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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.

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subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

907 results found.

  1. GRB 260511B : MITSuME Akeno optical afterglow candidate detection
  2. EP260321a: Upper limits from VLA radio observations
  3. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  4. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  5. EP260321a: Gemini-South confirmation of a supernova
  6. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  7. GRB 260310A / AT2026fgk: SAO RAS optical observations
  8. GRB 260310A / AT2026fgk: OASDG optical observations
  9. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  10. EP260119a: Mondy and SAO RAS optical upper limits
  11. EP260119a: SAO RAS optical observations
  12. GRB 260114A : MITSuME Akeno optical upper limits
  13. Fermi-LAT Gamma-ray Observations of IceCube-260111A
  14. GRB 251205A : MITSuME Akeno optical afterglow candidate detection
  15. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  16. LIGO/Virgo/KAGRA S251112cm: SOAR spectroscopy of three TROVE TNS candidates
  17. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  18. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 4-Update Localization Volume
  19. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 3-Initial Localization Volume
  20. GRB 251103B: MITSuME Akeno optical upper limits
  21. GRB 251013C: Leavitt Observatory optical photometry
  22. GRB 251017A : MITSuME Akeno optical afterglow candidate detection
  23. GRB 251013C: Kilonova-Catcher optical afterglow detection
  24. GRB 251007A: AKO Optical Upper Limit
  25. GRB 251002A: AKO Early Optical Afterglow Detection
  26. GRB 250925A : MITSuME Akeno optical upper limits
  27. EP250827b: Gemini Spectroscopic Confirmation of AT2025wkm as a Ic-BL Supernova
  28. EP 250827B: Detection of supernova counterpart by LCO.
  29. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  30. GRB 250821A: Kilonova-Catcher optical upper limits
  31. GRB 250702F: AKO Optical Afterglow Detection
  32. GRB 250502A: AKO Optical Afterglow Detection
  33. GRB 250430A : MITSuME Akeno optical upper limits
  34. GRB 250430A: AKO Optical Afterglow Detection
  35. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  36. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  37. GRB 250419A: AKO Optical Afterglow Detection
  38. EP250304a: ATCA radio observations
  39. EP250404a: AKO Optical Afterglow Detection
  40. IceCube-250330A: MASTER detection of PKS 2032+107 blazar flare with Zhirkov effect
  41. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  42. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  43. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  44. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  45. GRB 250221A: AKO Optical Upper Limit
  46. GRB 250129A: AKO Optical Afterglow Detection
  47. Fermi-LAT Gamma-ray Observations of IceCube-250101A
  48. EP 250108A: Late-time optical observation by LCO
  49. EP250108a / SN2025kg: Gemini GMOS-S confirmation of an associated broad-lined SN Ic
  50. EP250108a/AT 2025kg: NOT spectroscopy in agreement with SN Ic-BL
  51. GRB 250114B : MITSuME Akeno optical afterglow candidate detection
  52. GRB 250103A: Montarrenti Observatory optical detection
  53. GRB 250101A: OASDG optical observations
  54. GRB 250101A: AKO Optical Afterglow Detection
  55. Fermi-LAT gamma-ray observations of IceCube-241113A
  56. EP241107A: MASTER optical observations of xray transient
  57. EP241107a: AKO Optical Afterglow Follow-Up Observations
  58. EP241107a: AKO Optical Afterglow Detection
  59. GRB 241030B : MITSuME Akeno optical upper limits
  60. GRB 241030B: AKO Optical Afterglow Detection
  61. GRB 241030A: AKO Optical Afterglow Detection
  62. GRB 241030A : MITSuME Akeno optical afterglow detection
  63. GRB 241029A: AKO Optical Afterglow Detection
  64. GRB 241001A: JWST spectroscopic identification of a supernova counterpart
  65. Fermi-LAT Gamma-ray Observations of IceCube-241006A
  66. GRB 241002C : MITSuME Akeno optical upper limits
  67. Fermi-LAT Gamma-ray Observations of IceCube-240929A
  68. EP240918a: YAHPT Optical Upper Limit
  69. GRB 240905E: AKO Optical Upper Limit
  70. GRB 240828A: SAO RAS optical observations
  71. GRB 240825A: AKO Optical Follow-Up Observations
  72. GRB 240825A: AKO Optical Afterglow Detection
  73. Fermi-LAT gamma-ray observations of IceCube-240808A
  74. EP240801a: BTA BVRI photometry
  75. Fermi-LAT gamma-ray observations of IceCube-240725A
  76. Fermi-LAT gamma-ray observations of IceCube-240721A
  77. EP240703a: BTA observations
  78. GRB 240529A : MITSuME Akeno optical afterglow detection
  79. GRB 240529A: AKO Optical Afterglow Follow-Up Observations
  80. GRB 240529A: AKO Optical Afterglow Detection
  81. GRB 240511A : MITSuME Akeno optical upper limits
  82. X-ray transient EP240414a: Detection of associated supernova
  83. EP240426a: YAHPT optical upper limit
  84. LIGO/Virgo/KAGRA S240422ed: No significant candidates in GRANDMA and Kilonova-Catcher galaxy targeting observations
  85. GRB 240419B : MITSuME Akeno optical upper limits
  86. GRB 240418A: AKO Upper Limit
  87. GRB 240414A: AKO Optical Upper Limit
  88. GRB 240414A : MITSuME Akeno optical upper limits
  89. IceCube-240327B: GRANDMA/Kilonova-Catcher observations of 4FGL J0555.9+0030 and optical upper limits
  90. Fermi-LAT gamma-ray observations of IceCube-240327B
  91. IceCube-240327B: GRANDMA observations of 4FGL J0555.9+0030
  92. IceCube-240327B: Upper limits from a search for additional neutrino events in IceCube
  93. IceCube-240327B: No candidates from the Zwicky Transient Facility
  94. IceCube-240327B - IceCube observation of a high-energy neutrino candidate track-like event
  95. GRB 240225B : MITSuME Akeno optical afterglow candidate detection
  96. GRB 240123A : MITSuME Akeno optical afterglow candidate detection
  97. GRB 231215A: AKO Optical Upper Limit
  98. GRB 231215A : MITSuME Akeno optical afterglow candidate detection
  99. GRB 231205B : MITSuME Akeno optical upper limits
  100. GRB 231205B: AKO Optical Upper Limit

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