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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"

26362 results found.

  1. GRB 251126A: NOT optical observations
  2. GRB 251126A: 1.3m DFOT optical afterglow detection
  3. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  4. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  5. Fermi GRB 251127A: Global MASTER-Net observations report
  6. GRB 251126A: Enhanced Swift-XRT position
  7. GRB 251126A: Kilonova-Catcher optical afterglow detection
  8. GRB 251126A: Nanshan/HMT optical afterglow detection
  9. Swift GRB 251126A: Global MASTER-Net observations report
  10. GRB 251121A: Fermi GBM Observation
  11. GRB 251126A: GIT discovery of the likely optical afterglow
  12. GRB 251126A: Swift detection of a burst
  13. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  14. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  15. EP251124b: NOT r- and z-band optical upper limits
  16. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  17. Fermi GRB 251125B: Global MASTER-Net observations report
  18. EP251124b: Global MASTER-Net observations report
  19. EP251124b: EP-WXT detection of a fast X-ray transient
  20. EP251124a: Xinglong GWAC-F60A optical observation
  21. Fermi GRB 251125A: Global MASTER-Net observations report
  22. EP251124a: NOT r- and z-band optical upper limits
  23. EP251124a: Global MASTER-Net observations report
  24. EP251124a: Swift-XRT observations
  25. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  26. EP251124a: Optical upper limit with Kinder observations
  27. Fermi GRB 251124a: Global MASTER-Net observations report
  28. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  29. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  30. EP251124a: GROWTH-India Telescope optical upper limits
  31. EP251124a: Einstein Probe detection of an X-ray transient
  32. GRB 251116C: Swift-XRT confirmation of fading
  33. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  34. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  35. EP251118A: 3.6m DOT optical afterglow detection
  36. GRB 251122A / EP251122a: EP-FXT counterpart detection
  37. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  38. GRB 251122A / EP251122a: WFST optical observations
  39. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  40. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  41. GRB 251122A / EP251122a: LCO optical upper limits
  42. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  43. EP251122a: Global MASTER-Net observations report
  44. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  45. GRB 251122A / EP251122a: SVOM detection of a long burst
  46. EP251122a: Einstein Probe detection of an X-ray transient
  47. EP251118a: Continued Optical Detection with Kinder observations
  48. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  49. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  50. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  51. EP251118a: Xinglong-2.16m optical observation
  52. GRB 251115A: Fermi GBM Observation
  53. Fermi trigger No 785388351: Global MASTER-Net observations report
  54. EP251118A: 1.3m DFOT optical afterglow detection
  55. GRB 251118A: Swift/UVOT Detection
  56. EP251118a / GRB 251118C: SAO RAS optical observations
  57. GRB 251118A: Glowbug gamma-ray detection
  58. GRB 251118A: Fermi GBM Observation
  59. GRB 251118A: Swift-XRT afterglow detection
  60. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  61. EP251118a: Optical detection with Kinder observations
  62. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  63. GRB 251118A: NuSTAR detection of bright prompt emission
  64. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  65. GRB 251116C: NOT optical observations
  66. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  67. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  68. GRB 251117A: Swift-XRT observations
  69. EP251118A / GRB 251118C : MASTER optical counterpart observations
  70. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  71. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  72. EP251118a: VLT near-infrared observation
  73. GRB 251116D: SVOM/GRM observation of a long GRB
  74. GRB 251119A: SVOM detection of a possible burst
  75. EP251118a: Global MASTER-Net observations report
  76. LAT GRB251118.86: Global MASTER-Net observations report
  77. EP251118a: NOT candidate optical counterpart
  78. EP251118a: Einstein Probe detected of a fast X-ray transient
  79. Fermi GRB 251118B: Global MASTER-Net observations report
  80. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  81. GRB 251118A: BALROG localization (Fermi Trigger 785190695 / GRB 251118855)
  82. GRB 251117A: AstroSat CZTI detection
  83. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  84. LIGO/Virgo/KAGRA S251117dq: Updated Sky localization
  85. GRB 251115A: Swift-XRT observations
  86. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  87. GRB 251117A: SVOM/GRM observation of a short burst
  88. LAT GRB251117.51: Global MASTER-Net observations report
  89. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  90. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  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 251116D: Glowbug gamma-ray detection
  95. EP251023a: Assy AZT-20 optical observations
  96. EP251023a: UAFO and AbAO optical observations
  97. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  98. GRB 251116C: SVOM/VT optical upper limit
  99. GRB 251025B: further Mondy optical observations
  100. GRB 251111A: Mondy optical upper limit

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