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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"

5157 results found.

  1. HAWC-210507A: No neutrino counterpart candidates in ANTARES search
  2. Fermi GRB 210507A: Global MASTER-Net observations report
  3. GRB 210424B: AstroSat CZTI detection
  4. GRB 210504A: Swift-XRT refined Analysis
  5. GRB 210504A: MITSuME Akeno optical upper limits
  6. Fermi GRB 210503A: Global MASTER-Net observations report
  7. Swift GRB210502.74: Global MASTER-Net observations report
  8. Fermi GRB 210501A: Global MASTER-Net observations report
  9. GRB 210424B: MITSuME Akeno optical upper limits
  10. GRB 210424B: CALET Gamma-Ray Burst Monitor detection
  11. Fermi GRB 210427A: Global MASTER-Net observations report
  12. Fermi trigger No 640975205: Global MASTER-Net observations report
  13. GRB 210424A: Fermi GBM Final Real-time Localization
  14. GRB 210420B: Zeiss-1000 of Koshka optical observations
  15. GRB 210420B: continued Tautenburg observations
  16. GRB 210421A: MITSuME Akeno optical upper limits
  17. GRB 210421A: Swift-XRT refined Analysis
  18. Fermi GRB 210421C: Global MASTER-Net observations report
  19. GRB 210413B: MITSuME Okayama optical upper limits
  20. GRB 210419C: MITSuME Akeno optical upper limits
  21. GRB 210419A: Swift-XRT refined Analysis
  22. GRB 210410A: MITSuME Akeno optical upper limits
  23. Fermi GRB 210411A: Global MASTER-Net observations report
  24. GRB 210402A: Swift-XRT refined Analysis
  25. GRB 210324A: AstroSat CZTI detection
  26. GRB 210324C: AstroSat CZTI detection
  27. GRB 210323A: MASTER optical observation
  28. Fermi GRB 210324C: Global MASTER-Net observations report
  29. Fermi GRB 210324B: Global MASTER-Net observations report
  30. GRB 210324C: BALROG localization (Fermi Trigger 638308803 / GRB 210324833)
  31. GRB 210324C: Fermi GBM Final Real-time Localization
  32. GRB 210324B: Fermi GBM Final Real-time Localization
  33. GRB 210324A: Fermi GBM Final Real-time Localization
  34. GRB 210323A: Swift-XRT refined Analysis
  35. Swift GRB 210323A: Global MASTER-Net observations report
  36. GRB 210321A: Swift-XRT refined Analysis
  37. GRB 210318B: MITSuME Okayama optical upper limits
  38. GRB210318B: Swift detection of a burst
  39. Fermi trigger No 637521056: Global MASTER-Net observations report
  40. Fermi GRB 210312A: Global MASTER-Net observations report
  41. GRB 210308A: MITSuME Okayama optical upper limits
  42. GRB 210306A: continued Mondy optical observations
  43. GRB 210308A: Swift detection of a burst with an optical counterpart
  44. GRB 210306A: MITSuME Akeno optical observation
  45. GRB 210306A: iTelescope T24 optical observations
  46. GRB 210305A: Swift detection of a burst
  47. Fermi trigger No 636459103: Global MASTER-Net observations report
  48. GRB 210226A: Swift-XRT refined Analysis
  49. GRB 210222B: MITSuME Akeno optical upper limits
  50. GRB 210222B: Swift-XRT refined Analysis
  51. GRB 210222B: GOTO confirmation of afterglow detection
  52. uGMRT radio detection of GRB 210204A
  53. GRB 210218A: MITSuME Akeno optical upper limits
  54. GRB 210212B (TF21aakruew/AT2021cwd): Assy optical observations
  55. ZTF21aakruew/AT2021cwd: ZTF and LT discovery of a hostless, red, and rapidly fading optical transient
  56. GRB 210212A: MITSuME Akeno optical upper limits
  57. GRB 210212A: Swift-XRT refined Analysis
  58. GRB 210211A: Swift-XRT refined Analysis
  59. GRB 210209A: MITSuME Akeno optical upper limits
  60. GRB 210210A: Swift-XRT refined Analysis
  61. GRB 210209A: Swift-XRT refined Analysis
  62. ZTF21aahifke/AT2021clk: ZTF discovery of an optical fast transient (possible afterglow)
  63. Swift GRB 210210A: Global MASTER-Net observations report
  64. GRB 210207B: Continued LCO Observations
  65. GRB 210207B: Swift-XRT refined Analysis
  66. Fermi GRB 210207A: Global MASTER-Net observations report
  67. Konus-Wind detection of GRB 210204A / ZTF21aagwbjr
  68. GRB 210204A / ZTF21aagwbjr: Swift-XRT observations
  69. GRB 210205A: Swift-XRT refined Analysis
  70. ZTF21aagwbjr/AT2021buv: ZTF discovery of a fast optical transient likely associated with GRB 210104A
  71. Fermi GRB 210204B: Global MASTER-Net observations report
  72. GRB 210124B: AstroSat CZTI detection
  73. HAWC Transient event on 2021/01/25
  74. GECAM detection of a burst possibly from the X-ray burster 4U 0614+09 or GRB 210124A
  75. IPN triangulation of GRB 210121A
  76. Fermi GRB 210119A: Global MASTER-Net observations report
  77. Fermi trigger No 632573937: Global MASTER-Net observations report
  78. GRB 201221D: near-infrared observation with LBT
  79. ZTF21aaeyldq: NOT optical observations
  80. ZTF Discovery of ZTF21aaeyldq (AT2021any): a Hostless, Young, and Rapidly Fading Transient
  81. GRB 210112A: Swift-XRT refined Analysis
  82. GRB 210104A: Swift-XRT refined Analysis
  83. Konus-Wind detection of GRB 210104A
  84. GRB 210104B: Swift-XRT refined Analysis
  85. GRB 210104B: BOOTES network optical upper limit
  86. GRB 210104A: MITSuME Akeno optical observation
  87. Fermi GRB 210102C: Global MASTER-Net observations report
  88. Fermi trigger No 631119348: Global MASTER-Net observations report
  89. Fermi trigger No 631104264: Global MASTER-Net observations report
  90. GRB 201229A: Swift-XRT refined Analysis
  91. ZTF20acozryr/AT2020yxz (GRB 201103B): Maidanak optical observations
  92. Fermi trigger No 630681391: Global MASTER-Net observations report
  93. Baksan Neutrino Observatory Alert 201225.54: Global MASTER-Net observations report
  94. GRB 201223A: Swift-XRT refined Analysis
  95. GRB 201223A: NOT optical upper limit and NEXT powerlaw decay
  96. Baksan Neutrino Observatory Alert 201223.60: Global MASTER-Net observations report
  97. Swift-XRT observations of Icecube 201222A
  98. Fermi trigger No 630389391: Global MASTER-Net observations report
  99. GRB 201221D: Archival PS1 Imaging of the Putative Host Galaxy
  100. GRB 201221D: candidate optical counterpart from the NOT

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