GRB 030115: APO Optical Observations
  93. GRB 030115, no optical candidate
  94. GRB 030115, optical observations
  95. GRB 030115, optical candidate
  96. Possible GRB030113 seen by SPI ACS
  97. Probable GRB030112B seen by SPI ACS
  98. Probable GRB030112 seen by SPI ACS
  99. Information about where HETE will be pointing
  100. Possible GRB030111 seen by SPI ACS

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