Skip to main content
Updates to LVK & CHIME Notices, Schema v7.2.3! See news and announcements

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"

914 results found.

  1. SN 2026stf / GRB 260708A: ATLAS forced photometry
  2. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  3. EP260727a: 1.5m OSN optical counterpart detection
  4. IceCube-260712A: LAST optical follow-up observations of the IceCube neutrino candidate
  5. GRB 260610B / AT2026owq: OASDG optical observations
  6. GRB 260610B: IAC-80 Optical observations
  7. GRB 260511B: SAO RAS optical observations
  8. GRB 260511B : MITSuME Akeno optical afterglow candidate detection
  9. EP260321a: Upper limits from VLA radio observations
  10. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  11. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  12. EP260321a: Gemini-South confirmation of a supernova
  13. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  14. GRB 260310A / AT2026fgk: SAO RAS optical observations
  15. GRB 260310A / AT2026fgk: OASDG optical observations
  16. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  17. EP260119a: Mondy and SAO RAS optical upper limits
  18. EP260119a: SAO RAS optical observations
  19. GRB 260114A : MITSuME Akeno optical upper limits
  20. Fermi-LAT Gamma-ray Observations of IceCube-260111A
  21. GRB 251205A : MITSuME Akeno optical afterglow candidate detection
  22. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  23. LIGO/Virgo/KAGRA S251112cm: SOAR spectroscopy of three TROVE TNS candidates
  24. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  25. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 4-Update Localization Volume
  26. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 3-Initial Localization Volume
  27. GRB 251103B: MITSuME Akeno optical upper limits
  28. GRB 251013C: Leavitt Observatory optical photometry
  29. GRB 251017A : MITSuME Akeno optical afterglow candidate detection
  30. GRB 251013C: Kilonova-Catcher optical afterglow detection
  31. GRB 251007A: AKO Optical Upper Limit
  32. GRB 251002A: AKO Early Optical Afterglow Detection
  33. GRB 250925A : MITSuME Akeno optical upper limits
  34. EP250827b: Gemini Spectroscopic Confirmation of AT2025wkm as a Ic-BL Supernova
  35. EP 250827B: Detection of supernova counterpart by LCO.
  36. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  37. GRB 250821A: Kilonova-Catcher optical upper limits
  38. GRB 250702F: AKO Optical Afterglow Detection
  39. GRB 250502A: AKO Optical Afterglow Detection
  40. GRB 250430A : MITSuME Akeno optical upper limits
  41. GRB 250430A: AKO Optical Afterglow Detection
  42. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  43. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  44. GRB 250419A: AKO Optical Afterglow Detection
  45. EP250304a: ATCA radio observations
  46. EP250404a: AKO Optical Afterglow Detection
  47. IceCube-250330A: MASTER detection of PKS 2032+107 blazar flare with Zhirkov effect
  48. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  49. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  50. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  51. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  52. GRB 250221A: AKO Optical Upper Limit
  53. GRB 250129A: AKO Optical Afterglow Detection
  54. Fermi-LAT Gamma-ray Observations of IceCube-250101A
  55. EP 250108A: Late-time optical observation by LCO
  56. EP250108a / SN2025kg: Gemini GMOS-S confirmation of an associated broad-lined SN Ic
  57. EP250108a/AT 2025kg: NOT spectroscopy in agreement with SN Ic-BL
  58. GRB 250114B : MITSuME Akeno optical afterglow candidate detection
  59. GRB 250103A: Montarrenti Observatory optical detection
  60. GRB 250101A: OASDG optical observations
  61. GRB 250101A: AKO Optical Afterglow Detection
  62. Fermi-LAT gamma-ray observations of IceCube-241113A
  63. EP241107A: MASTER optical observations of xray transient
  64. EP241107a: AKO Optical Afterglow Follow-Up Observations
  65. EP241107a: AKO Optical Afterglow Detection
  66. GRB 241030B : MITSuME Akeno optical upper limits
  67. GRB 241030B: AKO Optical Afterglow Detection
  68. GRB 241030A: AKO Optical Afterglow Detection
  69. GRB 241030A : MITSuME Akeno optical afterglow detection
  70. GRB 241029A: AKO Optical Afterglow Detection
  71. GRB 241001A: JWST spectroscopic identification of a supernova counterpart
  72. Fermi-LAT Gamma-ray Observations of IceCube-241006A
  73. GRB 241002C : MITSuME Akeno optical upper limits
  74. Fermi-LAT Gamma-ray Observations of IceCube-240929A
  75. EP240918a: YAHPT Optical Upper Limit
  76. GRB 240905E: AKO Optical Upper Limit
  77. GRB 240828A: SAO RAS optical observations
  78. GRB 240825A: AKO Optical Follow-Up Observations
  79. GRB 240825A: AKO Optical Afterglow Detection
  80. Fermi-LAT gamma-ray observations of IceCube-240808A
  81. EP240801a: BTA BVRI photometry
  82. Fermi-LAT gamma-ray observations of IceCube-240725A
  83. Fermi-LAT gamma-ray observations of IceCube-240721A
  84. EP240703a: BTA observations
  85. GRB 240529A : MITSuME Akeno optical afterglow detection
  86. GRB 240529A: AKO Optical Afterglow Follow-Up Observations
  87. GRB 240529A: AKO Optical Afterglow Detection
  88. GRB 240511A : MITSuME Akeno optical upper limits
  89. X-ray transient EP240414a: Detection of associated supernova
  90. EP240426a: YAHPT optical upper limit
  91. LIGO/Virgo/KAGRA S240422ed: No significant candidates in GRANDMA and Kilonova-Catcher galaxy targeting observations
  92. GRB 240419B : MITSuME Akeno optical upper limits
  93. GRB 240418A: AKO Upper Limit
  94. GRB 240414A: AKO Optical Upper Limit
  95. GRB 240414A : MITSuME Akeno optical upper limits
  96. IceCube-240327B: GRANDMA/Kilonova-Catcher observations of 4FGL J0555.9+0030 and optical upper limits
  97. Fermi-LAT gamma-ray observations of IceCube-240327B
  98. IceCube-240327B: GRANDMA observations of 4FGL J0555.9+0030
  99. IceCube-240327B: Upper limits from a search for additional neutrino events in IceCube
  100. IceCube-240327B: No candidates from the Zwicky Transient Facility

Advanced

Download all Circulars as a .tar.gz archive (updated once a day):
Looking for U.S. government information and services? Visit USA.gov