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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"

19048 results found.

  1. GRB 251129A: SVOM detection of a burst
  2. GRB 251126A: Swift-BAT refined analysis
  3. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  4. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  5. GRB 251126A: further SAO RAS optical observations
  6. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  7. GRB251126A: MAO/AZT-22 optical observations
  8. GRB251126A: Continued optical observation from 1.3m DFOT
  9. GRB 251126A: Swift/UVOT Detection
  10. EP251124a: Pan-STARRS ri-band imaging and photometry
  11. GRB 251126A: Mondy and SAO RAS optical observations
  12. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  13. GRB 251126A: 1.3m DFOT optical afterglow detection
  14. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  15. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  16. GRB 251126A: Enhanced Swift-XRT position
  17. GRB 251126A: Kilonova-Catcher optical afterglow detection
  18. GRB 251126A: Nanshan/HMT optical afterglow detection
  19. GRB 251126A: GIT discovery of the likely optical afterglow
  20. GRB 251126A: Swift detection of a burst
  21. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  22. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  23. EP251124b: NOT r- and z-band optical upper limits
  24. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  25. EP251124b: EP-WXT detection of a fast X-ray transient
  26. EP251124a: Xinglong GWAC-F60A optical observation
  27. EP251124a: NOT r- and z-band optical upper limits
  28. EP251124a: Swift-XRT observations
  29. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  30. EP251124a: Optical upper limit with Kinder observations
  31. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  32. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  33. EP251124a: GROWTH-India Telescope optical upper limits
  34. EP251124a: Einstein Probe detection of an X-ray transient
  35. GRB 251116C: Swift-XRT confirmation of fading
  36. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  37. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  38. EP251118A: 3.6m DOT optical afterglow detection
  39. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  40. GRB 251122A / EP251122a: WFST optical observations
  41. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  42. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  43. GRB 251122A / EP251122a: LCO optical upper limits
  44. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  45. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  46. GRB 251122A / EP251122a: SVOM detection of a long burst
  47. EP251122a: Einstein Probe detection of an X-ray transient
  48. EP251118a: Continued Optical Detection with Kinder observations
  49. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  50. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  51. EP251118a: Xinglong-2.16m optical observation
  52. EP251118A: 1.3m DFOT optical afterglow detection
  53. GRB 251118A: Swift/UVOT Detection
  54. EP251118a / GRB 251118C: SAO RAS optical observations
  55. GRB 251118A: Swift-XRT afterglow detection
  56. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  57. EP251118a: Optical detection with Kinder observations
  58. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  59. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  60. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  61. EP251118A / GRB 251118C : MASTER optical counterpart observations
  62. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  63. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  64. EP251118a: VLT near-infrared observation
  65. GRB 251116D: SVOM/GRM observation of a long GRB
  66. GRB 251119A: SVOM detection of a possible burst
  67. EP251118a: NOT spectroscopic redshift of z = 1.216
  68. EP251118a: NOT candidate optical counterpart
  69. EP251118a: Einstein Probe detected of a fast X-ray transient
  70. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  71. GRB 251116C: SVOM/ECLAIRs refined analysis
  72. GRB 251116B: SVOM/ECLAIRs refined analysis
  73. GRB 251115A: Swift-XRT observations
  74. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  75. GRB 251117A: SVOM/GRM observation of a short burst
  76. GRB 251117A: Fermi-LAT detection
  77. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  78. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  79. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  80. EP251023a: Assy AZT-20 optical observations
  81. EP251023a: UAFO and AbAO optical observations
  82. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  83. GRB 251025B: further Mondy optical observations
  84. GRB 251111A: Mondy optical upper limit
  85. LIGO/Virgo/KAGRA S251116en: Identification of a GW compact binary merger candidate
  86. LIGO/Virgo/KAGRA S251112cm: Observations with the NSF-DOE Vera C. Rubin Observatory
  87. GRB 251116B: LCO optical upper limits
  88. GRB 251116C: LCO optical upper limits
  89. IceCube-Cascade 251112A: Upper limits from a search for additional neutrino events in IceCube
  90. LIGO/Virgo/KAGRA S251112cm: GRANDMA observations of the skymap
  91. GRB 251013C: joint SVOM/ECLAIRs-GRM refined analysis
  92. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 4-Update Localization Volume
  93. LIGO/Virgo/KAGRA S251112cm: DECam GW-MMADS candidates
  94. LIGO/Virgo/KAGRA S251112cm: Updated Sky localization and false alarm rate estimate
  95. GRB 251113A: AstroSat CZTI detection
  96. LIGO/Virgo/KAGRA S251112cm: ATLAS targeted observations of the skymap
  97. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  98. The EP-WXT trigger 01709248221 is likely a flaring star
  99. LIGO/Virgo/KAGRA S251112cm: FTW observations of galaxies within localization region
  100. GRB 251111A: SVOM/ECLAIRs refined analysis

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