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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"

54 results found.

  1. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  2. EP250821a: VLT X-shooter spectroscopic redshift z = 0.577
  3. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  4. EP250302a: VLT/MUSE optical redshift z = 1.131
  5. Gemini-South spectroscopic redshift of EP250207b host galaxy candidate (z=0.082)
  6. LIGO/Virgo/KAGRA S250206dm: Gemini-North spectroscopic observation of AT2025bbo and its host galaxy
  7. LIGO/Virgo/KAGRA S250206dm: MASTER detection AT2025bbo
  8. LIGO/Virgo/KAGRA S250206dm & FRB 20250206A: MASTER observations and possible mother galaxy
  9. GRB 240825A: VLT/X-shooter redshift
  10. LIGO/Virgo/KAGRA S240422ed: ENGRAVE VLT/XShooter spectroscopy of the host galaxy of J-GEM24a
  11. LIGO/Virgo/KAGRA S230627c: GECKO optical follow-up observations of host galaxy candidates and ZTF23aaptsuy/AT2023lxu
  12. GRB 230307A: Bad Time Intervals for Fermi GBM data
  13. GRB 221110A: COATLI Afterglow detection
  14. GRB 211227A: A possible short GRB with extended emission at z = 0.228?
  15. GRB 210205A: observations with the 3.6m DOT, a potential dark burst?
  16. GRB 201013A: 3.6m DOT Optical Observations
  17. IceCube-200926A: Upper limits from Insight-HXMT Observations
  18. GRB 200922A: chance superposition between optical afterglow and archival star
  19. LIGO/Virgo S200316bj: No Counterparts in DDOTI/OAN Optical Observations
  20. GRB 200228B: RATIR Optical Observations
  21. GRB 200224B: DDOTI/OAN optical observations report
  22. GRB 200125B: DDOTI/OAN optical observations report
  23. GRB 200115A: DDOTI/OAN optical observations report
  24. GRB 200114A: DDOTI/OAN optical observations report
  25. GRB 191019A: NOT optical spectroscopy of candidate counterpart
  26. LIGO/Virgo S190828j: No Counterparts in DDOTI/OAN Optical Observations
  27. GRB 190114C: X-shooter observations of a highly extinguished afterglow
  28. GRB 190114C: refined redshift by the 10.4m GTC
  29. GRB 190114C: NOT optical counterpart and redshift
  30. GRB 180728A: VLT/X-shooter redshift of a nearby energetic GRB
  31. GRB 170626B: The first GRB detected by the Insight-HXMT X-ray Telescope (revised)
  32. GRB 161214B: optical spectroscopy of the foreground SDSS object
  33. LIGO/Virgo G211117: INAF NOT follow-up of PanStarrs candidates
  34. ANTARES neutrino detection and Swift/XRT counterpart: GMG observation
  35. GRB 150101B/Swift J123205.1-105602: VLT observations and redshift
  36. Swift Trigger 600114: Optical spectroscopy from GTC
  37. GRB 130822A: nearby galaxy redshifts
  38. GRB 130612A: NOT optical observations
  39. GRB100925A/MAXI J1659-152: X-shooter identification as an X-ray binary
  40. GRB 090424: WHT ISIS spectroscopy
  41. Detailed Spectroscopic ID of SN 2008D (Transient in NGC 2770)
  42. Transient in NGC 2770: spectroscopic evidence for a SN
  43. GRB 061201: Nearby Galaxy Cluster Abell 995 is at z=0.0865
  44. GRB 060912: Redshift of nearby 2MASS galaxy
  45. GRB 060218 / SN 2006aj Nebular Spectrum
  46. GRB 060708: VLT spectroscopy
  47. GRB 060218/SN 2006aj, high resolution spectra
  48. GRB050904: Optical Observations
  49. GRB 050724: spectroscopy of object in the XRT error circle
  50. GRB050418: Null Optical Observations
  51. Type Ic SN2003L (SN/GRB?), optical spectrum
  52. SN2002ap (SN/GRB?) Echelle spectra
  53. SN2002ap (SN/GRB?) optical spectrographic observations
  54. GRB 990123: Updated Keck Spectroscopy Results

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