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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. The EP-WXT trigger 01709248783 is likely a flaring star
  2. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  3. EP251118A: 3.6m DOT optical afterglow detection
  4. GRB 251122A / EP251122a: EP-FXT counterpart detection
  5. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  6. GRB 251122A / EP251122a: WFST optical observations
  7. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  8. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  9. GRB 251122A / EP251122a: LCO optical upper limits
  10. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  11. EP251122a: Global MASTER-Net observations report
  12. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  13. GRB 251122A / EP251122a: SVOM detection of a long burst
  14. EP251122a: Einstein Probe detection of an X-ray transient
  15. EP251118a: Continued Optical Detection with Kinder observations
  16. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  17. LIGO/Virgo/KAGRA S251112cm: SOAR spectroscopy of three TROVE TNS candidates
  18. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  19. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  20. EP251118a: Xinglong-2.16m optical observation
  21. GRB 251115A: Fermi GBM Observation
  22. The EP-WXT trigger 01709248635 is likely a flaring star
  23. GRB 251121A: Fermi GBM Final Real-time Localization
  24. Fermi Gamma-ray Burst Monitor trigger 785388351 / 251121143 is not a GRB
  25. Fermi trigger No 785388351: Global MASTER-Net observations report
  26. EP251118A: 1.3m DFOT optical afterglow detection
  27. GRB 251118A: Swift/UVOT Detection
  28. EP251118a / GRB 251118C: SAO RAS optical observations
  29. GRB 251118A: Glowbug gamma-ray detection
  30. GRB 251118A: Fermi GBM Observation
  31. GRB 251118A: Swift-XRT afterglow detection
  32. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  33. EP251118a: Optical detection with Kinder observations
  34. GRB 251118A: GECAM-B detection
  35. EP-WXT trigger 01709248403: confirmation of a stellar flare by SVOM/VT
  36. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  37. EP251118a / GRB 251118C: SVOM/VT optical observation
  38. The EP-WXT trigger 01709248403 is likely a flaring star
  39. GRB 251118A: NuSTAR detection of bright prompt emission
  40. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  41. GRB 251116C: NOT optical observations
  42. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  43. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  44. GRB 251018A: FRAM-Auger optical detection
  45. GRB 251117A: Swift-XRT observations
  46. EP251118A / GRB 251118C : MASTER optical counterpart observations
  47. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  48. Konus-Wind detection of GRB 251118C (EP251118a)
  49. The EP-WXT trigger 01709248388 is likely a flaring star
  50. EP251118a: FTW optical and NIR observations
  51. GRB 251117A: Insight-HXMT/HE detection
  52. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  53. EP251118a: VLT near-infrared observation
  54. GRB 251116D: SVOM/GRM observation of a long GRB
  55. EP251118a: GOTO optical afterglow detection
  56. GRB 251119A: SVOM detection of a possible burst
  57. EP251118a: NOT spectroscopic redshift of z = 1.216
  58. EP251118a: Global MASTER-Net observations report
  59. EP251118a: preliminary result of EP-FXT follow-up observation
  60. LAT GRB251118.86: Global MASTER-Net observations report
  61. GRB 251118A: Fermi-LAT detection
  62. EP251118a: NOT candidate optical counterpart
  63. GRB 251118A: Swift ToO observations
  64. EP251118a: Einstein Probe detected of a fast X-ray transient
  65. Fermi GRB 251118B: Global MASTER-Net observations report
  66. GRB 251118B: Fermi GBM Final Real-time Localization
  67. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  68. GRB 251118A: BALROG localization (Fermi Trigger 785190695 / GRB 251118855)
  69. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  70. GRB 251118A: Fermi GBM Final Real-time Localization
  71. GRB 251116C: SVOM/ECLAIRs refined analysis
  72. GRB 251116B: SVOM/ECLAIRs refined analysis
  73. GRB 251117A: AstroSat CZTI detection
  74. GRB 251114B: Insight-HXMT/HE detection
  75. GRB 251114B: GECAM-B detection of a short burst
  76. GRB 251117A: Fermi GBM observation
  77. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  78. LIGO/Virgo/KAGRA S251117dq: Updated Sky localization
  79. GRB 251116D: Insight-HXMT/HE detection
  80. GRB 251115A: Swift-XRT observations
  81. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  82. GRB 251117A: SVOM/GRM observation of a short burst
  83. GRB 251117A: Tiled Swift observations
  84. GRB 251117A: Fermi-LAT detection
  85. LAT GRB251117.51: Global MASTER-Net observations report
  86. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  87. GRB 251116C: Swift/BAT arcminute localization of a burst
  88. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  89. LIGO/Virgo/KAGRA S251112cm: Classification of reported candidates with SOAR/Goodman
  90. GRB 251116B: SVOM/VT optical upper limit
  91. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  92. GRB 251116C: Swift-XRT observations
  93. LIGO/Virgo/KAGRA S251116en: Updated Sky localization
  94. GRB 251117A: Fermi GBM Final Localization Correction
  95. GRB 251116D: Glowbug gamma-ray detection
  96. EP251023a: Assy AZT-20 optical observations
  97. EP251023a: UAFO and AbAO optical observations
  98. GRB 251116D: AstroSat CZTI detection
  99. LIGO/Virgo/KAGRA S251112cm: EP-FXT follow-up observations
  100. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations

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