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

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