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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 210222B: Swift detection of a burst with an optical counterpart
  2. Swift GRB210222.94: Global MASTER-Net observations report
  3. GRB 210222A: MAXI/GSC detection
  4. GRB 210218A: Swift-XRT observations
  5. uGMRT radio detection of GRB 210204A
  6. GRB 210212A: Lowell Discovery Telescope observations
  7. GRB 210217A: 1.3m DFOT optical detection
  8. GRB 210217A: Swift-XRT refined Analysis
  9. GRB 210218A: Swift-BAT refined analysis
  10. Fermi GBM Sub-Threshold Detection of GRB 210217A
  11. GRB 210217A: Liverpool Telescope First Hour Observations
  12. GRB 210217A: Swift-BAT refined analysis
  13. GRB 210217A: KAIT Optical Observations
  14. GRB 210218A: MITSuME Akeno optical upper limits
  15. GRB 210218A： GWAC-F60A optical upper limit
  16. GRB 210218A: NEXT optical upper limit
  17. GRB 210218A: Swift detection of a burst
  18. ZTF21aakruew/AT2021cwd: GROND observations
  19. GRB 210212A: REM early-time optical/NIR upper limits
  20. GRB 210205A: observations with the 3.6m DOT, a potential dark burst?
  21. GRB 210217A: Enhanced Swift-XRT position
  22. Fermi/GBM observation of a burst from SGR 1830-0645
  23. GRB 210217A: NEXT early optical afterglow observations
  24. GRB 210212A: Mondy optical observations
  25. GRB 210217A: Swift detection of a burst with an optical counterpart
  26. GRB 210204A (ZTF21aagwbjr/AT2021buv): continued Assy and Mondy optical observations
  27. IceCube-210210A: Two Additional Optical Candidate Counterparts Found by DECam
  28. GRB 210208A: 1.3m DFOT Optical upper limit
  29. GRB 210210A: Konus-Wind detection and joint Konus-Wind + Swift-BAT spectral analysis
  30. Swift Trigger 1033144: Detection of SGR 1830-0645
  31. GRB 210211A: ePESSTO+ NTT optical observations
  32. Konus-Wind detection of GRB 210212B / ZTF21aakruew
  33. GRB 210212B: Swift ToO observations
  34. GRB 210212B (TF21aakruew/AT2021cwd): Assy optical observations
  35. IPN triangulation of GRB 210212B (consistent with ZTF21aakruew/AT2021cwd)
  36. GRB 210212A: 1.3m DFOT Optical upper limit
  37. GRB 210213B: Insight-HXMT/HE detection
  38. ZTF21aakruew/AT2021cwd: ZTF and LT discovery of a hostless, red, and rapidly fading optical transient
  39. GRB 210212A: Gemini South optical observations
  40. IceCube alert 134994_1103075 retraction
  41. Fermi GRB 210213A: Global MASTER-Net observations report
  42. IceCube Alert 210213.78: Global MASTER-Net observations report
  43. GRB 210213A: Fermi GBM Final Real-time Localization
  44. GRB 210210A: CAHA 2nd epoch and jet break confirmation
  45. IceCube-210210A: Four Candidate Optical Counterparts from DECam Observations
  46. Swift Trigger 1032350: Detection of SGR 1830-0645
  47. GRB 210204A (ZTF21aagwbjr/AT2021buv): continued CrAO and AbAO optical observations
  48. GRB 210212A: Possible host galaxy counterpart with the NOT
  49. Swift GRB 210212A: Global MASTER-Net observations report
  50. GRB 210212A: MITSuME Akeno optical upper limits
  51. GRB 210212A: Swift-XRT refined Analysis
  52. GRB 210212A: BOOTES-4/MET optical upper limit
  53. IceCube-210210A: Upper limits from a search for additional neutrino events in IceCube
  54. GRB 210212A: Swift/UVOT Upper Limits
  55. GRB 210212A: Swift-BAT refined analysis
  56. GRB 210204A: observations with the 3.6m Devasthal Optical Telescope and possible jet break
  57. GRB 210212A: Enhanced Swift-XRT position
  58. GRB 210210A : 1.3m DFOT optical observations
  59. GRB 210212A: Swift detection of a burst
  60. GRB 210207B: GECAM detection
  61. GRB 210211A: Swift/UVOT Detection
  62. GRB 210211A: Swift-XRT refined Analysis
  63. GRB 210211A: Swift-BAT refined analysis
  64. GRB 210211A: Fermi GBM observation
  65. GRB 210210A as a BdHN II
  66. Swift-XRT observations of IceCube-210210A
  67. GRB 210209A: Swift-BAT refined analysis
  68. GRB 210211A: Enhanced Swift-XRT position
  69. GRB 210211A: MASTER optical observation of REM OT
  70. GRB 210210A: CAHA detection and likely jet break
  71. IceCube-210210A: No neutrino counterpart in ANTARES
  72. GRB 210211A: REM optical/NIR afterglow detection
  73. Fermi-LAT Gamma-ray Observations of IceCube-210210A
  74. GRB 210211A: Swift detection of a burst
  75. Swift GRB210211.36: Global MASTER-Net observations report
  76. GRB 210211A: Fermi GBM Final Real-time Localization
  77. GRB 210210A: FRAM-ORM afterglow detection
  78. Fermi trigger No 634659312: Global MASTER-Net observations report
  79. GRB 210210A: Swift-BAT refined analysis
  80. IceCube Alert 210210.50: Global MASTER-Net observations report
  81. Fermi GRB 210210B: Global MASTER-Net observations report
  82. IceCube-210210A: Upper limits from Fermi-GBM Observations
  83. IceCube-210210A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  84. GRB 210210B: Fermi GBM Final Real-time Localization
  85. IceCube-210210A: Two Candidate Counterparts from the Zwicky Transient Facility
  86. GRB 210209A: BOOTES-4/MET optical upper limit
  87. GRB 210210A: LCO Optical Afterglow Detection
  88. Swift GRB 210209A: Global MASTER-Net observations report
  89. GRB 210210A: Swift/UVOT Detection
  90. GRB 210112A: LBT host detection and correction to GCN 29319 (CAHA observations)
  91. GRB 210209A: MITSuME Akeno optical upper limits
  92. IceCube-210210A: IceCube observation of a high-energy neutrino candidate event
  93. GRB 210209A: Swift/UVOT Upper Limits
  94. GRB 210210A: Swift-XRT refined Analysis
  95. GRB 210208A: GIT optical upper limit
  96. GRB 210210A: Redshift from OSIRIS/GTC
  97. GRB 210209A: Swift-XRT refined Analysis
  98. GRB 210210A: Enhanced Swift-XRT position
  99. GRB 210210A: MASTER afterglow observation
  100. ZTF21aahifke/AT2021clk: ZTF discovery of an optical fast transient (possible afterglow)

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