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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"

5816 results found.

  1. GRB 250922A: SVOM/GRM observation
  2. GRB 250924A: 1.6m Mephisto optical upper limits
  3. GRB 250924A: AstroSat CZTI detection
  4. GRB 250914A: AstroSat CZTI detection
  5. GRB 250920B: AstroSat CZTI detection
  6. GRB 250924A: SVOM/VT optical observation
  7. GRB 250924A: J-band detection with WINTER
  8. GRB 250924A: GROWTH-India Telescope Upper Limits
  9. GRB 250924A: Mondy optical observations, afterglow fading
  10. GRB 250922B: SVOM/GRM observation
  11. GRB 250920C: TRT optical observation
  12. GRB 250924A: COLIBRÍ optical observations
  13. Swift GRB 250924A: Global MASTER-Net observations report
  14. GRB 250924A: DDOTI Detection of the Optical Counterpart
  15. GRB 250924A: Swift detection of a burst with an optical counterpart
  16. GRB 250920B: AbAO optical upper limits
  17. GRB 250920B: CrAO ZTSH optical observations
  18. GRB 250920C: COLIBRÍ optical observations
  19. GRB 250922C: AstroSat CZTI detection of a short burst
  20. Fermi GRB 250922B: Global MASTER-Net observations report
  21. GRB 250920C: NIR observations with WINTER
  22. GRB 250920B: NIR observations with WINTER
  23. Fermi trigger No 780156732: Global MASTER-Net observations report
  24. IPN triangulation of GRB 250920A (long/bright)
  25. GRB 250920B: Glowbug gamma-ray detection
  26. GRB 250916A: CrAO ZTSh R-band optical observations
  27. GRB 250920B: Kitab-ISON optical upper limit
  28. GRB 250917B: Mondy and Zeiss-1000 SAO RAS optical observations, optical observations, afterglow candidate
  29. GRB 250920C: SVOM/GRM observation
  30. GRB 250920A: NuSTAR detection of bright prompt emission
  31. GRB 250920C: GROWTH-India Telescope optical observations
  32. GRB 250916A: FTW optical and NIR observations of the counterpart
  33. Swift GRB 250920C: Global MASTER-Net observations report
  34. GRB 250920B: FTW optical and NIR observations of the counterpart
  35. GRB 250920C: Optical counterpart detection by LCO
  36. GRB 250920A: SVOM/GRM observation
  37. GRB 250920B: SVOM/C-GFT optical observations
  38. GRB 250920C: GOTO optical counterpart candidate
  39. GRB 250920C: Swift detection of a burst
  40. LIGO/Virgo/KAGRA S250920bq: Coverage and upper limits from MAXI/GSC observations
  41. Swift GRB 250920B: Global MASTER-Net observations report
  42. GRB 250919A / EP250919a: Insight-HXMT detection
  43. GRB 250920A: AstroSat CZTI detection
  44. GRB 250920B: Swift detection of a burst with a bright optical counterpart.
  45. GRB 250919A/EP250919a: SVOM/VT optical observation
  46. GRB 250916A: Mondy R-band optical observations
  47. GRB 250919A: Glowbug gamma-ray detection
  48. Fermi GRB 250918A: Global MASTER-Net observations report
  49. GRB 250919A / EP250919a: NuSTAR detection of bright prompt emission
  50. GRB 250918A: SVOM/GRM observation
  51. GRB 250919A: SVOM/GRM observation of a very bright GRB
  52. EP250919a: Global MASTER-Net observations report
  53. EP250919a: Einstein Probe detection of an X-ray transient
  54. Fermi GRB 250919A: Global MASTER-Net observations report
  55. GRB 250917B: VLT/HAWK-I near-infrared observations
  56. GRB 250916A: NuSTAR detection of the prompt emission
  57. GRB 250916A: further SAO RAS optical observations
  58. GRB 250912A: SVOM/ECLAIRs refined analysis
  59. LIGO/Virgo/KAGRA S250918aw: 1 counterpart neutrino candidate event from an IceCube neutrino search
  60. GRB 250916A: OSIRIS+/GTC redshift z = 2.015
  61. GRB 250916A: Swift-XRT observations
  62. EP250916a: EP-FXT follow-up observation
  63. GRB 250916A : GIT optical observations
  64. LIGO/Virgo/KAGRA S250917aq: Three counterpart neutrino candidates from IceCube neutrino searches
  65. GRB 250916A: Glowbug gamma-ray detection
  66. GRB250917B: WFST optical observations
  67. LIGO/Virgo/KAGRA S250917aq: Identification of a GW compact binary merger candidate
  68. Fermi GRB 250917B: Global MASTER-Net observations report
  69. GRB 250916A: GOTO optical counterpart candidate
  70. The EP-WXT trigger 01709241037 is likely a flaring star
  71. GRB 250916A: AstroSat CZTI detection of a bright long burst
  72. GRB 250910A: SVOM/ECLAIRs refined analysis
  73. EP250916a: Einstein Probe detection of an X-ray transient
  74. Fermi GRB 250916A: Global MASTER-Net observations report
  75. LIGO/Virgo/KAGRA S250818k: HCT optical follow-up
  76. SVOM/sb25091517: Confirmation of a stellar flare by SVOM/VT
  77. SVOM/sb25091517: SVOM detection of an X-ray transient
  78. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  79. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  80. GRB 250911A: Insight-HXMT detection
  81. GRB 250912A: SVOM/GRM analysis suggests a possible short GRB with extended emission
  82. GRB 250912A:SVOM/VT optical upper limit
  83. GRB 250912A: LCO optical upper limit
  84. The EP-WXT trigger 01709240768 is likely a flaring star
  85. Fermi GRB 250912A: Global MASTER-Net observations report
  86. EP250911a: Global MASTER-Net observations report
  87. GRB 250912A: SVOM detection of a burst
  88. IceCube-Cascade 250911A: Upper limits from a search for additional neutrino events in IceCube
  89. LIGO/Virgo/KAGRA S250912s: 2 counterpart neutrino candidate events from an IceCube neutrino search
  90. EP250911a: Upper limit from Fermi-GBM Observations
  91. GRB 250911A: GECAM-B detection
  92. LIGO/Virgo/KAGRA S250912f: Identification of a GW compact binary merger candidate
  93. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  94. GRB 250910B: SVOM/GRM observation
  95. EP250911a: SVOM/VT optical observation
  96. GRB 250911A: MASTER optical counterpart observations
  97. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  98. GRB 250909B: Insight-HXMT detection
  99. GRB 250909B: SVOM/GRM observation
  100. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery

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