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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"

24778 results found.

  1. GRB 251129A / EP251129a: SAO RAS optical observations
  2. GRB 251126A: SAO RAS optical observations
  3. GRB 251128A: GECAM-B detection
  4. GRB 251128A: SVOM/GRM observation of a long burst
  5. SVOM GRB 251129A : MASTER optical counterpart detection
  6. GRB 251129A: Swift-XRT afterglow detection
  7. GRB 251129A: SVOM/VT optical fading
  8. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  9. GRB 251128A: Fermi GBM Observation
  10. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  11. GRB 251129A: SVOM detection of a burst
  12. GRB 251129A: SVOM detection of a burst
  13. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  14. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  15. GRB 251127A: Glowbug gamma-ray detection
  16. GRB 251126A: further SAO RAS optical observations
  17. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  18. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  19. GRB251126A: MAO/AZT-22 optical observations
  20. GRB251126A: Continued optical observation from 1.3m DFOT
  21. GRB 251126A: Swift/UVOT Detection
  22. GRB 251126A: Mondy and SAO RAS optical observations
  23. GRB 251126A: Swift-XRT refined Analysis
  24. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  25. GRB 251126A: 1.3m DFOT optical afterglow detection
  26. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  27. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  28. GRB 251125B: GECAM-B detection
  29. GRB 251126A: Enhanced Swift-XRT position
  30. GRB 251126A: Kilonova-Catcher optical afterglow detection
  31. GRB 251126A: Nanshan/HMT optical afterglow detection
  32. GRB 251121A: Fermi GBM Observation
  33. GRB 251126A: GIT discovery of the likely optical afterglow
  34. GRB 251126A: Swift detection of a burst
  35. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  36. EP251124b follow-up observation by EP-FXT
  37. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  38. EP251124b: NOT r- and z-band optical upper limits
  39. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  40. EP251124b: EP-WXT detection of a fast X-ray transient
  41. EP251124a: Xinglong GWAC-F60A optical observation
  42. EP251124a: NOT r- and z-band optical upper limits
  43. EP251124a: Swift-XRT observations
  44. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  45. EP251124a: Optical upper limit with Kinder observations
  46. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  47. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  48. EP251124a: GROWTH-India Telescope optical upper limits
  49. EP251124a: Einstein Probe detection of an X-ray transient
  50. GRB 251116C: Swift-XRT confirmation of fading
  51. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  52. The EP-WXT trigger 01709248783 is likely a flaring star
  53. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  54. EP251118A: 3.6m DOT optical afterglow detection
  55. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  56. GRB 251122A / EP251122a: WFST optical observations
  57. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  58. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  59. GRB 251122A / EP251122a: LCO optical upper limits
  60. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  61. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  62. GRB 251122A / EP251122a: SVOM detection of a long burst
  63. EP251122a: Einstein Probe detection of an X-ray transient
  64. EP251118a: Continued Optical Detection with Kinder observations
  65. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  66. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  67. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  68. EP251118a: Xinglong-2.16m optical observation
  69. GRB 251115A: Fermi GBM Observation
  70. The EP-WXT trigger 01709248635 is likely a flaring star
  71. Fermi trigger No 785388351: Global MASTER-Net observations report
  72. EP251118A: 1.3m DFOT optical afterglow detection
  73. GRB 251118A: Swift/UVOT Detection
  74. EP251118a / GRB 251118C: SAO RAS optical observations
  75. GRB 251118A: Glowbug gamma-ray detection
  76. GRB 251118A: Fermi GBM Observation
  77. GRB 251118A: Swift-XRT afterglow detection
  78. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  79. EP251118a: Optical detection with Kinder observations
  80. GRB 251118A: GECAM-B detection
  81. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  82. The EP-WXT trigger 01709248403 is likely a flaring star
  83. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  84. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  85. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  86. GRB 251117A: Swift-XRT observations
  87. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  88. Konus-Wind detection of GRB 251118C (EP251118a)
  89. The EP-WXT trigger 01709248388 is likely a flaring star
  90. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  91. EP251118a: VLT near-infrared observation
  92. GRB 251116D: SVOM/GRM observation of a long GRB
  93. GRB 251119A: SVOM detection of a possible burst
  94. EP251118a: NOT spectroscopic redshift of z = 1.216
  95. EP251118a: NOT candidate optical counterpart
  96. EP251118a: Einstein Probe detected of a fast X-ray transient
  97. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  98. GRB 251118A: BALROG localization (Fermi Trigger 785190695 / GRB 251118855)
  99. GRB 251116C: SVOM/ECLAIRs refined analysis
  100. GRB 251116B: SVOM/ECLAIRs refined analysis

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