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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"

22197 results found.

  1. EP251130a: Mondy optical observations
  2. EP251130a: Optical detections with Kinder observations
  3. EP251130a: SAO RAS optical observations
  4. EP251130A: Optical observation from 1.3m DFOT
  5. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  6. EP251130a: JinShan optical observations
  7. GRB 251127A: SVOM/GRM observation
  8. EP251130a: Swift-XRT counterpart detection
  9. EP251130a: COLIBRÍ optical counterpart candidate
  10. EP251130a: Einstein Probe detection of an X-ray transient
  11. GRB 251129A / EP251129a: SAO RAS optical observations
  12. GRB 251126A: SAO RAS optical observations
  13. GRB 251128A: SVOM/GRM observation of a long burst
  14. SVOM GRB 251129A : MASTER optical counterpart detection
  15. GRB 251129A: Swift-XRT afterglow detection
  16. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  17. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  18. GRB 251129A: SVOM detection of a burst
  19. GRB 251129A: SVOM detection of a burst
  20. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  21. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  22. GRB 251127A: Glowbug gamma-ray detection
  23. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  24. GRB 251126A: further SAO RAS optical observations
  25. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  26. GRB251126A: MAO/AZT-22 optical observations
  27. GRB251126A: Continued optical observation from 1.3m DFOT
  28. GRB 251126A: Swift/UVOT Detection
  29. EP251124a: Pan-STARRS ri-band imaging and photometry
  30. GRB 251126A: Mondy and SAO RAS optical observations
  31. GRB 251126A: Swift-XRT refined Analysis
  32. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  33. GRB 251126A: 1.3m DFOT optical afterglow detection
  34. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  35. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  36. GRB 251126A: Enhanced Swift-XRT position
  37. GRB 251126A: Kilonova-Catcher optical afterglow detection
  38. GRB 251126A: Nanshan/HMT optical afterglow detection
  39. GRB 251126A: GIT discovery of the likely optical afterglow
  40. GRB 251126A: Swift detection of a burst
  41. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  42. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  43. EP251124b: NOT r- and z-band optical upper limits
  44. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  45. EP251124b: EP-WXT detection of a fast X-ray transient
  46. EP251124a: Xinglong GWAC-F60A optical observation
  47. EP251124a: NOT r- and z-band optical upper limits
  48. EP251124a: Swift-XRT observations
  49. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  50. EP251124a: Optical upper limit with Kinder observations
  51. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  52. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  53. EP251124a: GROWTH-India Telescope optical upper limits
  54. EP251124a: Einstein Probe detection of an X-ray transient
  55. GRB 251116C: Swift-XRT confirmation of fading
  56. GRB 251122A/EP251122a: FTW optical and NIR observations
  57. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  58. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  59. EP251118A: 3.6m DOT optical afterglow detection
  60. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  61. GRB 251122A / EP251122a: WFST optical observations
  62. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  63. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  64. GRB 251122A / EP251122a: LCO optical upper limits
  65. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  66. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  67. GRB 251122A / EP251122a: SVOM detection of a long burst
  68. EP251122a: Einstein Probe detection of an X-ray transient
  69. EP251118a: Continued Optical Detection with Kinder observations
  70. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  71. LIGO/Virgo/KAGRA S251112cm: SOAR spectroscopy of three TROVE TNS candidates
  72. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  73. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  74. EP251118a: Xinglong-2.16m optical observation
  75. EP251118A: 1.3m DFOT optical afterglow detection
  76. GRB 251118A: Swift/UVOT Detection
  77. EP251118a / GRB 251118C: SAO RAS optical observations
  78. GRB 251118A: Glowbug gamma-ray detection
  79. GRB 251118A: Swift-XRT afterglow detection
  80. EP251118a: Optical detection with Kinder observations
  81. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  82. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  83. GRB 251116C: NOT optical observations
  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. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  89. EP251118a: VLT near-infrared observation
  90. GRB 251116D: SVOM/GRM observation of a long GRB
  91. GRB 251119A: SVOM detection of a possible burst
  92. EP251118a: NOT candidate optical counterpart
  93. EP251118a: Einstein Probe detected of a fast X-ray transient
  94. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  95. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  96. GRB 251115A: Swift-XRT observations
  97. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  98. GRB 251117A: SVOM/GRM observation of a short burst
  99. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  100. GRB 251116C: Swift/BAT arcminute localization of a burst

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