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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. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  2. LIGO/Virgo/KAGRA S251112cm: SOAR spectroscopy of three TROVE TNS candidates
  3. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  4. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  5. EP251118a: Xinglong-2.16m optical observation
  6. GRB 251115A: Fermi GBM Observation
  7. The EP-WXT trigger 01709248635 is likely a flaring star
  8. GRB 251121A: Fermi GBM Final Real-time Localization
  9. Fermi Gamma-ray Burst Monitor trigger 785388351 / 251121143 is not a GRB
  10. Fermi trigger No 785388351: Global MASTER-Net observations report
  11. EP251118A: 1.3m DFOT optical afterglow detection
  12. GRB 251118A: Swift/UVOT Detection
  13. EP251118a / GRB 251118C: SAO RAS optical observations
  14. GRB 251118A: Glowbug gamma-ray detection
  15. GRB 251118A: Fermi GBM Observation
  16. GRB 251118A: Swift-XRT afterglow detection
  17. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  18. EP251118a: Optical detection with Kinder observations
  19. GRB 251118A: GECAM-B detection
  20. EP-WXT trigger 01709248403: confirmation of a stellar flare by SVOM/VT
  21. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  22. EP251118a / GRB 251118C: SVOM/VT optical observation
  23. The EP-WXT trigger 01709248403 is likely a flaring star
  24. GRB 251118A: NuSTAR detection of bright prompt emission
  25. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  26. GRB 251116C: NOT optical observations
  27. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  28. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  29. GRB 251018A: FRAM-Auger optical detection
  30. GRB 251117A: Swift-XRT observations
  31. EP251118A / GRB 251118C : MASTER optical counterpart observations
  32. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  33. Konus-Wind detection of GRB 251118C (EP251118a)
  34. The EP-WXT trigger 01709248388 is likely a flaring star
  35. EP251118a: FTW optical and NIR observations
  36. GRB 251117A: Insight-HXMT/HE detection
  37. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  38. EP251118a: VLT near-infrared observation
  39. GRB 251116D: SVOM/GRM observation of a long GRB
  40. EP251118a: GOTO optical afterglow detection
  41. GRB 251119A: SVOM detection of a possible burst
  42. EP251118a: NOT spectroscopic redshift of z = 1.216
  43. EP251118a: Global MASTER-Net observations report
  44. EP251118a: preliminary result of EP-FXT follow-up observation
  45. LAT GRB251118.86: Global MASTER-Net observations report
  46. GRB 251118A: Fermi-LAT detection
  47. EP251118a: NOT candidate optical counterpart
  48. GRB 251118A: Swift ToO observations
  49. EP251118a: Einstein Probe detected of a fast X-ray transient
  50. Fermi GRB 251118B: Global MASTER-Net observations report
  51. GRB 251118B: Fermi GBM Final Real-time Localization
  52. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  53. GRB 251118A: BALROG localization (Fermi Trigger 785190695 / GRB 251118855)
  54. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  55. GRB 251118A: Fermi GBM Final Real-time Localization
  56. GRB 251116C: SVOM/ECLAIRs refined analysis
  57. GRB 251116B: SVOM/ECLAIRs refined analysis
  58. GRB 251117A: AstroSat CZTI detection
  59. GRB 251114B: Insight-HXMT/HE detection
  60. GRB 251114B: GECAM-B detection of a short burst
  61. GRB 251117A: Fermi GBM observation
  62. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  63. LIGO/Virgo/KAGRA S251117dq: Updated Sky localization
  64. GRB 251116D: Insight-HXMT/HE detection
  65. GRB 251115A: Swift-XRT observations
  66. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  67. GRB 251117A: SVOM/GRM observation of a short burst
  68. GRB 251117A: Tiled Swift observations
  69. GRB 251117A: Fermi-LAT detection
  70. LAT GRB251117.51: Global MASTER-Net observations report
  71. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  72. GRB 251116C: Swift/BAT arcminute localization of a burst
  73. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  74. LIGO/Virgo/KAGRA S251112cm: Classification of reported candidates with SOAR/Goodman
  75. GRB 251116B: SVOM/VT optical upper limit
  76. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  77. GRB 251116C: Swift-XRT observations
  78. LIGO/Virgo/KAGRA S251116en: Updated Sky localization
  79. GRB 251117A: Fermi GBM Final Localization Correction
  80. GRB 251116D: Glowbug gamma-ray detection
  81. EP251023a: Assy AZT-20 optical observations
  82. EP251023a: UAFO and AbAO optical observations
  83. GRB 251116D: AstroSat CZTI detection
  84. LIGO/Virgo/KAGRA S251112cm: EP-FXT follow-up observations
  85. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  86. GRB 251116C: SVOM/VT optical upper limit
  87. GRB 251025B: further Mondy optical observations
  88. GRB 251111A: Mondy optical upper limit
  89. GRB 251116B: EP-FXT follow-up observation
  90. LIGO/Virgo/KAGRA S251116en: Identification of a GW compact binary merger candidate
  91. LIGO/Virgo/KAGRA S251112cm: Observations with the NSF-DOE Vera C. Rubin Observatory
  92. GRB 251116B: LCO optical upper limits
  93. GRB 251116C: LCO optical upper limits
  94. SVOM GRB251116C: Global MASTER-Net observations report
  95. GRB 251116C: SVOM detection of a burst
  96. GRB 251116B: SVOM detection of a burst
  97. IceCube-Cascade 251112A: Upper limits from a search for additional neutrino events in IceCube
  98. GRB 251116A: Fermi GBM Final Real-time Localization
  99. LIGO/Virgo/KAGRA S251112cm: GRANDMA observations of the skymap
  100. LIGO/Virgo/KAGRA S251112cm: AT2025adht follow-up at Maidanak observatory by GRANDMA

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