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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 210204: Fermi GBM observation
  2. GRB 210204A: GECAM detection
  3. GRB 210204A: BALROG localization (Fermi Trigger 634112970 / GRB 210204270)
  4. GRB 210204A: Fermi GBM Final Real-time Localization
  5. GRB 210202A: AGILE/MCAL detection
  6. Fermi GBM Observations of a bright burst from SGR J1935+2154
  7. GRB 210202A: Fermi GBM detection
  8. GRB 210202A: Fermi-LAT detection
  9. Fermi GRB 210202A: Global MASTER-Net observations report
  10. Fermi trigger No 633963272: Global MASTER-Net observations report
  11. Recent activity of SGR 1935+2154 as observed by CGBM
  12. GRB 210202A: BALROG localization (Fermi Trigger / GRB 210202841)
  13. INTEGRAL detection of a short burst from SGR 1935+2154
  14. GRB 210202A: Fermi GBM Final Real-time Localization
  15. GRB 210131A: GECAM detection
  16. Fermi trigger No 633879387: Global MASTER-Net observations report
  17. GECAM observations of SGR 1935+2154
  18. GRB 210129A: Insight-HXMT/HE detection
  19. Continued Chandra observations of GW170817 at ~3.3 years since merger
  20. Fermi GBM Observations of SGR J1935+2154
  21. Konus-Wind detection of two bright bursts from SGR 1935+2154
  22. GRB 140330A: Swift-XRT refined Analysis
  23. GRB 140320B: Swift-XRT refined Analysis
  24. GRB 140402A: Swift-XRT refined Analysis
  25. GRB 140104B: Swift-XRT refined Analysis
  26. GRB 210126A: AstroSat CZTI detection
  27. GRB 210124B: AstroSat CZTI detection
  28. GRB 210123A: AstroSat CZTI detection
  29. IPN triangulation of a bright burst from SGR 1935+2154
  30. ZTF21aaeyldq: Observations with the 3.6m DOT
  31. GECAM detection of a short burst probably from SGR 1935+2154
  32. GRB 210127A: Fermi GBM Final Real-time Localization
  33. GRB 210120A: Fermi GBM detection
  34. Fermi trigger No 633348010: Global MASTER-Net observations report
  35. HAWC Transient event on 2021/01/25
  36. Konus-Wind detection of GRB 210121A
  37. Konus-Wind detection of GRB 210124B
  38. GRB 210126A: GECAM detection
  39. IPN triangulation of GRB 210124B (short)
  40. GRB 210126A: BALROG localization (Fermi Trigger / GRB 210126417)
  41. GRB 210124B: Insight-HXMT/HE detection
  42. Fermi trigger No 633257525: Global MASTER-Net observations report
  43. GRB 210123A: Fermi GBM Final Localization
  44. GECAM detection of a burst possibly from the X-ray burster 4U 0614+09 or GRB 210124A
  45. GRB 210123A: Insight-HXMT/HE detection
  46. IPN triangulation of GRB 210121A
  47. GRB 210121A: GECAM detection
  48. GRB 210121A: Insight-HXMT/HE detection
  49. GRB 210120A : 1.3m DFOT optical observations
  50. ZTF21aaeyldq: GROND and CAHA jet break confirmation
  51. ZTF20aaeyldq: VLA radio detection
  52. GRB 210116A: AstroSat CZTI detection
  53. GRB 210120A(MASTER OT J105242.66+152355.0 / AT2021axc): Mondy optical observations
  54. GRB 210116: AstroSat LAXPC detection
  55. GRB 210120A: MASTER OT (possibly) discovery
  56. GECAM In-Flight Trigger of GRB 210120A
  57. GRB 210104A: 3.6m DOT optical upper limit
  58. Fermi GRB 210120A: Global MASTER-Net observations report
  59. GRB 210120A: BALROG localization (Fermi Trigger 632819449 / GRB 210120299)
  60. GRB 210120A: Fermi GBM Final Real-time Localization
  61. GRB 210112A: 3.6m DOT optical detection
  62. GRB 210119A (Swift J1851.2-6148): Swift-BAT refined analysis
  63. GECAM detection of a short GRB 210119A or a new SGR candidate Swift J1851.2-6148
  64. ZTF21aaeyldq: GROND observations
  65. GRB 210119A: Insight-HXMT/HE detection
  66. GRB 210119A: Fermi GBM observation
  67. ZTF21aaeyldq: LBT near-infrared observations
  68. GRB 210112A: Insight-HXMT/HE detection
  69. Short Fermi GRB 210119A or new SGR Swift J1851.2-6148: Possible MASTER Short OT detection
  70. Fermi GRB 210119A: Global MASTER-Net observations report
  71. Swift detection of a new SGR Swift J1851.2-6148 or a short GRB 210119A
  72. GRB 210119A: Fermi GBM Final Real-time Localization
  73. ZTF21aaeyldq CAHA 2.2m detection and power-law decay
  74. GRB 200613A: Host galaxy redshift from OSIRIS/GTC
  75. GRB 210112A: Deep CAHA 2.2m detection
  76. GRB 210104A: Late-time CAHA 2.2m detection
  77. Fermi trigger No 632573937: Global MASTER-Net observations report
  78. ZTF21aaeyldq: KPED observations
  79. Konus-Wind detection of GRB 210112A
  80. Correction to GCN 29288: NuEm-210111A: No counterpart candidates in INTEGRAL SPI-ACS observation
  81. ZTF21aaeyldq (AT2021any): Detection of X-ray Emission with Swift/XRT
  82. ZTF21aaeyldq: 2.2m CAHA BVRI optical observations
  83. GRB 201221D: near-infrared observation with LBT
  84. ZTF21aaeyldq: NOT optical observations
  85. ZTF21aaeyldq: Lowell Discovery Telescope observations
  86. ZTF21aaeyldq: observations with the 3.6m Devasthal Optical Telescope
  87. ZTF21aaeyldq: GTC Redshift and GRB afterglow nature confirmation
  88. GRB 201015A: evidence of supernova in LBT spectra
  89. ZTF Discovery of ZTF21aaeyldq (AT2021any): a Hostless, Young, and Rapidly Fading Transient
  90. GRB 210104A: JCMT SCUBA-2 sub-mm observations
  91. GRB 210112A: Swift/UVOT Detection
  92. GRB 210112A: Mondy optical observations
  93. GRB 210112A: 1.3m DFOT Optical upper limit
  94. GRB 210112A: OSN second epoch, decay
  95. GRB 210104A: AstroSat CZTI detection
  96. NuEm-210111A: MAXI/GSC upper limit
  97. GRB 210112A: Swift-BAT refined analysis
  98. GRB 210112A: OSN Reddened Afterglow Detection
  99. GRB 210112A: Swift-XRT refined Analysis
  100. NuEm-210111A : No neutrino counterpart in ANTARES

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