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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. EP251118A: 6 GHz VLA Detection
  2. Fermi GRB 251124a: Global MASTER-Net observations report
  3. GRB 251124a: Fermi GBM Final Localization
  4. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  5. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  6. EP251124a: GROWTH-India Telescope optical upper limits
  7. EP251124a: Einstein Probe detection of an X-ray transient
  8. GRB 251116C: Swift-XRT confirmation of fading
  9. GRB 251122A/EP251122a: FTW optical and NIR observations
  10. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  11. The EP-WXT trigger 01709248783 is likely a flaring star
  12. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  13. EP251118A: 3.6m DOT optical afterglow detection
  14. GRB 251122A / EP251122a: EP-FXT counterpart detection
  15. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  16. GRB 251122A / EP251122a: WFST optical observations
  17. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  18. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  19. GRB 251122A / EP251122a: LCO optical upper limits
  20. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  21. EP251122a: Global MASTER-Net observations report
  22. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  23. GRB 251122A / EP251122a: SVOM detection of a long burst
  24. EP251122a: Einstein Probe detection of an X-ray transient
  25. EP251118a: Continued Optical Detection with Kinder observations
  26. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  27. LIGO/Virgo/KAGRA S251112cm: SOAR spectroscopy of three TROVE TNS candidates
  28. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  29. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  30. EP251118a: Xinglong-2.16m optical observation
  31. GRB 251115A: Fermi GBM Observation
  32. The EP-WXT trigger 01709248635 is likely a flaring star
  33. GRB 251121A: Fermi GBM Final Real-time Localization
  34. Fermi Gamma-ray Burst Monitor trigger 785388351 / 251121143 is not a GRB
  35. Fermi trigger No 785388351: Global MASTER-Net observations report
  36. EP251118A: 1.3m DFOT optical afterglow detection
  37. GRB 251118A: Swift/UVOT Detection
  38. EP251118a / GRB 251118C: SAO RAS optical observations
  39. GRB 251118A: Glowbug gamma-ray detection
  40. GRB 251118A: Fermi GBM Observation
  41. GRB 251118A: Swift-XRT afterglow detection
  42. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  43. EP251118a: Optical detection with Kinder observations
  44. GRB 251118A: GECAM-B detection
  45. EP-WXT trigger 01709248403: confirmation of a stellar flare by SVOM/VT
  46. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  47. EP251118a / GRB 251118C: SVOM/VT optical observation
  48. The EP-WXT trigger 01709248403 is likely a flaring star
  49. GRB 251118A: NuSTAR detection of bright prompt emission
  50. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  51. GRB 251116C: NOT optical observations
  52. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  53. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  54. GRB 251018A: FRAM-Auger optical detection
  55. GRB 251117A: Swift-XRT observations
  56. EP251118A / GRB 251118C : MASTER optical counterpart observations
  57. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  58. Konus-Wind detection of GRB 251118C (EP251118a)
  59. The EP-WXT trigger 01709248388 is likely a flaring star
  60. EP251118a: FTW optical and NIR observations
  61. GRB 251117A: Insight-HXMT/HE detection
  62. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  63. EP251118a: VLT near-infrared observation
  64. GRB 251116D: SVOM/GRM observation of a long GRB
  65. EP251118a: GOTO optical afterglow detection
  66. GRB 251119A: SVOM detection of a possible burst
  67. EP251118a: NOT spectroscopic redshift of z = 1.216
  68. EP251118a: Global MASTER-Net observations report
  69. EP251118a: preliminary result of EP-FXT follow-up observation
  70. LAT GRB251118.86: Global MASTER-Net observations report
  71. GRB 251118A: Fermi-LAT detection
  72. EP251118a: NOT candidate optical counterpart
  73. GRB 251118A: Swift ToO observations
  74. EP251118a: Einstein Probe detected of a fast X-ray transient
  75. Fermi GRB 251118B: Global MASTER-Net observations report
  76. GRB 251118B: Fermi GBM Final Real-time Localization
  77. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  78. GRB 251118A: BALROG localization (Fermi Trigger 785190695 / GRB 251118855)
  79. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  80. GRB 251118A: Fermi GBM Final Real-time Localization
  81. GRB 251116C: SVOM/ECLAIRs refined analysis
  82. GRB 251116B: SVOM/ECLAIRs refined analysis
  83. GRB 251117A: AstroSat CZTI detection
  84. GRB 251114B: Insight-HXMT/HE detection
  85. GRB 251114B: GECAM-B detection of a short burst
  86. GRB 251117A: Fermi GBM observation
  87. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  88. LIGO/Virgo/KAGRA S251117dq: Updated Sky localization
  89. GRB 251116D: Insight-HXMT/HE detection
  90. GRB 251115A: Swift-XRT observations
  91. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  92. GRB 251117A: SVOM/GRM observation of a short burst
  93. GRB 251117A: Tiled Swift observations
  94. GRB 251117A: Fermi-LAT detection
  95. LAT GRB251117.51: Global MASTER-Net observations report
  96. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  97. GRB 251116C: Swift/BAT arcminute localization of a burst
  98. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  99. LIGO/Virgo/KAGRA S251112cm: Classification of reported candidates with SOAR/Goodman
  100. GRB 251116B: SVOM/VT optical upper limit

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