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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"

18430 results found.

  1. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  2. EP251124b: EP-WXT detection of a fast X-ray transient
  3. EP251124a: Xinglong GWAC-F60A optical observation
  4. EP251124a: NOT r- and z-band optical upper limits
  5. EP251124a: Swift-XRT observations
  6. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  7. EP251124a: Optical upper limit with Kinder observations
  8. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  9. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  10. EP251124a: GROWTH-India Telescope optical upper limits
  11. EP251124a: Einstein Probe detection of an X-ray transient
  12. GRB 251116C: Swift-XRT confirmation of fading
  13. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  14. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  15. EP251118A: 3.6m DOT optical afterglow detection
  16. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  17. GRB 251122A / EP251122a: WFST optical observations
  18. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  19. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  20. GRB 251122A / EP251122a: LCO optical upper limits
  21. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  22. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  23. GRB 251122A / EP251122a: SVOM detection of a long burst
  24. EP251122a: Einstein Probe detection of an X-ray transient
  25. EP251118a: Continued Optical Detection with Kinder observations
  26. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  27. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  28. EP251118a: Xinglong-2.16m optical observation
  29. Fermi trigger No 785388351: Global MASTER-Net observations report
  30. EP251118A: 1.3m DFOT optical afterglow detection
  31. GRB 251118A: Swift/UVOT Detection
  32. EP251118a / GRB 251118C: SAO RAS optical observations
  33. GRB 251118A: Swift-XRT afterglow detection
  34. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  35. EP251118a: Optical detection with Kinder observations
  36. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  37. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  38. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  39. GRB 251117A: Swift-XRT observations
  40. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  41. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  42. EP251118a: VLT near-infrared observation
  43. GRB 251116D: SVOM/GRM observation of a long GRB
  44. GRB 251119A: SVOM detection of a possible burst
  45. EP251118a: NOT candidate optical counterpart
  46. GRB 251118A: Swift ToO observations
  47. EP251118a: Einstein Probe detected of a fast X-ray transient
  48. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  49. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  50. GRB 251117A: SVOM/GRM observation of a short burst
  51. GRB 251117A: Tiled Swift observations
  52. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  53. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  54. EP251023a: Assy AZT-20 optical observations
  55. EP251023a: UAFO and AbAO optical observations
  56. LIGO/Virgo/KAGRA S251112cm: EP-FXT follow-up observations
  57. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  58. GRB 251025B: further Mondy optical observations
  59. GRB 251111A: Mondy optical upper limit
  60. LIGO/Virgo/KAGRA S251116en: Identification of a GW compact binary merger candidate
  61. LIGO/Virgo/KAGRA S251112cm: Observations with the NSF-DOE Vera C. Rubin Observatory
  62. GRB 251116B: LCO optical upper limits
  63. GRB 251116C: LCO optical upper limits
  64. GRB 251116B: SVOM detection of a burst
  65. LIGO/Virgo/KAGRA S251112cm: GRANDMA observations of the skymap
  66. GRB 251115A: Tiled Swift observations
  67. GRB 251013C: joint SVOM/ECLAIRs-GRM refined analysis
  68. LIGO/Virgo/KAGRA S251112cm: DECam GW-MMADS candidates
  69. LIGO/Virgo/KAGRA S251112cm: Candidates from the Zwicky Transient Facility
  70. LIGO/Virgo/KAGRA S251112cm: TROVE Vetting of TNS Candidates
  71. LIGO/Virgo/KAGRA S251112cm: FTW observations of galaxies within localization region
  72. GRB 251112A: Swift/UVOT Upper Limits
  73. LIGO/Virgo/KAGRA S251112cm: Coverage and upper limits from MAXI/GSC observations
  74. Swift Trigger 1413695: a possible GRB 251112A
  75. GRB251111A: 1.3m DFOT optical upper limit
  76. LIGO/Virgo/KAGRA S251112cm: Identification of a GW compact binary merger candidate
  77. GRB 251111A: Swift-XRT afterglow detection
  78. GRB 251111A: SVOM/VT optical observations with X-band data
  79. GRB 251111A: SVOM/VT optical observations with VHF data
  80. GRB 251111A: LCO optical observation
  81. GRB 251111A: SVOM/COLIBRÍ (FM-GFT) optical counterpart detection
  82. GRB 251106A: Swift/UVOT Upper Limits
  83. LIGO/Virgo/KAGRA S251108fi: DDOTI Optical Candidate
  84. LIGO/Virgo/KAGRA S251108fi: Identification of a GW compact binary merger candidate
  85. GRB 251102B: SVOM/GRM observation
  86. LIGO/Virgo/KAGRA S251108dn: Identification of a GW compact binary merger candidate
  87. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) fading of the optical counterpart
  88. GRB 251106A: Swift-XRT afterglow detection
  89. GRB 251106A: Kilonova-Catcher optical upper limit
  90. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) detection of a likely optical counterpart
  91. GRB 251106A: MASTER optical observations
  92. GRB 251106A: SVOM detection of a burst
  93. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  94. GRB 251105A: Swift/BAT-GUANO localization skymap of a burst
  95. GRB 251104A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  96. GRB 251105B: AstroSat CZTI detection of a short burst with extended emission
  97. GRB 251023A: SVOM/ECLAIRs detection of a burst through targeted search
  98. GRB 251103B: Swift/UVOT Upper Limits
  99. LIGO/Virgo/KAGRA S251105aj: Identification of a GW compact binary merger candidate
  100. GRB 251104A: SVOM detection of a burst

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