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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"

23154 results found.

  1. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  2. Swift GRB 251201B: Global MASTER-Net observations report
  3. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  4. GRB 251130B: AstroSat CZTI detection
  5. GRB 251201B: Swift detection of a burst with an optical counterpart
  6. EP251130a: Optical detections with Kinder observations
  7. EP251130a: KAIT optical observations
  8. GRB 251201A: MAXI/GSC detection
  9. EP251130a: Swift-XRT counterpart detection
  10. EP251130a: COLIBRÍ optical counterpart candidate
  11. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  12. GRB 251129A / EP251129a: OSN and CAHA optical follow-up
  13. GRB 251128A: AstroSat CZTI detection
  14. GRB 251129A / EP251129a: SAO RAS optical observations
  15. Swift trigger 1418333 is not an astrophysical source
  16. GRB 251128A: Fermi GBM Observation
  17. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  18. GRB 251126A: Swift-BAT refined analysis
  19. GRB 251127A: Glowbug gamma-ray detection
  20. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  21. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  22. GRB 251126A NUTTelA-TAO Early Measurements
  23. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  24. EP251124a: Pan-STARRS ri-band imaging and photometry
  25. GRB 251126A: Swift-XRT refined Analysis
  26. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  27. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  28. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  29. GRB 251126A: Kilonova-Catcher optical afterglow detection
  30. GRB 251126A: Swift detection of a burst
  31. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  32. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  33. EP251124a: Swift-XRT observations
  34. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  35. EP251124a: Optical upper limit with Kinder observations
  36. EP251118A: 6 GHz VLA Detection
  37. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  38. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  39. GRB 251116C: Swift-XRT confirmation of fading
  40. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  41. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  42. GRB 251122A / EP251122a: SVOM detection of a long burst
  43. EP251118a: Continued Optical Detection with Kinder observations
  44. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  45. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  46. GRB 251115A: Fermi GBM Observation
  47. GRB 251118A: Swift/UVOT Detection
  48. EP251118a / GRB 251118C: SAO RAS optical observations
  49. GRB 251118A: Glowbug gamma-ray detection
  50. GRB 251118A: Swift-XRT afterglow detection
  51. EP251118a: Optical detection with Kinder observations
  52. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  53. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  54. GRB 251117A: Swift-XRT observations
  55. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  56. Konus-Wind detection of GRB 251118C (EP251118a)
  57. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  58. EP251118a: GOTO optical afterglow detection
  59. GRB 251118A: Fermi-LAT detection
  60. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  61. GRB 251116C: SVOM/ECLAIRs refined analysis
  62. GRB 251116B: SVOM/ECLAIRs refined analysis
  63. GRB 251117A: AstroSat CZTI detection
  64. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  65. GRB 251115A: Swift-XRT observations
  66. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  67. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  68. LIGO/Virgo/KAGRA S251112cm: Classification of reported candidates with SOAR/Goodman
  69. GRB 251116B: SVOM/VT optical upper limit
  70. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  71. GRB 251116C: Swift-XRT observations
  72. GRB 251116D: Glowbug gamma-ray detection
  73. EP251023a: Assy AZT-20 optical observations
  74. GRB 251116D: AstroSat CZTI detection
  75. GRB 251116C: SVOM/VT optical upper limit
  76. LIGO/Virgo/KAGRA S251116en: Identification of a GW compact binary merger candidate
  77. LIGO/Virgo/KAGRA S251112cm: Observations with the NSF-DOE Vera C. Rubin Observatory
  78. GRB 251116B: LCO optical upper limits
  79. GRB 251116C: LCO optical upper limits
  80. GRB 251116C: SVOM detection of a burst
  81. GRB 251116B: SVOM detection of a burst
  82. LIGO/Virgo/KAGRA S251112cm: GRANDMA observations of the skymap
  83. LIGO/Virgo/KAGRA S251112cm: AT2025adht follow-up at Maidanak observatory by GRANDMA
  84. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 4-Update Localization Volume
  85. GRB 251113A: Glowbug gamma-ray detection
  86. GRB 251113A: AstroSat CZTI detection
  87. GRB 251112A: Swift-BAT refined analysis
  88. Konus-Wind detection of GRB 251108C
  89. Konus-Wind detection of GRB 251103A
  90. LIGO/Virgo/KAGRA S251112cm: ATLAS targeted observations of the skymap
  91. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  92. LIGO/Virgo/KAGRA S251112cm: Candidates from the Zwicky Transient Facility
  93. LIGO/Virgo/KAGRA S251112cm: TROVE Vetting of TNS Candidates
  94. GRB 251111A: SVOM/ECLAIRs refined analysis
  95. GRB 251025B: SVOM/ECLAIRs refined analysis
  96. LIGO/Virgo/KAGRA S251112cm: ATLAS pre-detections of AT2025adgp and AT2025adgq
  97. GRB 251108C: AstroSat CZTI detection
  98. GRB 251112B: MAXI/GSC detection
  99. LIGO/Virgo/KAGRA S251112cm: Coverage and upper limits from MAXI/GSC observations
  100. LIGO/Virgo/KAGRA S251112cm: Initial GOTO-South observations

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