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Brackett-Gamma emission in MAXI J1535-571

ATel #10816; Christopher T Britt (MSU), Arash Bahramian (MSU), Jay Strader (MSU)
on 4 Oct 2017; 16:14 UT
Credential Certification: Christopher Britt (chrisbritt86@gmail.com)

Subjects: Infra-Red, Binary, Black Hole, Transient

Gemini observed the X-ray transient MAXI J1535-571 (GCN #21788, ATels #10699, #10700, #10702, #10704, #10708, #10711, #10714, #10716, #10734, #10745, #10761, #10768) with the FLAMINGOS-2 instrument on October 2nd, 2017 at 00:12:39 UT. The IR counterpart was observed at a position of

RA = 15:35:19.71

DEC = -57:13:46.7

which is consistent with its position previously reported in ATEL #10704 and ATEL #10716. The observation was taken with the R3K grism and the Ks filter with a 2-pixel slit. MAXI J1535-571 was observed in 24 exposures of 106 seconds with a resolving power of R=2900. The IR counterpart was observed in H band during acquisition and had a magnitude of approximately H = 15.0 mag so that it has faded by approximately 2.2 magnitudes since it was observed in ATEL #10716. The magnitude quoted is in reference to nearby 2MASS stars (7"-9") away and the acquisition image was not flat-fielded so the magnitude quoted is uncertain by the small scale flat-fielding corrections on that part of the CCD, of order 10%.

The K-band spectrum of MAXI J1535-571 shows Brackett-gamma in emission, centered at 21667 Angstroms with a FWHM of 79.0 Angstroms or 1090 +/- 60 km/s, well above the intrinsic instrumental resolution of 8.3 Angstroms as measured from sky emission lines. The emission line profile shows no evidence of being double-peaked.

We thank Gemini staff for approving and carrying out this observation.

The spectrum is available below.

FLAMINGOS-2 spectrum of MAXI J1535-571