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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 090510: NOT afterglow confirmation
  2. GRB 090510: Swift-BAT refined analysis
  3. GRB 090510: Fermi GBM detection
  4. GRB 090509: Swift-BAT refined analysis
  5. Fermi LAT detection of GRB 090510
  6. GRB 090509, SMARTS optical/IR afterglow observations
  7. GRB 090510: Swift/UVOT Detection of a Candidate Optical Afterglow
  8. GRB 090510: Swift detection of a short hard burst
  9. GRB 090408: optical upper limit
  10. GRB 090418A: optical observation
  11. GRB 090509: GROND further analysis and redshift limit
  12. GRB 090509: REM NIR afterglow
  13. GRB 090509: GROND afterglow candidate
  14. GRB 090509: Swift detection of a burst
  15. GRB 090323: optical observations
  16. GRB 090423: optical limit
  17. GRB 090423: 250 GHz upper limit for a z=8.2 GRB with MAMBO-2 at the IRAM 30m
  18. GRB 080913: 250 GHz upper limit for a z=6.7 GRB with MAMBO-2 at the IRAM 30m
  19. GRB 090424: optical observations
  20. GRB 090427: GROND observations
  21. GRB 090429A: ROVOR magnitude limit
  22. ICSP VLF observation of GRB090427 from two receivers
  23. ICSP VLF observation of GRB090424 from four receivers
  24. Refined analysis of ICSP VLF observation of SGR J1550-5418 bursts on 22nd January, 2009
  25. GRB 090428B: Suzaku WAM observation of the prompt emission
  26. GRB 090424, SMARTS optical/IR afterglow monitoring
  27. GRB 090426: optical observations
  28. GRB 090429D: Fermi GBM detection
  29. GRB 090429C: Fermi GBM detection
  30. GRB 090429B: Swift/UVOT Upper Limits
  31. GRB 090429A: Swift/UVOT Upper Limits
  32. GRB 090427: pseudo-z= 1.48 from prompt emission spectrum
  33. GRB 090429B: Gemini-N further nIR observations
  34. GRB 090424: YNAO-GMG observations
  35. GRB 090429A: Swift-XRT refined analysis
  36. GRB 090429A: GROND upper limits
  37. GRB 090427C: Fermi GBM detection
  38. GRB 090427B: Fermi GBM detection
  39. GRB 090426C: Fermi GBM detection
  40. GRB 090426B: Fermi GBM detection/observation
  41. GRB 090429B: Swift XRT refined analysis
  42. GRB 090429A: Enhanced Swift-XRT position
  43. Konus-Wind observation of very bright GRB 090427
  44. GRB 090428B: Fermi GBM detection
  45. GRB 090428: Fermi GBM detection
  46. GRB 090418A BVRcIc field calibration
  47. GRB 090426: GAO 150cm telescope Optical Observation
  48. GRB 090429B: RIMOTS optical upper limits
  49. GRB 090429B: Swift-BAT refined analysis
  50. GRB 090429A: Swift-BAT refined analysis
  51. GRB 090429B: Enhanced Swift-XRT position
  52. GRB 090429A - Correction to XRT position
  53. GRB090429B: Gemini-N infrared IR candidate
  54. GRB 090426: YNAO-GMG observations
  55. GRB 090429B: VLT upper limits
  56. GRB 090429B: GROND Observations
  57. GRB 090429B: Super-LOTIS early observations
  58. GRB 090429B: Swift detection of a burst
  59. GRB 090429: Swift detection of a burst
  60. GRB 090423: pseudo burst at z=1 and its relation to GRB 080913
  61. GRB 090424 : Multiband Optical observation from Nainital
  62. IPN triangulation of very bright GRB 090427
  63. GRB 090426: R-band limit
  64. GRB 090424: Continued R-band monitoring
  65. GRB 090423: CARMA mm observations
  66. GRB 090423: millimeter detection
  67. GRB 090426: Swift/BAT spectral lag results
  68. GRB 090425: Fermi GBM detection
  69. GRB 090424: Suzaku WAM observation of the prompt emission
  70. GRB 090426: VLT spectroscopy
  71. GRB 090426: GROND Observations of the Optical/NIR Afterglow
  72. GRB 090426: Near infrared observation with ISLE at OAO
  73. GRB 090426: Okayama MITSuME optical observation
  74. GRB090426 Swift/UVOT observations
  75. GRB 090426 Keck LRIS redshift
  76. GRB 090426: Swift-BAT refined analysis
  77. GRB 090426: Swift-XRT refined analysis
  78. GRB 090423: GROND second epoch imaging and refined SED
  79. Detection of bright radio afterglow of GRB 090424 with the VLA
  80. GRB 090426: Enhanced Swift-XRT position
  81. GRB090426: Observation for Optical counterpart from MIRO
  82. GRB 090426, RIMOTS optical upper limits
  83. GRB 090426: inspection of SDSS images
  84. GRB 090426: TNT confimation of optical counterpart
  85. GRB 090426: Swift detection of a burst with an optical counterpart
  86. GRB090424: R-band detection (37.5 hrs post-burst), jet break?
  87. GRB 090424: MASTER-Net prompt optical limit
  88. GRB 090423: Fermi GBM observation (correction of isotropic equivalent energy)
  89. GRB 090424: WHT ISIS spectroscopy
  90. VLA radio observation of high-z GRB 090423
  91. GRB090424: BVRI/R-band detection after 15 hrs burst
  92. GRB 090424 : Lulin 1m telescope optical observations
  93. GRB 090424: THO optical observations
  94. GRB 090424: GROND Observations of the Optical/NIR Afterglow
  95. GRB090423: Y-band limit
  96. GRB 090424 Gemini-South Redshift
  97. GRB 090423: Y-band field calibration update/correction
  98. GRB 090423: Swift/BAT spectral lag results
  99. GRB 090424 : TAOS optical detection
  100. GRB 090424 optical observations

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