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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. IPN triangulation of GRB030127 (annulus)
  2. GRB030115 submm upper limit
  3. IPN triangulation of GRB030119 (two large error boxes)
  4. GRB 030115: Further IR observations with IRSF/SIRIUS
  5. IPN triangulation of GRB030117 (two large error boxes)
  6. Publicizing GRB Discoveries - A Message from NASA HQ
  7. GRB 030115: Radio detection of IR candidate
  8. GRB 030115, simultaneous observations by BOOTES-1
  9. GRB 030115: IR observations with IRSF/SIRIUS
  10. IPN triangulation of GRB030115C (large error box)
  11. GRB030115: R-band counterpart of IR candidate
  12. GRB030115, afterglow candidate
  13. GRB 021211: R-band observations at late-time
  14. GRB030115: Optical Observations, Swiss Telescope at La Silla (ESO, Chile)
  15. IPN triangulation of GRB030115B (small error box)
  16. GRB 030115 : Possible IR counterpart
  17. GRB 030115: Radio Observations
  18. GRB030115 (=H2533): A Long GRB Localized by the HETE WXM and SXC
  19. Distribution of INTEGRAL SPI-ACS triggers for GRB bursts
  20. IPN triangulation of GRB030115B (annulus)
  21. ANNOUNCEMENT ON INTEGRAL GRB ALERTS
  22. Distribution of INTEGRAL SPI-ACS triggers
  23. GRB030115: R-band observations at Asiago
  24. GRB030115: TAROT optical observations
  25. GRB 021211: VLT spectrum
  26. GRB 030115: APO Optical Observations
  27. GRB 030115, no optical candidate
  28. GRB 030115, optical observations
  29. GRB 030115, optical candidate
  30. Possible GRB030113 seen by SPI ACS
  31. Probable GRB030112B seen by SPI ACS
  32. Probable GRB030112 seen by SPI ACS
  33. Information about where HETE will be pointing
  34. Possible GRB030111 seen by SPI ACS
  35. Possible GRB030110b seen by SPI ACS
  36. Possible GRB 030110 seen by SPI ACS
  37. IPN triangulation of GRB030109 (annulus)
  38. IPN triangulation of GRB030105 (large error box)
  39. IPN triangulation of GRB030102B (refined localization - portion of annulus)
  40. Possible GRB 20030109 seen by SPI ACS
  41. IPN triangulation of GRB030102A - correction to peak flux
  42. IPN triangulation of GRB030102B (portion of annulus)
  43. IPN triangulation of GRB030102A (large error box)
  44. Coronas-F -Wind triangulation of GRB030102
  45. Possible GRB20030107 seen by SPI-ACS
  46. Possible GRB 20030105 seen by SPI ACS
  47. IPN triangulation of GRB030102 (annulus)
  48. GRB on 20030102 seen by SPI-ACS
  49. VLT spectroscopy of the probable host of GRB 021211
  50. GRB on 20030101 seen by SPI-ACS
  51. IPN triangulation of GRB030101 (two large error boxes)
  52. GRB021226
  53. GRB 021211: Probable Host and Underlying Supernova
  54. GRB 021226 registration by Helicon/Coronas-F
  55. Probable GRB in INTEGRAL SPI-ACS
  56. IPN triangulation of GRB021223 (two large error boxes)
  57. GRB021211, radio observations
  58. GRB 021112: Evidence for Another Dark Optical Afterglow
  59. GRB 021219: OSN optical observations
  60. GRB021219: Radio Observations
  61. GRB021219, optical observations
  62. IPN triangulation of GRB021219 - CORRECTION
  63. IPN triangulation of GRB021219
  64. GRB021219, optical observation by MASTER
  65. GRB021219: Correction to GCN 1766
  66. GRB021219 refined position with INTEGRAL
  67. VLT spectra of GRB 021211 revisited
  68. GRB021219: a long GRB localized by INTEGRAL
  69. GRB021211: APO optical observations
  70. IPN detection of continued activity from SGR1806-20
  71. IPN triangulation of GRB021215 (large error box)
  72. IPN triangulation of GRB021214 (annulus)
  73. XRF 020903 : HST observations
  74. GRB 021201: Optical Observations
  75. GRB 021211, optical observations
  76. GRB 021211: CTIO observations
  77. GRB021211: Measurement of Early Time Afterglow
  78. VLT spectrum of GRB 021211
  79. IPN triangulation of GRB021211B (two large error boxes)
  80. GRB 021211: early break in light curve
  81. GRB021211, BVRI field photometry
  82. GRB021211: Optical observations in CrAO
  83. GRB 021211, IR observations
  84. GRB 021211, optical observations
  85. GRB 021211: Optical Observations
  86. GRB021211: Kiso Observations
  87. GRB021204: Kiso Observations
  88. GRB 021201, optical observations
  89. GRB 021211: Radio Observations
  90. GRB021211: Optical observations
  91. GRB 021201 (short/hard), NOT observations
  92. SUB-MM SEARCH FOR GRB 021211
  93. Chandra observation of the IPN error box of GRB021201 (short/hard)
  94. GRB 021211 Milagro GeV/TeV Observations
  95. GRB 021211, R- and I-band observations
  96. GRB021211 - Upper limits from recent and historical observations
  97. GRB021211, OT at 108 s
  98. GRB021211 (HETE2493), OT at 143 sec
  99. GRB 021204: I-band Observations
  100. GRB021211 (=H2493): A Bright, Long GRB Localized by HETE-2 in Near-Real Time

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