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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 191228A: UKIRT NIR upper limit
  2. LIGO/Virgo S191222n: No transient candidates in CALET observations
  3. GRB 191228A: Swift detection of a burst
  4. Swift GRB191228.00: Global MASTER-Net observations report
  5. GRB 191227A: Fermi GBM detection
  6. GRB 191227A: Marginal detection by Fermi-LAT
  7. GRB 191227A: MITSuME Akeno optical upper limits
  8. Swift GRB191227A: Global MASTER-Net OT detection
  9. GRB 191227A: Swift detection of a burst
  10. Swift GRB191227.07: Global MASTER-Net observations report
  11. GRB 191227A: Fermi GBM Final Real-time Localization
  12. Swift Trigger 946234: further Swift analysis
  13. LIGO/Virgo S191213g: AT2019wxt 10.4m GTC further spectroscopy
  14. Swift GRB191226.25: Global MASTER-Net observations report
  15. Swift Triggers 946256 and 946257 are not a GRB
  16. Swift GRB191226.02: Global MASTER-Net observations report
  17. Swift Trigger 946234 is probably not a GRB
  18. Swift trigger 946234/GRB 191226.02 : MASTER obervation
  19. LIGO/Virgo S191225aq: Retraction of GW compact binary merger candidate
  20. LIGO/Virgo S191225aq: Global MASTER-Net observations report
  21. GRB 191225B: BALROG localization (Fermi Trigger 598988276 / GRB 191225735)
  22. Fermi trigger No 598988276: Global MASTER-Net observations report
  23. GRB 191225B: Fermi GBM Final Real-time Localization
  24. GRB 191221B: ATCA detection of the radio afterglow
  25. GRB 191225A: Fermi GBM Final Real-time Localization
  26. LIGO/Virgo S191205ah: MASTER OT detection
  27. LIGO/Virgo S191213g: Pan-STARRS monitoring shows PS19hgw (AT2019wxt) to be fading quickly
  28. Konus-Wind observation of GRB 191221B
  29. LIGO/Virgo S191222n : No significant candidates in FRAM-TAROT-GRANDMA observations
  30. GRB 191221B: Swift/UVOT Detection
  31. GRB 191221B: Insight-HXMT/HE detection
  32. LIGO/Virgo S191222n: Updated Sky Localization
  33. LIGO/Virgo S191222n: no counterpart candidate in SVOM/GWAC observations
  34. LIGO/Virgo S191216ap: Updated Source Classification
  35. LIGO/Virgo S191216ap: Upper limits from Insight-HXMT/HE observations
  36. GRB 191220.59: AstroSat CZTI detection
  37. GRB 191221B: AstroSat CZTI detection
  38. GRB 191221B: iTelescope T17 detection
  39. GRB 191221B: iTelescope optical observations
  40. GRB 191221B: ALMA detection
  41. LIGO/Virgo S191216ap: No significant candidates found in Pan-STARRS observations
  42. GRB 191221B: Swift-BAT refined analysis
  43. GRB 191221B: Zadko observatory - Gingin optical observations
  44. GRB 191221B: LCO Optical Detection
  45. GRB 191221B: Swift-XRT refined Analysis
  46. LIGO/Virgo S191213g : No significant candidates found in GRANDMA citizen science observations
  47. LIGO/Virgo S191222n: no counterpart candidates in the Swift/BAT observations
  48. LIGO/Virgo S191222n: No counterpart candidates in Fermi-LAT observations
  49. GRB 191221B: MASTER VWFC OT yearly detection
  50. LIGO/Virgo S191222n: not observable by Fermi-GBM
  51. GRB 191221B: VLT/X-shooter redshift
  52. GRB 191221B: Correction to GCN26551 - VIRT OT observation
  53. GRB 191221B: VIRT Optical Upper Limits
  54. LIGO/Virgo S191222n : no neutrino counterpart candidate in ANTARES search
  55. GRB 191221B: AGILE/MCAL observations
  56. LIGO/Virgo S191222n: upper limits from AGILE-GRID observations
  57. LIGO/Virgo S191222n: upper limits from AGILE/MCAL observations
  58. LIGO/Virgo S191222n: Coverage and upper limits from MAXI/GSC observations
  59. LIGO/Virgo S191222n: INTEGRAL was inactive at the time of the event
  60. LIGO/Virgo S191222n: No counterpart candidates in HAWC observations
  61. LIGO/Virgo S191222n: Identification of a GW compact binary merger candidate
  62. LIGO/Virgo S191222n: Upper limits from IceCube neutrino searches
  63. LIGO/Virgo S191222n: Global MASTER-Net observations report
  64. GRB 191221B: Enhanced Swift-XRT position
  65. Baksan Neutrino Observatory Alert 191222.09: Global MASTER-Net observations report
  66. GRB 191221B: Swift/UVOT redshift
  67. GRB 191221B: MASTER OT detection
  68. Swift GRB 191221B: Global MASTER-Net observations report
  69. GRB 191220A: Swift-BAT refined analysis
  70. GRB 191221B: Swift detection of a burst and a very bright optical candidate
  71. Fermi trigger No 598648473: Global MASTER-Net observations report
  72. GRB 191221A: Fermi GBM Final Real-time Localization
  73. LIGO/Virgo S191216ap: VLA/JAGWAR radio monitoring of the 1-sigma HAWC region
  74. LIGO/Virgo S191216ap: No radio candidates so far in the VLA/JAGWAR galaxy targeted search
  75. LIGO/Virgo S191216ap: MASTER optical observation
  76. LIGO/Virgo S191216ap : No significant candidates in FRAM-TAROT-GRANDMA observations
  77. LIGO/Virgo S191213g: VLA follow-up of AT2019wxt/PS19hg
  78. GRB 191220A: Swift/UVOT Upper Limits
  79. GRB 191220A: AbAO optical observations
  80. GRB 191220A: Swift-XRT refined Analysis
  81. Fermi trigger No 598543714: Global MASTER-Net observations report
  82. GRB 191220A: Enhanced Swift-XRT position
  83. LIGO/Virgo S191213g: AT2019wxt 10.4m GTC spectroscopy
  84. LIGO/Virgo S191213g : SAO 1-m optical observation of AT2019wxt (PS19hgw)
  85. GRB 191220A: SAO RAS possible OT detection
  86. LIGO/Virgo S191215w: Updated Sky Localization
  87. LIGO/Virgo S191213g: DCT observation of AT2019wxt
  88. GRB 191220A: Swift detection of a burst
  89. GRB 191220A: Prompt enhanced Swift-XRT position
  90. Swift GRB191220.56: Global MASTER-Net observations report
  91. LIGO/Virgo S191220af: Retraction of GW compact binary merger candidate
  92. LIGO/Virgo S191220af: Global MASTER-Net observations report
  93. LIGO/Virgo S191216ap: AstroSat CZTI upper limits
  94. LIGO/Virgo S191213g: YAHPT Observations of AT2019wxt(PS19hgw)
  95. LIGO/Virgo S191216ap: Subaru/Hyper Suprime-Cam observations of GW+IceCube+HAWC error region
  96. LIGO/Virgo S191213g: LBT spectrum of AT2019wxt (PS19hgw) reveals a type IIb supernova
  97. LIGO/Virgo S191216ap: UPDATED list of galaxies coincident with LIGO/Virgo LALInference skymap and HAWC positions
  98. Konus-Wind observation of GRB 191218A
  99. LIGO/Virgo S191216ap: Updated Sky Localization
  100. LIGO/Virgo S191213g: VLT spectrum of AT2019wxt (PS19hgw) - a probable Ib supernova

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