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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. ZTF21aaeyldq: NOT optical observations
  2. ZTF21aaeyldq: Lowell Discovery Telescope observations
  3. ZTF21aaeyldq: observations with the 3.6m Devasthal Optical Telescope
  4. ZTF21aaeyldq: GTC Redshift and GRB afterglow nature confirmation
  5. GRB 201015A: evidence of supernova in LBT spectra
  6. ZTF Discovery of ZTF21aaeyldq (AT2021any): a Hostless, Young, and Rapidly Fading Transient
  7. GRB 210104A: JCMT SCUBA-2 sub-mm observations
  8. GRB 210112A: Swift/UVOT Detection
  9. GRB 210112A: Mondy optical observations
  10. GRB 210112A: 1.3m DFOT Optical upper limit
  11. GRB 210112A: OSN second epoch, decay
  12. GRB 210104A: AstroSat CZTI detection
  13. NuEm-210111A: MAXI/GSC upper limit
  14. GRB 210112A: Swift-BAT refined analysis
  15. GRB 210112A: OSN Reddened Afterglow Detection
  16. GRB 210112A: Swift-XRT refined Analysis
  17. NuEm-210111A : No neutrino counterpart in ANTARES
  18. GRB 210112A: AGILE detection
  19. GRB 210112A: Kitab a optical upper limit
  20. GRB 210104A: AROMA-N Optical Afterglow Detection
  21. GRB 210112A: Enhanced Swift-XRT position
  22. GRB 210112A: Swift detection of a burst with an optical counterpart
  23. NuEm-210111A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  24. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-210111A
  25. GRB 210104A: Mondy optical observations, light curve
  26. MAXI GRB210110.64: Global MASTER-Net observations report
  27. GRB 210110A: MAXI/GSC detection
  28. GRB 210104A: Assy continued optical observations, correction to GCN circ. 29265
  29. GRB 210109A: MAXI/GSC detection
  30. GRB 201227A: continued Chilescope confirmation of variability of possible optical counterpart, redshift estimating
  31. Correction to GCN 29278: GRB 201216C XRT refined analysis
  32. GRB 210108A: BALROG localization (Fermi Trigger 631793415 / GRB 210108424)
  33. GRB 201216C: Swift-XRT refined Analysis
  34. GRB 210104A: SAO RAS optical observations
  35. GRB 201227A: ASIM observation
  36. GRB 210104A: GMG observations
  37. GRB210104A: VIRT optical transient detection.
  38. GRB 210104A: SARA-KP 0.9m Optical Afterglow Detection
  39. Fermi trigger No 631602681: Global MASTER-Net observations report
  40. GRB 210102B: further Swift-XRT observations
  41. GRB 210102B: Assy optical afterglow identification
  42. GRB 210104A: iTelescope optical upper limit
  43. GRB 210104A: CALET Gamma-Ray Burst Monitor detection
  44. Fermi trigger No 631584650: Global MASTER-Net observations report
  45. GRB 210104B: Swift-BAT refined analysis
  46. GRB 210104A: Assy continued optical observations
  47. Fermi GRB 210105A: Global MASTER-Net observations report
  48. GW170817: HST observations at 3.4 years from merger
  49. GRB 210104A: early ATLAS detections of the bright afterglow
  50. GRB 210105A: Fermi GBM Final Real-time Localization
  51. GRB 210104A: Swift-XRT refined Analysis
  52. GRB 210104B: Swift/UVOT Upper Limits
  53. Konus-Wind detection of GRB 210104A
  54. GRB 210104A: 1.3m DFOT Optical Afterglow Detection
  55. GRB 210104B: Swift-XRT refined Analysis
  56. GRB 210104B: Assy optical upper limit
  57. GRB 210104A: DOAO optical afterglow observations
  58. GRB 210104B: Enhanced Swift-XRT position
  59. GRB 210104A: Nanshan/NEXT optical powerlaw decay
  60. GRB 210104A: Swift-BAT refined analysis
  61. GRB 210104B: Nanshan/NEXT optical upper limit
  62. GRB 210104B: BOOTES network optical upper limit
  63. GRB 210104A: MASTER OT rebrightening detection
  64. GRB 210104A: Swift/UVOT Detection
  65. GRB 210104A: Fermi GBM detection
  66. GRB 210104A: Enhanced Swift-XRT position
  67. GRB 210102B: Tiled Swift observations
  68. GRB 210104B: Swift detection of a burst
  69. Swift GRB210104.88: Global MASTER-Net observations report
  70. GRB 210104A: MITSuME Ishigaki optical observation
  71. GRB 210102B: Assy optical observations
  72. Fermi GRB 210104A: Global MASTER-Net observations report
  73. GRB 210104A: Assy optical observations
  74. GRB 210104A: MITSuME Akeno optical observation
  75. GRB 210104A: BOOTES-4/MET early optical afterglow detection
  76. GRB 210104A: GWAC-F60A optical afterglow observations
  77. GRB 210104A: BALROG localization (Fermi Trigger 631452424 / GRB 210104477)
  78. GRB 210104A: Swift detection of a burst with a bright optical counterpart
  79. GRB 210104A: Fermi GBM Final Real-time Localization
  80. GRB 210102C: Swift-BAT refined analysis
  81. GRB 210102B: Swift-XRT observations
  82. Fermi GRB 210102C: Global MASTER-Net observations report
  83. GRB 210102C: Fermi GBM detection
  84. Swift GRB 210102C: Global MASTER-Net observations report
  85. GRB 210102C: Swift detection of a burst
  86. MAXI GRB210102.38: Global MASTER-Net observations report
  87. GRB 210102B: Tiled Swift observations
  88. GRB 210102B: MAXI/GSC detection
  89. Fermi GRB 210101A: Global MASTER-Net observations report
  90. INTEGRAL Weak #8913: AROMA-N Optical Observation
  91. Swift Trigger 1015615 is not a GRB
  92. Swift GRB210102.01: Global MASTER-Net observations report
  93. Fermi trigger No 631226368: Global MASTER-Net observations report
  94. Fermi trigger No 631119348: Global MASTER-Net observations report
  95. GRB 210101A: BALROG localization (Fermi Trigger 631205591 / GRB 210101620)
  96. GRB 210101A: Fermi GBM Final Real-time Localization
  97. Fermi trigger No 631113166: Global MASTER-Net observations report
  98. GRB 201229A: Swift/UVOT Detection
  99. Fermi trigger No 631118376: Global MASTER-Net observations report
  100. Fermi trigger No 631104264: Global MASTER-Net observations report

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