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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 140104B: Swift-XRT refined Analysis
  2. GRB 210126A: AstroSat CZTI detection
  3. GRB 210124B: AstroSat CZTI detection
  4. GRB 210123A: AstroSat CZTI detection
  5. IPN triangulation of a bright burst from SGR 1935+2154
  6. ZTF21aaeyldq: Observations with the 3.6m DOT
  7. GECAM detection of a short burst probably from SGR 1935+2154
  8. GRB 210127A: Fermi GBM Final Real-time Localization
  9. GRB 210120A: Fermi GBM detection
  10. Fermi trigger No 633348010: Global MASTER-Net observations report
  11. HAWC Transient event on 2021/01/25
  12. Konus-Wind detection of GRB 210121A
  13. Konus-Wind detection of GRB 210124B
  14. GRB 210126A: GECAM detection
  15. IPN triangulation of GRB 210124B (short)
  16. GRB 210126A: BALROG localization (Fermi Trigger / GRB 210126417)
  17. GRB 210124B: Insight-HXMT/HE detection
  18. Fermi trigger No 633257525: Global MASTER-Net observations report
  19. GRB 210123A: Fermi GBM Final Localization
  20. GECAM detection of a burst possibly from the X-ray burster 4U 0614+09 or GRB 210124A
  21. GRB 210123A: Insight-HXMT/HE detection
  22. IPN triangulation of GRB 210121A
  23. GRB 210121A: GECAM detection
  24. GRB 210121A: Insight-HXMT/HE detection
  25. GRB 210120A : 1.3m DFOT optical observations
  26. ZTF21aaeyldq: GROND and CAHA jet break confirmation
  27. ZTF20aaeyldq: VLA radio detection
  28. GRB 210116A: AstroSat CZTI detection
  29. GRB 210120A(MASTER OT J105242.66+152355.0 / AT2021axc): Mondy optical observations
  30. GRB 210116: AstroSat LAXPC detection
  31. GRB 210120A: MASTER OT (possibly) discovery
  32. GECAM In-Flight Trigger of GRB 210120A
  33. GRB 210104A: 3.6m DOT optical upper limit
  34. Fermi GRB 210120A: Global MASTER-Net observations report
  35. GRB 210120A: BALROG localization (Fermi Trigger 632819449 / GRB 210120299)
  36. GRB 210120A: Fermi GBM Final Real-time Localization
  37. GRB 210112A: 3.6m DOT optical detection
  38. GRB 210119A (Swift J1851.2-6148): Swift-BAT refined analysis
  39. GECAM detection of a short GRB 210119A or a new SGR candidate Swift J1851.2-6148
  40. ZTF21aaeyldq: GROND observations
  41. GRB 210119A: Insight-HXMT/HE detection
  42. GRB 210119A: Fermi GBM observation
  43. ZTF21aaeyldq: LBT near-infrared observations
  44. GRB 210112A: Insight-HXMT/HE detection
  45. Short Fermi GRB 210119A or new SGR Swift J1851.2-6148: Possible MASTER Short OT detection
  46. Fermi GRB 210119A: Global MASTER-Net observations report
  47. Swift detection of a new SGR Swift J1851.2-6148 or a short GRB 210119A
  48. GRB 210119A: Fermi GBM Final Real-time Localization
  49. ZTF21aaeyldq CAHA 2.2m detection and power-law decay
  50. GRB 200613A: Host galaxy redshift from OSIRIS/GTC
  51. GRB 210112A: Deep CAHA 2.2m detection
  52. GRB 210104A: Late-time CAHA 2.2m detection
  53. Fermi trigger No 632573937: Global MASTER-Net observations report
  54. ZTF21aaeyldq: KPED observations
  55. Konus-Wind detection of GRB 210112A
  56. Correction to GCN 29288: NuEm-210111A: No counterpart candidates in INTEGRAL SPI-ACS observation
  57. ZTF21aaeyldq (AT2021any): Detection of X-ray Emission with Swift/XRT
  58. ZTF21aaeyldq: 2.2m CAHA BVRI optical observations
  59. GRB 201221D: near-infrared observation with LBT
  60. ZTF21aaeyldq: NOT optical observations
  61. ZTF21aaeyldq: Lowell Discovery Telescope observations
  62. ZTF21aaeyldq: observations with the 3.6m Devasthal Optical Telescope
  63. ZTF21aaeyldq: GTC Redshift and GRB afterglow nature confirmation
  64. GRB 201015A: evidence of supernova in LBT spectra
  65. ZTF Discovery of ZTF21aaeyldq (AT2021any): a Hostless, Young, and Rapidly Fading Transient
  66. GRB 210104A: JCMT SCUBA-2 sub-mm observations
  67. GRB 210112A: Swift/UVOT Detection
  68. GRB 210112A: Mondy optical observations
  69. GRB 210112A: 1.3m DFOT Optical upper limit
  70. GRB 210112A: OSN second epoch, decay
  71. GRB 210104A: AstroSat CZTI detection
  72. NuEm-210111A: MAXI/GSC upper limit
  73. GRB 210112A: Swift-BAT refined analysis
  74. GRB 210112A: OSN Reddened Afterglow Detection
  75. GRB 210112A: Swift-XRT refined Analysis
  76. NuEm-210111A : No neutrino counterpart in ANTARES
  77. GRB 210112A: AGILE detection
  78. GRB 210112A: Kitab a optical upper limit
  79. GRB 210104A: AROMA-N Optical Afterglow Detection
  80. GRB 210112A: Enhanced Swift-XRT position
  81. GRB 210112A: Swift detection of a burst with an optical counterpart
  82. NuEm-210111A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  83. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-210111A
  84. GRB 210104A: Mondy optical observations, light curve
  85. MAXI GRB210110.64: Global MASTER-Net observations report
  86. GRB 210110A: MAXI/GSC detection
  87. GRB 210104A: Assy continued optical observations, correction to GCN circ. 29265
  88. GRB 210109A: MAXI/GSC detection
  89. GRB 201227A: continued Chilescope confirmation of variability of possible optical counterpart, redshift estimating
  90. Correction to GCN 29278: GRB 201216C XRT refined analysis
  91. GRB 210108A: BALROG localization (Fermi Trigger 631793415 / GRB 210108424)
  92. GRB 201216C: Swift-XRT refined Analysis
  93. GRB 210104A: SAO RAS optical observations
  94. GRB 201227A: ASIM observation
  95. GRB 210104A: GMG observations
  96. GRB210104A: VIRT optical transient detection.
  97. GRB 210104A: SARA-KP 0.9m Optical Afterglow Detection
  98. Fermi trigger No 631602681: Global MASTER-Net observations report
  99. GRB 210102B: further Swift-XRT observations
  100. GRB 210102B: Assy optical afterglow identification

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